Coelophysis

Coelophysis (/sɛˈlɒfɪsɪs/ seh-LOF-ih-sis traditionally; /ˌsɛloʊˈfaɪsɪs/ SEL-o-FY-sis or /ˌsiːloʊˈfaɪsɪs/ SEE-lo-FY-sis are heard more commonly in recent decades[5]) is an extinct genus of coelophysid theropod dinosaur that lived approximately 216 to 196 million years ago during the latter part of the Triassic Period in what is now the southwestern United States[6] and also in South Africa and Zimbabwe.[7]

Coelophysis was a small, slenderly-built, ground-dwelling, bipedal carnivore, that could grow up to 3 m (9.8 ft) long. Coelophysis is one of the earliest known dinosaur genera. Scattered material representing similar animals has been found worldwide in some Late Triassic and Early Jurassic formations.

The type species C. bauri, originally given to the genus Coelurus by Edward Drinker Cope in 1887, was described by the latter in 1889. The names Longosaurus and Rioarribasaurus are synonymous with Coelophysis. Another dinosaur genus, Megapnosaurus, has also been considered to be a synonym. This primitive theropod is notable for being one of the most specimen-rich dinosaur genera.

Coelophysis
Temporal range: Late TriassicEarly Jurassic, 216–196 Ma
Coelophysis bauri mount
Mounted skeleton at the Cleveland Museum of Natural History
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Coelophysidae
Genus: Coelophysis
Cope, 1889
Type species
Coelurus bauri
Cope, 1887
Species
Synonyms

Description

Coelophysis size
Size of C. bauri compared to a human

Coelophysis is known from a number of complete fossil skeletons of the species C. bauri, which was a lightly built dinosaur which measured up to 3 metres (9.8 ft) in length[8] and which was more than a meter tall at the hips. Paul (1988) estimated the weight of the gracile form at 15 kg (33 lb), and the weight of the robust form at 20 kg (44 lb).[9] Coelophysis was a bipedal, carnivorous, theropod dinosaur that was a fast and agile runner.[10] Despite being an early dinosaur, the evolution of the theropod body form had already advanced greatly from creatures like Herrerasaurus and Eoraptor. The torso of Coelophysis conforms to the basic theropod body shape, but the pectoral girdle displays some interesting special characteristics: C. bauri had a furcula (wishbone), the earliest known example in a dinosaur. Coelophysis also preserves the ancestral condition of possessing four digits on the hand (manus). It had only three functional digits, the fourth embedded in the flesh of the hand.[11]

Coelophysis had narrow hips, forelimbs adapted for grasping prey, and narrow feet.[12] Its neck and tail were long and slender.[6] The pelvis and hindlimbs of C. bauri are also slight variations on the theropod body plan. It has the open acetabulum and straight ankle hinge that define the Dinosauria. The hindlimb ended in a three-toed foot (pes), with a raised hallux. The tail had an unusual structure within its interlocking prezygapophysis of its vertebrae, which formed a semi-rigid lattice, apparently to stop the tail from moving up and down.[13]

Coelophysis-bauri head
C. bauri profile

Coelophysis had a long narrow head (approximately 270 mm (0.9 ft)), with large, forward-facing eyes that afforded it stereoscopic vision and as a result excellent depth perception. Rinehart et al. (2004) described the complete sclerotic ring found for a juvenile Coelophysis bauri (specimen NMMNH P-4200), and compared it to data on the sclerotic rings of reptiles and birds and concluded that Coelophysis was a diurnal, visually oriented predator.[14] The study found that the vision of Coelophysis was superior to most lizards' vision, and ranked with that of modern birds of prey. The eyes of Coelophysis appear to be the closest to those of eagles and hawks, with a high power of accommodation. The data also suggested poor night vision, which would mean this dinosaur had a round rather than a split pupil.[10]

Coelophysis had an elongated snout with large fenestrae which helped to reduce skull weight, while narrow struts of bones preserved the structural integrity of the skull. The neck had a pronounced sigmoid curve. The braincase is known in Coelophysis bauri but little data could be derived because the skull was crushed.[12] Unlike some other theropods, the cranial ornamentation of Coelophysis was not located at the top of its skull. Low, laterally raised bony ridges were present on the dorsolateral margin of the nasal and lacrimal bones in the skull, directly above the antorbital fenestra.[15]

Distinguishing anatomical features

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group.

According to Ezcurra (2007), and Bristowe and Raath (2004) Coelophysis can be distinguished based on the following features: the absence of an offset rostral process of the maxilla; the quadrate is strongly caudally; a small external mandibular fenestra, which is 9–10% of the mandibular length;[16] and the anteroposterior length of the ventral lacrimal process is greater than 30% of its height.[17]

Several paleontologists consider Coelophysis bauri to be the same dinosaur as Coelophysis rhodesiensis (formerly Syntarsus, alternately Megapnosaurus), however this has been refuted by the following: Downs (2000) concluded that C. bauri differs from C. rhodesiensis in cervical length, proximal and distal hindlimb proportions and proximal caudal vertebral anatomy;[18] Tykoski and Rowe (2004) concluded that C. bauri differs from C. rhodesiensis in that it lacks a pit at the base of the nasal process of the premaxilla;[12] and Bristowe and Raath (2004) concluded that C. bauri differs from C. rhodesiensis in having a longer maxillary tooth row.[17]

History of discovery

Coelophysis bauri
Two Ghost Ranch specimens preserved together, including the neotype, AMNH

Named in 1887, the type species of Coelophysis was originally named as a species of Coelurus.[19] Edward Drinker Cope first named Coelophysis in 1889 to name a new genus, outside of Coelurus and Tanystrophaeus to which C. bauri was previously classified in for C. bauri, C. willistoni and C. longicollis.[20] An amateur fossil collector working for Cope, David Baldwin, had found the first remains of the dinosaur in 1881 in the Chinle Formation in northwestern New Mexico.[21] Early in 1887, Cope referred the specimens collected to two new species, C. bauri and C. longicollis of the genus Coelurus. Later in 1887 Cope reassigned the material to a yet another genus, Tanystrophaeus. Two years later, Cope corrected his classification after realizing differences in the vertebrae, and named Coelophysis, with C. bauri as the type species,[20] which was named for Georg Baur, a comparative anatomist whose ideas were similar to Cope's.[21][22] The name Coelophysis comes from the Greek words κοῖλος/koilos (meaning 'hollow') and φύσις/physis (meaning 'form'), thus "hollow form" which is a reference to its hollow vertebrae.[20][23] However, these first finds were too poorly preserved to give a complete picture of this new dinosaur. In 1947, a substantial 'graveyard' of Coelophysis fossils was found by George Whitaker, the assistant of Edwin H. Colbert, in New Mexico, at the Ghost Ranch, close to the original find. American Museum of Natural History paleontologist Edwin H. Colbert conducted a comprehensive study[15] of all the fossils found up to that date and assigned them to Coelophysis. The Ghost Ranch specimens were so numerous, including many well-preserved and fully articulated specimens, that one of them has since become the diagnostic, or type specimen, for the entire genus, replacing the original, poorly preserved specimen.[24]

"Syntarsus" rhodesiensis was first described by Raath (1969) and assigned to Podokesauridae.[25] The taxon "Podokesauridae", was abandoned since its type specimen was destroyed in a fire and can no longer be compared to new finds. Over the years paleontologists assigned this genus to Ceratosauridae (Welles, 1984), Procompsognathidae (Parrish and Carpenter, 1986) and Ceratosauria (Gauthier, 1986). In 2004 "Syntarsus" was found synonymous with Coelophysis by Tykoski and Rowe (2004). Ezcurra and Novas (2007) and Ezcurra (2007) also concluded that "Syntarsus" was synonymous with Coelophysis, which is the current scientific consensus.[26]

Classification

Coelophysis cast
Cast of the neotype specimen AMNH FR 7224, Redpath Museum
Theropoda
Herrerasauridae

Staurikosaurus

Herrerasaurus

Chindesaurus

Eoraptor

Daemonosaurus

Tawa

Neotheropoda
Coelophysidae

Megapnosaurus

Coelophysis

Liliensternus

Zupaysaurus

Cryolophosaurus

Dilophosaurus

Jurassic theropods

Theropod cladogram based on the phylogenetic analysis conducted by Sues et al., 2011.[27]

Coelophysis is a distinct taxonomic unit (genus), composed of two species; C. bauri and C. rhodesiensis (the latter formerly classified as the genus Megapnosaurus).[1] Two additional originally described species, C. longicollis and C. willistoni, are now considered synonymous with C. bauri. C. rhodesiensis is probably part of this generic complex, and is known from the Jurassic of southern Africa.[1] A third possible species is Coelophysis kayentakatae, previously referred to the genus Megapnosaurus.[28][29] There is not a clear consensus at this point.

In the early 1990s, there was debate over the diagnostic characteristics of the first specimens collected, compared to the material excavated at the Ghost Ranch Coelophysis quarry. Some paleontologists were of the opinion that the original specimens were not diagnostic beyond themselves and, therefore, that the name C. bauri could not be applied to any additional specimens. They therefore applied a different name, Rioarribasaurus, to the Ghost Ranch quarry specimens.[30]

Since the numerous well-preserved Ghost Ranch specimens were used as Coelophysis in most of the scientific literature, the use of Rioarribasaurus would have been very inconvenient for researchers, so a petition was given to have the type specimen of Coelophysis transferred from the poorly preserved original specimen to one of the well-preserved Ghost Ranch specimens. This would make Rioarribasaurus a definite synonym of Coelophysis, specifically a junior objective synonym.[19] In the end, the International Commission on Zoological Nomenclature (ICZN) voted to make one of the Ghost Ranch samples the actual type specimen for Coelophysis and dispose of the name Rioarribasaurus altogether (declaring it a nomen rejectum, or "rejected name"), thus resolving the confusion. The name Coelophysis therefore became a nomen conservandum ("conserved name").[24]

In a situation affecting many dinosaur taxa, some more recently discovered fossils were originally classified as new genera but may be species of Coelophysis. For example, Prof. Mignon Talbot's 1911 discovery[31] which she named Podokesaurus holyokensis, has long been considered to be related to Coelophysis,[32] and some modern scientists consider Podokesaurus a synonym of Coelophysis.[1] Another specimen from the Portland Formation of the Hartford Basin, now at the Boston Museum of Science, has also been referred to Coelophysis.[33][34] This specimen consists of sandstone casts of a pubis, tibia, three ribs, and a possible vertebra, and probably originated in a quarry in Middletown, Connecticut. However, both the type specimen of Podokesaurus and the Middletown specimen are typically considered indeterminate theropods today.[35]

Coelophysis rhodesiensis
Profile of the head of Coelophysis rhodesiensis

Sullivan & Lucas (1999) referred one specimen from Cope's original material of Coelophysis (AMNH 2706) to what they thought was a newly discovered theropod, Eucoelophysis.[36] However, subsequent studies have shown that Eucoelophysis was misidentified, and is actually a primitive, non-dinosaurian ornithodiran closely related to Silesaurus.[37]

The genus Syntarsus was named by Raath in 1969 for the type species Syntarsus rhodesiensis from Africa, and later applied to the North American Syntarsus kayentakatae.[25] It was renamed by American entomologist Dr. Michael Ivie (Montana State University of Bozeman), Polish Australian Dr. Adam Ślipiński, and Polish Dr. Piotr Węgrzynowicz (Muzeum Ewolucji Instytutu Zoologii PAN of Warsaw), the three scientists who discovered that the genus name Syntarsus was already taken by a colydiine beetle described in 1869.[38] Many paleontologists did not like the naming of Megapnosaurus, partially because taxonomists are generally expected to allow original authors of a name to correct any mistakes in their work. Raath was aware of the homonymy between the dinosaur Syntarsus and beetle Syntarsus, but the group who published Megapnosaurus were led to believe Raath was deceased and therefore unable to correct his mistake, and proceeded accordingly. Mortimer (2012) pointed out that "Paleontologists might have reacted more positively if the replacement name (Megapnosaurus) hadn't been facetious, translating to "big dead lizard".[39] Yates (2005) analyzed Coelophysis and Megapnosaurus and concluded that the two genera are almost identical, and suggested that Megapnosaurus was possibly synonymous with Coelophysis.[40] In 2004, Raath co-authored two papers in which he argued that Megapnosaurus (formerly Syntarsus) was a junior synonym of Coelophysis.[1] Megapnosaurus was regarded by Paul (1988) and Downs (2000) as being congeneric with Coelophysis.[9][18] Then in 1993, Paul suggested that Coelophysis should be placed in Megapnosaurus (then known as Syntarsus) to get around the above-mentioned taxonomic confusion.[41] Downs (2000) examined Camposaurus and concluded that it was a junior synonym of Coelophysis, because of its similarity to some of the Coelophysis Ghost Ranch specimens.[18] However, a reassessment of the Camposaurus holotype by Martin Ezcurra and Stephen Brusatte published in 2011 revealed a pair of autapomorphies in the holotype, indicating that C. arizonensis was not a synonym of C. bauri, although it was a close relative of C. rhodesensis.[42]

Paleobiology

Feeding

Coelophysis with crocodylomorph bones AMNH
Bones in a skeleton of C. bauri at the American Museum of Natural History, now interpreted as those of a crocodylomorph

The teeth of Coelophysis were typical of predatory dinosaurs, blade-like, recurved, sharp and jagged with fine serrations on both the anterior and posterior edges. Its dentition shows that it was carnivorous, probably preying on the small, lizard-like animals that were discovered with it.[43] It may also have hunted in packs to tackle larger prey.[9]Coelophysis bauri has approximately 26 teeth on the maxillary bone of the upper jaw and 27 teeth on the dentary bone of the lower jaw.[15] Carpenter (2002) examined the bio-mechanics of theropods forelimbs and attempted to evaluate their usefulness in predation. He concluded that the forelimb of Coelophysis was flexible and had a good range of motion, but its bone structure suggested that it was comparatively weak. The "weak" forelimbs and small teeth in this genus, suggested that Coelophysis preyed upon animals that were substantially smaller than itself. Rinehart et al. agreed that Coelophysis was a "hunter of small, fast-moving prey".[10] Carpenter also identified three distinct models of theropod forelimb use and noted that Coelophysis was a "combination grasper-clutcher" as compared to other dinosaurs that were "clutchers" or "long armed graspers".[44]

Coelophysis skeletons
Two C. bauri casts mounted at the Denver Museum of Nature and Science

It has been suggested that C. bauri was a cannibal, based on supposed juvenile specimens found "within" the abdominal cavities of some Ghost Ranch specimens.[23] However, Robert J. Gay showed in 2002 that these specimens were misinterpreted. Several specimens of "juvenile coelophysids" were actually small crurotarsan reptiles such as Hesperosuchus.[45] Gay's position was lent support in a 2006 study by Nesbitt et al.[46] In 2009, new evidence of cannibalism came to light when additional preparation of previously excavated matrix revealed regurgitate material in and around the mouth of Coelophysis specimen NMMNH P-44551. This material included tooth and jaw bone fragments that Rinehart et al. considered "morphologically identical" to a juvenile Coelophysis.[10]

In 2010, Gay examined the bones of juveniles found within the thoracic cavity of AMNH 7224, and calculated that the total volume of these bones was 17 times greater than the maximum estimated stomach volume of the Coelophysis specimen. Gay observed that the total volume would be even greater when considering that there would have been flesh on these bones. This analysis also noted the absence of tooth marks on the bones as would be expected in defleshing, and the absence of expected pitting by stomach acids. Finally, Gay demonstrated that the alleged cannibalized juvenile bones were deposited stratigraphically below the larger animal that had supposedly cannibalized them. Taken together these data suggested that the Coelophysis specimen AMNH 7224 was not a cannibal and that the bones of the juvenile and adult specimens were found in their final position as a result of "coincidental superposition of different sized individuals.[47]

Pack behavior

Coelophysis block
Specimen block, New Mexico Museum

The discovery of over 1000 specimens of Coelophysis at the Whitaker quarry at Ghost Ranch, has suggested gregarious behavior to researchers like Schwartz and Gillette.[48] There is a tendency to see this massive congregation of animals as evidence for huge packs of Coelophysis roaming the land.[23] No direct evidence for flocking exists; the deposits only indicate that large numbers of Coelophysis, along with other Triassic animals, were buried together. Some of the evidence from the taphonomy of the site indicates that these animals may have been gathered together to feed or drink from a depleted water hole or to feed on a spawning run of fish, and then became buried in a catastrophic flash flood[23][48] or a drought.[23]

CMNH Coelophysis Block
The Cleveland Museum of Natural History's Coelophysis block, originally American Museum of Natural History block XII collected by Colbert in 1948.[10]

With 30 specimens of C. rhodesiensis found together in Zimbabwe some palaeontologists have suggested that Coelophysis was indeed gregarious. Again there is no direct evidence of flocking in this case and it has also been suggested that these individuals were also victims of flash flooding as it appears to have been commonplace during this period.[25][49][50]

Growth and sexual dimorphism

Rinehart (2009) assessed the ontogenic growth of this genus using data gathered from the length of its upper leg bone (femur) and concluded that Coelophysis juveniles grew rapidly, especially during the first year of life.[10] Coelophysis likely reached sexual maturity between the second and third year of life and reached its full size, just above 10 feet in length, by its eighth year. This study identified four distinct growth stages: 1-year, 2-year, 4-year, and 7+ year.[10] It was also thought, that as soon as they were hatched, they would have to fend for themselves.[23]

Two "morphs" of Coelophysis have been identified: a more gracile form, as in specimen AMNH 7223, and a slightly more robust form, as in specimens AMNH 7224 and NMMNH P-42200. Skeletal proportions were different between these two forms;[51] the gracile form has a longer skull, a longer neck, shorter forelimbs, and has sacral neural spines that are fused; and the robust form has a shorter skull, a shorter neck, longer forelimbs, and unfused sacral neural spines.[15] Historically, many arguments have been made that this represents some sort of dimorphism in the population of Coelophysis, probably sexual dimorphism.[9][15][52][53] Raath agreed that dimorphism in Coelophysis is evidenced by the size and structure of the forelimb.[52] Rinehart et al. studied 15 individuals, and agreed that two morphs were present, even in juvenile specimens, and suggested that sexual dimorphism was present early in life, prior to sexual maturity. Rinehart concluded that the gracile form was female and the robust form was male based on differences in the sacral vertebrae of the gracile form, which allowed for greater flexibility for egg laying.[10] Further support for this position was provided by an analysis showing that each morph comprised 50% of the population, as would be expected in a 50/50 sex ratio.[54]

However, more recent research has found that C. bauri and C. rhodesiensis had highly variable growth between individuals, with some specimens being larger in their immature phase than smaller adults were when completely mature; this indicates that the supposed presence of distinct morphs is simply the result of individual variation. This highly variable growth was likely ancestral to dinosaurs but later lost, and may have given such early dinosaurs an evolutionary advantage in surviving harsh environmental challenges.[55]

Reproduction

Through the compilation and analysis of a database of nearly three dozen birds and reptiles, and comparison with existing data about the anatomy of Coelophysis Rinehart et al. (2009) drew the following conclusions. It was estimated that average egg of Coelophysis was 31–33.5 millimeters across its minor diameter, and that each female would lay between 24–26 eggs in each clutch. The evidence suggested that some parental care was necessary to nurture the relatively small hatchlings during the first year of life, where they would reach 1.5 meters in length by the end of their first growth stage. Coelophysis bauri invested as much energy in reproduction as other extinct reptiles of its approximate size.[10][56]

Paleopathology

In a 2001 study conducted by Bruce Rothschild and other paleontologists, 14-foot bones referred to Coelophysis were examined for signs of stress fracture, but none were found.[57]

In C. rhodesiensis, healed fractures of the tibia and metatarsus have been observed, but are very rare. "[T]he supporting butresses of the second sacral rib" in one specimen of Syntarsus rhodesiensis showed signs of fluctuating asymmetry. Fluctuating asymmetry results from developmental disturbances and is more common in populations under stress and can therefore be informative about the quality of conditions a dinosaur lived under.[58]

Paleoecology

Coelophysis Jeff Martz
Restoration showing hypothetical wattle and feathers.

Distribution

Specimens of Coelophysis have been recovered from the Chinle Formation of New Mexico and Arizona, more famously at the Ghost Ranch (Whitaker) quarry in the Rock Point member[10] among other quarries in the underlaying Petrified Forest member, the sediments of which have been dated to approximately 212 million years ago, making them part of the middle Norian stage of the Late Triassic.[59][23]

C. rhodesiensis has been recovered in the Upper Elliott Formation in the Cape and Free State provinces of South Africa as well as the Chitake River bonebed quarry at the Forest Sandstone Formation in Zimbabwe.

Fauna and habitat

Ghost Ranch was located close to the equator over 200 million years ago, and had a warm, monsoon-like climate with heavy seasonal precipitation. Hayden Quarry, a new excavation site at Ghost Ranch, New Mexico, has yielded a diverse collection of fossil material that included the first evidence of dinosaurs and less-advanced dinosauromorphs from the same time period. The discovery indicates that the two groups lived together during the early Triassic period 235 million years ago.[60]

Therrien and Fastovsky (2001) examined the paleoenvironment of Coelophysis and other early theropods from Petrified Forest National Park in Arizona, and determined that this genus lived in an environment that consisted of floodplains marked by distinct dry and wet seasons. There was a great deal of competition during drier times when animals struggled for water in riverbeds that were drying up.[61]

In the upper sections of the Chinle Formation where Coelophysis is found, dinosaurs were rare, so far only Chindesaurus and Daemonosaurus[62] are known, the terrestrial fauna being dominated instead by other reptiles like the rhynchocephalian Whitakersaurus;[63] the pseudosuchian Revueltosaurus;[64] the aetosaurs Desmatosuchus,[64] Typothorax[64] and Heliocanthus;[64] the crocodilomorph Hesperosuchus;[64] the "rauisuchians" Shuvosaurus,[64] Effigia[65] and Vivaron;[66] along other rare components like the dinosauriform Eucoelophysis,[67] and the amniote Kraterokheirodon.[64] In the waterways we find the phytosaur Machaeroprosopus;[64] the archosauromorph Vancleavea;[64] the amphibians Apachesaurus[64] and Koskinonodon;[68] and the fishes Reticulodus,[64] Arganodus[64] and Lasalichthyes.[64]

The Upper Elliot Formation is thought to have been an ancient floodplain. Fossils of the prosauropod dinosaur Massospondylus and Ignavusaurus have been recovered from the Upper Elliot Formation, which boasts the world's most diverse fauna of early Jurassic ornithischian dinosaurs, including Abrictosaurus, Fabrosaurus, Heterodontosaurus, and Lesothosaurus, among others. The Forest Sandstone Formation was the paleoenvironment of protosuchid crocodiles, sphenodonts, the dinosaur Massospondylus and indeterminate remains of a prosauropod. Paul (1988) noted that Megapnosaurus rhodesiensis lived among desert dunes and oases and hunted juvenile and adult prosauropods.[69]

Taphonomy

The multitude of specimens deposited so closely together at Ghost Ranch was probably the result of a flash flood, which swept away a large number of Coelophysis and buried them quickly and simultaneously. In fact, it seems that such flooding was commonplace during this period of the Earth's history and, indeed, the Petrified Forest of nearby Arizona is the result of a preserved log jam of tree trunks that were caught in one such flood. Whitaker quarry at Ghost Ranch is considered a monotaxic site because it features multiple individuals of a single taxon. The quality of preservation and the ontogenic (age) range of the specimens helped make Coelophysis one of the best known of all genera.[70] In 2009, Rinehart et al. noted that in one case the Coelophysis specimens were "washed into a topographic low containing a small pond, where they probably drowned and were buried by a sheet flood event from a nearby river."[10]

The 30 specimens of C. rhodesiensis found together in Zimbabwe was also probably the result of a flash flood, which swept away a large number of Coelophysis and buried them quickly and simultaneously as well.[25][49][50]

Ichnology

Edwin H. Colbert has suggested that the theropod footprints referred to the ichnogenus Grallator, located in the Connecticut River Valley across Connecticut and Massachusetts, may have been made by Coelophysis.[71] The footprints are from the Late Triassic to Early Jurassic aged Newark Supergroup. They clearly show digits II III and IV but not I or V. That condition is strange for footprints of their age. The digits were presumed to be stubby and ineffective, not touching the ground when the dinosaur was walking or running. They have been thought to be from an unidentified, primitive saurischian similar to Coelophysis by David B. Weishampel and L. Young more recently.[72] Skeletal remains resembling Coelophysis have also been found in the valley, supporting the idea that a species similar to Coelophysis is responsible for the footprints.[73]

Dinosaur footprints that were later attributed to C. rhodesiensis were discovered in Rhodesia in 1915. These tracks were discovered at the Nyamandhlovu Sandstones Formation, in eolian red sandstone that was deposited in the Late Triassic, approximately 235 to 201 million years ago.[74]

In popular culture

Coelophysis was the second dinosaur in space, following Maiasaura (STS-51-F).[75] A Coelophysis skull from the Carnegie Museum of Natural History was aboard the Space Shuttle Endeavour mission STS-89 when it left the atmosphere on 22 January 1998. It was also taken onto the space station Mir before being returned to Earth.[75][76]

As being over 100 years old, Coelophysis is one of the best-known dinosaurs in literature. It was designated as the official state fossil of New Mexico in 1981, and is now the logo of the New Mexico Museum of Natural History.[19][77]

References

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External links

Camposaurus

Camposaurus ( KAMP-o-SOR-əs) is a coelophysoid dinosaur genus from the Norian stage of the Late Triassic period of North America. The pertinent fossil remains date back to the early to middle Norian stage, and is widely regarded as the oldest known neotheropod.

Coelophysidae

Coelophysidae is 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, and has been found on numerous continents. Many members of Coelophysidae are characterized by long, slender skulls and light skeletons built for speed. One member, Coelophysis, displays the earliest known furcula in a dinosaur.Under cladistic analysis, Coelophysidae was first defined by Paul Sereno in 1998 as the most recent common ancestor of Coelophysis bauri and Procompsognathus triassicus, and all of that common ancestor's descendants. However, Tykoski (2005) has advocated for the definition to change to include the additional taxa of "Syntarsus" kayentakatae and Segisaurus halli. Coelophysidae is part of the superfamily Coelophysoidea, which in turn is a subset of the larger Neotheropoda clade. As part of Coelophysoidea, Coelophysidae is often placed as sister to the Dilophosauridae family, however, the monophyly of this clade has often been disputed. The older term "Podokesauridae", named 14 years prior to Coelophysidae (which would normally grant it priority), is now usually ignored, since its type specimen was destroyed in a fire and can no longer be compared to new finds.

Coelophysis kayentakatae

Coelophysis kayentakatae is an extinct species of coelophysid dinosaur that lived approximately 196 million years ago during the early part of the Jurassic Period in what is now the southwestern United States. Originally included in the genus Syntarsus, it has been reclassified as Coelophysis along with the African species, Coelophysis rhodesiensis.The name C. kayentakatae refers to the Kayenta Formation, where all known fossil specimens have been found.

Coelophysis rhodesiensis

Coelophysis rhodesiensis is an extinct species of coelophysid theropod dinosaur that lived approximately 188 million years ago during the early part of the Jurassic Period in what is now Africa. The species was a small to medium-sized, lightly built, ground-dwelling, bipedal carnivore, that could grow up to 3 m (9.8 ft) long. It was formerly called Syntarsus, but that name was already taken by a beetle, and was subsequently given the name Megapnosaurus by Ivie, Ślipiński & Węgrzynowicz, in 2001, though many subsequent studies have classified it in the genus Coelophysis.

Coelophysoidea

Coelophysoidea were common dinosaurs of the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a superficial similarity to the coelurosaurs, with which they were formerly classified, and some species had delicate cranial crests. Sizes range from about 1 to 6 m in length. It is unknown what kind of external covering coelophysoids had, and various artists have portrayed them as either scaly or feathered. Some species may have lived in packs, as inferred from sites where numerous individuals have been found together.

Examples of coelophysoids include Coelophysis, Procompsognathus and Liliensternus. Most dinosaurs formerly referred to as being in the dubious taxon "Podokesauridae" are now classified as coelophysoids.

Daemonosaurus

Daemonosaurus (pron.:"DAY-mow-no-SORE-us") is an extinct genus of theropod dinosaur from the Late Triassic of New Mexico. Fossils have been found from deposits in the Chinle Formation, which is latest Triassic in age. While theropods had diversified into several specialized groups by this time, Daemonosaurus is a basal theropod that lies outside the clade Neotheropoda. Daemonosaurus is unusual among early theropods in that it had a short skull and long protruding teeth.

Gojirasaurus

Gojirasaurus (meaning "Godzilla Lizard") is a dubious genus of coelophysoid theropod dinosaur named after the giant monster movie character Gojira (the Japanese name for the monster Godzilla).

Hesperosuchus

Hesperosuchus is an extinct genus of crocodylomorph reptile that contains a single species, Hesperosuchus agilis. Remains of this pseudosuchian have been found in Late Triassic (Carnian) strata from Arizona and New Mexico. Because of similarities in skull and neck anatomy and the presence of hollow bones Hesperosuchus was formerly thought to be an ancestor of later carnosaurian dinosaurs, but based on more recent findings and research it is now known to be more closely related to crocodilians rather than dinosaurs.

Lepidus praecisio

Lepidus is a genus of extinct coelophysoidean theropod from the Upper Triassic of the United States. It lived in the Otis Chalk localities of the Dockum Group in Texas, around 223 million years ago.

Neotheropoda

Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.

Paleontology in New Mexico

Paleontology in New Mexico refers to paleontological research occurring within or conducted by people from the U.S. state of New Mexico. The fossil record of New Mexico is exceptionally complete and spans almost the entire stratigraphic column. More than 3,300 different kinds of fossil organisms have been found in the state. Of these more than 700 of these were new to science and more than 100 of those were type species for new genera. During the early Paleozoic, southern and western New Mexico were submerged by a warm shallow sea that would come to be home to creatures including brachiopods, bryozoans, cartilaginous fishes, corals, graptolites, nautiloids, placoderms, and trilobites. During the Ordovician the state was home to algal reefs up to 300 feet high. During the Carboniferous, a richly vegetated island chain emerged from the local sea. Coral reefs formed in the state's seas while terrestrial regions of the state dried and were home to sand dunes. Local wildlife included Edaphosaurus, Ophiacodon, and Sphenacodon.

Triassic New Mexico had a seasonal climate and was home to a richly vegetated flood plain where early dinosaurs such as Coelophysis lived. During the Jurassic New Mexico had a relatively dry climate and was home to dinosaurs such as Allosaurus, Stegosaurus, and the huge long-necked sauropods. Seawater covered eastern New Mexico during the Cretaceous, while on land dinosaurs, including tyrannosaurs, maintained their dominance. Early in the Cenozoic New Mexico was swampy, but gradually the local climate cooled. Local wildlife included creatures such as amblypods, carnivorans, condylarths, the 7-foot tall flightless bird Diatryma, three-toed horses, marsupials, multituberculates, and taeniodonts. Cooler climates eventually ushered in the Ice Age, when the state was home to mastodons.

Local Native Americans devised myths to explain local fossil bones and petrified wood. New Mexico's fossils first came to the attention of formally trained scientists by the mid-19th century. Major finds in the state include Coryphodon, a mummy of the ground sloth Nothrotherium, Triassic Coelophysis bonebeds, bonebeds of Triassic amphibians and the gigantic sauropod formerly known as Seismosaurus. The Triassic dinosaur Coelophysis bauri is the New Mexico state fossil.

Panguraptor

Panguraptor ("Pangu [a Chinese god] plunderer") is a genus of coelophysid theropod dinosaur known from fossils discovered in Lower Jurassic rocks of southern China. The type and only known species is Panguraptor lufengensis. The generic name refers to the deity Pangu but also to the supercontinent Pangaea for which in a geological context the same characters are used: 盘古. Raptor means "seizer", "robber" in Latin. The specific name is a reference to the Lufeng Formation.The holotype specimen was recovered on 12 October 2007 from the Lufeng Formation of Yunnan, which is noted for sauropodomorph fossils. It was described in 2014 by You Hai-Lu and colleagues.

Podokesaurus

Podokesaurus ("swift-footed lizard") was a small carnivorous dinosaur that lived during the Pliensbachian–Toarcian stages of the Early Jurassic Period, and as such is one of the earliest known dinosaurs to inhabit the eastern United States.

Postosuchus

Postosuchus, meaning "Crocodile from Post", is an extinct genus of rauisuchid reptiles comprising two species, P. kirkpatricki and P. alisonae, that lived in what is now North America during the Late Triassic. Postosuchus is a member of the clade Pseudosuchia, the lineage of archosaurs that includes modern crocodilians (the other main group of archosaurs is Avemetatarsalia, the lineage that includes non-avian dinosaurs and their descendants, birds). Its name refers to Post Quarry, a place in Texas where many fossils of the type species, P. kirkpatricki, were found. It was one of the apex predators of its area during the Triassic, larger than the small dinosaur predators of its time (such as Coelophysis). It was a hunter which probably preyed on dicynodonts and many other creatures smaller than itself.

The skeleton of Postosuchus is large and robust with a deep skull and a long tail. The total body length is about 4 to 5 metres (13 to 16 ft). The extreme shortness of the forelimbs relative to the hind limbs, the very small hands, and measurements of the vertebrae suggest that Postosuchus may have been committed to bipedal locomotion.

Segisaurus

Segisaurus (meaning "Segi canyon lizard") is a genus of small coelophysoid theropod dinosaur, that measured approximately 1 metre (3.3 feet) in length. The only known specimen was discovered in early Jurassic strata in Tsegi Canyon, Arizona, for which it was named. Segisaurus is the only dinosaur to have ever been excavated from the area.

Tawa hallae

Tawa (named after the Hopi word for the Puebloan sun god) is a genus of theropod dinosaur from the Late Triassic period. The fossil remains of Tawa hallae, the type and only species were found in the Hayden Quarry of Ghost Ranch, New Mexico, US. Its discovery alongside the relatives of Coelophysis and Herrerasaurus supports the hypothesis that the earliest dinosaurs arose in Gondwana during the early Late Triassic period in what is now South America, and radiated from there around the globe. The specific name honours Ruth Hall, founder of the Ghost Ranch Museum of Paleontology.

Timeline of coelophysoid research

This timeline of coelophysoid research is a chronological listing of events in the history of paleontology focused on the coelophysoids, a group of primitive theropod dinosaurs that were among Earth's dominant predators during the Late Triassic and Early Jurassic epochs. Although formally trained scientists didn't discover coelophysoid fossils until the late 19th century, Native Americans of the modern southwestern United States may have already encountered their fossils. Navajo creation mythology describes the early Earth as being inhabited by a variety of different kinds of monsters who hunted humans for food. These monsters were killed by storms and the heroic Monster Slayers, leaving behind their bones. As these tales were told in New Mexico not far from bonebeds of Coelophysis, this dinosaur's remains may have been among the fossil remains that inspired the story.The first scientifically documented coelophysoid taxon was Coelophysis bauri itself. However, when the species was first described by Edward Drinker Cope in 1887, it was thought to belong to a genus of small carnivorous dinosaurs called Coelurus. Later that same year Cope changed his mind and transferred it to the genus Tanystropheus. Tanystropheus turned out to be a long-necked reptile not regarded by scientists as a true dinosaur. As such, "Tanystrophaeus" bauri was soon given its own genus, Coelophysis in 1889. Over the ensuing decades, many new coelophysoids would be discovered, like Podokesaurus, Procompsognathus, and Segisaurus.In 1947, a paleontological team led by Edwin Colbert made a major discovery in New Mexico. While on an expedition to Petrified Forest National Park in Arizona, he made a detour to Ghost Ranch, New Mexico where many phytosaur fossils had been found. There they discovered a massive bonebed preserving hundreds of Coelophysis, many of which were complete and articulated. The find has been considered the most significant Triassic fossil discovery in North America. Later, other coelophysoids and even other bonebeds would be discovered. Notable coelophysoids discovered during the mid to late 20th century include Syntarsus (now Megapnosaurus) and Gojirasaurus. Despite this extensive history of research, the formal recognition of the Coelophysoidea as a distinct group of dinosaurs is relatively recent and the group would not be formally named until a 1994 by Thomas Holtz.

Walking with Dinosaurs

Walking with Dinosaurs is a six-part documentary television miniseries created by Tim Haines and produced by BBC Natural History Unit. The series first aired on the BBC in the United Kingdom in 1999 with narration by Kenneth Branagh. The series was subsequently aired in North America on the Discovery Channel in 2000, with Avery Brooks replacing Branagh. The programme explores ancient life of the Mesozoic Era, portraying dinosaurs and their contemporaries in the style of a traditional nature documentary.

Developed by Haines and producer Jasper James, Walking with Dinosaurs recreated extinct species through the combined use of computer-generated imagery and animatronics that were incorporated with live action footage shot at various locations. The Guinness Book of World Records reported that the series was the most expensive documentary series per minute ever produced. A re-edited version of Walking with Dinosaurs aired on Discovery Kids for the first season of Prehistoric Planet. It was made more appropriate for children by removing most of the graphic content and trimming down some footage to fit the run time.

The series received critical acclaim, winning two BAFTA Awards, three Emmy Awards and a Peabody Award in 2000. Walking with Dinosaurs began a franchise that was followed by two additional miniseries, several television specials, spin-offs, a live-theatrical show, and a feature film of the same name.

When Dinosaurs Roamed America

When Dinosaurs Roamed America (shortened to When Dinosaurs Roamed outside of the U.S.) is a two-hour American television program (produced in the style of a traditional nature documentary) that first aired on the Discovery Channel on July 15, 2001. The show features the reign of the dinosaurs in America over the course of more than 160 million years, through five different segments, each with their own variety of flora and fauna. Unlike Walking with Dinosaurs, the show's creatures are almost entirely composed of computer-generated imagery, and is also one of the first documentaries to depict dromaeosaurs and therizinosaurs with nearly full coats of feathers.

When Dinosaurs Roamed America premiered to 5 million viewers and was released on VHS and DVD a few months after its initial airing. Dinosaur Planet, which aired in December 2003, followed the success of the 2001 program using the same cast, crew, and techniques as its predecessor.

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