Eupelycosauria
Encyclopedia
The Eupelycosauria originally referred to a suborder of 'pelycosaur
s' (Reisz 1987), but has been redefined (Laurin and Reisz 1997) to designate a clade
of synapsid
s that includes most pelycosaurs, as well as all therapsids and mammals. They first appear during the Early Pennsylvanian epoch (i.e: Archaeothyris
, and perhaps an even earlier genus, Protoclepsydrops
), and represent just one of the many stages in the acquiring of mammal-like characteristics (Kemp 1982), in contrast to their earlier amniote ancestors. The defining characteristics
which separate these animals from the Caseasauria
(also Pelycosaurs) are based on details of proportion of certain bones of the skull
. These include a long, narrow supratemporal bone (in contrast to caseasaurs where this bone is almost as wide as it is long), and a frontal bone
with a wider connection to the upper margin of the orbit (Laurin and Reisz 1997).
to the end of the early Permian
epoch. Ophiacodontids were common since their appearance, from late Carboniferous
(Pennsylvanian
) to early Permian, but they became progressively smaller as early Permian went by. The Edaphosaurids, along with the Caseids, were the dominant herbivore
s in the early part of Permian, ranging from the size of a pig
to the size of rhinoceroses. The most renowned Edaphosaurid is Edaphosaurus
, a large [10–12 ft (3–3.7 m)] herbivore which had a sail on its back, probably used for regulating heat and mating. Sphenacodontid
s, a family of carnivorous eupelycosaurs, included the famous Dimetrodon
, which is sometimes mistaken for a dinosaur
, and was the largest predator of the period. Like Edaphosaurus, Dimetrodon also had a distinctive sail on its back, and it probably served the same purpose - regulating heat. The Varanopseid family somewhat resembled today's monitor lizard
s and may have had the same lifestyle.
Therapsids descended from a clade closely related to the Sphenacodontids. They became the succeeding dominant land animals for the rest of the Permian and in the later part of the Triassic
, therapsids gave rise to the first mammal
s. All non-therapsid pelycosaurs, as well as many other life forms, became extinct at the end of Permian
period.
Pelycosaur
The pelycosaurs are an informal grouping composed of basal or primitive Late Paleozoic synapsid amniotes. Some species were quite large and could grow up to 3 meters or more, although most species were much smaller...
s' (Reisz 1987), but has been redefined (Laurin and Reisz 1997) to designate a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of 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...
s that includes most pelycosaurs, as well as all therapsids and mammals. They first appear during the Early Pennsylvanian epoch (i.e: 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....
, and perhaps an even earlier 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....
), and represent just one of the many stages in the acquiring of mammal-like characteristics (Kemp 1982), in contrast to their earlier amniote ancestors. The defining characteristics
Synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...
which separate these animals from the Caseasauria
Caseasauria
The Caseasauria are one of the two main clades of early synapsids, the other being the Eupelycosauria. They are currently known only from the Permian, and include two superficially different families, the small insectivorous or carnivorous Eothyrididae, and the large herbivorous CaseidaeThese two...
(also Pelycosaurs) are based on details of proportion of certain bones of the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
. These include a long, narrow supratemporal bone (in contrast to caseasaurs where this bone is almost as wide as it is long), and a frontal bone
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
with a wider connection to the upper margin of the orbit (Laurin and Reisz 1997).
Evolution
Many non-therapsid Eupelycosaurs were the dominant land animals from the latest CarboniferousCarboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
to the end of the early Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
epoch. Ophiacodontids were common since their appearance, from late Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
(Pennsylvanian
Pennsylvanian
The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...
) to early Permian, but they became progressively smaller as early Permian went by. The Edaphosaurids, along with the Caseids, were the dominant herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s in the early part of Permian, ranging from the size of a pig
Pig
A pig is any of the animals in the genus Sus, within the Suidae family of even-toed ungulates. Pigs include the domestic pig, its ancestor the wild boar, and several other wild relatives...
to the size of rhinoceroses. The most renowned Edaphosaurid is Edaphosaurus
Edaphosaurus
Edaphosaurus is a genus of prehistoric synapsid which lived around 303 to 265 million years ago, during the late Carboniferous to early Permian periods. The name Edaphosaurus means "ground lizard" and is derived from the Greek edaphos/εδαφος and σαυρος/sauros...
, a large [10–12 ft (3–3.7 m)] herbivore which had a sail on its back, probably used for regulating heat and mating. Sphenacodontid
Sphenacodontidae
Sphenacodontidae is a family of small to large, advanced, carnivorous, Late Pennsylvanian to middle Permian pelycosaurs. Primitive forms were generally small in size , but during the later part of the early Permian these animals grew progressively larger , to become the top predators of their...
s, a family of carnivorous eupelycosaurs, included the famous Dimetrodon
Dimetrodon
Dimetrodon was a predatory synapsid genus that flourished during the Permian period, living between 280–265 million years ago ....
, which is sometimes mistaken for a 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...
, and was the largest predator of the period. Like Edaphosaurus, Dimetrodon also had a distinctive sail on its back, and it probably served the same purpose - regulating heat. The Varanopseid family somewhat resembled today's monitor lizard
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...
s and may have had the same lifestyle.
Therapsids descended from a clade closely related to the Sphenacodontids. They became the succeeding dominant land animals for the rest of the Permian and in the later part of the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
, therapsids gave rise to the first 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...
s. All non-therapsid pelycosaurs, as well as many other life forms, became extinct at the end of Permian
Permian-Triassic extinction event
The Permian–Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 Ma ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras...
period.
Classification
- Series Amniota
- CLASS SYNAPSIDA *
- Order PelycosaurPelycosaurThe pelycosaurs are an informal grouping composed of basal or primitive Late Paleozoic synapsid amniotes. Some species were quite large and could grow up to 3 meters or more, although most species were much smaller...
ia *- Suborder †CaseasauriaCaseasauriaThe Caseasauria are one of the two main clades of early synapsids, the other being the Eupelycosauria. They are currently known only from the Permian, and include two superficially different families, the small insectivorous or carnivorous Eothyrididae, and the large herbivorous CaseidaeThese two...
- Suborder Eupelycosauria *
- Family †EdaphosauridaeEdaphosauridaeEdaphosauridae is a family of mostly large advanced, Late Pennsylvanian to early Permian pelycosaurs.They were the earliest known herbivorous amniotes, and along with the Diadectidae the earliest known herbivorous tetrapods...
- Family †Lupeosauridae
- Family †OphiacodontidaeOphiacodontidaeOphiacodontidae were pelycosaur synapsids. They appeared in the late Carboniferous period. Archaeothyris, and Clepsydrops were among the earliest Ophiacodontids. Archaeothyris and its relatives were the members of this family. Some ophiacodonts were semi-aquatic, and few were fully aquatic, but...
- Family †VaranopidaeVaranopidaeVaranopidae was a family of synapsid "pelycosaurs" that resembled monitor lizards and might have had the same lifestyle, hence their name. No known varanopids developed a sail like Dimetrodon. Their size varied from lizard-sized to dog-sized creatures. Varanopids already showed some advanced...
- (unranked) SphenacodontiaSphenacodontiaSphenacodontia is the name given to the clade that includes the Sphenacodontidae and all their descendants . They first appear during the Late Pennsylvanian epoch. The defining characteristics include a thickening of the maxilla visible on its internal surface, above the large front teeth; and...
*- Family †SphenacodontidaeSphenacodontidaeSphenacodontidae is a family of small to large, advanced, carnivorous, Late Pennsylvanian to middle Permian pelycosaurs. Primitive forms were generally small in size , but during the later part of the early Permian these animals grew progressively larger , to become the top predators of their...
- Family †Sphenacodontidae
- Family †Edaphosauridae
- Suborder †Caseasauria
- Order TherapsidaTherapsidaTherapsida is a group of the most advanced synapsids, and include the ancestors of mammals. Many of the traits today seen as unique to mammals had their origin within early therapsids, including hair, lactation, and an erect posture. The earliest fossil attributed to Therapsida is believed to be...
*
- Order Pelycosaur
- Class MAMMALIA
- CLASS SYNAPSIDA *