This is a tentative list of transitional fossils (fossil remains of a creature that exhibits primitive traits in comparison with more derived organisms to which it is related). The fossils are listed in series, showing the transition from one group to another, representing significant steps in the evolution of major features in various lines. These changes often represent major changes in anatomy, related to mode of life, like the acquisition of feathered wings for an aerial lifestyle in birds, or legs in the fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

/tetrapod

Tetrapod

Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...

 transition. As noted already by Darwin

Charles Darwin

Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...

, the fossil record is incomplete.

Ideally, this list would only recursively include 'true' transitionals, fossils representing ancestral specie from which later groups evolved, but most if not all, of the fossils shown here represent extinct side branches, more or less closely related to the true ancestor. They will all include details unique to their own line as well. Fossils having relatively few such traits are termed "transitional", while those with a host of traits found neither in the ancestral or derived group are called "intermediate". Since all species will always be subject to natural selection, the very term "transitional fossil" is essentially a misconception. It is however a commonly used term and a useful concept in evolutionary biology. The fossils listed represent significant steps in the evolution of major features in various lines and therefore fit the common usage of the phrase.

Nautiloid

Nautiloid

Nautiloids are a large and diverse group of marine cephalopods belonging to the subclass Nautiloidea that began in the Late Cambrian and are represented today by the living Nautilus. Nautiloids flourished during the early Paleozoic era, where they constituted the main predatory animals, and...

s to Ammonoids

The Nautiloids → Ammonoids Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
>500 Ma	Subclass: Nautiloidea
390 Ma	Order: Bactritida Bactritida The Bactritida form a small order of more or less straight-shelled cephalopods that first appeared during the Emsian Stage of the Devonian Period and persisted until the Carnian Stage of the Triassic Period...	Member of the Nautiloids. Direct ancestor of the ammonoids.
370 Ma	Subclass: Ammonoidea	Direct descendants of Bactirida.

Cephalopod

Cephalopod

A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...

s

The Cephalopod Cephalopod A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
296 Ma	Genus Pohlsepia			The earliest described octopod.
164 Ma	Genus: Proteroctopus			A primitive octopod.
165–164 Ma	Genus: Vampyronassa			An early Vampyromorphida Vampyromorphida Vampyromorphida is an order of cephalopods comprising one known extant species and many extinct taxa. Physically, they somewhat resemble octopuses, but the eight main tentacles are united by a web of skin, and two smaller tentacles are also present.-Classification:*Order Vampyromorphida**?Suborder... .
89 - 71 Ma	Genus: Palaeoctopus			A primitive octopod.

Evolution of insects

The Insect Insect Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
400 Ma	Genus: Rhyniognatha Rhyniognatha Rhyniognatha hirsti is the world’s oldest known insect. It emerged very early during the Early Devonian Period, around 400 million years ago, when earth’s first terrestrial ecosystems were being formed.-Evidence:...			The world’s oldest known insect.
400 Ma	Genus: Rhyniella			Early springtail Springtail Springtails form the largest of the three lineages of modern hexapods that are no longer considered insects... .
300 Ma	Genus: Archimylacris Archimylacris Archimylacris is an extinct genus of cockroach-like Blattopterans, a group of insects ancestral to cockroaches, mantids and termites.Archimylacris lived on the warm swampy forest floors of North America and Europe 300 million years ago, in the Late Carboniferous times...			An ancestral to cockroach Cockroach Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations... es, mantids and termites.
316.5 Ma	Genus: Aphthoroblattina			A primitive cockroach.
140 Ma	Genus: Archaeolepis Archaeolepis Archaeolepis mane is the earliest known Lepidopteran fossil. It dates from the Lower Jurassic and according to Grimaldi & Engel a recent re-examination of the specimen has given additional support to its ordinal placement...			The earliest known Lepidopteran.
92 Ma	Genus: Melittosphex			The oldest known species of bee Bee Bees are flying insects closely related to wasps and ants, and are known for their role in pollination and for producing honey and beeswax. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila... .
80 Ma	Genus: Sphecomyrma			The earliest known species of ant Ant Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than... .
56 - 34 Ma	Genus: Eophyllium			First leaf insect from the fossil record.

Evolution of spiders

The Spider Spider Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
390 Ma	Genus: Attercopus Attercopus Previously interpreted as the world's oldest spider, Attercopus fimbriunguis belongs to an extinct order of arachnids named Uraraneida; thought to be close to the origins of spiders...			Previously thought to be the world's oldest spider.
165 Ma	Genus Eoplectreurys Eoplectreurys Eoplectreurys is an extinct monotypic genus of spider from the family Plectreuridae, with a sole species, Eoplectreurys gertschi...			The oldest known haplogyne spider.

Invertebrates to Fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

The Invertebrates → Fish Fish Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
??? Ma	Genus: Pikaia Pikaia Pikaia gracilens is an extinct animal known from the Middle Cambrian Burgess Shale of British Columbia. -Discovery:It was discovered by Charles Walcott and was first described by him in 1911. It was named after Pika Peak, a mountain in Alberta, Canada. Based on the obvious and regular segmentation...			Lancelet Lancelet The lancelets , also known as amphioxus, are the modern representatives of the subphylum Cephalochordata, formerly thought to be the sister group of the craniates. They are usually found buried in sand in shallow parts of temperate or tropical seas. In Asia, they are harvested commercially as food... -like in appearance. Oldest known ancestor of modern vertebrates Vertebrate characters Very primitive proto-notochord Notochord The notochord is a flexible, rod-shaped body found in embryos of all chordates. It is composed of cells derived from the mesoderm and defines the primitive axis of the embryo. In some chordates, it persists throughout life as the main axial support of the body, while in most vertebrates it becomes... .
??? Ma	Class: Conodont Conodont Conodonts are extinct chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils now called conodont elements, found in isolation. Knowledge about soft tissues remains relatively sparse to this day...	Had fin rays, chevron-shaped muscles and a notochord.
530 Ma	Genus: Haikouichthys Haikouichthys Haikouichthys is an extinct genus of craniate believed to have lived c. 530 million years ago, during the Cambrian explosion of multicellular life...			Appears to have a cranium, thus being a craniat Craniata Craniata is a proposed clade of chordate animals that contains the Myxini , Petromyzontida , and Gnathostomata as living representatives... .
480 to 470 Ma	Genus: Arandaspis Arandaspis Arandaspis prionotolepis is an extinct species of jawless fish that lived in the Ordovician period, about 480 to 470 million years ago. It is the oldest known vertebrate....		Jawless fish Agnatha Agnatha is a superclass of jawless fish in the phylum Chordata, subphylum Vertebrata. The group excludes all vertebrates with jaws, known as gnathostomes....	A well armoured jawless fish Agnatha Agnatha is a superclass of jawless fish in the phylum Chordata, subphylum Vertebrata. The group excludes all vertebrates with jaws, known as gnathostomes.... , resembling a large tadpole in life
??? Ma	Genus: Birkenia Birkenia Birkenia is a genus of extinct anaspid fish from the Late Silurian to the Early Devonian of Europe. It reached a length of 4 in and was an active swimmer....		An anaspid Anaspida The Anaspida are stem gnathostomes, and are classically regarded as the ancestors of lampreys. Anaspids were small marine agnathans that lacked scales and paired fins, but have a striking highly hypocercal tail... , ancestral to the jawed vertebrates,	A rather lightly armoured jawless fish Agnatha Agnatha is a superclass of jawless fish in the phylum Chordata, subphylum Vertebrata. The group excludes all vertebrates with jaws, known as gnathostomes....
419 Ma	Genus: Guiyu Guiyu (fish) Guiyu is an extinct genus of bony fish, and is the earliest known one. It lived during the Late Silurian in China...		Oldest known bony fish Osteichthyes Osteichthyes , also called bony fish, are a taxonomic group of fish that have bony, as opposed to cartilaginous, skeletons. The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of over 29,000 species...

Chondrichthyes

Chondrichthyes

Chondrichthyes or cartilaginous fishes are jawed fish with paired fins, paired nares, scales, two-chambered hearts, and skeletons made of cartilage rather than bone...

The Chondrichthyes Chondrichthyes Chondrichthyes or cartilaginous fishes are jawed fish with paired fins, paired nares, scales, two-chambered hearts, and skeletons made of cartilage rather than bone... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
370 Ma	Genus: Cladoselache Cladoselache Cladoselache is a genus of extinct shark. It appeared in the Devonian period.This primitive shark grew to be up to long and roamed the oceans of North America. It is known to have been a fast moving and fairly agile predator due to its streamlined body and deep forked tail...			An early primitive shark.
70 - 65 Ma	Genus: Dalpiazia Dalpiazia Dalpiazia is a prehistoric genus of saw fish whose fossils are found in rocks dating from the Maastrichtian stage in Morocco. It was named in honor of Ernst Stromer.-Classification:...			A early Sawfish Sawfish Sawfish, also known as the Carpenter Shark, are a family of rays, characterized by a long, toothy nose extension snout. Several species can grow to approximately . The family as a whole is largely unknown and little studied...
99 – 65 Ma	Genus: Cyclobatis Cyclobatis Cyclobatis is an extinct genus of stingray-like skate from the Upper Cretaceous of what is now Lebanon. The genus is typified by a circular form, hence the prefix "Cyclo-," meaning "wheel-like," and the presence of an extremely short tail....			An early stingray Stingray The stingrays are a group of rays, which are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae , Plesiobatidae , Urolophidae , Urotrygonidae , Dasyatidae , Potamotrygonidae The... -like skate Skate Skates are cartilaginous fish belonging to the family Rajidae in the superorder Batoidea of rays. There are more than 200 described species in 27 genera. There are two subfamilies, Rajinae and Arhynchobatinae .... .

Bony Fish

The Bony Fish Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
420 Ma	Genus: Adreolepis			The earliest-known Actinopterygii Actinopterygii The Actinopterygii or ray-finned fishes constitute a class or sub-class of the bony fishes.The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines , as opposed to the fleshy, lobed fins that characterize... an.
??? Ma	Genus: Amphistium Amphistium Amphistium is a fossil fish which has been identified as an early relative of the Flatfish, and as a Transitional fossil. In a typical modern flatfish, the head is asymmetric with both eyes on one side of the head...			An early relative of the Flatfish Flatfish The flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development... .
48 – 37 Ma	Genus: Eobothus Eobothus Eobothus is an extinct genus of flatfish from the Eocene period of China, India and Europe.Eobothus is significant as one of the earliest genera of flatfish, one of the last major fish groups to evolve. It closely resembled modern flatfish, with an oval-shaped body about long, surrounded by...			An early flatfish Flatfish The flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development...
183.7–125.0 Ma	Genus: Leptolepis Leptolepis Leptolepis is an extinct genus of teleost fish that lived in the Mesozoic era. It was one of the first teleosts.- Appearance :...			One of the first teleosts.
99 – 93 Ma	Genus: Aguillavus			The oldest known eel Eel Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators... .
13 Ma	Genus: Hippocampus sarmaticus Hippocampus sarmaticus Hippocampus sarmaticus is an extinct species of seahorse, found in 2005 in the coprolitic horizon of the Tunjice hills Lagerstätte in Slovenia, along with the related Hippocampus slovenicus. The horizon dates 13 million years back to the lower Sarmatian during the middle Miocene period, making the...			One of the oldest known seahorse Seahorse Seahorses compose the fish genus Hippocampus within the family Syngnathidae, in order Syngnathiformes. Syngnathidae also includes the pipefishes. "Hippocampus" comes from the Ancient Greek hippos meaning "horse" and kampos meaning “sea monster”.There are nearly 50 species of seahorse... .
13 Ma	Genus: Hippocampus slovenicus Hippocampus slovenicus Hippocampus slovenicus is an extinct species of seahorse found in 2005 in the coprolitic horizon of the Tunjice hills Lagerstätte in Slovenia along with remains of the related species Hippocampus sarmaticus. The horizon dates 13 million years back to the lower Sarmatian during the middle Miocene...			One of the oldest known seahorse Seahorse Seahorses compose the fish genus Hippocampus within the family Syngnathidae, in order Syngnathiformes. Syngnathidae also includes the pipefishes. "Hippocampus" comes from the Ancient Greek hippos meaning "horse" and kampos meaning “sea monster”.There are nearly 50 species of seahorse... .
83 - 70 Ma	Genus: Nardovelifer Nardovelifer Nardovelifer altipinnis is the oldest known lamprid fish. It dates from the Campanian epoch of Nardò, Italy....			The oldest known lamprid fish
56 - 34 Ma	Genus: Eomola Eomola Eomola is an extinct genus of sunfish from the middle Eocene. Its fossils have been found in Russia. Eomola was described in 1992 by James Tyler and Alexandre Bannikov, and the type species is E. bimaxillaria.-External links:*...			A primitive sunfish Molidae Molidae is the family of the molas or ocean sunfishes, unique fish whose bodies come to an end just behind the dorsal and anal fins, giving them a "half-a-fish" appearance...
58 - 55 Ma	Genus: Corydoras revelatus Corydoras revelatus Corydoras revelatus is an extinct species of callichthyid known from a single specimen found in Late Paleocene strata of the Mais Gordo Formation in Salta, Argentina. According to chronological dating of the strata, the fossil specimen is about 58.2–58.5 million years old.Compared to modern...			The oldest known member of the catfish Catfish Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...  family Callichthyidae Callichthyidae Callichthyidae is a family of catfishes , called armored catfishes due to the two rows of bony plates running down the length of the body. This family contains some of the most popular freshwater aquarium fish, such as the Corydoras.-Taxonomy:The family derives its name from the Greek words kallis... .
56 - 34 Ma	Genus: Ruffoichthys			A primitive rabbitfish Rabbitfish Rabbitfishes or spinefoots are perciform fishes in the family Siganidae. The 28 species are in a single genus, Siganus. In some now obsolete classifications, the species having prominent face stripes—colloquially called foxfaces–are in the genus Lo. Other species like the Masked... .
48 - 37 Ma	Genus: Palaeoperca Palaeoperca Palaeoperca is an extinct genus of prehistoric bony fish that lived from the early to middle Eocene.-See also:* Prehistoric fish* List of prehistoric bony fish...			A primitive perch Perch Perch is a common name for fish of the genus Perca, freshwater gamefish belonging to the family Percidae. The perch, of which there are three species in different geographical areas, lend their name to a large order of vertebrates: the Perciformes, from the Greek perke meaning spotted, and the...
58 - 55 Ma	Genus: Trachicaranx Trachicaranx Trachicaranx tersus is a primitive, pompano-like jack fish from what is now Turkmenistan. It lived in an ocean upwelling with its relative, Archaeus oblongus during the Thanetian epoch of the late Paleocene. Some incomplete fossil specimens were once identified as being a separate species,...			A primitive pomfret Pomfret Pomfret are perciform fishes belonging to the family Bramidae.They are found in the Atlantic, Indian, and Pacific Oceans, and the largest species, the Atlantic pomfret, Brama brama, grows up to long....
48 - 40 Ma	Genus: Histionotophorus			A early handfish Handfish Handfish are anglerfish in the family Brachionichthyidae, a group which comprises five genera and fourteen extant species.They are small bottom-dwelling marine fish found in coastal waters of southern Australia and Tasmania. Their skin is covered with denticles , giving them the name warty anglers...
48 - 40 Ma	Genus: Eolactoria Eolactoria Eolactoria sorbinii is an extinct prehistoric boxfish that lived during the Lutetian epoch of the middle Eocene, in Monte Bolca. It had two pairs of long spines, one over each eye, and one pair beneath the anal and caudal fins, arranged very similarly to those possessed by the modern genus...			The oldest ostraciid boxfish Boxfish Ostraciidae is a family of squared, bony fish belonging to the order Tetraodontiformes, closely related to the pufferfishes and filefishes. Fish in the family are known variously as boxfishes, cofferfishes, cowfishes and trunkfishes...
48 - 40 Ma	Genus: Proaracana Proaracana Proaracana dubia is an extinct, prehistoric aracanid boxfish that lived during the Lutetian of middle Eocene Monte Bolca.-See also:* Eolactoria* Prehistoric fish* List of prehistoric bony fish...			A primitive aracanid boxfish Boxfish Ostraciidae is a family of squared, bony fish belonging to the order Tetraodontiformes, closely related to the pufferfishes and filefishes. Fish in the family are known variously as boxfishes, cofferfishes, cowfishes and trunkfishes...
48 - 40 Ma	Genus: Gazolaichthys			A basal surgeonfish
48 - 40 Ma	Genus: Psettopsis Psettopsis Psettopsis subarcuatus is an extinct, prehistoric moonyfish that lived during the Lutetian epoch of Monte Bolca, Italy.It had large, rounded dorsal and anal fins, and was a comparatively large fish, being about 45 centimeters long, much larger than its relative, Pasaichthys.-See also:* Pasaichthys*...			A primitive monodactylid moonyfish
48 - 40 Ma	Genus: Pasaichthys Pasaichthys Pasaichthys pleuronectiformis is an extinct, prehistoric moonyfish that lived during the Lutetian epoch of Monte Bolca, Italy. The average length of its fossils is about 6 centimeters. In life, it would probably resemble its living relatives of the genus Monodactylus.-See also:* Prehistoric fish*...			A primitive monodactylid moonyfish
48 - 40 Ma	Genus: Eozanclus Eozanclus Eozanclus is an extinct genus of prehistoric bony fish that lived from the early to middle Eocene.-See also:* Prehistoric fish* List of prehistoric bony fish...			A short-snouted ancestor of the modern Moorish Idol Moorish Idol The moorish idol, Zanclus cornutus , is a small marine fish species, the sole extant representative of the family Zanclidae in order Perciform. A common inhabitant of tropical to subtropical reefs and lagoons, the moorish idol is notable for its wide distribution throughout the Indo-Pacific... .
83 - 65 Ma	Genus: Cretatriacanthus Cretatriacanthus Cretatriacanthus is an extinct genus of prehistoric bony fish.-See also:* Prehistoric fish* List of prehistoric bony fish...			A primitive Tetraodontidae
83 - 65 Ma	Genus: Nardoichthys Nardoichthys Nardoichthys francisci is an extinct species of bony fish from the Campanian/Maastrichtian epoch of Nardò, Italy....			A primitive Perciforme
58 - 55 Ma	Genus: Protozeus Protozeus Protozeus kuehnei is an extinct species of fish from the Thanetian epoch....			A primitive Zeidae Zeidae The Zeidae are a family of large, showy, deep-bodied zeiform marine fish—the "true dories". Found in the Atlantic, Indian, and Pacific Ocean, the family contains just six species in two genera...
58 - 55 Ma	Genus: Archaeozeus Archaeozeus Archaeozeus skamolensis is an extinct genus of fish from the Ypresian epoch Fur Formation of Denmark....			A primitive Zeidae Zeidae The Zeidae are a family of large, showy, deep-bodied zeiform marine fish—the "true dories". Found in the Atlantic, Indian, and Pacific Ocean, the family contains just six species in two genera...
??? Ma	Genus: Cooyoo			A primitive Ichthyodectidae Ichthyodectidae The family Ichthyodectidae was a family of marine actinopterygian fish. Sometimes classified in the primitive bony fish order Pachycormiformes, they are today generally regarded as members of the "bulldog fish" order Ichthyodectiformes in the far more advanced Osteoglossomorpha...
65 Ma	Genus: Protriacanthus Protriacanthus -Sources:* New superfamily and three new families of tetraodontiform fishes from the Upper Cretaceous : the earliest and most morphologically primitive plectognaths by James C. Tyler*...			A primitive tetraodontid

Fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 to Tetrapods

The Fish Fish Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups... → Tetrapods Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
416-359 Ma	Genus: Osteolepis Osteolepis Osteolepis is an extinct genus of lobe-finned fish from the Devonian period. It lived in the Orcadian Lakes of northern Scotland....	An early member of the Tetrapodomorpha Tetrapodomorpha Tetrapodomorpha is a clade of vertebrates, consisting of tetrapods and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish... , the piscine line leading to tetrapods, Osteolepis Osteolepis Osteolepis is an extinct genus of lobe-finned fish from the Devonian period. It lived in the Orcadian Lakes of northern Scotland.... is generalised enough to give a fair approximation of the common ancestor of tetrapods and lungfish Lungfish Lungfish are freshwater fish belonging to the Subclass Dipnoi. Lungfish are best known for retaining characteristics primitive within the Osteichthyes, including the ability to breathe air, and structures primitive within Sarcopterygii, including the presence of lobed fins with a well-developed... .	Fish	A small to medium sized sarcopterygian fish with internal nostrils and pectoral fins stiffened by bony components broadly homologous Homology (biology) Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...  to the humerus Humerus The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....  and radius Radius (bone) The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally... /ulna Ulna The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...  found in tetrapods.
385 Ma	Genus: Eusthenopteron Eusthenopteron Eusthenopteron is a genus of prehistoric lobe-finned fish which has attained an iconic status from its close relationships to tetrapods. Early depictions of this animal show it emerging onto land, however paleontologists now widely agree that it was a strictly aquatic animal...	Belonging to the family Tristichopteridae Tristichopteridae Tristichopterids , were a diverse and successful group of tetrapodomorph fishes throughout the Late Devonian stage. They first appeared in the Givetian epoch of the Middle Devonian stage... , a family Family (biology) In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...  that form a sister group to Panderichthys Panderichthys Panderichthys is a 90–130 cm long fish from the Devonian period 397 million years ago, of Latvia. It is named after the german-baltic palaeontologist Christian Heinrich Pander. It has a large tetrapod-like head... and the tetrapods.	Though not on the evolutionary path to tetrapods, Eusthenopteron is of fairly general build and is very well known, serving as an iconic model organism in tetrapod evolution.	A medium sized, mainly pelagic fish, Eusthenopteron Eusthenopteron Eusthenopteron is a genus of prehistoric lobe-finned fish which has attained an iconic status from its close relationships to tetrapods. Early depictions of this animal show it emerging onto land, however paleontologists now widely agree that it was a strictly aquatic animal... mainly use the pectoral and pelvic fins for navigation, and the tail for propulsion. The fin was of diphycercal, foreshadowing the straightening of the spine and the evolution of a contiguous fin in fish like Panderichthys Panderichthys Panderichthys is a 90–130 cm long fish from the Devonian period 397 million years ago, of Latvia. It is named after the german-baltic palaeontologist Christian Heinrich Pander. It has a large tetrapod-like head...
380 Ma	Genus: Panderichthys Panderichthys Panderichthys is a 90–130 cm long fish from the Devonian period 397 million years ago, of Latvia. It is named after the german-baltic palaeontologist Christian Heinrich Pander. It has a large tetrapod-like head...	Very close to the origin of tetrapods, a "fishapod".	Fish	A large, predatory shallow water fish. As common in shallow water fish, the pectoral and pelvic fins was flexible and paddle-like for propulsion. The dorsal and anal fins are lost, the tail fin contiguous. The spiracle Spiracle Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar... s were short and wide, indication large amount of oxygen were taken up by the lungs rather than through the gills.
375 Ma	Genus: Tiktaalik Tiktaalik Tiktaalik is a genus of extinct sarcopterygian from the late Devonian period, with many features akin to those of tetrapods . It is an example from several lines of ancient sarcopterygian "fish" developing adaptations to the oxygen-poor shallow-water habitats of its time, which led to the...	A "fishapod" more tetrapod-like than Panderichthys Panderichthys Panderichthys is a 90–130 cm long fish from the Devonian period 397 million years ago, of Latvia. It is named after the german-baltic palaeontologist Christian Heinrich Pander. It has a large tetrapod-like head... .	A fish, transitional between fish and the early, fish-like labyrinthodonts.	"Fish" with stout, fleshy pectoral fins with a joint between the innermost and the two next bony elements, corresponding to the elbow in higher tetrapods. The cleithrum Cleithrum The cleithrum is a membrane bone which first appears as part of the skeleton in primitive bony fish, where it runs vertically along the scapula. Its name is derived from Greek κλειθρον = "key ", by analogy with "clavicle" from Latin clavicula = "little key".In modern fishes, the cleithrum is a...  bone was free of the skull, functioning as anchoring for the pectoral fins, and at the same time allowing for movement of the neck.
368 Ma	Genus: Elginerpeton Elginerpeton Elginerpeton is a monotypic genus of early tetrapod, the fossils of which were recovered from Scat Craig, Scotland, in rocks dating to the late Devonian Period...		A fairly fragmentary find, Elginerpeton straddles the fish/tetrapod divide with a mosaic of features resembling 'Panderichthys Panderichthys Panderichthys is a 90–130 cm long fish from the Devonian period 397 million years ago, of Latvia. It is named after the german-baltic palaeontologist Christian Heinrich Pander. It has a large tetrapod-like head... , Ichthyostega Ichthyostega Ichthyostega is an early tetrapod genus that lived at the end of the Upper Devonian period . It was a labyrinthodont, one of the first fossil record of tetrapods. Ichthyostega possessed lungs and limbs that helped it navigate through shallow water in swamps... and Hynerpeton Hynerpeton Hynerpeton was a basal carnivorous tetrapod that lived in the lakes and estuaries of the Late Devonian period around 360 million years ago. Like many primitive tetrapods, it is sometimes referred to as an "amphibian", though it is not a true member of the modern Lissamphibia... . Probably one of the "fishapods".
365 Ma	Genus: Ventastega Ventastega Ventastega was a basal tetrapod that lived during the Famennian subdivision of the Late Devonian period approximately 374.5 to 359.2 million years ago, though Ventastega origins as a tetrapod lineage are probably seated in the preceding Frasnian period of the Late Devonian when a surge of...	Morphologically midway between Tiktaalik Tiktaalik Tiktaalik is a genus of extinct sarcopterygian from the late Devonian period, with many features akin to those of tetrapods . It is an example from several lines of ancient sarcopterygian "fish" developing adaptations to the oxygen-poor shallow-water habitats of its time, which led to the... and Acanthostega Acanthostega Acanthostega is an extinct labyrinthodont genus, among the first vertebrate animals to have recognizable limbs. It appeared in the Upper Devonian about 365 million years ago, and was anatomically intermediate between lobe-finned fishes and the first tetrapods fully capable of coming onto... /Ichthyostega Ichthyostega Ichthyostega is an early tetrapod genus that lived at the end of the Upper Devonian period . It was a labyrinthodont, one of the first fossil record of tetrapods. Ichthyostega possessed lungs and limbs that helped it navigate through shallow water in swamps... .	Possibly oldest animal to have feet rather than fins.	A large, dorso-ventrally flattened predatory fish with a well armoured labyrinthodont-like skull. While the fins themselves has not been found, the shoulder girdle is essentially similar to that of Acanthostega, indicating it too had feet rather than fins.
365 Ma	Genus: Acanthostega Acanthostega Acanthostega is an extinct labyrinthodont genus, among the first vertebrate animals to have recognizable limbs. It appeared in the Upper Devonian about 365 million years ago, and was anatomically intermediate between lobe-finned fishes and the first tetrapods fully capable of coming onto...		Together with Ichthyostega Ichthyostega Ichthyostega is an early tetrapod genus that lived at the end of the Upper Devonian period . It was a labyrinthodont, one of the first fossil record of tetrapods. Ichthyostega possessed lungs and limbs that helped it navigate through shallow water in swamps...  the sole early labyrinthodont known from fairly complete skeletons. It is the oldest animal known to have feet rather than fins, thus making it a true tetrapod Tetrapod Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian... .	First known animal with toes rather than fins. The feet was broad and paddle-like, adapted for movement in water. It retained functional gills in adulthood, behind a fleshy operculum Operculum Operculum may refer to:*Operculum , a stiff structure resembling a lid or a small door that opens and closes**Operculum , a lid on the shell of some gastropods**Operculum , a lid on the orifice of some bryozoans... .
365 Ma	Genus: Ichthyostega Ichthyostega Ichthyostega is an early tetrapod genus that lived at the end of the Upper Devonian period . It was a labyrinthodont, one of the first fossil record of tetrapods. Ichthyostega possessed lungs and limbs that helped it navigate through shallow water in swamps...	Fairly closely related to Acanthostega Acanthostega Acanthostega is an extinct labyrinthodont genus, among the first vertebrate animals to have recognizable limbs. It appeared in the Upper Devonian about 365 million years ago, and was anatomically intermediate between lobe-finned fishes and the first tetrapods fully capable of coming onto... . It possibly represent an early (and ultimately unsuccessful) line adapted to moving on land by inchworm Inchworm Inchworms are the caterpillars of geometer moths.Inchworm can also mean:*Inchworm , a song from the film Hans Christian Andersen*Inchworm , a ride-on toy manufactured by Hasbro in the 1970s... -like movements.	Together with Acanthostega the sole early labyrinthodont known from fairly complete skeletons.	Early labyrinthodont with polydactylous Polydactyly in early tetrapods Polydactyly in early tetrapod aquatic animals is not to be confused with polydactyly in the medical sense, i.e., it was not an anomaly in the sense it was not a condition of having more than the typical number of digits for a given taxon. The condition appear to have arisen from a limb with a fin... , paddle-like feet and reinforced vertebrae and neural spines. It probably spent time on land, yet retained gills and a tail with fin rayes.
360 Ma	Genus: Hynerpeton Hynerpeton Hynerpeton was a basal carnivorous tetrapod that lived in the lakes and estuaries of the Late Devonian period around 360 million years ago. Like many primitive tetrapods, it is sometimes referred to as an "amphibian", though it is not a true member of the modern Lissamphibia...			A large, basically salamander Salamander Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant... -like creature. The shoulder girdle was powerful, indicating it was a competent walker.
??? Ma	Genus: Tulerpeton Tulerpeton Tulerpeton is a fossil of an extinct genus of Devonian labyrinthodont that was found in the Tula Region of Russia at a site named Andreyevka...			A large animal with paddle-like six-toed feet. It did however not have gills in adulthood, and is thus the oldest labyrinthodont known to depend entirely on breathing with its lungs.
359 - 345 Ma	Genus: Pederpes Pederpes Pederpes is an extinct genus of early Carboniferous tetrapod, dating from the Tournaisian age . Pederpes contains one species, P...	Hailing from the fossil-poor Romer's Gap Romer's gap Romer's Gap is an example of a gap in the fossil record used in the study of evolution. Such gaps represent a period from which excavators have found no or very few fossils. Romer's gap is named after paleontologist Dr... , Pederpes may be ancestral to the higher labyrinthodonts.	Intermediate between the earlier Ichthyostegalian and the later, more advanced labyrinthodonts.	Despite an extra toe on the forelimbs, Pederpes had limbs that terminated in feet adapted primarely for walking rather than paddles for combined swimming and walking like the earlier groups.
295 Ma	Genus: Eryops Eryops Eryops meaning "drawn-out face" because most of its skull was in front of its eyes is a genus of extinct, semi-aquatic amphibian found primarily in the Lower Permian-aged Admiral Formation of Archer County, Texas, but fossils are also found in New Mexico and parts of the eastern United...	The Temnospondyli Temnospondyli Temnospondyli is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent...  are derived paleozoic amphibians, possibly ancestral to modern amphibians Lissamphibia The subclass Lissamphibia includes all recent amphibians and means smooth amphibia.Extant amphibians fall into one of three orders — the Anura , the Caudata or Urodela , and the Gymnophiona or Apoda .Although the ancestry of each group is still unclear, all share certain common characteristics,...	A "classical" temnospondyl Temnospondyli Temnospondyli is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent... , an advanced labyrinthodont group.	One of the best known labyrinthodonts, Eryops combines the large, flat skull and short limbs typical of the group.

Labyrinthodonts to Modern amphibians

Lissamphibia

The subclass Lissamphibia includes all recent amphibians and means smooth amphibia.Extant amphibians fall into one of three orders — the Anura , the Caudata or Urodela , and the Gymnophiona or Apoda .Although the ancestry of each group is still unclear, all share certain common characteristics,...

The Labyrinthodontia Labyrinthodontia Labyrinthodontia is an older term for any member of the extinct subclass of amphibians, which constituted some of the dominant animals of Late Paleozoic and Early Mesozoic times . The group is ancestral to all extant landliving vertebrates, and as such constitutes an evolutionary grade rather... → Lissamphibia Lissamphibia The subclass Lissamphibia includes all recent amphibians and means smooth amphibia.Extant amphibians fall into one of three orders — the Anura , the Caudata or Urodela , and the Gymnophiona or Apoda .Although the ancestry of each group is still unclear, all share certain common characteristics,... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
290 Ma	Genus: Gerobatrachus Gerobatrachus Gerobatrachus, also referred to as a frogamander, is an extinct genus of amphibamid temnospondyl that lived in the Permian period, approximately 290 million years ago, in the area that is now Baylor County, Texas...	Colloquially referred to as a "frogamander" due to this taxon being both chronologically and morphologically basal to both anurans and salamanders	One of the first transitional fossils towards modern amphibians (Lissamphibia Lissamphibia The subclass Lissamphibia includes all recent amphibians and means smooth amphibia.Extant amphibians fall into one of three orders — the Anura , the Caudata or Urodela , and the Gymnophiona or Apoda .Although the ancestry of each group is still unclear, all share certain common characteristics,... ).	Plesiomorphic traits Backbone with intermediate characteristics Retains a fully developed tail Derived traits Bears a large space for a tympanic ear Ankle bones are fused together like in salamanders Lightly built wide skull as in frogs
250 Ma	Genus: Triadobatrachus Triadobatrachus Triadobatrachus is an extinct genus of frog-like amphibian, including only one known species, Triadobatrachus massinoti. It is the oldest frog known to science, and an excellent example of a transitional fossil...	Intermediate between generalized amphibians and derived frogs	Early "almost frog" transitional amphibian	Plesiomorphic traits Possessed short limbs and therefore was unable to hop, unlike all extant anurans Retains fourteen vertebra unlike modern frogs who have four to nine vertebra Tibia and fibula are not fused into a tibiofibula Derived traits Skull resembles that of modern anuran skull with a latticework of thin bones in skull
190 Ma	Genus: Prosalirus Prosalirus Prosalirus bitis is the name given to a fossil proto-frog found in Arizona in 1995, which has primitive features, but has mostly lost the salamander-like traits of its ancestors. It has a skeleton designed to absorb the force of jumping with its hind legs and tail. It is thought to have lived 190...	Another transitional form which could be properly classified as a frog	An intermediate form which may replace Triadobatrachus Triadobatrachus Triadobatrachus is an extinct genus of frog-like amphibian, including only one known species, Triadobatrachus massinoti. It is the oldest frog known to science, and an excellent example of a transitional fossil...  as the "ultimate" ancestor of anurans	Plesiomorphic traits Still possess relatively short limbs Derived traits Tail is greatly reduced Does not have greatly enlarged legs, but shows some adaptations for hopping, such as a three-pronged pelvis
213-188 Ma	Genus: Vieraella Vieraella Vieraella is an extinct genus of frog from the Jurassic period of Argentina, and the oldest true frog known.Despite living around 200 million years ago, Vieraella was anatomically very similar to modern frogs. For example, its hind legs were adapted for jumping, and the skull already possessed the...	A derived fossil frog completing the series of transitional fossils between early amphibians and modern anurans	The oldest "true" frog	Plesiomorphic traits Retains ten presacral vertebra Derived traits Hind legs are adapted for hopping
210 Ma	Genus: Eocaecilia Eocaecilia Eocaecilia micropodia is an extinct species of caecilian from the Early Jurassic Period in Arizona, USA. It shared some characteristics with salamanders and the now extinct Microsauria...	Intermediate between basal amphibians and caecilian Caecilian The caecilians are an order of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, making them the least familiar order of amphibians. All extant caecilians and their closest fossil relatives are grouped as the clade Apoda. They are mostly... s	An early caecilian Caecilian The caecilians are an order of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, making them the least familiar order of amphibians. All extant caecilians and their closest fossil relatives are grouped as the clade Apoda. They are mostly...	Plesiomorphic traits Bears three-toed vestigial limbs The size of the orbits indicates well developed eyes and suggest a non-subterranean lifestyle Derived traits The body has been adapted to a sort of serpentine shape

Amphibians to Amniotes (early reptiles)

The Amphibians → Reptiles Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
326 - 318 Ma	Genus: Proterogyrinus Proterogyrinus Proterogyrinus was an anthracosaur, a large group of reptilian reptiliomorphs. It is likely that the first reptiles, such as Petrolacosaurus, evolved from reptilomorphs...	One of the early reptile-like Reptiliomorpha Reptiliomorpha refers to an order or subclass of reptile-like amphibians, which gave rise to the amniotes in the Carboniferous. Under phylogenetic nomenclature, the Reptiliomorpha includes their amniote descendants though, even in phylogenetic nomenclature, the name is mostly used when referring to...  amphibians	Amphibian	A large, somewhat lizard-like labyrinthodont with a deep skull, laterally placed eyes and five digits to each foot.
??? Ma	Genus: Limnoscelis Limnoscelis Limnoscelis is a genus of large, very reptile-like diadectomorph from the Early Permian of North America. Contrary to other diadectomorphans, Limnoscelis appear to have been a carnivore...	The order Diadectomorpha Diadectomorpha Diadectomorpha are a clade of large reptile-like amphibians that lived in Euramerica during the Carboniferous and Early Permian periods, and are very close to the ancestry of the Amniota. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully...  is the sister group of the amniote Amniote The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes... s.	The Limnoscelis was originally described as a "cotylosaur" (early reptiles) together with the other diadectomorpha Diadectomorpha Diadectomorpha are a clade of large reptile-like amphibians that lived in Euramerica during the Carboniferous and Early Permian periods, and are very close to the ancestry of the Amniota. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully... ns. Today the large-bodied diadectomorphs are thought to have had a larval stage, falling close to, but just outside the amphibian/reptile divide.	A large, predatory reptile-like amphibian. The limbs are extremely heavily built, indicating it fed on slow moving prey.
??? Ma	Genus: Tseajaia Tseajaia Tseajaia is an extinct genus of tetrapod. It was an anthracosaurian that lived in the Permian of North America. The skeleton is that of a medium sized, rather advanced reptile-like amphibian. In life it was about a meter long and may have looked vaguely like an iguana, though slower and and with...	Uncertain phylogeny, possibly a Seymouriamorph Seymouriamorpha Seymouriamorpha were a small but widespread group of reptiliomorphs. Many seymouriamorphs were terrestrial or semi-aquatic. However, aquatic larvae bearing external gills and grooves from the lateral line system has been found, making them unquestionably amphibians. The adults were terrestrial...  or Diadectomorph Diadectomorpha Diadectomorpha are a clade of large reptile-like amphibians that lived in Euramerica during the Carboniferous and Early Permian periods, and are very close to the ancestry of the Amniota. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully...	Amphibian	A medium sized, probably herbivorious animal
350 Ma	Genus: Westlothiana Westlothiana Westlothiana lizziae was a reptile-like amphibian or possibly early reptile that bore a superficial resemblance to modern-day lizards. It lived during the Carboniferous period, about 350 million years ago. The type specimen was discovered in East Kirkton Quarry, Bathgate, Scotland, in 1984, and was...	Uncertain phylogenetic position. Westlothiana may be a small-bodied diadectopmorph Diadectomorpha Diadectomorpha are a clade of large reptile-like amphibians that lived in Euramerica during the Carboniferous and Early Permian periods, and are very close to the ancestry of the Amniota. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully... , falling just outside the amphibian/reptile divide	Originally described as the first reptile Reptile Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors... , it is now considered an advanced reptile-like amphibian Reptiliomorpha Reptiliomorpha refers to an order or subclass of reptile-like amphibians, which gave rise to the amniotes in the Carboniferous. Under phylogenetic nomenclature, the Reptiliomorpha includes their amniote descendants though, even in phylogenetic nomenclature, the name is mostly used when referring to... .	Small, probably insectovorious animal. The body and tail was long, the limbs small, somewhat like a modern skink Skink Skinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae , they comprise the superfamily or infraorder Scincomorpha... .
320-305 Ma	Genus: Solenodonsaurus Solenodonsaurus Solenodonsaurus is an extinct genus of Reptiliomorpha, which lived about 320-305 million years ago. Classification is uncertain, but it was possibly an early reptile or an amphibian close to the diadectomorphs. Its remains were found in the Czech Republic...	Possibly allied to the Diadectomorpha Diadectomorpha Diadectomorpha are a clade of large reptile-like amphibians that lived in Euramerica during the Carboniferous and Early Permian periods, and are very close to the ancestry of the Amniota. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully... , or belinging to a sister group to Diadectomorpha and Amniota	Likely an amphibian	Smallish, likely carnivorious.
340 Ma	Genus: Casineria Casineria Casineria was a tetrapod which lived 340 million years ago in the Mississippian epoch. Casineria was a small animal with a total length estimated to have been 15 centimeters. It lived in what was then a fairly dry environment in Scotland. It is noted for its mix of primitive and advanced ...	The fragmentary nature of the fossil (it lacks a cranium) makes an exact phylogenetic position hard to establish.	Possibly the first animal with an amniote Amniote The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...  egg, and thus the first reptile.	Small lizard-like animal, the first known tetrapod Tetrapod Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...  to possess claws, indicating it has reptilian type skin with scute Scute A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:... s.
315 Ma	Genus: Hylonomus Hylonomus Hylonomus was a very early reptile. It lived 312 million years ago during the Late Carboniferous period.It is the earliest unquestionable reptile ....	One of several small, basal reptile genera	Reptile	An early anapsid Anapsid An anapsid is an amniote whose skull does not have openings near the temples.While "anapsid reptiles" or "anapsida" are traditionally spoken of as if they were a monophyletic group, it has been suggested that several groups of reptiles that had anapsid skulls may be only distantly related...  reptile, considered to be ancestral to both the synapsid Synapsid Synapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...  and sauropsid Sauropsida Sauropsida is a group of amniotes that includes all existing reptiles and birds and their fossil ancestors, including the dinosaurs, the immediate ancestors of birds...  lines, and thus the oldest representative of the crown group Crown group A crown group is a group consisting of living representatives, their ancestors back to the most recent common ancestor of that group, and all of that ancestor's descendants. The name was given by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms...  amniotes.
312 - 304 Ma	Genus: Paleothyris Paleothyris Paleothyris was a small, agile, anapsid reptile which lived in the Middle Pennsylvanian epoch in Nova Scotia . Paleothyris had sharp teeth and large eyes, meaning that it was a nocturnal hunter. It was about a foot long. It probably fed on insects and other smaller animals found on the floor of its...	One of several small, basal reptile genera	Reptile (most likely a sauropsid Sauropsida Sauropsida is a group of amniotes that includes all existing reptiles and birds and their fossil ancestors, including the dinosaurs, the immediate ancestors of birds... )	An early anapsid Anapsid An anapsid is an amniote whose skull does not have openings near the temples.While "anapsid reptiles" or "anapsida" are traditionally spoken of as if they were a monophyletic group, it has been suggested that several groups of reptiles that had anapsid skulls may be only distantly related...  reptile. In phylogenetic analysis it falls on the sauropsid Sauropsida Sauropsida is a group of amniotes that includes all existing reptiles and birds and their fossil ancestors, including the dinosaurs, the immediate ancestors of birds...  side, it is thus likely a progenitor of the diapsid Diapsid Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara... s

Turtles

The Turtle Turtle Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
220 Ma	Genus: Odontochelys Odontochelys Odontochelys semitestacea is an extinct turtle species, the oldest known one. It is the only known species in the genus Odontochelys and the family Odontochelyidae. O. semitestacea was first described from three 220 million year-old specimens excavated in Triassic deposits in Guizhou,...			The oldest known turtle.
210 Ma	Genus: Proganochelys Proganochelys Proganochelys quenstedti is the second oldest turtle species discovered to date, known only from fossils found in Germany and Thailand in strata from the late Triassic, dating to approximately 210 million years ago...
164 Ma	Genus: Eileanchelys Eileanchelys Eileanchelys is an extinct genus of pond turtle from the Middle Jurassic period some 164 million years ago of Britain. It was once the earliest swimming turtle known to science, and was thought to be an evolutionary bridge between early land turtles and sea turtles...			An evolutionary bridge between early land turtles and sea turtles.

From Lizard

Lizard

Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

s to Snake

Snake

Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s

The Lizard Lizard Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains... → Snake Snake Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
92 Ma	Genus: Eupodophis Eupodophis Eupodophis is an extinct genus of snake from the Late Cretaceous period. It has two small hind legs and is considered a transitional form between Cretaceous lizards and limbless snakes. The feature, described as vestigial, was most likely useless to Eupodophis. The type species Eupodophis...			A transitional form between Cretaceous Cretaceous The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...  lizard Lizard Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains... s and limbless snakes retaining distinct, if non-functional, legs.
90 Ma	Genus: Najash			A basal snake with two hind-limbs.

Lizards

The Lizard Lizard Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
61 - 58 Ma	Genus: Anqingosaurus			The earliest known chameleon Chameleon Chameleons are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, the possession by many of a... .
92 Ma	Genus: Dallasaurus Dallasaurus Dallasaurus is a basal mosasauroid from the Upper Cretaceous of North America. The genus is based upon two partial skeletons recovered from the Arcadia Park Shale , approximately 15 meters above its contact with the older Kamp Ranch Limestone in Dallas County in north-central Texas...			A basal mosasauroid from the Upper Cretaceous of North America North America North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas... .
71 - 82 Ma	Genus: Palaeosaniwa Palaeosaniwa Palaeosaniwa is an extinct genus of varanoid lizard from the late Cretaceous of North America. The name, given by Charles Whitney Gilmore in 1928, means "ancient Saniwa."- Description :...			One of the earliest Varanoidea Varanoidea Varanoidea is a superfamily of lizards, including the well-known family Varanidae . Also included in the Varanoidea are such extinct marine and semi-aquatic forms as mosasaurs and dolichosaurs, the venomous helodermatids , the Lanthanotidae , and the extinct Necrosauridae.Throughout their long... .
146–100 Ma	Genus: Gangiguana Gangiguana Gangiguana armatus is an extinct genus of primitive iguanid from the Early Cretaceous of India, known primarily from bone fragments...			An primitive iguanid
97–100 Ma	Genus: Cretaceogekko Cretaceogekko Cretaceogekko is a prehistoric genus of gecko known from a single partial specimen Cretaceogekko burmae described in 2008 by E. Nicholas Arnold and George Poinar. The foot and partial tail were preserved in Burmese amber for 97 to 110 million years...			The oldest known gecko Gecko Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....

Pterosaurs

Rhamphorhynchoidea Rhamphorhynchoidea The Rhamphorhynchoidea forms one of the two suborders of pterosaurs and represent an evolutionary grade of primitive members of this group of flying reptiles. This suborder is paraphyletic in relation to the Pterodactyloidea, which arose from within the Rhamphorhynchoidea, not from a more distant... → Pterodactyloidea Pterodactyloidea Pterodactyloidea forms one of the two suborders of pterosaurs , and contains the most derived members of this group of flying reptiles... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
160 Ma	Genus: Darwinopterus Darwinopterus Darwinopterus is a genus of pterosaur, discovered in China and named after biologist Charles Darwin. Between 30 and 40 fossil specimens have been identified, all collected from the Tiaojishan Formation, which dates to the middle Jurassic period. The type species, D. modularis, was described in...			Basal to both rhamphorhynchoids and pterodactyloids
160 Ma	Genus Pterorhynchus Pterorhynchus Pterorhynchus was a genus of rhamphorhynchid "rhamphorhynchoid" pterosaur from the Late Jurassic-age Daohugou Formation of Inner Mongolia, China....

Archosaurs to Dinosaurs

Evolution of dinosaurs

Dinosaurs evolved from the archosaurs 232-234 Ma in the Ladinian age, the latter part of the middle Triassic. Dinosauria is a well-supported clade, present in 98% of bootstraps...

The Archosauria → Dinosauria Series
Appearance	Taxa	Relationships	Status	Description	Image
??? Ma	Genus: Proterosuchus Proterosuchus Proterosuchus is an extinct genus of Early Triassic proterosuchid archosaur. Remains have been found from South Africa and China. The genus Chasmatosaurus is considered a junior synonym of Proterosuchus, as all species of Chasmatosaurus, including C. aleandri, C. vanhoepeni, and C. yuani, have...			The oldest known archosaur.
??? Ma	Genus: Marasuchus Marasuchus Marasuchus is a genus of dinosaur-like ornithodiran from the middle Triassic Chañares Formation of Argentina. The species Marasuchus lilloensis was originally described as a second species of Lagosuchus, L. lilloensis...
??? Ma	Genus: Asilisaurus Asilisaurus Asilisaurus , and Greek, σαυρος is an extinct genus of silesaurid archosaur. It is the oldest avian-line archosaur, dating to about 245 million years ago....
??? Ma	Genus: Spondylosoma Spondylosoma Spondylosoma is a genus of archosaur of uncertain affinities from the late Ladinian-age Middle Triassic Lower Santa Maria Formation in Geopark of Paleorrota, Brazil. Recent studies have gone back and forth on its identity, suggesting rauisuchian or basal saurischian dinosaur...
228 Ma	Genus: Eoraptor Eoraptor Eoraptor was one of the world's earliest dinosaurs. It was a two-legged saurischian, close to the ancestry of theropods and sauropodomorphs. It lived ca. 231.4 million years ago, in what is now the northwestern region of Argentina...

Dinosauria

The Dinosauria Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
228 to 216.5 Ma	Genus: Pisanosaurus Pisanosaurus Pisanosaurus is a genus of primitive ornithischian dinosaur from the Late Triassic of what is now South America. It was a bipedal herbivore described by Argentine paleontologist Rodolfo Casamiquela in 1967. Only one species, the type, Pisanosaurus mertii, is known, based on a single partial skeleton...			The oldest known ornithischian.
216–200 Ma	Genus: Thecodontosaurus Thecodontosaurus Thecodontosaurus is a genus of herbivorous basal sauropodomorph dinosaur which lived during the late Triassic period ....			The most primitive well-known representative of the sauropodomorph dinosaurs.
??? Ma	Genus: Huayangosaurus Huayangosaurus Huayangosaurus is a genus of stegosaurian dinosaur from the Middle Jurassic of China. The name derives from "Huayang", an alternate name for Sichuan , and "saurus", meaning "lizard"...			The oldest and most primitive known stegosaur.
??? Ma	Genus: Stenopelix Stenopelix Stenopelix is a genus of small ornithischian dinosaur from the Early Cretaceous of Germany. It was perhaps a basal ceratopsian from the Barremian Stage of the Cretaceous period, sometime between 130 and 125 million years ago...			A basal pachycephalosaur from the Barremian Stage of the Cretaceous Cretaceous The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the... .
160 Ma	Genus: Yinlong Yinlong Yinlong is a genus of basal ceratopsian dinosaur from the Late Jurassic Period of central Asia. It was a small, primarily bipedal herbivore, approximately 1.2 meters long...			A genus of basal ceratopsian dinosaur from the Late Jurassic Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...  Period of central Asia.
160 Ma	Genus: Guanlong Guanlong Guanlong was a genus of proceratosaurid tyrannosauroid dinosaur, one of the earliest known examples of the lineage.-Description and discovery:...			A genus of proceratosaurid tyrannosauroid dinosaur, one of the earliest known examples of the lineage.
126 Ma	Genus: Falcarius Falcarius Falcarius is a genus of therizinosaurian dinosaur found in east-central Utah, United States. Its name is derived from the word sickle , which scientists have used to describe its unwieldy clawed hands...			A early genus of therizinosaur Therizinosaur Therizinosaurs are theropod dinosaurs belonging to the clade Therizinosauria. Therizinosaur fossils have been found in Early through Late Cretaceous deposits in Mongolia, the People's Republic of China and Western North America... .
208–194 Ma	Genus: Scelidosaurus Scelidosaurus Scelidosaurus is a genus of quadrupedal, lightly plated, herbivorous dinosaur about long. It lived during the Early Jurassic Period, during the Hettangian to Sinemurian stages around 199.6 to 194 million years ago. Its fossils have been found in both England and in Arizona, in the United...			One of the most primitive thyreophorans.
130–125 Ma	Genus: Probactrosaurus Probactrosaurus Probactrosaurus is an early herbivorous hadrosauroid iguanodont dinosaur. It lived in China during the Early Cretaceous period....			A possible ancestor of the duck-billed dinosaurs.
??? Ma	Genus: Pelecanimimus Pelecanimimus Pelecanimimus is a genus of basal ornithomimosaurian theropod dinosaur from the Early Cretaceous of Spain...			A primitive (basal) ornithomimosaur.

Dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s to birds

The Dinosaur Dinosaur Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of... s → birds Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
168-140 Ma	Genus: Pedopenna Pedopenna Pedopenna is a genus of small, feathered, maniraptoran dinosaur from the Daohugou Beds in China. It is possibly older than Archaeopteryx, though the age of the Daohugou Beds where it was found is debated...
155 Ma	Genus: Anchiornis Anchiornis Anchiornis is a genus of small, feathered, deinonychosaurian dinosaur. The genus Anchiornis contains the type species Anchiornis huxleyi, named in honor of Thomas Henry Huxley, an early proponent of biological evolution, and the first to propose a close evolutionary relationship between birds and...	Although once classified as a bird, Anchiornis is now considered a basal troodontid Troodontidae Troodontidae is a family of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and scrappy and they have therefore been allied, at various times, with many dinosaurian lineages...  which bears pennaceous, symmetrical feathers on all four limbs.		Plesiomorphic traits Wings symmetrical and rounded, probably not used for flight or even sustained gliding Long legs similar to that of other troodontids Derived traits Wrists more similar to aves than other theropods Like dromaeosaurs and birds, and unlike troodontids, Anchiornis had arms nearly the same length as the hindlegs Bore primary and secondary pennaceous wings on both arms, legs, toes, and wrist
164-158 Ma	Genus: Scansoriopteryx Scansoriopteryx Scansoriopteryx is a genus of avialan dinosaur. Described from only a single juvenile fossil specimen found in Liaoning, China, Scansoriopteryx is a sparrow-sized animal that shows adaptations in the foot indicating an arboreal lifestyle. It possessed an unusual, elongated third finger...	A small arboreal dinosaur with long arms with wing feathers, Scansoriopteryx could climb well and possibly glide	Maniraptora Maniraptora Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauroidea... n dinosaur Dinosaur Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of... , representative of the family Scansoriopterygidae Scansoriopterygidae Scansoriopterygidae is a family of maniraptoran dinosaurs, known from three well-preserved fossils unearthed in the Daohugou fossil beds of Liaoning, China....	Plesiomorphic traits Forward pointing pubis Pubis Pubis may refer to:* Pubis * Mons pubis, a padding of fat that protects the pubis bone... Long tail Derived traits Arms longer than hindlegs, adapted for climbing Curved slimbing claw Claw A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end... s on all digits Foot with grasping ability
150–145 Ma	Genus: Archaeopteryx Archaeopteryx Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...	Known for its mosaic of avian and theropod characteristics Archaeopteryx Archaeopteryx Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...  is both the first primitive bird in the fossil record and one of the first transitional fossils discovered.	Traditionally seen as the first proper bird, though it is not directly ancestral to modern birds. An excellent intermediate form between dinosaurs and birds. Capable of gliding, but lacking alula Alula The alula, or bastard wing, is a small projection on the anterior edge of the wing of modern birds. The alula is the freely moving first digit, a bird's "thumb," and is typically covered with three to five small feathers, with the exact number depending on the species...  and keel Keel (bird) A keel or carina in bird anatomy is an extension of the sternum which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight... , it could likely not sustain powered flight.	Plesiomorphic traits Slower dinosaur-like growth rate No keel Keel (bird) A keel or carina in bird anatomy is an extension of the sternum which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight... Spine attaches to the back end of the skull rather than the base Forelimbs have three unfused, clawed fingers, no alula Alula The alula, or bastard wing, is a small projection on the anterior edge of the wing of modern birds. The alula is the freely moving first digit, a bird's "thumb," and is typically covered with three to five small feathers, with the exact number depending on the species... Maxilla and premaxilla bore unserrated teeth Moderately long tail Derived traits Fully developed asymmetrical flight feathers Fused furcula Furcula The ' is a forked bone found in birds, formed by the fusion of the two clavicles. In birds, its function is the strengthening of the thoracic skeleton to withstand the rigors of flight....  from two joined clavicles Backward and elongated pubis similar to maniraptors, but not found in more primitive theropods
120 Ma	Genus: Confuciusornis Confuciusornis Confuciusornis is a genus of primitive crow-sized birds from the Early Cretaceous Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago...	Found in the famous Liaoning province Liaoning ' is a province of the People's Republic of China, located in the northeast of the country. Its one-character abbreviation is "辽" , a name taken from the Liao River that flows through the province. "Níng" means "peace"...  Confuciusornis is the first primitive bird with a pygostyle Pygostyle Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these.... .	With its short tail and toothless beak, Confuciusornis is very modern looking compared to Archaeopteryx Archaeopteryx Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"... . The toothless beak is however a case of convergent evolution Convergent evolution Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are... , as more advanced birds retained teeth, illustration the sometimes confusing mosaic evolution Mosaic evolution Mosaic evolution is the concept that evolutionary change takes place in some body parts or systems without simultaneous changes in other parts...  of the dinosaur-bird transition.	Plesiomorphic traits Skull more primitive than Archaeopteryx Retained unfused clawed digits, no alula Alula The alula, or bastard wing, is a small projection on the anterior edge of the wing of modern birds. The alula is the freely moving first digit, a bird's "thumb," and is typically covered with three to five small feathers, with the exact number depending on the species... Sideways-facing glenoid joint Derived traits Short tail with fused vertebrae at the end (pygostyle Pygostyle Pygostyle refers to a number of the final few caudal vertebrae fused into a single ossification, supporting the tail feathers and musculature. In modern birds, the rectrices attach to these.... ) Larger sternum with a low keel Keel (bird) A keel or carina in bird anatomy is an extension of the sternum which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight... Unlike other early birds Confuciusornis had a toothless beak
115 Ma	Genus: Eoalulavis Eoalulavis Eoalulavis was an enantiornithine bird. It lived during the Aptian in the Early Cretaceous, about 115 mya and is known from fossils found at Las Hoyas, Spain...	Primitive bird and possibly a descendant of "urvogels" like Archaeopteryx. First bird to possess an alula.		Derived traits First digit bearing an alula Alula The alula, or bastard wing, is a small projection on the anterior edge of the wing of modern birds. The alula is the freely moving first digit, a bird's "thumb," and is typically covered with three to five small feathers, with the exact number depending on the species...  rather than claw
93.5-75 Ma	Genus: Ichthyornis Ichthyornis Ichthyornis is a genus of toothed seabirds from the Late Cretaceous of North America. Its fossil remains are known from the chalks of Alberta, Alabama, Kansas, New Mexico, Saskatchewan, and Texas, in strata that were laid down in the Western Interior Seaway during the Turonian-Campanian ages,...	Considered a close relative to the ancestor to modern birds	A flying bird found in several epochs in the late Cretaceous which still bore teeth, but in most respects very similar to Neornithes Modern birds Modern birds are the most recent common ancestor of all living birds and all its descendants.Modern birds are characterised by feathers, a beak with no teeth , the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton... .	Plesiomorphic traits Numerous sharp teeth in much of the beak Derived traits Fused bones (metacarpals) II & III of the hand Rigid ribcage with a well developed carina No functional claw Claw A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end... s on the hand Short childhood with distinct adult stage.

Bird Evolution

The Bird Bird Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
60-58 Ma	Genus: Waimanu Waimanu Waimanu is a genus of early penguin which lived soon after the Cretaceous-Paleogene extinction event. Its discovery helped support the idea that the radiation of the Neoaves either took place before the extinction of the dinosaurs, or that it must have been extremely rapid in geological terms...			The earliest-known Penguin Penguin Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers... .
??? Ma	Genus: Elornis			An early flamingo Flamingo Flamingos or flamingoes are gregarious wading birds in the genus Phoenicopterus , the only genus in the family Phoenicopteridae... .
??? Ma	Genus: Colymboides Colymboides The genus Colymboides contains two species of early loon dating from the late Oligocene or early Miocene. They are considered to be the earliest known unambiguous gaviiform fossils...			An early gaviiform Gaviiformes Gaviiformes is an order of aquatic birds containing the loons or divers and their closest extinct relatives. Modern gaviiformes are found in many parts of North America and northern Eurasia , though prehistoric species were more widespread.-Classification and evolution:There are five living... .
55-48 Ma	Genus: Mopsitta			An early psittacine.
??? Ma	Genus: Masillaraptor Masillaraptor Masillaraptor is an extinct genus of basal falconiform from the Middle Eocene, a long-legged relative of the living falcons. Classifying the Falconiformes is confusing, since Europe has placed the families into two orders .- Etymology :Masillaraptor comes from the Latin word masilla, which is the...			An basal falconiform.
50 Ma	Genus: Primapus Primapus Primapus is an extinct genus of apodiform bird from the Early Eocene of the United Kingdom. Its fossils were found in the London Clay, which was deposited around 50 million years ago. The type species is P. lacki.-Sources:...			An early apodiform.

Synapsid

Synapsid

Synapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...

 ("mammal-like reptiles") to mammals

The Synapsids → Mammals Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
??? Ma	Genus: Protoclepsydrops Protoclepsydrops Protoclepsydrops was an early amniote, and its skeletal remains indicate that it may have been more closely related to synapsids than to sauropsids, making it a possible synapsid member. If so, it is the oldest synapsid known, though its status is unconfirmed because its remains were fragmentary....
306 Ma	Genus: Archaeothyris Archaeothyris Archaeothyris was a very early mammal-like reptile, which lived in the late Carboniferous period. Dated to 306 million years ago, it is the oldest undisputed synapsid known....
??? Ma	Genus: Clepsydrops Clepsydrops Clepsydrops was a primitive amniote from the early Late Carboniferous that was related to Archaeothyris and the synapsids—the ancestors of mammals. Like many other terrestrial early amniotes, it had the diet of insects and smaller animals. It also laid eggs on land rather than in the water, as...
265 Ma	Genus: Dimetrodon Dimetrodon Dimetrodon was a predatory synapsid genus that flourished during the Permian period, living between 280–265 million years ago ....
??? Ma	Genus: Procynosuchus Procynosuchus Procynosuchus was a cynodont from the Late Permian. It is considered to be one of the earliest and most basal cynodonts. Remains of Procynosuchus have been found in Germany, Zambia and South Africa...
248-245 Ma	Genus: Thrinaxodon Thrinaxodon Thrinaxodon was a cynodont, an ermine-sized therapsid. Pits on the skull suggest that Thrinaxodon may have had whiskers, and by extension a protective covering of fur. There are suggestions that it was warm-blooded...
205 Ma	Genus: Morganucodon Morganucodon Morganucodon is an early mammalian genus which lived during the Late Triassic. It first appeared about 205 million years ago. This has also been identified with Eozostrodon. Unlike many other early mammals, Morganucodon is well represented by abundant and well preserved, though in the vast...
125 Ma	Genus: Yanoconodon Yanoconodon Yanoconodon is a monotypic genus of extinct early mammal whose representative species Yanoconodon allini lived 125 million years ago during the Mesozoic in what is now China. It is considered to be a transitional fossil due to the formation of its middle ear, which is a cross between those of...		An early crown group Crown group A crown group is a group consisting of living representatives, their ancestors back to the most recent common ancestor of that group, and all of that ancestor's descendants. The name was given by Willi Hennig, the formulator of phylogenetic systematics, as a way of classifying living organisms...  mammal.

Evolution of mammals

Evolution of mammals

__FORCETOC__The evolution of mammals within the synapsid lineage was a gradual process that took approximately 70 million years, beginning in the mid-Permian. By the mid-Triassic, there were many species that looked like mammals, and the first true mammals appeared in the early Jurassic...

The Mammal Mammal Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
100–104 Ma	Genus: Kollikodon Kollikodon Kollikodon ritchiei is a fossil monotreme species. It is known only from an opalised dentary fragment, with one premolar and two molars in situ...			The earliest-known monotreme Monotreme Monotremes are mammals that lay eggs instead of giving birth to live young like marsupials and placental mammals...  to date.
125 Ma	Genus: Sinodelphys Sinodelphys Sinodelphys is an extinct mammal from the Early Cretaceous. To date, it is the oldest metatherian fossil known, estimated to be 125 million years old...			The oldest metatherian known.
?? Ma	Genus: Djarthia Djarthia Djarthia is an extinct genus of marsupial. It is the oldest marsupial found in Australia, discovered at the Murgon fossil site in south-eastern Queensland. Skeletal materal described include molar, incomplete cochlear and tarsal bone either complete or in fragmented state of preservation....			The earliest-known marsupial Marsupial Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central... .
125 Ma	Genus: Eomaia Eomaia Eomaia is an extinct fossil mammal, discovered in rocks that were found in the Yixian Formation, Liaoning Province, China, and dated to the Barremian Age of the Lower Cretaceous about . The fossil is in length and virtually complete. An estimate of the body weight is between . It is exceptionally...			The oldest known eutherian.
63-50 Ma	Genus: Eritherium Eritherium Eritherium is an extinct genus of early Proboscidea found in Ouled Abdoun basin , Morocco. It was first named by Emmanuel Gheerbrant in 2009 and the type species is Eritherium azzouzorum. Eritherium is the oldest, smallest and most primitive known elephant relative....			The earliest known proboscidean.
60-55 Ma	Genus: Miacis Miacis The 'genus' Miacis contains extinct species of carnivorous mammals that appeared in the late Paleocene and continued through the Eocene. The genus Miacis is not monophyletic but a diverse collection of species that belong to the stemgroup within the Carnivoramorpha...			The ancestor of the modern Order Carnivora Carnivora The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal... .
15.97–11.61 Ma	Genus: Heteroprox Heteroprox Heteroprox is an extinct genus of cervid from the Miocene of Europe.- Sources :* Mammoths, Sabertooths, and Hominids by Jordi Agusti and Mauricio Anton...			The earliest known cervid.
20-18 Ma	Genus: Eotragus Eotragus Eotragus is an early bovid from Europe, Africa, and Asia during the Miocene some 20-18 million years ago. It is related to the modern Nilgai and Four-horned Antelope. It was small and probably lived in woodland environments.-External links:**...			The earliest known bovid Bovid A bovid is any of almost 140 species of cloven-hoofed ruminant mammal at least the males of which bear characteristic unbranching horns covered in a permanent sheath of keratin.... .
45-40 Ma	Genus: Protylopus Protylopus Protylopus is an extinct genus of camel, lived during middle to late Eocene some 45-40 million years ago in North America.The oldest camel known, it was also the smallest, reaching a length of , and probably weighing around . Based on its teeth, it probably fed on the soft leaves of forest plants...			The oldest camel Camel A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...  known, it was also the smallest.
??? Ma	Genus: Hyrachyus Hyrachyus Hyrachyus is an extinct genus of perissodactyl mammal that lived in Eocene Europe and North America. Its remains have also been found in Jamaica. It is closely related to Lophiodon....			Suspected to be the ancestor of modern tapirs and rhinoceroses.
55.4—48.6 Ma	Genus: Heptodon Heptodon Heptodon is an extinct genus of tapir-type herbivore of the family Helaletidae endemic to North America during the Eocene epoch. It lived from 55.4—48.6 mya, existing for approximately .-Taxonomy:...			Suspected to be the ancestor of modern tapirs.
38—33.9 Ma	Genus: Hesperocyon Hesperocyon Hesperocyon is an extinct genus of canids, family of Canidae and subfamily Hesperocyoninae which was endemic to North America from southern Canada to appearing during the Uintan age-Bridgerian age of the Mid-Eocene 42.5 mya—31.0 Ma. . Hesperocyon existed for approximately .-Taxonomy:Hesperocyon...			The earliest of the canids.
??? Ma	Genus: Eurymylus			The earliest of the lagomorphs.
52.5 Ma	Genus: Onychonycteris Onychonycteris Onychonycteris is the most primitive of the two oldest known monospecific genera of bat, having lived in the area that is current day Wyoming during the Eocene period, 52.5 million years ago.-History and description:...			One of the most primitive of the two oldest known monospecific genera of bat Bat Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,... .
2 Ma	Genus: Ailuropoda microta Ailuropoda microta Ailuropoda microta, rarely called the Dwarf Panda, Dwarf Giant Panda, or Pygmy Giant Panda, is the earliest known ancestor of the Giant Panda. It measured 1 m in length; the modern Giant Panda grows to a size in excess of 1.5 m . Wear patterns on its teeth suggest it lived on a diet of...			The earliest known ancestor of the Giant Panda Giant Panda The giant panda, or panda is a bear native to central-western and south western China. It is easily recognized by its large, distinctive black patches around the eyes, over the ears, and across its round body. Though it belongs to the order Carnivora, the panda's diet is 99% bamboo... .
63 - 61.7Ma	Genus: Purgatorius Purgatorius Purgatorius is the genus of the four extinct species believed to be the earliest example of a primate or a proto-primate, a primatomorph precursor to the Plesiadapiformes...			Believed to be the earliest example of a primate Primate A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...  or a proto-primate, a primatomorph precursor to the Plesiadapiformes Plesiadapiformes Plesiadapiformes is an extinct order of mammals. It is either closely related to the primates or a precursor to them. Many are too derived to be ancestral to primates, but the earliest Plesiadapiformes have teeth that are strongly indicative of a common ancestor... .
12.5-8.5 Ma	Genus: Sivapithecus Sivapithecus Sivapithecus is a genus of extinct primates. Fossil remains of animals now assigned to this genus, dated from 12.5 million to 8.5 million years old in the Miocene, have been found since the 19th century in the Siwalik Hills in what is now India, Nepal, and Pakistan...			This genus may have been the ancestor to the modern orangutan Orangutan Orangutans are the only exclusively Asian genus of extant great ape. The largest living arboreal animals, they have proportionally longer arms than the other, more terrestrial, great apes. They are among the most intelligent primates and use a variety of sophisticated tools, also making sleeping... s.
16 - 8 Ma	Genus: Kenyapotamus Kenyapotamus Kenyapotamus is a possible ancestor of living hippopotamids that lived in Africa roughly 16 million to 8 million years ago during the Miocene epoch...			An possible ancestor of living hippopotamids.
?? Ma	Genus: Eomanis Eomanis Eomanis is the earliest known true pangolin from the Middle Eocene of Europe. Fossils collected from the Messel Pit, Germany, indicate that this 50 cm long animal was rather similar to living pangolins. However, unlike modern pangolins, its tail and legs did not bear scales...			The earliest known true (and scaled) pangolin Pangolin A pangolin , also scaly anteater or Trenggiling, is a mammal of the order Pholidota. There is only one extant family and one genus of pangolins, comprising eight species. There are also a number of extinct taxa. Pangolins have large keratin scales covering their skin and are the only mammals with... .

Early Artiodactylans to whale

Whale

Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...

s (Evolution of whales)

The whale Whale Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
55.8 ± 0.2 - 33.9 ± 0.1 Ma	Genus: Pakicetus Pakicetus Pakicetus is a genus of extinct terrestrial carnivorous mammal of the family Pakicetidae which was endemic to Pakistan from the Eocene .Pakicetus existed for approximately...
50 Ma	Genus: Ambulocetus Ambulocetus Ambulocetus was an early cetacean that could walk as well as swim. It lived during early Eocene some 50-49 million years ago. It is a transitional fossil that shows how whales evolved from land-living mammals. The Ambulocetus fossils were found in Pakistan by anthropologist Johannes Thewissen...
46 Ma	Genus: Kutchicetus Kutchicetus Kutchicetus is an extinct genus of early carnivorous freshwater whales of the family Remingtonocetidae endemic to the coastline of the ancient Tethys Ocean during the Eocene living from 55.8—40.4 mya, existing for approximately .-Taxonomy:...
47 Ma	Genus: Artiocetus Artiocetus Artiocetus clavis is an extinct genus of early whales belonging to the family Protocedidae. Their name arises from a combination of Cetacean and Artiodactyl, as this fossil was the first to show that early whales possessed artiodactyl-like ankles....
41-33 Ma	Genus: Dorudon Dorudon Dorudon was a genus of ancient cetacean that lived alongside Basilosaurus 41 to 33 million years ago, in the Eocene. They were about five meters long and were most likely carnivorous, feeding on small fish and mollusks. Dorudontines lived in warm seas around the world...
25 Ma	Genus: Aetiocetus Aetiocetus Aetiocetus is an extinct genus of baleen whale that lived 25 million years ago, in the Oligocene period. Its fossils have been found in the North Pacific, around Oregon. It was first named by Douglas Emlong in 1966 and currently contains four species, A cotylalveus, A. polydentatus, A. tomitai,...
40-34 Ma	Genus: Basilosaurus Basilosaurus Basilosaurus is a genus of cetacean that lived from in the Late Eocene. Its fossilized remains were first discovered in the southern United States . The American fossils were initially believed to be some sort of reptile, hence the suffix -"saurus", but later found to be a marine mammal...
8-15 Ma	Genus: Eurhinodelphis Eurhinodelphis Eurhinodelphis is an extinct genus of Miocene cetacean. Its fossils have been found in France, Belgium, Maryland and California.-Description:...
26 Ma	Genus: Mammalodon Mammalodon Mammalodon is an extinct genus of whale that was discovered in 1932. It is an early baleen whale which still had teeth, as opposed to baleen plates. It is one of two genera in the family Mammalodontidae....

Evolution of sirenians

Evolution of sirenians

Sirenia is the order of placental mammals which comprise modern "sea cows" and their extinct relatives. They are the only extant herbivorous marine mammals and the only group of herbivorous mammals to have become completely aquatic. Sirenians are thought to have a 50-million-year-old fossil record...

The Sirenia Sirenia Sirenia is an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. Four species are living, in two families and genera. These are the dugong and manatees... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
50 Ma	Genus: Pezosiren Pezosiren Pezosiren portelli is the name given to an early sirenian represented by a Jamaican fossil skeleton, described in 2001 by Daryl Domning, a marine mammal paleontologist at Howard University in Washington, DC...			A primitive sirenian.
40 Ma	Genus: Prorastomus Prorastomus Prorastomus sirenoides is an extinct species of primitive sirenian that lived during the Eocene Epoch 40 million years ago in Jamaica.-Description:...
??? Ma	Genus: Protosiren Protosiren Protosiren is an extinct early genus of the order Sirenia. Protosiren existed throughout the Lutetian and Bartonian stages of the Middle Eocene. Its geographic distribution was intercontinental: fossils have been found in the United States , Egypt, France, Hungary, India, and Pakistan...
48.6–33.9 Ma	Genus: Eotheroides Eotheroides Eotheroides is an extinct genus of Eocene sirenian. It is an early member of the family Dugongidae, which includes the extant dugong. Fossils have been found from Egypt, India, and Madagascar...			An evolutionary bridge between primitive land-dwelling sirenians to aquatic sirenians
??? Ma	Genus: Halitherium Halitherium Halitherium was an early sea cow that started in the late Eocene, then the Oligocene. Its fossils are common in European shales. Inside its flippers were finger bones that did not stick out. Halitherium also had the residues of back legs, which did not show externally. It did, however, have a basic...

Evolution of the Pinnipeds

The Pinniped Pinniped Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
21 to 24 Ma	Genus: Puijila Puijila Puijila darwini is an extinct species of pinniped which lived during the Miocene epoch about 21 to 24 million years ago. Approximately a metre in length, the animal possessed only minimal physical adaptations for swimming...			The oldest known pinniped.
??? Ma	Genus: Potamotherium Potamotherium Potamotherium an extinct genus from the Miocene period, which has been assigned both to the mustelids and to the pinnipeds....			A very basal pinniped.
24-22 Ma	Genus: Enaliarctos Enaliarctos Enaliarctos is an extinct genus of pinniped.Prior to the discovery of Puijila, the five species in the genus Enaliarctos represented the oldest known pinniped fossils, having been recovered from late Oligocene and early Miocene strata of California and Oregon.It had a short tail and developed...			An early seal, but with more primitive skull and feet.

Evolution of the horse

Evolution of the horse

The evolution of the horse pertains to the phylogenetic ancestry of the modern horse from the small dog-sized, forest-dwelling Hyracotherium over geologic time scales...

The Hyracotherium Hyracotherium Hyracotherium , also known as Eohippus or the dawn horse, is an extinct genus of very small perissodactyl ungulates that lived in the woodlands of the northern hemisphere, with species ranging throughout Asia, Europe, and North America during the early Tertiary Period and the early to mid Eocene... → Equus Equus (genus) Equus is a genus of animals in the family Equidae that includes horses, donkeys, and zebras. Within Equidae, Equus is the only extant genus. Like Equidae more broadly, Equus has numerous extinct species known only from fossils. This article deals primarily with the extant species.The term equine... Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
60-45 Ma	Genus: Hyracotherium Hyracotherium Hyracotherium , also known as Eohippus or the dawn horse, is an extinct genus of very small perissodactyl ungulates that lived in the woodlands of the northern hemisphere, with species ranging throughout Asia, Europe, and North America during the early Tertiary Period and the early to mid Eocene...
40-30 Ma	Genus: Mesohippus Mesohippus Mesohippus is an extinct genus of early horse. It lived some 40 to 30 million years ago from the late Eocene to the mid-Oligocene...
20 Ma	Genus: Parahippus Parahippus Parahippus is an extinct relative of the modern horse, very similar to Miohippus, but slightly larger, at around tall, at the withers....
17-11 Ma	Genus: Merychippus Merychippus Merychippus is an extinct proto-horse of the family Equidae that was endemic to North America during the Miocene from 20.43—10.3 Ma living for approximately .It had three toes on each foot and is the first horse known to have grazed...
12 Ma	Genus: Pliohippus Pliohippus Pliohippus is an extinct genus of Equidae, the "horse family". Pliohippus arose in the middle Miocene, around 12 million years ago, probably from Calippus. It was similar in appearance to Equus, but had two long extra toes on both sides of the hoof, externally barely visible as callused stubs...
1.8-0 Ma	Genus: Equus Equidae Equidae is the taxonomic family of horses and related animals, including the extant horses, donkeys, and zebras, and many other species known only from fossils. All extant species are in the genus Equus...

Human evolution

Human evolution

Human evolution refers to the evolutionary history of the genus Homo, including the emergence of Homo sapiens as a distinct species and as a unique category of hominids and mammals...

The Human Human Humans are the only living species in the Homo genus...  Evolutionary Series
Appearance	Taxa	Relationships	Status	Description	Image
36-32 Ma	Genus Apidium Apidium The genus Apidium is that of at least three extinct primates living in the early Oligocene, roughly 36 to 32 millions years ago. Apidium fossils are common in the Fayoum deposits of Egypt...	The oldest primitive monkey known in the fossil record, dating back before the split between Old and New world monkeys.	Basal to both Old and New world monkeys.	Plesiomorphic traits Smaller canines than later monkeys such as Parapithecus Parapithecus Parapithecus is an extinct genus of primates. There are two known species.-Species:*†Parapithecus fraasi Schlosser 1910*†Parapithecus grangeri Simons 1974... Retains some post-cranial characters seen in prosimians Derived traits Fused mandibular symphysis Scapula similar to modern squirrel monkeys Low rounded molar cusps rather than high cusps as is seen in tarsier Tarsier Tarsiers are haplorrhine primates of the genus Tarsius, a genus in the family Tarsiidae, which is itself the lone extant family within the infraorder Tarsiiformes... s and strepsirrhine
33 Ma	Genus Aegyptopithecus Aegyptopithecus Aegyptopithecus zeuxis means “linking Egyptian ape”. It was discovered by E. Simons in 1965. There is controversy over whether or not Aegyptopithecus should be a genus on its own or whether it should be moved into the genus Propliopithecus. If Aegyptopithecus is placed in its own genus, then there...	A Miocene monkey which bridges the gap between the Eocene ancestors of Old world monkeys and Miocene ancestor of Hominoidae.	Tentatively positioned transitional form prior to the Old world monkey/ape split.	Plesiomorphic traits Retained auditory features similar to Old world monkeys Incapable of true brachiation Brachiation Brachiation is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms.- Brachiators :...  unlike extant apes Reduced capitular tail, but was proportionally smaller than Apidium Apidium The genus Apidium is that of at least three extinct primates living in the early Oligocene, roughly 36 to 32 millions years ago. Apidium fossils are common in the Fayoum deposits of Egypt... Derived traits Ape-like teeth including broad, flat incisors and sexually dimorphic canines A low sagittal keel and strong temporalis muscles Increased size in the visual cortex
27-14 Ma	Genus Proconsul	This primate has very ape-like features like its teeth, but much of its post-cranial remains are more similar to monkeys.	Universally accepted to be intermediate between 'ape-like monkeys' such as Aegyptopithecus and later apes including hominids.	Plesiomorphic traits Monkey-like wrist Narrow, monkey-like illium Derived traits Completely lacked a fully formed tail 5-Y pattern on lower molar cusps as also seen in hominoids
13 Ma	Genus: Pierolapithecus	A European ape which is considered to be the predecessor of the great apes.	Some objections have been raised to this fossils status due to its location in Spain, but Pierolapithecus is likely a transitional taxon between generalized apes and the lineage which led to great apes.	Pleisomorphic traits Relatively short fingers and walked in a similar quadrupedal fashion like baboons Lacks adaptations for both gibbon-style brachaition as well as derived knuckle-walking like in chimpanzee's and gorilla's Derived traits Flat, wider rib cage like great apes for tree-climbing The clavicle is large and similar to modern chimps suggesting a dorsally positioned scapula
4.4 Ma	Genus: Ardipithecus Ardipithecus Ardipithecus is a very early hominin genus. Two species are described in the literature: A. ramidus, which lived about 4.4 million years ago during the early Pliocene, and A. kadabba, dated to approximately 5.6 million years ago ....	A woodland hominid adapted to quadruped arboreal locamotion, but also for bipedalism.	Intermediate between the last common ancestor of chimps and humans, and the australopithecines Australopithecus Australopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct... .	Plesiomorphic traits Brains smaller than later hominids ranging from about 300-350 cc Foot thumb is not retracted into the foot as a 'big toe' Hallux In tetrapods, the hallux is the innermost toe of the foot. Despite its name it may not be the longest toe on the foot of some individuals... Phalanges are more heavily curved than in Australopithecus Australopithecus Australopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct... Derived traits Reduced size in canines, however still retained dimorphic characters Hind leg dominant, bipedal locomotion while walking, however were quadrupedal while climbing trees
4.4-2.0 Ma	Genus: Australopithecus Australopithecus Australopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct...	First known genus of fully bipedal apes which are probably ancestral to robust australopiths Paranthropus The robust australopithecines, members of the extinct hominin genus Paranthropus , were bipedal hominids that probably descended from the gracile australopithecine hominids...  and the genus Homo Homo Homo may refer to:*the Greek prefix ὅμο-, meaning "the same"*the Latin for man, human being*Homo, the taxonomical genus including modern humans...	Intermediate between extinct quadrupedal and bipedal apes. While the relationship between some species are being revised, Australopithecus afarensis Australopithecus afarensis Australopithecus afarensis is an extinct hominid that lived between 3.9 and 2.9 million years ago. A. afarensis was slenderly built, like the younger Australopithecus africanus. It is thought that A...  is considered to be, by most experts, the ancestor to all later hominids.	Plesiomorphic traits Some species retain a sagittal crest Sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull of many mammalian and reptilian skulls, among others.... Curved phalanges, indicating semi-arboreal lifestyle Semisectorial premolar is present Prognathic face to varying degrees Derived traits Fully bipedal as indicated by many features including the knee joint, hips, lumbar curve in the spine, position of the foramen magnum, and feet Increase in brain size ranging from about 375-500 cc Development of a parabolic jaw
2.5-1.5 Ma	Species: Homo habilis Homo habilis Homo habilis is a species of the genus Homo, which lived from approximately at the beginning of the Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who found fossils in Tanzania, East Africa, between 1962 and 1964. Homo habilis Homo...	An early human which is the morphological link between australopithecine Australopithecine The term australopithecine refers generally to any species in the related genera Australopithecus or Paranthropus. These species occurred in the Plio-Pleistocene era, and were bipedal and dentally similar to humans, but with a brain size not much larger than modern apes, lacking the... s and later human species.	Perfect intermediate between early hominids and later humans, possibly ancestral to modern humans.	Plesiomorphic traits Pronounced brow ridge Foramen magnum is not positioned as anteriorly like in modern humans, giving a slightly semi-erect appearance Although reduced in size the teeth are still fairly large Derived traits Increase brain size ranging from 510-800 cc Face is slightly prognathic, but at a much steeper angle Bulge in the Broca area, possibly the first hominid to use rudimentary speech Associated with the first use of stone tools
2.0-1.0 Ma	Species: Homo erectus Homo erectus Homo erectus is an extinct species of hominid that lived from the end of the Pliocene epoch to the later Pleistocene, about . The species originated in Africa and spread as far as India, China and Java. There is still disagreement on the subject of the classification, ancestry, and progeny of H...	Very successful hominid, which was probably ancestral to both modern humans and neanderthals. Probably the first hominid to leave and successfully colonize territories outside of Africa.	Ancestral to modern humans and neanderthals.	Plesiomorphic traits Still retains a heavy brow ridge and nuchal torus Lacked the complexity of modern human language, but does show increase in the Broca area Thicker bones and larger teeth than modern humans Derived traits Rounder and larger brain (about 900-1100 cc) than H. habilis Face is orthognathic compared to H. habilis Probably lived in bands and was an active group hunter Associated with advanced stone tools and possibly the first hominid to use and produce fire
500 Ka-recent	Species 'Archaic' sapiens Archaic Homo sapiens Archaic Homo sapiens is a loosely defined term used to describe a number of varieties of Homo, as opposed to anatomically modern humans , in the period beginning 500,000 years ago....	Archaic sapiens were the immediate ancestors of modern humans which evidently displaced the neanderthal Neanderthal The Neanderthal is an extinct member of the Homo genus known from Pleistocene specimens found in Europe and parts of western and central Asia... s in Europe and the island 'hobbits' Homo floresiensis Homo floresiensis is a possible species, now extinct, in the genus Homo. The remains were discovered in 2003 on the island of Flores in Indonesia. Partial skeletons of nine individuals have been recovered, including one complete cranium...  of southeast Asia. 'Archaic' sapiens evolved from H. erectus about half a million years ago but still retains some primitive characteristics such as relatively thick bones and molars larger than modern humans.	Ancestral to modern humans.

See also

• Chimpanzee genome project — Genes of the Chromosome 2 fusion site
• List of fossil sites (with link directory)
• List of human evolution fossils
• Transitional fossil
  Transitional fossil
  A transitional fossil is any fossilized remains of a lifeform that exhibits characteristics of two distinct taxonomic groups. A transitional fossil is the fossil of an organism near the branching point where major individual lineages diverge...
  
  

External links

• Vuletic.com, Section V: Paleontology – Transitional fossils between every animal group
• Palaeos.com, Palaeos vertebrates starting with lobe-finned fish (very comprehensive)
• Talk.origins.org, FAQ: Transitional vertebrate fossils
• (A few) transitional fossils