At one time Theropods were classified according to size (Carnosauria for big ones, Coelurosauria for little ones. With the exclusion of Tyrannosauridae (now considered a giant Coelurosaur lineage), only the Allosaurids and their relatives make up the Carnosauria. The name "Allosauria" was coined by Greg Paul in his superb book Predatory Dinosaurs of the World and seems to have caught on, although "Carnosauria" is still sometimes used. I would consider Allosauroidea a superfamily that evolved from the equally formidable Megalosauroidea, both being members of the Carnosauria (I am aware this evolutionary systematic approach differs from the now traditional cladistic position). In any case, these were big to enormous bipedal terrestrial preditors, that for some one hundred million years or so were the dominant form of life on land.
Generally, the Allosauria - or rather, its subgroup, the Allosauroidea - is considered a monophyletic clade divided into three similiarily mmonophyletic families: the Sinraptoridae, the Allosauridae, and the Carcharodontosauridae. Greg Paul considers the small late Jurassic Ornitholestes and the earlier and larger Proceratosaurus to be also Allosaurs. Other dinosaurologists tend to classify Ornitholestes as a basal (i.e. primitive/ancestral) coelurosaur. I wonder whether both options may not be correct, and that perhaps Ornitholestes is a non-missing link between the two groups, with only the cladistic insistence on pigeonholing everything into precise monophyletic clades obscuring the fact. (This is not to say that Ornitholestes itself is the link, but rather an animal much like Ornitholestes, and living same ten or twenty million years earlier).
All Allosaurs were pretty similar in overall form, representing a very sucessful evolutionary lineage and formidable top preditor. All have a large head decorated with small hornlets or ridges in front of the eyes (these were clearly for intraspecific display purposes, most certainly brightly-coloured in life), three fingered hands (the famous Tyrannosaurids can be distinguished by the fact they only have two fingers), the fore-arms relatively long and strong (again in contrast to the Cretaceous Tyrannosaurids and the Abelisaurids), clearly adapted for holding the food (there is a beautiful painting (see above) by Charles Knight of a feeding Allosaurus). The total animnal could be (depending on the species) anywhere from four 5 to 14 meters in length, and upto several tons in weight (the big Carcharodontasaurs exceeded (although only marginally) even Tyrannosaurus in size).
These are the most primitive allosaurs, although even at this early stage they were equipped with elaborate crests. There are a number of theropods that probably belong here, but many are poorly known, and only a few are officially included in the family. This group may even consist of two (or more?) families. Most Sinraptorids are known from China, but that is more likely because Chinese dinosaur fossils are the best representatives of the middle Jurassic, rather than the group itself being limited to that region. However, it is still possible that Eastern China was cut off from the rest of Laurasia, as a distinctive fauna (Shunosaurine sauropods, Beinotheroides tritylodontids, and brachyopoid labyrinthodonts, seem to be indiginous to that region.
Representative genera include Becklespinax, Marshosaurus, Monolophosaurus, Sinraptor, Yangchuanosaurus, and possibly Metriacanthosaurus, Cryolophosaurus, Gasosaurus, Siamotyrannus, and Lourinhanosaurus.
Cryolophosaurus ellioti Hammer and Hickerson, 1994Horizon: Falla Formation of Antartica
Comments: As the name implies, Cryolophosaurus is a crested theropod from a cold land. This in fact is misleading, because during the early Jurassic Antarctica was part of the vast and warm (if not tropical, then certainly very temperate) landmass of Gondwana. This animal was found in association with prosauropods. It is probably too primitive to go under the Sinraptoridae proper, but could perhaps be considered a proto-sinraptorid. This advanced (for its time) animal was a contemporary of the big Dilophosaurs, but is more heavily built and provably had different feeding strategies.
Gasosaurus constructus Dong Tang, 1985synonyms: ?Kaijiangosaurus lini He, 1984
Comments: a poorly known, medium-sized theropod, it appears to be closer to Piatnitzkysaurus than Eustreptospondylus, and so is included among the Sinraptoridae. It has features characteristic of an ancestral coelurosaurian or ancestral avetheropod (common ancestor of the coelurosaurians and allosaurs.)
Monolophosaurus jiangi Zhao and Currie, 1995synonyms: "Jiangjunmiaosaurus"
Comments: This animal is characterised by what seems to be a single ridge-like head crest running from its nose to the rear of the skull. This feature is not found in any other theropod, so either this is a very distinctive form or it is simply an artifact of preservation.
Sinraptor dongi: Currie and Zhao, 1993Horizon: Wucaiwan Formation of Junggar Basin, Xinjiang, China
Comments: A typical large theropod. It's cranial ornamentation is rather modest. Size info here is for S. hepingensis Gao, 1992, a related species
Yangchuanosaurus shangyouensis Dong, Chang, Li and Zhou, 1978
Comments: The largest carnivore of its time, this three and a half tonne preditor dominated its enviroment. The cranial ornamentation involves dual ridges above the snout and eyes. It also has a low fin fin, down its back, again, possibly for display purposes. Greg Paul considers this species similiar enough to go under Metriacanthosaurus
Szechuanosaurus campi Yang, 1942bHorizon: Shangshaximiao Formation of Sichuan, China
Comments: The type is based on some shed teeth which cannot be diagnosed to species or genus. Later, a partial skeleton was found and referred to this taxon. The name "Szechuanosaurus campi" will eventually be discarded (as it refers to the teeth) and the skeleton redescribed and given a new name. This animal is smaller and more slender than Yangchuanosaurus and lacks the "fin" on the back. If this represents an adult form it was a medium-sized preditor, filling the ecological niche between the giant Yangchuanosaurus and small theropods
Metriacanthosaurus parkeri Walker, 1964Megalosaurus parkeri Huene, 1926a
Comments: Rather similar to Yangchuanosaurus and other Sinraptorids, and living at more or less the same time. The fact that it is known from Europe shows that these animals had a wide distribution. The presence of fin-like ridge along back (as indicated by the tall-spined vertebrae) meant that for a long time this animal was considered an ancestral spinosaurian.
Piatnitzkysaurus floresi Bonaparte, 1979bHorizon: Cerro Condor Formation of Argentina
Comments: a moderately sized but fairly advanced theropod for its time, Piatnitzkysaurus is generally considered a primitive allosaur. Greg Paul points out the interesting fact that this Jurassic South American animal is more advanced than the South American Abelisaurs that lived later, in the Cretaceous period.
Marshosaurus bicentesimus Madsen, 1976bHorizon: Morrison formation of Utah and ?Colorado
Comments: This is a poorly known animal of uncertain relationships, it may be a primitive allosaur, or alternatively a megalosaur. It is intermediate in both size and evolutionary development between the contemporary small but advanced coelurosaurs and large but primitive ceratosaurs, but also the same size as the earlier Gasosaurus and Piatnitzkysaurus. The pelvis alone contains features reminiscent of coelophysoids, coelurids, sinraptorids, and allosaurids. The forearms seem to have been quite short (a megalosaurid feature).
Lourinhanosaurus antunesi Mateus, 1998Horizon: (formation not specified), Lourinha, Portugal
Becklespinax altispinax (Paul,1988)synonyms: Altispinax dunkeri, Acrocanthosaurus altispinax Paul,1988, Becklespinax altispinax Olshevsky, 1991
Comments: the tall-spined vertebrae resemble those of Acrocanthosaurus, but this poorly known carnivore is now classed among the Sinraptoridae. It may have resembled a smaller version of Yangchuanosaurus, a much earlier animal that likewise had a low fin along the back.
The nomenclature of this species is rather convoluted. Becklespinax is based on the high-spined vertebrae that were at one time combined with a Megalosaur tooth species to produce Altispinax dunkeri, which was placed in the family Spinosauridae (on the basis of the vertebrae), being assumed to be a more primitive species in which the vertebrae had not yet extended into a "sail". It was then found that the teeth could not confidently be assigned to the same animal as the postcrania, which were reassigned to a new species of Acrocanthosaurus, another high-spined theropod. The species was thus called Acrocanthosaurus altispinax. But further study showed it could not confidently be placed with the genus Acrocanthosaurus either. So it was placed in a new genus and is now known as Becklespinax altispinax.
If this is a Sinraptorid it is one of the last of its kind
?Siamotyrannus isanensis Buffetaut, Suteethorn, and Tong, 1996Horizon: (formation not specified) - Isan region of Thailand
The Allosaurids evolved from Sinraptorids, and replaced them as the top carnivores of the Kimmeridgian and Tithonian ages (latest Jurassic period). The two groups are pretty similiar in size and appearance, and differ in only minor technical details. Representatives of this family include Allosaurus, Neovenator, Valdoraptor, Acrocanthosaurus (although this genus is sometimes considered a Carcharodontosaurid), and probably Wakinosaurus and the poorly known Mongolian form "Chilantaisaurus maortuensis"
Allosaurus fragilis Marsh, 1877bsynonyms: Antrodemus fragilis (Marsh)
Comments: the type species of Allosaurus. Antrodemus is a name for Allosaurus in old books on dinosaurs. It is possible that the remains assigned to A. fragilis don't all pertain to one species. I have however followed Gregory Paul in distinguishing this second species. A. fragilis is much rarer than A. atrox (making it unlikely the differences are due to sexual dimorphism), has taller, more pointed horns just above the eyes, and seems to have a more slender build, especially in the neck and forelimbs. According to Robert Bakker it also occurs in earlier strata (the Garden Park and other quarries of the lower Morrison formation), so it may be an ancestor of A. atrox. Portuguese material has also been assigned to A. fragilis, but it may also pertain to a different but closely related species (perhaps - in view of the time range, A. atrox)
Allosaurus atrox (Marsh, 1878)Creosaurus atrox Marsh, 1878a, "Poekilopleuron" valens Leidy, 1870, Antrodemus valens (Leidy)
Comments: Usually considered a synonym of A. fragilis, A. atrox has been suggested by Bob Bakker and Gregory Paul as a second valid species, but its status remains unclear. A specimen from the the late Kimmeridgian-early Tithonian of Portugal may also belong here, or it may be a closley related species or subspecies. This was a common animal and seems to have replaced the earleir A.fragilis, being somewhat later in time. The Cleveland-Lloyd quarry contains the disarticulated remains of over sixty individuals; peresumably this was a preditor trap, like the pleistocene La Brear tar pits. There is still controversy over whether this is one or two species.
Allosaurus maximus (Chure, 1995)Saurophaganax maximus Chure, 1995, Epanterias amplexus Cope, 1878b, Allosaurus amplexus (Cope)
Comments: These Tyrannosaurus-sized giants were the last and largest of the Morrison Allosaurs. The climate was growing more arid, and the animals, interestingly, were becoming bigger (perhaps to be able to manage the long journeys between water holes). Unfortuantely little is known about them because they are only known from fragmentary remains. This giant allosaur preyed on the enormopus sauropods with which it shared its environment
"Allosaurus" tendagurensis Janensch, 1925Horizon: Tendaguru of Tanzania
Comments: Known only from a single limb bone, this animal is too fragmentary to be classified with certainty. But it is most likely that it is an Allosaurid.
Allosaurus sp.Horizon: of Australia
Comments: the distinctive ankle bone shows that this animal is actually an allosaur. (Yes, it is (in some instances) possible to identify an animal from a single bone!) This dwarf polar species survived for millions of years after allosaurs elsewhere had become extinct. It may have been an island-dweller
Acrocanthosaurus atokensis Stovall and Langston, 1950Horizon: Trinity Formation and Antlers Formation of Oklahoma, Paluxy River Formation and Twin Mountains Formation of Texas, Middle Cedar Mountain Formation of Utah, and related strata of Arizona and Maryland (not known from the Cloverly)
Comments: A huge preditor, filling the same ecological role in the north as the Charcharodontosaurs did in the south, Acrocanthosaurus is distinguished by tall vertebral spines giving it a metricanthosaur-like appearance. The ?Sinraptorid Becklespinax has a similar but taller fin. This animal, or one very much like it, made some of the famous Paluxy River dinosaur tracks in Texas, including a sequence where an individual appears to pursue a large brachiosaurid (probably Pleurocoelus), which also left its geeat basin-sized prints in the mud. (silly trivia note: creationists argue that some of the Pleurocoelus fore-foot prints are actually "man tracks" made by giant humans). This indicates that this Tyrannosaurid-sized carnivore was not afraid to take on even the biggest sauropods in its environment. It has been suggested that this animal was a charcharodontosaurid, although another option may be taht it represents a form transitional between te etwo families. This was the last-known large Allosaur. These beasts dissapear at the end of the mid Cretaceous, perhaps victims of the Cenomanian mass-extinction. The Tyrannosaurids take their place in the north. In the south, Chachrodontasaurs are replaced by Abelisaurs.
Neovenator salerii Hutt, Martill, and Barker, 1996
Comments: usually considered an Allosaurid, there is some evidence to suggest this large animal may be a carcharodontosaurid. It has a very distinctive puffin-like snout.
Carcharodontosaurids are Allosaurid descendents that flourished in Gondwanaland (but not, strangely enough, in the north). They include the largest ever land carnivores, even exceeding Tyrannosaurus rex in size (although not by much). The skull of carcharodontosaurids is long and narrow; unlkike the Tyrannosaurs, these animals did not posess binocular vision. This group includes Bahariasaurus, Carcharodontosaurus, Giganotosaurus, and possibly Acrocanthosaurus (although this form is generally considered an Allosaurid). They show some unusual convergences with the abelisaurids, another group of Gondwana theropods. As yet it is not clear whether this means the abelisaurs, despite their many very primitive features, are actually allosaurs, or whether the two lineages had to evolve in similiar ways to similiar unique environmental conditions
Bahariasaurus ingens Stromer, 1934Horizon: Baharije Formation of Egypt, ?Niger
Comments: A huge but poorly known form. . Some material once assigned to this species has since been referred to Deltadromeus
Carcharodontosaurus saharicus Stromer, 1931Megalosaurus saharicus Deperet and Savornin, 1927, Chacharodontosaurus saharicus (Deperet & Savornin, 1927), Megalosaurus africanus Huene, 1956,
Comments: As the name indicates, this animal was originally based on some shark-like teeth. Later, better material has been discovered, including, recently, a very large, nearly complete skull
Giganotosaurus carolinii Coria and Salgado, 1995Horizon: Rio Limay Formation, Neuquen, Argentina
Comments: With Carcharodontosaurus, this is the largest known land carnivore; longer and heavier than the famous Tyrannosaurus rex. It probably preyed on the huge titanosaurid sauropods with which it shared its envoronment
These are smallish theropods of uncertain relationships. Greg Paul, who named the family, considers them allosaurs (he even made them a subfamily of the Allosauridae). Others have called Ornitholestes a basal maniraptoran, or basal coelurosaur. It is not even certain if this is a natural group. If they are a proper lineage, then they may well constitute transitional forms between allosaurs and coelurosaurs. But they may equally be simply small allosaurs, only distantly related to the coelurosaurs. All the animals included in this group had similarly-designed skulls, and an unusual difference in teeth size - the teeth in the front of the skull differ from those behind them by being smaller and more conical in shape (usually reptilian - including dinosaurian - teeth are equal in size and shape throughout the entire jaw). It is also possible that they all shared a nasal ridge (this is known with certainty only from Proceratosaurus, but seems present in Ornitholestes as well). This would have been most certainly brightly coloured in life, and served for sexual and intra-specific display
Proceratosaurus bradleyi Huene, 1926aMegalosaurus bradleyi Woodward, 1910
Comments: The nasal horn (partially preserved) led to the idea that this animal was an ancestor of Ceratosaurus. In fact, it is a much more advanced form, and the skull is very similiar to that of Ornitholestes. This is one of the earliest if not the earliest coelurosaurs.
Ornitholestes hermanni Osborn, 1903Horizon: Morrison Formation of Wyoming
Comments: This small theropod as been confused with its contemporary Coelurus, but is only distantly related. The head is unusually small in proportion to the body, and the limbs are quite short as well. The tail however is very long. Probably this animal lived in the undergrowth, hunting small vertebrates and keeping out of the way of larger carnivores
Nedcolbertia justinhofmanni Kirkland, Britt, Whittle, Madsen, and Burge, 1998Horizon: Yellow Cat Member, Cedar Mountain Formation, of Utah
Comments: Appears similar to Ornitholestes, but lived many millions of years later in time, indicating that this was a long-lived lineage. The generic name honors the vertebrate paleontologist Edwin Colbert (I greatly enjoyed reading his books on dinosaurs and paleontology when I was a kid)
Santanaraptor placidus Kellner, 1999Horizon: Romualdo Member, Santana Formation of Brazil
Comments: a rather primitive coelurosaur, possibly an Ornitholestid. If it does belong to this family it is the last known representative of the group.
cautionary note (please read before using this page as reference material!)
|Books, DVDs and Web Links|
Lectures 17 and 18 The Real Jurassic Park - Morrison and Tendaguru Formations - by Professor Paul Eric Olsen, part of DINOSAURS AND THE HISTORY OF LIFE - GEOLOGY V1001x Best of the Web
Neocoelurosauria - cladogram, and short but useful description of every species - from Thescelosaurus!
Carnosauria by T. Mike Keesey - short essay, cladogram, and list of every known genus
Robert L. Carroll. Vertebrate Paleontology and Evolution
Molnar, R. E., Kurzanov, S. M., & Dong, Z., 1990: Carnosauria. in Weishampel, D. B., Dodson, P., & Osmólska, H. (eds.), 1990: The Dinosauria, University of California Press, Berkley, Los Angeles, Oxford, pp.169-209
Gregory S. Paul, Predatory Dinosaurs of the World Simon and Schuster, New York, 1988 - okay it's out of print and dated in parts; and needs to be revised in the light of more recent discoveries - I still give it Best Book rating