The Coelophysoidea represent the earliest theropod radiation, flourishing during the late Triassic and early Jurassic. These graceful animals were characterised by a long, low body, a long neck, and short three-fingered hands for clutching prey. The long fairly lightly built skull (left) bears a distinctive kink between the premaxilla (upper jaw tip) and maxilla (in main upper jaw). It was thought that this kink meant that coelophysids could not attack live prey due to skull weakness, but it appears to have been reinforced. Gregory Paul argued that Spinosaurid Megalosaurs like Baryonyx, which also have such a kink, were be late coelophysoids, but this is now not considered the case.
Coelophysoids probably died out during the Toarcian turnover, perhaps due to the extinction of the prosauropod dinosaurs (their main food source perhaps) at the same time. It is possible that some stragglers (e.g., Elaphrosaurus) continued on to the late Jurassic. It can be assumed that the Coelophysoidea were the ancestors of all later theropod dinosaurs.
Together with Ceratosauridae and the Abelisauroidae, the Coelophysoidea are included in the taxa Ceratosauria, ( strict definition here), generally considered a monophyletic clade (no descendents). It is I feel more likely that earlier and unspecialised Coelophysoids gave rise to more advanced theropods, which would then have lost their original ceratosaurian characteristics. It is not even certain that the three component groups of Ceratosaurs even belong together.
The following is a very tentative and speculative cladogram, which differs a little from other cladograms for this group (mainly in speculating on links to later taxa):
<<-o COELOPHYSIODEA [?=Podokesauroidea] `--o Procompsognathidae |-+- Procompsognathus triassicus | `-- Segisaurus halli |--- CERATOSAURIODEA | ?--Elaphrosaurus bambergi | ??- ABELISAURIA `+-o-Coelophysidae [= Podokesauridae] `--o Dilophosaurinae [= Halticosaurinae] |--+ Gojirasaurus quayi | |- Dilophosaurus wetherilli | `?-+- Dilophosaurus sinensis | `?- MEGALOSAURIA | ?-- Liliensternus airelensis `--+-? Liliensternus orbitoangulatus `-+- Liliensternus liliensterni `-o Coelophysinae `-+?- Eucoelophysis baldwini |-?- Coelophysis holyokensis [=Podokesaurus] |-- Coelophysis bauri `--+--Syntarsus rhodesiensis `-- Syntarsus kayentakatae
The Procompsognathids and Segisaurids, previously considered seperate families, are now sometimes included under the Coelophysidae. These are both small lightly built forms, not unlike Coelophysis. Very little is known of the procompsognathids. There are currently two species, each based on a single poorly preserved partial postcranial skeleton.
Procompsognathus triassicus Fraas, 1913Horizon: Middle Keuper of Württemberg, Germany
Comments: Procompsognathus possess relatively broad pubes (hip-bones), a primitive feature that distinguishes it from all other Theropods. The previously associated skull does not to belong with the type specimen (the postcrania), although it is possible it belongs to this species. It is low and elongate, about 8 cm long, and appears to lack the distinctiove kink. In all other respects it resembles Coelophysis. The teeth are relatively large.
Segisaurus halli Camp, 1936Horizon: Navajo Sandstone of Arizona
Comments: Previously placed in its own family, the Segisauridae, this is a small, very slender animal. Unusual for the fact that some of its limb bones are not hollow, like all other small theropods, but solid. I wonder whether this might not be an artifact of preservation, or a pathological specimen, not hollow. Also, for a long time it was unusual for being one of the few theropods for which a good clavicle was known. Its hip bones have unusual holes and flattening. According to Gregory Paul, it also possesses some advanced features.
These early theropod dinosaurs are generally divided into two groups, the smaller Coelophysines and the larger Dilophosaurines (also called Halticosaurines). Althiough it would logically seem that the small Coelophysines evolved from the big Dilophosaurines, in fact the Dilophosaurs are more primitive, and a recent revision of Triassic stratigraphy by S. G. Lucas Coelophysis bauri to be late Norian or Rhaetic (latest Triassic) in age, rather than late Carnian as origionally believed. The implication then is that the Dilophosaurs appeared first, and after some fifteen million years or so gave rise to the smaller Coelophysines. In any case, both lineages existed alongside each other for some 20 million years or more. Both were graceful, active predators, both lineages continued for several tens of millions of years, indicating that these animals were very successful in their environment. Coelophysids show a tendency for head ornamentation in the form of crests, almost certainly for intraspecific display
The Dilophosaurs, or Haltcosaurs, include some of the earliest theropod dinosaurs. They were also the first of the great dinosaurian carnivores. These were large graceful bipedal preditors with lengths of upto 6 to 7 metres. Evolving, one would assume, from a small Procompsognathid ancestor, these animals very quickly attained an optimal size. Even the earliest forms, such as Liliensternus liliensterni and Gojirasaurus quayi equalled in size later and more specialised types like the early Jurassic Dilophosaurus wetherilli; all attaining estimated adult weights of 300 to 500 kg. Dilophosaurus is also distinctive for having some of the largest teeth relative to head size of all theropods. These clearly succesful animal sontinued with little change for some 40 million years
Gojirasaurus quayi Carpenter, 1997Horizon: Dockum formation of New Mexico
Comments: One of the largest and also one of the earliest theropods of the Triassic, Gojirasaurus has the honour of being named after the Japanese movie monster Godzilla (Gojira)..
Dilophosaurus wetherilli (Welles, 1954)Megalosaurus wetherilli Welles, 1954
Comments: The dominant preditor of the early Jurassic, this animal is distinguished by its large low build, unusually long teeth, and distinctive twin crests (left). Apart from its distinctive head-crest, Dilophosaurus is one of the most unspecialsed of the Coelophysids. The fact that this animal lived much later than otehr more advanced types shows that there were actually a number of coelophysid lines evolving in parallel over many millions of years.
This handsome animal has had the misfortune of being represented in the movie Jurassic Park as a sort of cross between a gremlin and a frill-necked lizard. Not only is the size in the movie version wrong (too small), but the lower jaw is the wrong shape as well. The fallacy that the delicate head crests and "weak" snout (actually now known to be reinforced) only capable of made it unable to tackle live prey may also have led to the most unkely assumption (which first appears in Michael Chrichton's novel) that it spat poison (no archosaur is known to). D. breedorum Welles vide Welles and Pickering, 1999 is probably a synonym. It has been suggested on basis of an imprint of a similarly-sized theropod sitting down that these animals may have been feathered.
Dilophosaurus sinensis Hu, 1993Horizon: Lower Lufeng Series - Yunnan, China
Comments: same size as D. wetherilli but with taller, more robust crest. The skull is somewhat similar to that of Ceratosaurus. Recently, the placement of the species in this genus has been questioned. It has been proposed that it is actually a primitive relative of the Allosauria. Its crests are farther forward on the skull, and its scapula is expanded. It may well be that this species represents a transitional form between Dilophosaurs and higher theropods
Liliensternus liliensterni (von Huene, 1934)synonym: Halticosaurus liliensterni Huene 1934
Comments: intermediate between the Coelophysines and Dilophosaurus in anatomy; both known specimens are juveniles, so adults may have attained about 7 meters.
Liliensternus airelensis Curry & Galton, 1993Horizon: Rhaetian of France
Comments: originally just "Halticosaurus sp."
?Liliensternus orbitoangulatus (von Huene, 1932)synonym: Halticosaurus orbitoangulatus Huene, 1932
Comments: This poorly known animal would seem to be an earlier version of Dilophosaurus, with a smaller crest. It is not clear if it belongs in teh genus Liliensternus (or even if it really is a coelophysid)
Sinosaurus triassica Young 1948Horizon: Dull Purplish Beds, Lower Lufeng Series of Yunnan, China
Comments: The jaws and postcrania previously included under the taxon "Sinosaurus triassica" are now known to come from two totally different animals; the jaws and teeth (Sinosaurus triassica proper) from a large carnivore; either a Rauisuchian [Galton] (which would then make these beds Rhaetian in age) or a large theropod, probably a Dilophosaurid [Bakker, Sci Am], while the post-crania are from a large prosauropod dinosaur.
The Coelophysines probably evolved from early Dilophosaurs. They were an important component of latest Triassic and early Jurassic vertebrate faunas. The best known early type is Coelophysis bauri (see above sketch), a small (about the size of an average dog) and very graceful creature known from the late Triassic Chinle formation of Arizona. Remains of a very similar form are known from early Jurassic rocks in South Africa. Since at this time all the land-masses were joined into a single supercontinent, Pangea, it is likely that the Coelophysids had a world-wide distribution over many millions of years.
The better known Coelophysines consist of several closely related species, with very little to separate them. As far as the build and proportions of the skeleton go they are very is to those of the late Jurassic Compsognathus and proto-bird Archaeopteryx. In life these creatures probably had a very bird-like appearance (it is not known whether or not they had feathers, although an impression left by a Dilophosaurus-sized theropod may indicate belly feathers). These animals may have hunted in packs, like modern jackals.
Coelophysines are sometimes found in groups ranging from a couple to hundreds of individuals. This relative abundance of specimens makes it possible for two types to be distinguished; robust or gracile. These most likely correspond to sexual differences. Robust forms have relatively longer necks and skulls, thicker limbs, and more developed muscle attachments.
Coelophysis bauri(Cope, 1887)synonyms: Coelurus bauri Cope 1887; Coelophysis bauri Cope, 1889c; Rioarribasaurus colberti, Camposaurus arizonensis Hunt, Lucas, Heckert, and Lockely, 1998
Comments: This was a pretty typical early unspecialised Coelophysine. It may have evolved from an animal like Liliensternus. It is best known from the hundreds of specimens from the Ghost Ranch quarry in New Mexico. It is believed that this animal practiced cannibalism (not uncommon among crocodilians), because some Ghost Ranch skeletons have juvenile-sized skeletons in the area of their stomachs. Eucoelophysis baldwini Sullivan and Lucas, 1999, based on a rediscription of Cope's original type specimen of "Coelurus" bauri (= Coelophysis bauri) appears to be a distinct, if closley related, species.
Syntarsus rhodesiensis Raath, 1969Horizon: Upper Elliot Formation, Cape Province, South Africa; and Forest Sandstone of Matabeleland, Zimbabwe,
Comments: A descendent of the Triassic Coelophysis, this active little hunter shows a number of more advanced features, such as a much larger "window" (the antorbital fenestra) in the front side of the snout, possibly for housing a gland of some kind, and teeth that are entirely forward of the eye. There is also the fusion of some of the upper foot-bones (metatarsals), a bird-like characteristic that would increase the strength of the leg. Gregory Paul suggests (Predatory Dinosaurs of the World) that this species should be included under Coelophysis, but in view of its more advanced characteristics it should perhaps be reatined a sa seperate genus
The behaviour appears to be the same as Coelophysis, for the remains of large numbers of this species, in various ages, are found concentrated together in a single small quarry area [Paul, p.262]. Like present-day birds, Syntarsus seems to have lived in large groups or flocks of individuals.
"Syntarsus" kayentakatae Rowe, 1989Horizon: Kayenta Formation, Arizona
Comments: This species possesses two small crests, similar to those of it's larger cousin Dilophosaurus. Some have suggetse dthat because of this this species represents a new genus.
Coelophysis holyokensis Talbot, 1911
synonym: Podokesaurus holyokensis
Horizon: Unnamed unit (= ?Portland Formation), Massachusetts
Age: late? Pliensbachian or Toarcian
Place: north-west Pangea
Remains: incomplete skeleton lacking skull
Length: about 1 meter
Comments: Known only from a single, poorly-preserved skeleton, the original fossil of which was destroyed in a fire some years ago, it is not known whether this small theropod belongs to either Coelophysis or a closley related genus. It differs from C. bauri in possessing less elongate neural spines and a differnt shaped ischia. Clearly, this was one of a number of small bipedal carnivores that were around at the time. In older books this dinosaur is called "Podokesaurus".
Elaphrosaurus bambergi Janensch, 1920Horizon: Tendaguru beds of Tanzania
Comments: Elaphrosaurus may or may not be a late surviving coelophysoid. In build it is one of the slenderest and longest (in proprtion to height) of the theropods. It has been variously considered a typical "coelurosaur" (in the old non-cladistic sense), a coelophysid, and an ancestral ornithomimid. The last-named option, which for a while was the standard position, is now considered more unlikely in view of the difference in hip structure. In the absense of a skull, more cannot be determined. I am going along with Greg Paul and considering ita coelophysid.
Elaphrosaurus philtippetorum Pickering, 1995Horizon: Morrison Formation of Colorado
Comments: isolated remains indicate contemporary French and North American species which may tentatively be assigned to Elaphrosaurus
|some Links and References|
Dilophosaurus - A Narrated Exhibition - a guided tour of Dilophosaurus - narrated by the discoverer of Dilophosaurus, Sam Welles, formerly a professor at the University of California Museum of Paleontology (UCMP). Dr Welles has also done important work in the study of the giant Cretaceous Elasmosaurid plesiosaurs
Ceratosauria - Palaeos
Great Triassic Assemblages Pt 1 - The Chinle and Newark by Professor Paul Eric Olsen - part of DINOSAURS AND THE HISTORY OF LIFE - GEOLOGY V1001x
Neotheropoda - includes coverage of the Coelophysoidea - Thescelosaurus!
Coelophysoidea - Dinosauricon
Ceratosauria Mikko's phylogeny site
Jurassic Gallery - fantastic artwork by M. Shiraishi. By Japanese and English
Dilophosaurus - ArtistCandi Marshall
Gregory S. Paul, Predatory Dinosaurs of the World Simon and Schuster, 1988
Rodney Steele, "Saurischia", Part 14, Encyclopedia of Paleoherpetology, Gutsav Fischer Verlag, Stuttgart and New York, 1970
Rowe, T., & Gauthier, J., "Ceratosauria", pp. 151-168, in Weishampel, D. B., Dodson, P., & Osmólska, H. (eds.), The Dinosauria University of California Press, Berkley, Los Angeles, Oxford, 1990
Lucas, S.G., 1998. Global Triassic tetrapod biostratigraphy and biochronology: Palaeogeogr. Palaeoclimat. Palaeoecol., 143: 345-382
cautionary note (please read before using this page as reference material!)
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