Prehistoric Life/Dinosaurs/Large Theropods

This section talks about "carnosaurs", but first a word about its meanings. In old sources, this term included all large theropods, from Tyrannosaurus to Allosaurus, from Ceratosaurus to Megalosaurus, to Baryonyx, Spinosaurus, and sometimes even Dilophosaurus. Science Marches On however, and now “carnosaurs” has a much narrower meaning, indicating only the natural lineage including Allosaurus and its closest relatives, which make together the most advanced and bird-like giant theropods after the tyrannosaurs. But this change has happened only at the beginning of the 1990s (ceratosaurs and Dilophosaurus were removed earlier). That’s why pre-Jurassic Park dino-fans still have the habit to call “carnosaurs” all the big meat-eaters in the dino-world - and let’s admit it, “carnosaur” is a very apt name, just meaning meat[-eating] lizards. Thus, to avoid Taxonomic Term Confusion, we’ll use here the term “allosauroids” more often than “carnosaurs” to indicate Allosaurus relatives. ^[1]

The Myth's Twin: Tarbosaurus

• Let’s start our long trip among non-stock dinosaurs with one of the closest relatives of Tyrannosaurus Rex: Tarbosaurus. If you want to describe it, don’t worry, it’s a simple thing: just say it was the Asian twin of T. rex, and you’ve given the idea. To be more accurate, Tarbosaurus was slightly smaller than Tyrannosaurus, but shared the same familiar body-shape, with large head, huge teeth, short neck, tiny forelimbs with only two functional digits, and whatnot. Those forelimbs were even smaller than those of T. rex, sometimes cited as “the smallest arms in the dinosaur world” - even though the “horned” theropod Carnotaurus had even more reduced arms, as did the weird alvarezsaurids and many flightless birds. Obviously, Tarbosaurus shows up in books and documentaries as the king of the predators in its habitat, Late Cretaceous Asia, just like T. rex in North America. In fact, these two dinosaurs are so similar that some scientists have suggested that Tarbosaurus is another species of the genus Tyrannosaurus, but new studies seem to disagree. Tarbosaurus has been first discovered in 1955 in Mongolia, more precisely in the Gobi Desert. Mongolia, a sparsely populated Asian country bordered by Russia and China, has always had a major role in the brief history of paleontology: despite being much smaller than China, Canada or the USA, it has given us the same number of fossils of the latter, almost all from Late Cretaceous. Among them, most of the classic Asian dinosaurs: from the famed Protoceratops/Velociraptor battle to the first Mesozoic dinosaur eggs ever discovered, from Oviraptor to the huge forelimbs of Deinocheirus, from Gallimimus to the scythe-claws of Therizinosaurus. And Tarbosaurus as well. Interesting that the succession of geological periods (Cretaceous-Jurassic-Triassic) of the Mesozoic era, have also a distribution in latitude which is amazingly specular in Asia and in North America. In both continents, the Cretaceous terrains are those in the northern part of the range (Alberta, Canada/Montana, USA, and Mongolia/Inner Mongolia/Northern China); the Triassic terrains are the most southern (Arizona/New Mexico, USA, and the province of Yunnan, southern China); while the Jurassic one were in the middle (Utah/Colorado/Wyoming, and the province of Szechuan, central China). Also note that most North American dinosaurs have been discovered in western USA and western Canada (not in the coastal region however, but only in the Mountains and Plains); while the Asian dinosaurs are concentrated in only two countries, Mongolia and China, both in the Far East. Some of the most astonishing recent discoveries about dinosaurs just come from China, especially the northern province of Liaoning (see “Birdlike theropods”).

Smaller Tyrants: Albertosaurus, Gorgosaurus, and Daspletosaurus

• Albertosaurus is the most abundant tyrannosaur in fossil record, and also the second big-sized theropod by wealth of fossil material, just after the unbeatable Allosaurus. And yet, Albertosaurus has not gained much attention in films and comics as Tyrannosaurus - tyrannosaurids are so similar to each other that if one appears in cinema, people will always call it T. rex. To compensate, Albertosaurus is a very common sight in many paleo-books, just as common as several Stock Theropods. Naturally, it is portrayed as the superpredator of its time, North America 80-75 million years ago, 10 million years before T. rex. The menu of an Albertosaurus was probably not monotonous; several kinds of herbivores roamed North American plains at the time, from ceratopsians to hadrosaurs, from the armored ankylosaurs to small swift "hypsilophodonts" and ornithomimids. Even though tyrannosaurids are classically shown battling some powerful prey, they more probably hunted young individuals more often, to avoid the risk of fatal injuries or consequent infections. Compared with the mythical Tyrannosaurus Rex, Albertosaurus was like a leopard compared with a lion; smaller (25 ft long against the 40 ft of T. rex), it was also more slender, with longer, thinner jaws, smaller teeth, and more agile legs apt to faster runs than Tyrannosaurus. Even the herbivores which shared their world were conformed to these predators; those which lived alongside T. rex were bigger, slower and more powerful than those living with Albertosaurus. Albertosaurus was also the first dinosaur ever discovered in Canada, at the end of the XIX century, but was named only in 1905 (incidentally, the same year of Tyrannosaurus) after the Canadian province of Alberta, where most of the abundant Canadian dinos have been discovered. Albertosaurus has also contributed indirectly to the popular image of tyrannosaurs. The forelimbs of Albertosaurus have been known since its very first find, while those of T. rex were first discovered only in the 1990s; for almost a century the well-known two-fingered hands of "rex" have been modeled upon those of Albertosaurus, debunking at the time the old pop-cultural Hand Wave about portraying three-fingered tyrannosaurs. ^[2] Discovered in 1914, Gorgosaurus is another North American tyrannosaurid which was long considered a distinct genus compared to Albertosaurus. Then, in the 1970s, Canadian paleontologist Dale Russell found the two animals so similar they had to been put under a single name: since the first created name always has priority, so was Albertosaurus. Only in recent years, scientists changed idea again separating "Gorgosaurus" from "Albertosaurus" ^[3]. There has also been a curious sequence in pop-portraits: Gorgosaurus has long been the most depicted non-"rex" tyrannosaur in classic paleo-art and old books; but its long-lasting synonimization with Albertosaurus has definitively harmed its relevance, and today Albertosaurus is the new prototypical “small” North-American tyrannosaur. Also note that the name Gorgosaurus recalls that of an old Godzilla-like movie-monster; it’s an incidental thing, or not? In the 1970s, a third North American tyrannosaur was recognized as distinct: Daspletosaurus. The same size of the other two and living in the same epoch, Daspletosaurus was actually more similar to T. rex than to Albertosaurus in anatomy, and was probably the direct ancestor of Tyrannosaurus. Many scientists think the more agile Albertosaurus/Gorgosaurus specialized on relatively easier preys such as hadrosaurs, young ceratopsians, troodonts or ornithomimids, while the more powerfully-built Daspletosaurus hunted “armored” herbivores like adult ceratopsians and ankylosaurs, and possibly Albertosaurus and Gorgosaurus themselves!

Not exactly T. rexes: Dryptosaurus, Eotyrannus, and Yutyrannus

• Not all tyrannosauroids were tyrannosaurids, remember this. Basal tyrannosauroids were often very different animals: smaller, more slender, with three fingered hands. Not exactly T. rexes… only their skull structure was analogue to the tyrannosaurids. The most long-standing basal tyrannosauroid is Dryptosaurus, the first theropod discovered in North America from not-only-teeth, in 1866, before the Bone Wars. Because of its apparently untyrannosauroidian nature and scant remains, Dryptosaurus was long considered a hard-to-classify theropod. After the discover of the close relative Appalachiosaurus (guess where this one has been discovered), Dryptosaurus is firmly put in the tyrannosauroid realm. However, it was more slender than tyrannosaurids, and we don’t know if it had two- or three-fingered hands (they have never been found). Dryptosaurus has also the distinction to be one of the few dinosaurs discovered in eastern USA, contrary to the quasi-totality of North American dinosaurs. But the main distinction of Dryptosaurus is to be the first dinosaur ever depicted by the famous paleo-artist Charles Knight (when the dinosaur was still called “Laelaps”), with two individuals fighting each other. Other small-sized tyrannosauroids are classified as tyrannosaurids, but many are (or could be) simple juveniles of other well-known tyrannosaurids: for example, Nanotyrannus (“dwarf tyrant”). It is indeed the smallest tyrannosaurid ever discovered in North America, merely 18 ft long. Living alongside the much bigger cousin T. rex, its only remain (a fragmentary skull) could have been actually based on a juvenile of what very likely is Tyrannosaurus rex. Another alleged North American small tyrannosaur described as early as the 1860s, "Aublysodon", is known mainly from teeth, and it too may be just represent juveniles from known tyrannosaurids. Small tyrannosauroids are also known from Asia: Alioramus was once thought the juvenile of Tarbosaurus, but has revealed a truly small tyrannosaurid with a crested, untyrannosaurian skull. Another, Alectrosaurus, is more probably a basal tyrannosauroid like Dryptosaurus. The New Mexican Bistahieversor was once considered a southern species of Daspletosaurus, but probably lies just outside Tyrannosauridae proper. All these dinosaurs were Late Cretaceous, either Asian or North-American, but some basal tyrannosauroids have been found elsewhere: Eotyrannus “dawn tyrant” lived in Early Cretaceous Europe along with Iguanodon. Known since 2001, its find in England made sensation both because of its earliness, and because was small (10 ft long, even though it too could be a juvenile), similar to a large “coelurosaur” with a tyrannosaur-like head, and long, three-fingered forelimbs. Eotyrannus has definitively shown that tyrannosaurs were more related to birds than to the other “carnosaurs” in traditional sense. In 2012, a new tyrannosauroid was described: the 30-foot long, feathered Yutyrannus (appropriately "feathered tyrant") from the Early Cretaceous of China, which suggested that even large true tyrannosaurids were feathered. However, it may be an allosauroid instead (which, if true, would be even more revolutionary, as no definitely feathered members of the group are known). Other basal tyrannosauroids or possible basal tyrannosauroids have been discovered in Northern continents: some of them are listed in the “small/birdlike theropods” sections.

Missed Moment of Glory: Carcharodontosaurus and Deltadromeus

• In 1995, an unexpected find deeply shook the paleontological world as well as the dino-fandom. The obscure-at-the-time Carcharodontosaurus has revealed not to be a smallish, unclassifiable theropod as always thought. It was a much more Badass animal, whose name “great white shark lizard” has revealed stunningly apt. A predatory dinosaur even bigger than T. rex! Obviously, popular media ballyhooed the discover a lot… totally forgetting that some other giant theropods were already T. rex contestants for the “biggest” title much before 1995! Spinosaurus makes the most striking example, but there is also the obscure “Epanterias” (maybe just an overgrown Allosaurus); not to mention Deinocheirus and Therizinosaurus (see “Bird-like theropods”). But the glory of Carcharodontosaurus didn’t last a long time; merely one year later, it was surpassed by the just-discovered, almost-identical, only a bit bigger, and now stock, Giganotosaurus. Our “white shark dino” was a quite unlucky dinosaur, really. However, in the 2000s, Spinosaurus has done justice to "Carcharo", taking in turn the popularity of Giganotosaurus out thanks to Jurassic Park 3. The awesome thing is, in Real Life Carcharodontosaurus and Spinosaurus, living together in Cretaceous Africa where today is Sahara, maybe contended with each other the “top-predator” niche; while Carcharodontosaurus was better-weaponed with huge jaws, Spinosaurus was more enormous-bodied and could have been even twice its weight. They can be considered the “tiger” and the “grizzly bear” of their time respectively, and it’s not a thing to exclude that Spinosaurus sometimes chased away Carcharodontosaurus from their kills like modern bears do with big cats when they live side-by-side. Another less-impressive but still formidable carnivore was found alongside Carcharodontosaurus one year later: Deltadromeus. Around 30 ft long, nearly as big as an Allosaurus, Deltadromeus had long, unusually slender hind limbs for its size. This suggests it was one of the fastest-running giant theropods, and a predator as efficient as its bigger but clumsier neighbors Spinosaurus and Carcharodontosaurus. Its name just means “delta runner” - a reference to the Nile's delta.

Pack hunters, or what?: Mapusaurus, Tyrannotitan, and Concavenator

• As a consolation prize, our Carcharodontosaurus has been chosen as the official namesake of its own family, a recently-identified group of gigantic Cretaceous allosauroids which were also the most evolved carnosaurs: carcharodontosaurids. Other than Carcharodontosaurus and Giganotosaurus, they include other animals discovered in the 2000s: among these, Mapusaurus. Found only in 2006 in Argentina, it was the closest relative of Giganotosaurus, and may have been its descendant in Real Life. Just as big as “Giga”, Mapusaurus was almost identical to it and to Carcharodontosaurus, with huge skull filled with crests and protuberances, and the usual powerful three-fingered hands of all allosauroids. However, the most interesting thing is that its fossils seem to show proof of gregarious behavior. Even though this doesn’t automatically indicate “pack hunting”, many have now fun to imagine awesome scenarios, with pack of Mapusaurus killing together the immense sauropods of the time like Argentinosaurus. This behaviour was also speculatively attributed to Giganotosaurus in the “Land of Giants” episode of the WWD series… four years before Mapusaurus was discovered! Among other carcharodontosaurids, Tyrannotitan is worthy of note because of its name “titanic tyrant”, the most "rex"-like of all theropods, even though its owner, being an allosauroids, was not so closely related with T. rex. Just few time ago, Europe has gifted us a new member, Concavenator from Early Cretaceous Spain. This one is maybe one of the greatest dino-discoveries of the year 2010. It not only had a small “hump” on its hips made by elongated neural spines; its arms also show possible attachment points for filament-like structures. This would mean: Concavenator could be the first non-coelurosaur theropod found with some feathers. Now our imagination can travel further and further, imagining feathered Allosaurus, feathered Spinosaurus… but wait: don’t get too excited. Other researchers have pointed out that these attachment points are more similar to those for muscles in crocodiles than feathers in birds, so this supposed evidence for feathers in Concavenator may not be valid at all.

Sailbacks. Or maybe not: Acrocanthosaurus, Metriacanthosaurus, and Becklespinax

• Spinosaurus was not the only theropod with a ridge on its back made by elongated neural spines: there were others as well. Acrocanthosaurus is the most well-known among “these others”. However, its “sail” was very different; only one foot tall, it extended from the neck to the tail-tip, while that of Spinosaurus was far higher but limited to the back. Actually, the sail of Acrocanthosaurus could have been buried in flesh in the living animal, making it looking even bigger when seen from the side, just like what could have been for Spinosaurus. Furthermore, Acrocanthosaurus was not a spinosaur relative at all (even though was classified such in the past just because of its sail): actually was an allosauroid, usually classified as being between Giganotosaurus and Allosaurus phylogenetically – maybe closer to the giganotosaur. Acrocanthosaurus lived in Early Cretaceous North America, rather between Allosaurus and Tyrannosaurus in the time scale. Apart from the “sail”, it was similar to a robust Allosaurus in shape, and with its 12 m long body was as big as Tyrannosaurus Rex. One could even say Acrocanthosaurus combined the best powers of the four most popular giant theropods. The size of "rex", the overall robustness of “Giga”, the powerful three-clawed forelimbs of “Allo”, and a crested back like “Spino”. And yet, have you sometimes seen this dinosaur outside dino-books (apart from the pseudo-docu Monsters Resurrected)? Things get even worse if you think Acrocanthosaurus has been known since the 1940s from rather complete remains, was the top-predator of Early Cretaceous North America, and shared the same habitat with another famous (but much smaller) “killer dinosaur”, Deinonychus. However, Bob Bakker’s scientific novel Raptor Red does justice to Acrocanthosaurus, portraying it as the great predator of the world in which Utahraptor are the main characters. Other two less-known “sailbacks” of smaller size and with a even less-evident crest were Becklespinax (once called “Altispinax”) and Metriacanthosaurus, both European. Once placed in the “Megalosaurus wastebasket”, both are carnosaurs of uncertain classification. Surprisingly, in spite of being a very obscure dinosaur, “Metriacanthosaurus” long name appears on one of the embryo-containing vials in the first Jurassic Park film, but this detail has passed rather unnoticed.

Allosaurs vs Tyrannosaurs: Epanterias and Saurophaganax

• One of the reasons behind the Poor Man's Substitute role Allosaurus has played in pop-culture is surely its smaller size compared with Tyrannosaurus Rex. But this is true only if you count the most known allosaurian species, Allosaurus fragilis (the second term, ironically, means “fragile”). Another species was bigger, 12 m long, as much as a Tyrannosaurus rex. Once classified Allosaurus maximus (“maximus” just means “the biggest”), it has recently been thought distinct enough to be classified in its own genus, Saurophaganax. Nonetheless, the latter was so similar to the classic Allosaurus, it might well return to the genus Allosaurus again. Still another close kin has been described as a really huge animal, 15 m long, clearly bigger than a T. rex: "Epanterias". The astonishing thing is, "Epanterias" is known to science since as early as year 1878, 25 years before T. rex was discovered! This awesome oversight is due to its extremely scant remains. But the main point is another: "Epanterias" might be another overgrown Allosaurus species as well. If true, then our Allosaurus would deserve to be considered a real rival of T. rex, "Giga", and "Spino" for the “King of Dinosaurs” title.

Imitators, forgers and river gods: Suchomimus, Irritator, and Oxalaia

• No other group of large theropods was as specialized as spinosaurids. Their croc-like heads, their hook-like thumbclaws, and their flat crests on their backs make them immediately recognizable; even though some other theropods had sail-backs or hook-thumbs, no one had the crocodilian-like jaws. However, spinosaurids as a group are recognized only since the 1990s; before, the only-two known members, Spinosaurus and Baryonyx, were believed so different that each was put in its own family. In year 1998, a third spinosaurid was discovered in Early Cretaceous North Africa: Suchomimus, “the imitator of the crocodile”. 11 m long, bigger than Baryonyx but smaller than the unbeatable Spinosaurus, it’s the only dinosaur ending in -mimus that is definitely not a small bird-like coelurosaur. Very similar to Baryonyx (and perhaps a species of the latter), Suchomimus was probably a fishing specialist as well, but was distinct by spotting a noticeable spinal ridge analogue to Spinosaurus, though far shorter. Since its discovery this dinosaur has gained much consideration: as an example, both Suchomimus and Baryonyx are cited in Jurassic Park 3, when the little boy asks Alan Grant about spinosaurids. There is also a debate among dino-fans about the true identity of Rudy (the villain of Ice Age 3), and many think is a Suchomimus; actually he's a Baryonyx, but he’s so modified that correct identification is hard without asking the Word of God. Another less-known spinosaurid has a name which reveals an astounding backstory: Irritator. Scientists are not robots. They too have feelings, and sometimes project them in their dinosaurs’ names. This Brazilian theropod is known only from one skull. Sadly, this skull was badly affected by some fossil-poachers which rebuilt it making it longer than it originally was, even before the animal was named! When was found, scientists had hard time to rebuilt it correctly: when they finished the work, decided to call it Irritator, the “irritating one”. As if it was not enough, Irritator could also be synonymous with Angaturama, another possible spinosaurid genus also discovered in Brazil, even though the two could simply be the same specimen called two times with a different name! Whatever the name, this mistreated skull pertains to a spinosaurid closer to Spinosaurus than to Baryonyx; for obvious reasons, we don’t know if it had a “sail” or not. In year 2011, another spinosaurid was discovered in Brazil from skull remains, Oxalaia: estimated to be 12-14 m in length, is now the second largest known spinosaurid and one of the biggest known theropods, maybe even bigger than a Tyrannosaurus or a Giganotosaurus.

The modern megalosaurs: Eustreptospondylus, Piatnitzkysaurus, and Torvosaurus

• More than twenty-five theropod dinosaurs have once been labeled Megalosaurus at one point. Many have revealed to be totally unrelated animals (Carcharodontosaurus, Dilophosaurus), but others were really cousins of the proper Megalosaurus. The most important is Eustreptospondylus. From Middle Jurassic Europe like Megalosaurus but smaller-sized (being 2 m shorter and more slender), its well-preserved skeleton is actually from a juvenile, and could just be a young specimen of Megalosaurus: if so, “Eustreptospondylus” will become an invalid synonim, while “Megalosaurus” will become a well-known genus. Being today the most well-preserved large Jurassic theropod, Eustreptospondylus was chosen as the go-to dinosaur in the episode of the 1999 docu Walking with Dinosaurs dedicated to marine reptiles… somehow living in the Late instead of the Middle Jurassic. Here our megalosaur is depicted as an inoffensive scavenger which has to hang on its world made by small islands, eating the occasional carrion the sea brings on the shore. But the most remembered scene is at the beginning: a specimen of Eustreptospondylus apparently described as “the most fearsome predator of the Jurassic”… only to be eaten alive by the gigantic… erhm… OVERSIZED marine reptile Liopleurodon. Among other modern megalosaurids, there is one which has received a deceptive name: Piatnitzkysaurus was not discovered in Russia as it seems, but in Argentina. On the other hand, the larger Afrovenator has an apt name, as it lived in Africa. However, the most impressive megalosaurids were found in North-America: Torvosaurus (“grim lizard”) and (maybe the same animal) Edmarka rex (not that rex). Both 10 m long or more, the same size of Allosaurus but more powerfully-built, they shared the same habitat and sometimes took some prey out of it. However, as the fossil record seems to show, these giant megalosaurs didn’t make true rival for allosaurs: they were much, much rarer than the latter, and this leads to speculation that allosaurids were more efficient hunters, and finally replaced definitively megalosaurids.

Claws, Claws Everywhere: Megaraptor, Neovenator, and Aerosteon

• Several theropods have evolved one enormous claw on their hands/feet which vividly contrast with the smaller ones: just think about Baryonyx and Deinonychus, whose names are just references to this condition. But the following one makes the Up to Eleven example: Megaraptor. Discovered in the late 1990s and initially thought to be a large dromaeosaurid (hence its name), this smallish South American Late Cretaceous theropod was variably classified in the past, from a small spinosaurid to a large noasaurid – all families characterized by some sort of oversized claws. Indeed, an one-foot-long claw was the first discovered Megaraptor remain, and was wrongly put on its foot. But then other bones were discovered, and we now know this claw was on its thumb instead. Baryonyx too had enormous thumbclaws the same size of those of Megaraptor; however, since Megaraptor was a much smaller theropod, this means its claw could be the biggest among all dinosaurs in respect to the overall body size. How Megaraptor used those impressive weapons is still a mystery; for obvious reasons, many have fun to imagine incredible massacres of herbivores, including severed throats, disemboweled bellies and whatnot. Since 2009 or so, Megaraptor is classified as an allosauroid, more precisely as a very specialized member of the family Neovenatoridae. This recently-created family is based on Neovenator, a much more normally-looking 7.5 long theropod which lived in Early Cretaceous England alongside Iguanodon. Discovered in the 1990s, Neovenator (“new hunter”) made unwillingly an Hilarious in Hindsight case. It has indirectly made Truth In Books a classic in old dinosaurian portraits: that is, the battle between Iguanodon and an anachronistic Megalosaurus, which in Real Life lived in Middle Jurassic. ^[4]. The 2009 discovery of the megaraptoran Australovenator, "southern hunter", has likely revealed the true identity of the mysterious 'dwarf Allosaur' seen in Walking with Dinosaurs. Another interesting member is Aerosteon: discovered in Argentina only in 2009, this one shows prominent air sacs in its bones, providing more evidence that birds are dinosaurs.

Exotic names in Asia (except one): Yangchuanosaurus, Monolophosaurus, and Gasosaurus

• Many allosauroids have been found in Asia, notably in China. This is evident if you read their names: just as an example, Yangchuanosaurus. This one was basically the “Chinese Allosaurus”: only a bit smaller and with a shorter, taller skull with the usual Allosaurus-like crests on the snout; robust, three-fingered forelimbs, and perhaps a small ridge on its back. It was probably the top-predator of Late Jurassic Asia (155-145 million years ago), and lived alongside Mamenchisaurus “the Chinese Brontosaur” and Tuojiangosaurus “the Chinese Stegosaur”. However, one alleged Yangchuanosaurus skeleton has been renamed Sinraptor (“Chinese robber”) in the nineties. Now the latter has become the official prototype of the carnosaur family also containing Yangchuanosaurus, the Sinraptorids, more basal than Allosaurids. Other possible Chinese allosauroids are known only from extremely scant remains: "Szechuanosaurus" (the first large theropod found in China, but known only from teeth), and the Early Cretaceous Chilantaisaurus (maybe a neovenatorid similar to Megaraptor, but maybe a spinosaurid instead). Another more complete Late Jurassic theropod from China is not an allosauroid but a more basal tetanuran related to megalosaurids & spinosaurids: Monolophosaurus (“one-crested lizard”), so-called because of its single cranial crest vaguely similar to each branch of the double-crest of the unrelated Dilophosaurus (“two-crested lizard”). As you can easily tell now, many large theropods aren’t exactly the simplest things to pronounce. But there’s also a curious exception which comes just from China. This one makes a sort of comic relief among many huge theropod names, having one of the simplest, most obvious names one could imagine: Gasosaurus just comes from a gasoline company that funded the excavation of its skeleton. A smallish theropod, 4 m / 15 ft at the most, Gasosaurus lived in Middle Jurassic, and its appearance was a sort of middle-way between a gracile “carnosaur” and a stocky “coelurosaur” (in the older sense of these words). Its classification has long been uncertain, from a basal tetanuran to the most ancient coelurosaur known, but now has since been found to be a sinraptorid carnosaur, related to Yangchuanosaurus.

Tyrannosaurs in the Deep South: Abelisaurus, Majungasaurus, and Aucasaurus

• The theropods here are not tyrannosaurs and didn’t live in the Deep South, but the definition works well. Even though much more basal than tyrannosaurids, Abelisaurids shared with the latter some specializations: robust skulls, long hindlimbs and shortened forelimbs. But most were only 7 m long, much smaller than tyrannosaurs as well as Spinosaurids and many Carnosaurs. Their unofficial prototype is the “horned” Carnotaurus; the official one, Abelisaurus. Both from Late Cretaceous South America, these dinosaurs didn’t look so similar; Abelisaurus skull was long-snouted and totally horn-lacking, more similar to a miniaturized Giganotosaurus. However, the shape of the orbits, the narrow lower jaw, and other “small” things indicate that it was a close relative of Carnotaurus. Always remember that in systematics external appearance is usually a minor factor. Unfortunately, the only thing we know from Abelisaurus is just the skull. But other relatives are much more known: for example, Aucasaurus. Discovered in the 2000s also in Late Cretaceous South-America, Aucasaurus was one of the smallest members of the family (only 5 m long). Despite not showing neither horns nor a shortened skull, it was the closest relative of Carnotaurus. And, like the latter, had a strange look: forelimbs even more reduced than Carnotaurus itself, tiny stubs without any digits. Most abelisaurids were Late Cretaceous and have been found in South America, but remains have been found in most southern continents (once reuned in one landmass, Gondwanaland). In the same period, tyrannosaurids roamed Laurasia (the northern landmass): hence “tyrannosaurs in the DeepSouth”. Majungasaurus is an excellent example of non-South-American abelisaurid. Found in Madagascar, it was not bigger than Carnotaurus and shared a similar overall look, but with one single horn atop of its head. This dinosaur has had a curious Science Marches On story: initially only its blunt horn was known, and because of its shape was thought to be the domehead of a tiny pachycephalosaur called “Majungatholus”. Then, this name was applied to the carnivore until few years ago; for example, in JurassicFightClub this theropod appears named “Majungatholus”. Here, two adults are shown cannibalizing a young of their own species; this was based upon some marks of teeth on the bones of young Majungasaurus specimens, whose shape match the teeth of adult Majungasaurus.

Even palaeontologists have fun: Cryolophosaurus and Gojirasaurus

• Paleontologists are not necessarily those nerdy people one could believe. Many do fit more in the Adventurer Archaeologist and Badass Bookworm tropes - think about the famed Australopithecus specimen nicknamed Lucy; the cowboy-looking Bob Bakker; the “Bone Wars” fought by two archenemical guys…. and above all, Roy Chapman Andrews. And yes, paleontologists do consume pop-cultural products just like all the other people. In the 1990s, even the most sceptical people were forced to change their idea about, in front of these two new-discovered theropods: Cryolophosaurus and Gojirasaurus. Because the uniquely curly shape of its crest, the former was initially named "Elvisaurus"; the latter has been named after “Gojira”, which is the Japanese name of Godzilla. And since Rule of Cool undisputly dominates every time dinosaurs are involved... some paleo-artists have been giving to our Godzillasaur unlikely features such as prominent/raised scutes along its back, just to make it look like its namesake!. Talking more seriously, these two theropods are interesting because, along with Dilophosaurus and other less-known animals such as Liliensternus, they are among the earliest large-sized carnivores. Cryolophosaurus means “crested lizard from ice”; this because was the third dinosaur found in Antarctica, and the first one named, in 1993. But wait, it has not been found enclosed in ice. Even though is cool to think, this is an impossible thing in Real Life. Not counting ice has formed on Antarctica only after the Cretaceous mass-extinction, bones cannot turn in stone when surrounded by solid water… Antarctic dinosaurs have been found encased in rocks like everywhere in the world, in the rare ice-free portions of Antarctica at its extreme “north”. Cryolophosaurus was an Early Jurassic theropod 5-6 m long, which the latest studies find a close relative of Dilophosaurus. Found in Texas in 1997, Gojirasaurus was an ever more primitive theropod from Triassic: 15 ft long, was several times heavier than most carnivorous dinosaur from Triassic. Thus, it has been hailed as “the first big-sized meat-eating dino” just like the “younger” Dilophosaurus. Despite this, Gojirasaurus had a quite incospicuous look, similar to a robust Coelophysis and lacking any crest, and was probably more closely related to Coelophysis than to Dilophosaurus.

An only-historical relevance: Deinodon and Teratosaurus

• We can also mention two virtually-unknown animals which have had nonetheless a great relevance in the past, but have lost it due to Science Marches On. Teratosaurus: (“monster lizard”) lived in Europe during the Triassic period. Discovered as early as the middle of the XIX century, it was 6 m long, and has long detained the record of “the first giant meat-eating dinosaur”. In old books, Teratosaurus was portrayed as a generic-looking “carnosaur” which hunted the neighboring prosauropod Plateosaurus. Then, in the mid 1980s, it was discovered that Teratosaurus was actually reconstructed upon very fragmentary remains mixed with bones belonging to Plateosaurus: these new studies showed it was not even a dinosaur, but a four-legged, non-dinosaurian archosaur related to Postosuchus, and now has totally gone out of fashion. The other example is "Deinodon" (“terrible tooth”). Few people today are aware of this pratically unknown dinosaur, described only from teeth. Nonetheless, “Deinodon” has been the very first carnivorous dinosaur described in North America, in 1856, when dinosaurs were still only-European things. Its describer, Joseph Leidy, didn’t realize that he named the first tyrannosaur. Now scientists think the “Deinodon” teeth pertain to another better-known tyrannosaurid, perhaps Albertosaurus. However, “Deinodon” has left one memory: once, the tyrannosaurid family used to be called “deinodontids”. Or rather, this should be the correct name for tyrannosaurids, but is obscured by how ingrained the term "tyrannosaurid" now is.

1. ↑ Note that Allosauroidea is slightly less inclusive than Carnosauria, however.
2. ↑ Beware, we’re talking about functional fingers, not the so-often cited third vestigial digit present in T. rex
3. ↑ The whole process is always quite arbitrary, never forget this
4. ↑ This portrait was based on some uncertain theropod remains discovered in Early Cretaceous England in the XIX century, which fell in the usual “Megalosaurus wastebasket” thing