Coelurus
Encyclopedia
Coelurus is a genus
of coelurosaur dinosaur
from the Late Jurassic
period (mid-late Kimmeridgian
faunal stage
, 153–150 million years ago). The name means "hollow tail", referring to its hollow tail vertebrae (Greek
κοιλος, koilos = hollow + ουρα, oura = tail). Although its name is linked to one of the main divisions of theropods (Coelurosauria
), it has historically been poorly understood, and sometimes confused with its better-known contemporary Ornitholestes
. Like many dinosaurs studied in the early years of paleontology, it has had a confusing taxonomic
history, with several species being named and later transferred to other genera
or abandoned. Only one species is currently recognized as valid: the type species
, C. fragilis, described by Othniel Charles Marsh
in 1879. It is known from one partial skeleton found in the Morrison Formation
of Wyoming
, United States
. It was a small bipedal carnivore
with elongate legs.
Coelurus is known from most of the skeleton of a single individual, including numerous vertebrae, partial pelvic
and shoulder girdles, and much of the arms and legs, stored at the Peabody Museum of Natural History; however, the relative completeness of the skeleton was not known until 1980. The fossils were recovered from Reed's Quarry 13 at Como Bluff
, Wyoming. Additionally, two arm bones possibly belonging to this genus are known from the Cleveland Lloyd Dinosaur Quarry
in Utah
. It was not a large dinosaur. Its weight has been estimated at around 13 to 20 kg (28.7 to 44.1 lb), with a length of about 2.4 meters (7.9 ft) and a hip height of 0.7 meters (2.3 ft). From reconstructions of the skeleton, Coelurus had a relatively long neck and torso due to its long vertebrae, a long slender hindlimb due to its long metatarsus
, and potentially a small slender skull.
The skull is unknown except for possibly a portion of lower jaw found at the same site as the rest of the known Coelurus material. Although it has the same preservation and coloring as the fossil
s known to belong to the Coelurus skeleton, it is very slender, which may mean it doesn't belong to the skeleton; this bone is 7.9 centimeters long (3.1 in) but only 1.1 centimeters tall (0.43 in). In general, its vertebrae were long and low, with low neural spines
and thin walls to the bodies
of the vertebrae. Its neck vertebrae were very pneumatic, with numerous hollow spaces on their surfaces (pleurocoels); these hollows were not evenly distributed among the vertebrae and varied in size. The neck vertebrae were very elongate, with bodies four times longer than wide, and they articulated with concave faces on both ends (amphicoely). The back vertebrae were not as elongate, lacked surface hollows, and had less developed concave faces and bodies that were hourglass
-shaped. The tail vertebrae also lacked surface hollows.
The only bone known from the shoulder girdle is a fragment of scapula
. The upper arm
had a distinct S-shaped curve in side view and was slightly longer than the forearm
(11.9 centimeters [4.7 in] versus 9.6 centimeters [3.8 in]). The wrist had a semilunate carpal
similar to that of Deinonychus
, and the fingers were long and slender. The only bone known from the pelvic girdle is paired and fused pubis
bones, which had a prominent, long "foot" at the end. The thigh bones
had an S-shape when viewed from the front. The metatarsals
were unusually long and slender, nearly the length of the thigh bones (the best preserved thigh bone is about 21 centimeters long [8.3 in]).
, and Tanycolagreus
— were generalized coelurosaurs, and they have been mistaken for each other at various times. Now that Coelurus and Ornitholestes have been more fully described, it is possible to distinguish them by various characteristics of their anatomy. For example, they had visibly different proportions: Coelurus had a longer back and neck than Ornitholestes, and longer, more slender legs and feet. Coelurus and Tanycolagreus are more similar, but differ in a variety of details. Such details include the shape of the upper arm, forearm, and thigh bones; the location of muscle attachments on the thigh bone, proportionally longer back vertebrae; and, again, the very long metatarsus of Coelurus.
studies in the 1980s, Coelurus has usually been found to be a coelurosauria
n of uncertain affinities, not fitting with the better-known clade
s of the Cretaceous. It, along with several other generalized coelurosaurians such as the compsognathids
, Ornitholestes, and Proceratosaurus
, has had multiple placements around the base of Coelurosauria. However, a work published by Phil Senter in 2007 following the description of Tanycolagreus
found it and Coelurus to be closely related at the base of Tyrannosauroidea
. Coelurus is sometimes put into its own family, Coeluridae
, although the membership of the family has not been stable. Oliver Rauhut (2003) proposed a Coeluridae composed of Coelurus plus the compsognathids, but he and others have not since found the compsognathids to group with Coelurus. Phil Senter proposed that Coelurus and Tanycolagreus were the only coelurids and were actually tyrannosauroids
.
Before the use of phylogenetic analyses, Coeluridae and Coelurosauria were taxonomic wastebaskets used for small theropods that didn't belong to other groups; thus, they accumulated many dubious
genera. As late as the 1980s, popular books recognized over a dozen "coelurids", including such disparate forms as the noasaurid
Laevisuchus
and the oviraptorosauria
n Microvenator
, and considered them descendants of the coelophysids
. A wastebasket Coeluridae lingered into the early 1990s in some sources (and appears in at least one 2006 source) but since then it has only been recognized in a much reduced form.
" with Edward Drinker Cope
. At the time, he only described what he interpreted as vertebrae from the back and tail, found at the same location as the type specimen
of his new genus and species Camptonotus dispar (later renamed Camptosaurus
because Camptonotus was already in use for a cricket
). Marsh was impressed with the hollow interiors of the thin-walled vertebrae, a characteristic that gave the type species
its name: Coelurus fragilis. He thought of his new genus as an "animal about as large as a wolf, and probably carnivorous". Coelurus would prove to be the first named small theropod from the Morrison Formation, although at the time Marsh was not certain that it was a dinosaur. He returned to it in 1881 and provided illustrations of some bones, along with putting it in a new order
(Coeluria) and family (Coeluridae
).
From there, the story becomes more complex. Apparently, the skeleton was scattered throughout the quarry, with the remains being recovered from September 1879 to September 1880. Marsh elected to place some of the material in a new species, C. agilis, on the strength of a pair of fused pubic bones he thought belonged to an animal three times the size of C. fragilis. He returned to the genus in 1888 to add C". gracilis, based on unknown remains only represented today by a single claw bone
pertaining to a small theropod from the Early Cretaceous
Arundel Formation
of Maryland
. This species is not currently accepted as representing Coelurus in reviews of the genus, but has not been given its own genus.
Despite their professional animosity, Cope also assigned species to Coelurus; in 1887, he named fossils from the Late Triassic
of New Mexico
as C. bauri and C. longicollis. He later gave them their own genus, Coelophysis
.
In 1903, Henry Fairfield Osborn
named a second genus of small theropod from the Morrison Formation, Ornitholestes
. This genus was based on a partial skeleton from Bone Cabin Quarry, north of Como Bluff. Ornitholestes became intertwined with Coelurus in 1920, when Charles Gilmore
, in his influential study of theropod dinosaurs, concluded that the two were synonyms
. This was followed in the literature for decades. The two genera were not formally compared, however, nor was there a full accounting of what actually belonged to Coelurus, until John Ostrom
's study in 1980.
Gilmore had suspected that C. fragilis and C. agilis were the same, but Ostrom was able to demonstrate this synonymy. This greatly expanded the known material pertaining to C. fragilis, and Ostrom was able to demonstrate that Ornitholestes was quite different from Coelurus. At the time, Dale Russell
had proposed that C. agilis was a species of Elaphrosaurus
based on the incomplete information then published; Ostrom was also able to demonstrate that this was not the case. Additionally, he showed that one of the three vertebrae Marsh had illustrated for C. fragilis was actually a composite of two vertebrae, one of which was later shown to come from another quarry and belonged not to Coelurus but to another, unnamed small theropod. This unnamed genus would not be the last small theropod from the Morrison Formation to be confused with Coelurus; a later discovery (1995) of a partial skeleton in Wyoming was first thought to be a new larger specimen of Coelurus, but further study showed it belonged to a different but related genus, Tanycolagreus
.
C. fragilis, is still recognized as valid today, although six other species have been named over the years. C. agilis, as discussed, was named by Marsh in 1884 for what turned out to be additional parts of the skeleton of C. fragilis. Cope's C. bauri and C. longicollis, named in 1887 from Late Triassic fossils from New Mexico, were transferred by Cope in 1889 to his new genus Coelophysis. C. daviesi was named by Richard Lydekker
in 1888 for Harry Seeley
's Thecospondylus
daviesi, a neck vertebra from the Early Cretaceous
of England
, but this species was later transferred to its own genus, Thecocoelurus
. C. gracilis, another Early Cretaceous species, was also named in 1888. It was coined by Marsh for what seems to be an assortment of limb remains, but Gilmore could only find a single claw when he reviewed the species in 1920. This species has been proposed as outside Coelurus since the 1920s (when Gilmore assigned it to Chirostenotes
), and has been regarded as a dubious
species outside of Coelurus in recent reviews. Finally, during the period when Ornitholestes was thought to be the same as Coelurus, its type species was recognized as distinct by Steel, as C. hermanni.
is interpreted as a semiarid environment with distinct wet
and dry season
s, and flat floodplain
s. Vegetation varied from river-lining forests of conifers, tree ferns, and fern
s, to fern savanna
s with rare trees. It has been a rich fossil hunting ground, holding fossils of green algae
, fungi, moss
es, horsetails, ferns, cycad
s, ginkgo
es, and several families of conifers. Other fossils discovered include bivalves, snail
s, ray-finned fishes
, frog
s, salamander
s, turtle
s, sphenodonts
, lizard
s, terrestrial and aquatic crocodylomorpha
ns, several species of pterosaur
, numerous dinosaur species, and early mammals such as docodonts
, multituberculates
, symmetrodonts
, and triconodonts
. Such dinosaurs as the theropods Ceratosaurus
, Allosaurus
, Ornitholestes, and Torvosaurus
, the sauropods Apatosaurus
, Brachiosaurus
, Camarasaurus
, and Diplodocus
, and the ornithischia
ns Camptosaurus
, Dryosaurus
, and Stegosaurus
are known from the Morrison. Coelurus is regarded as a small terrestrial carnivore, feeding on small prey items like insect
s, mammal
s, and lizard
s. It is thought to have been a fast animal, certainly faster than the similar but shorter-footed Ornitholestes. Present in stratigraphic zones 2 and 5 of the Morrison Formation.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of coelurosaur 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...
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 (mid-late Kimmeridgian
Kimmeridgian
In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....
faunal stage
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
, 153–150 million years ago). The name means "hollow tail", referring to its hollow tail vertebrae (Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
κοιλος, koilos = hollow + ουρα, oura = tail). Although its name is linked to one of the main divisions of theropods (Coelurosauria
Coelurosauria
Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. In the past, it was used to refer to all small theropods, although this classification has been abolished...
), it has historically been poorly understood, and sometimes confused with its better-known contemporary Ornitholestes
Ornitholestes
Ornitholestes was a small theropod dinosaur of the late Jurassic of Western Laurasia . To date, it is known only from a single partial skeleton, and badly crushed skull found at the Bone Cabin Quarry near Medicine Bow, Wyoming, in 1900...
. Like many dinosaurs studied in the early years of paleontology, it has had a confusing taxonomic
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
history, with several species being named and later transferred to other genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
or abandoned. Only one species is currently recognized as valid: the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, C. fragilis, described by Othniel Charles Marsh
Othniel Charles Marsh
Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
in 1879. It is known from one partial skeleton found in the Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
of Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. It was a small bipedal carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
with elongate legs.
Description
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
and shoulder girdles, and much of the arms and legs, stored at the Peabody Museum of Natural History; however, the relative completeness of the skeleton was not known until 1980. The fossils were recovered from Reed's Quarry 13 at Como Bluff
Como Bluff
Como Bluff is a long ridge extending east-west, located between the towns of Rock River and Medicine Bow, Wyoming. The ridge is an anticline, formed as a result of compressional geological folding. Three geological formations, the Sundance, the Morrison, and the Cloverly Formations, containing...
, Wyoming. Additionally, two arm bones possibly belonging to this genus are known from the Cleveland Lloyd Dinosaur Quarry
Cleveland Lloyd Dinosaur Quarry
The Cleveland Lloyd Dinosaur Quarry National Natural Landmark, located in The San Rafael Swell, near Cleveland, Utah contains the densest concentration of Jurassic dinosaur fossils ever found. Well over 15,000 bones have been excavated from this Jurassic 'predator trap' and there are many...
in Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
. It was not a large dinosaur. Its weight has been estimated at around 13 to 20 kg (28.7 to 44.1 lb), with a length of about 2.4 meters (7.9 ft) and a hip height of 0.7 meters (2.3 ft). From reconstructions of the skeleton, Coelurus had a relatively long neck and torso due to its long vertebrae, a long slender hindlimb due to its long metatarsus
Metatarsus
The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth...
, and potentially a small slender skull.
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s known to belong to the Coelurus skeleton, it is very slender, which may mean it doesn't belong to the skeleton; this bone is 7.9 centimeters long (3.1 in) but only 1.1 centimeters tall (0.43 in). In general, its vertebrae were long and low, with low neural spines
Spinous process
The spinous process of a vertebra is directed backward and downward from the junction of the laminae , and serves for the attachment of muscles and ligaments. In animals without an erect stance, the process points upward and may slant forward or backward...
and thin walls to the bodies
Body of vertebra
The body is the largest part of a vertebra, and is more or less cylindrical in shape. For vertebrates other than humans, this structure is usually called a centrum....
of the vertebrae. Its neck vertebrae were very pneumatic, with numerous hollow spaces on their surfaces (pleurocoels); these hollows were not evenly distributed among the vertebrae and varied in size. The neck vertebrae were very elongate, with bodies four times longer than wide, and they articulated with concave faces on both ends (amphicoely). The back vertebrae were not as elongate, lacked surface hollows, and had less developed concave faces and bodies that were hourglass
Hourglass
An hourglass measures the passage of a few minutes or an hour of time. It has two connected vertical glass bulbs allowing a regulated trickle of material from the top to the bottom. Once the top bulb is empty, it can be inverted to begin timing again. The name hourglass comes from historically...
-shaped. The tail vertebrae also lacked surface hollows.
The only bone known from the shoulder girdle is a fragment of scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
. The upper arm
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
had a distinct S-shaped curve in side view and was slightly longer than the forearm
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...
(11.9 centimeters [4.7 in] versus 9.6 centimeters [3.8 in]). The wrist had a semilunate carpal
Carpus
In tetrapods, the carpus is the sole cluster of bones in the wrist between the radius and ulna and the metacarpus. The bones of the carpus do not belong to individual fingers , whereas those of the metacarpus do. The corresponding part of the foot is the tarsus...
similar to that of Deinonychus
Deinonychus
Deinonychus was a genus of carnivorous dromaeosaurid dinosaur. There is one described species, Deinonychus antirrhopus. This 3.4 meter long dinosaur lived during the early Cretaceous Period, about 115–108 million years ago . Fossils have been recovered from the U.S...
, and the fingers were long and slender. The only bone known from the pelvic girdle is paired and fused pubis
Pubis (bone)
In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons pubis....
bones, which had a prominent, long "foot" at the end. The thigh bones
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
had an S-shape when viewed from the front. The metatarsals
Metatarsus
The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth...
were unusually long and slender, nearly the length of the thigh bones (the best preserved thigh bone is about 21 centimeters long [8.3 in]).
Coelurus, Ornitholestes, and Tanycolagreus
The three best-known small theropods of the Morrison Formation — Coelurus, OrnitholestesOrnitholestes
Ornitholestes was a small theropod dinosaur of the late Jurassic of Western Laurasia . To date, it is known only from a single partial skeleton, and badly crushed skull found at the Bone Cabin Quarry near Medicine Bow, Wyoming, in 1900...
, and Tanycolagreus
Tanycolagreus
Tanycolagreus is a genus of coelurid theropod from the Late Jurassic of North America. The holotype is a partial skeleton recovered from the Bone Cabin Quarry West locality, Albany County, Wyoming, from the Morrison Formation...
— were generalized coelurosaurs, and they have been mistaken for each other at various times. Now that Coelurus and Ornitholestes have been more fully described, it is possible to distinguish them by various characteristics of their anatomy. For example, they had visibly different proportions: Coelurus had a longer back and neck than Ornitholestes, and longer, more slender legs and feet. Coelurus and Tanycolagreus are more similar, but differ in a variety of details. Such details include the shape of the upper arm, forearm, and thigh bones; the location of muscle attachments on the thigh bone, proportionally longer back vertebrae; and, again, the very long metatarsus of Coelurus.
Classification
Since the growth of phylogeneticPhylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
studies in the 1980s, Coelurus has usually been found to be a coelurosauria
Coelurosauria
Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. In the past, it was used to refer to all small theropods, although this classification has been abolished...
n of uncertain affinities, not fitting with the better-known 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...
s of the Cretaceous. It, along with several other generalized coelurosaurians such as the compsognathids
Compsognathidae
Compsognathidae is a family of small carnivorous dinosaurs, generally conservative in form, from the Jurassic and Cretaceous Periods. Compsognathids lie at or near the origin of feathers—skin impressions are known from four genera, Compsognathus, Sinosauropteryx, Sinocalliopteryx, and Juravenator...
, Ornitholestes, and Proceratosaurus
Proceratosaurus
Proceratosaurus is a genus of small-sized carnivorous theropod dinosaur from the Middle Jurassic of England. It was originally thought to be an ancestor of Ceratosaurus, due to the similar small crest on its snout...
, has had multiple placements around the base of Coelurosauria. However, a work published by Phil Senter in 2007 following the description of Tanycolagreus
Tanycolagreus
Tanycolagreus is a genus of coelurid theropod from the Late Jurassic of North America. The holotype is a partial skeleton recovered from the Bone Cabin Quarry West locality, Albany County, Wyoming, from the Morrison Formation...
found it and Coelurus to be closely related at the base of Tyrannosauroidea
Tyrannosauroidea
Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period...
. Coelurus is sometimes put into its own family, Coeluridae
Coeluridae
Coeluridae is a historically polyphyletic family of generally small, carnivorous dinosaurs from the late Jurassic Period...
, although the membership of the family has not been stable. Oliver Rauhut (2003) proposed a Coeluridae composed of Coelurus plus the compsognathids, but he and others have not since found the compsognathids to group with Coelurus. Phil Senter proposed that Coelurus and Tanycolagreus were the only coelurids and were actually tyrannosauroids
Tyrannosauroidea
Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period...
.
Before the use of phylogenetic analyses, Coeluridae and Coelurosauria were taxonomic wastebaskets used for small theropods that didn't belong to other groups; thus, they accumulated many dubious
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
genera. As late as the 1980s, popular books recognized over a dozen "coelurids", including such disparate forms as the noasaurid
Noasauridae
Noasaurids were a group of theropod dinosaurs from the Cretaceous Period . They were generally small in size...
Laevisuchus
Laevisuchus
Laevisuchus is a genus of abelisauroid theropod dinosaur from the Late Cretaceous.Its remains were discovered by Charles Alfred Matley near Jabalpur in Maastrichtian deposits in the Lameta Formation in India, and named and described by paleontologists Friedrich von Huene and Matley in 1933. The...
and the oviraptorosauria
Oviraptorosauria
Oviraptorosaurs are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot - like skulls, with or without bony crests atop the head...
n Microvenator
Microvenator
Microvenator is a genus of dinosaur from the Early Cretaceous Cloverly Formation in what is now south central Montana. Microvenator was an oviraptorosaurian theropod. The holotype fossil is an incomplete skeleton, most likely a juvenile, with a living length of about four feet. The adult size of...
, and considered them descendants of the coelophysids
Coelophysidae
The Coelophysidae are a family of primitive carnivorous theropod dinosaurs. Most species were relatively small in size. The family flourished in the Late Triassic and Early Jurassic periods....
. A wastebasket Coeluridae lingered into the early 1990s in some sources (and appears in at least one 2006 source) but since then it has only been recognized in a much reduced form.
History
Coelurus was described in 1879 by Othniel Charles Marsh, an American paleontologist and naturalist known for his "Bone WarsBone Wars
The Bone Wars, also known as the "Great Dinosaur Rush", refers to a period of intense fossil speculation and discovery during the Gilded Age of American history, marked by a heated rivalry between Edward Drinker Cope and Othniel Charles Marsh...
" with Edward Drinker Cope
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
. At the time, he only described what he interpreted as vertebrae from the back and tail, found at the same location as the type specimen
Biological type
In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...
of his new genus and species Camptonotus dispar (later renamed Camptosaurus
Camptosaurus
Camptosaurus is a genus of plant-eating, beaked ornithischian dinosaurs of the Late Jurassic period of western North America. The name means 'flexible lizard', ....
because Camptonotus was already in use for a cricket
Cricket (insect)
Crickets, family Gryllidae , are insects somewhat related to grasshoppers, and more closely related to katydids or bush crickets . They have somewhat flattened bodies and long antennae. There are about 900 species of crickets...
). Marsh was impressed with the hollow interiors of the thin-walled vertebrae, a characteristic that gave the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
its name: Coelurus fragilis. He thought of his new genus as an "animal about as large as a wolf, and probably carnivorous". Coelurus would prove to be the first named small theropod from the Morrison Formation, although at the time Marsh was not certain that it was a dinosaur. He returned to it in 1881 and provided illustrations of some bones, along with putting it in a new order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
(Coeluria) and family (Coeluridae
Coeluridae
Coeluridae is a historically polyphyletic family of generally small, carnivorous dinosaurs from the late Jurassic Period...
).
From there, the story becomes more complex. Apparently, the skeleton was scattered throughout the quarry, with the remains being recovered from September 1879 to September 1880. Marsh elected to place some of the material in a new species, C. agilis, on the strength of a pair of fused pubic bones he thought belonged to an animal three times the size of C. fragilis. He returned to the genus in 1888 to add C". gracilis, based on unknown remains only represented today by a single claw bone
Ungual
An ungual is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and other ungulates have ungual phalanges, as did the sauropods and horned dinosaurs. A claw is a highly modified ungual phalange.As an adjective, ungual means related to nail, as in periungual .-External...
pertaining to a small theropod from the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
Arundel Formation
Arundel Formation
The Arundel Formation, also known as the Arundel Clay, is a clay-rich sedimentary rock formation, within the Potomac Group, found in Maryland of the United States of America. It is of Aptian age . This rock unit had been economically important as a source of iron ore, but is now more notable for...
of Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
. This species is not currently accepted as representing Coelurus in reviews of the genus, but has not been given its own genus.
Despite their professional animosity, Cope also assigned species to Coelurus; in 1887, he named fossils from the Late Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
of New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
as C. bauri and C. longicollis. He later gave them their own genus, Coelophysis
Coelophysis
Coelophysis , meaning "hollow form" in reference to its hollow bones , is one of the earliest known genera of dinosaur...
.
In 1903, Henry Fairfield Osborn
Henry Fairfield Osborn
Henry Fairfield Osborn, Sr. ForMemRS was an American geologist, paleontologist, and eugenicist.-Early life and career:...
named a second genus of small theropod from the Morrison Formation, Ornitholestes
Ornitholestes
Ornitholestes was a small theropod dinosaur of the late Jurassic of Western Laurasia . To date, it is known only from a single partial skeleton, and badly crushed skull found at the Bone Cabin Quarry near Medicine Bow, Wyoming, in 1900...
. This genus was based on a partial skeleton from Bone Cabin Quarry, north of Como Bluff. Ornitholestes became intertwined with Coelurus in 1920, when Charles Gilmore
Charles W. Gilmore
Charles Whitney Gilmore was an American paleontologist, who named dinosaurs in North America and Mongolia, including the Cretaceous sauropod Alamosaurus, Alectrosaurus, Archaeornithomimus, Bactrosaurus, Brachyceratops, Chirostenotes, Mongolosaurus, Parrosaurus, Pinacosaurus, Styracosaurus and...
, in his influential study of theropod dinosaurs, concluded that the two were synonyms
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
. This was followed in the literature for decades. The two genera were not formally compared, however, nor was there a full accounting of what actually belonged to Coelurus, until John Ostrom
John Ostrom
John H. Ostrom was an American paleontologist who revolutionized modern understanding of dinosaurs in the 1960s, when he demonstrated that dinosaurs are more like big non-flying birds than they are like lizards , an idea first proposed by Thomas Henry Huxley in the 1860s, but which had garnered...
's study in 1980.
Gilmore had suspected that C. fragilis and C. agilis were the same, but Ostrom was able to demonstrate this synonymy. This greatly expanded the known material pertaining to C. fragilis, and Ostrom was able to demonstrate that Ornitholestes was quite different from Coelurus. At the time, Dale Russell
Dale Russell
Dale A. Russell is a Canadian geologist/palaeontologist, currently Research Professor at The Department of Marine Earth and Atmospheric Sciences of North Carolina State University...
had proposed that C. agilis was a species of Elaphrosaurus
Elaphrosaurus
Elaphrosaurus is a genus of theropod dinosaur from the Kimmeridgian stage of the Late Jurassic of Tanzania. Elaphrosaurus was probably a ceratosaur about 6 meters long. Suggestions that it is a late surviving coelophysoid have been entertained but are generally dismissed. It was first...
based on the incomplete information then published; Ostrom was also able to demonstrate that this was not the case. Additionally, he showed that one of the three vertebrae Marsh had illustrated for C. fragilis was actually a composite of two vertebrae, one of which was later shown to come from another quarry and belonged not to Coelurus but to another, unnamed small theropod. This unnamed genus would not be the last small theropod from the Morrison Formation to be confused with Coelurus; a later discovery (1995) of a partial skeleton in Wyoming was first thought to be a new larger specimen of Coelurus, but further study showed it belonged to a different but related genus, Tanycolagreus
Tanycolagreus
Tanycolagreus is a genus of coelurid theropod from the Late Jurassic of North America. The holotype is a partial skeleton recovered from the Bone Cabin Quarry West locality, Albany County, Wyoming, from the Morrison Formation...
.
Species
Only one species of Coelurus, the type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
C. fragilis, is still recognized as valid today, although six other species have been named over the years. C. agilis, as discussed, was named by Marsh in 1884 for what turned out to be additional parts of the skeleton of C. fragilis. Cope's C. bauri and C. longicollis, named in 1887 from Late Triassic fossils from New Mexico, were transferred by Cope in 1889 to his new genus Coelophysis. C. daviesi was named by Richard Lydekker
Richard Lydekker
Richard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.-Biography:...
in 1888 for Harry Seeley
Harry Seeley
Harry Govier Seeley was a British paleontologist.-Career:Seeley was born in London, the son of Richard Hovill Seeley, goldsmith, and his second wife Mary Govier. He attended classes at the Royal School of Mines, Kensington before becoming an assistant to Adam Sedgwick at the Woodwardian Museum,...
's Thecospondylus
Thecospondylus
Thecospondylus is a dubious genus of dinosaur from the Early Cretaceous of EnglandDr. A.C. Horner, an amateur geologist living at Tonbridge, in the nineteenth century acquired a fossil found in the quarry of Southborough...
daviesi, a neck vertebra from the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, but this species was later transferred to its own genus, Thecocoelurus
Thecocoelurus
Thecocoelurus is a genus of theropod dinosaur from the early Cretaceous period of England.Thecocoelurus is known only from half of a single cervical vertebra, discovered by the Rev. William Darwin Fox on the Isle of Wight during the 19th century. After his death the Fox Collection was acquired by...
. C. gracilis, another Early Cretaceous species, was also named in 1888. It was coined by Marsh for what seems to be an assortment of limb remains, but Gilmore could only find a single claw when he reviewed the species in 1920. This species has been proposed as outside Coelurus since the 1920s (when Gilmore assigned it to Chirostenotes
Chirostenotes
Chirostenotes is a genus of oviraptorosaurian dinosaur from the late Cretaceous of Alberta, Canada. The type species is Chirostenotes pergracilis. Some researchers recognize a second species, C...
), and has been regarded as a dubious
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
species outside of Coelurus in recent reviews. Finally, during the period when Ornitholestes was thought to be the same as Coelurus, its type species was recognized as distinct by Steel, as C. hermanni.
Paleobiology and paleoecology
The Morrison FormationMorrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
is interpreted as a semiarid environment with distinct wet
Wet season
The the wet season, or rainy season, is the time of year, covering one or more months, when most of the average annual rainfall in a region occurs. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the...
and dry season
Dry season
The dry season is a term commonly used when describing the weather in the tropics. The weather in the tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year...
s, and flat floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
s. Vegetation varied from river-lining forests of conifers, tree ferns, and fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s, to fern savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
s with rare trees. It has been a rich fossil hunting ground, holding fossils of green algae
Chlorophyta
Chlorophyta is a division of green algae, informally called chlorophytes. The name is used in two very different senses so that care is needed to determine the use by a particular author...
, fungi, moss
Moss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
es, horsetails, ferns, cycad
Cycad
Cycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...
s, ginkgo
Ginkgo
Ginkgo , also spelled gingko and known as the Maidenhair Tree, is a unique species of tree with no close living relatives...
es, and several families of conifers. Other fossils discovered include bivalves, snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s, ray-finned fishes
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...
, frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s, 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...
s, 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...
s, sphenodonts
Sphenodontia
Sphenodontia is an order of lizard-like reptiles that includes only one living genus, the tuatara , and only two living species...
, 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, terrestrial and aquatic crocodylomorpha
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
ns, several species of pterosaur
Pterosaur
Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
, numerous dinosaur species, and early mammals such as docodonts
Docodonta
Docodonta is an order of extinct proto-mammals that lived during the mid- to late-Mesozoic era. Their most distinguishing physical features were their relatively sophisticated set of molars, from which the order gets its name. In the fossil record, Docodonta is represented primarily by isolated...
, multituberculates
Multituberculata
The Multituberculata were a group of rodent-like mammals that existed for approximately one hundred and twenty million years—the longest fossil history of any mammal lineage—but were eventually outcompeted by rodents, becoming extinct during the early Oligocene. At least 200 species are...
, symmetrodonts
Symmetrodonta
Symmetrodonta is a basal group of Mesozoic mammals characterized by the triangular aspect of the molars when viewed from above and the absence of a well-developed talonid. The traditional group of symmetrodonts ranges in age from the latest Triassic to the Late Cretaceous. One species,...
, and triconodonts
Triconodonta
Triconodonta is the generic name for a group of early mammals which were close relatives of the ancestors of all present-day mammals. Triconodonts lived between the Triassic and the Cretaceous. They are one of the groups that can be classified as mammals by any definition...
. Such dinosaurs as the theropods Ceratosaurus
Ceratosaurus
Ceratosaurus meaning "horned lizard", in reference to the horn on its nose , was a large predatory theropod dinosaur from the Late Jurassic Period , found in the Morrison Formation of North America, in Tanzania and Portugal...
, Allosaurus
Allosaurus
Allosaurus is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period . The name Allosaurus means "different lizard". It is derived from the Greek /allos and /sauros...
, Ornitholestes, and Torvosaurus
Torvosaurus
Torvosaurus is a genus of large theropod dinosaur that lived during the Late Jurassic period...
, the sauropods Apatosaurus
Apatosaurus
Apatosaurus , also known by the popular but scientifically deprecated synonym Brontosaurus, is a genus of sauropod dinosaur that lived from about 154 to 150 million years ago, during the Jurassic Period . It was one of the largest land animals that ever existed, with an average length of and a...
, Brachiosaurus
Brachiosaurus
Brachiosaurus is a genus of sauropod dinosaur from the Jurassic Morrison Formation of North America. It was first described by Elmer S. Riggs in 1903 from fossils found in the Grand River Canyon of western Colorado, in the United States. Riggs named the dinosaur Brachiosaurus altithorax,...
, Camarasaurus
Camarasaurus
Camarasaurus meaning 'chambered lizard', referring to the hollow chambers in its vertebrae was a genus of quadrupedal, herbivorous dinosaurs. It was the most common of the giant sauropods to be found in North America...
, and Diplodocus
Diplodocus
Diplodocus , or )is a genus of diplodocid sauropod dinosaur whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a Neo-Latin term derived from Greek "double" and "beam", in reference to its double-beamed chevron bones...
, and the ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
ns Camptosaurus
Camptosaurus
Camptosaurus is a genus of plant-eating, beaked ornithischian dinosaurs of the Late Jurassic period of western North America. The name means 'flexible lizard', ....
, Dryosaurus
Dryosaurus
Dryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont . Fossils have been found in the western United States, and were first discovered in the late 19th century...
, and Stegosaurus
Stegosaurus
Stegosaurus is a genus of armored stegosaurid dinosaur. They lived during the Late Jurassic period , some 155 to 150 million years ago in what is now western North America. In 2006, a specimen of Stegosaurus was announced from Portugal, showing that they were present in Europe as well...
are known from the Morrison. Coelurus is regarded as a small terrestrial carnivore, feeding on small prey items like 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...
s, 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, and 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. It is thought to have been a fast animal, certainly faster than the similar but shorter-footed Ornitholestes. Present in stratigraphic zones 2 and 5 of the Morrison Formation.
External links
- Coelurus from Palaeos.com.