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Here you'll find both very basal theropods like the coelophysids and more advanced kinds like the compsognathids and even some small tyrannosauroids. At one point, these were all called coelurosaurs ("hollow-tailed reptiles"), though that term now has a different meaning. As in most other Prehistoric Life pages you'll also find some animals which actually are (or could be) misplaced taxonomically speaking, but are there because scientists once believed they're related with the other examples in the page.

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The most common in popular documentary works (other than Compsognathus, Coelophysis, and Ornitholestes) include Coelurus, Elaphrosaurus, Noasaurus, Segisaurus, "Syntarsus", Procompsognathus, and the alleged theropod Saltopus. In recent media, Guanlong and Scipionyx have gained notable consideration as well, expecially Guanlong. Here you can see a (quite affected by Rule of Scary) close-up of Masiakasaurus.

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    From Middle Jurassic to Cretaceous 


A successful name: Coelurus

  • After Archaeopteryx, Coelophysis, and Compsognathus, the couple Coelurus - Ornitholestes makes the fourth most portrayed Jurassic/Triassic small theropods, despite their scanty remains. This because both lived in Late Jurassic North America alongside many stock dinosaurs like Allosaurus, Stegosaurus, and Apatosaurus, and both were described more than a century ago: thus, they have often been depicted in many old and recent paleo-art — although often confused with each other in the past. Both were slender animals the same length/size of the Real Life Velociraptor, and with a rather incospicuous appearance. Within their habitat, Coelurus and Ornitholestes arguably played the role of the “small cunning predators” (while Allosaurus and Torvosaurus were the top predators and Ceratosaurus was between the two extremes). Although there are no evidences, their preys were possibly lizards, mammals, frogs and insects, and sometimes, also ate the eggs and hatchlings of bigger dinosaurs. Found during the Bone Wars, the incomplete skeleton of Coelurus was the first small theropod remain discovered in USA, a bit later than Compsognathus in Europe. Its full scientifical name is Coelurus fragilis, "fragile hollow tail" — recalling that of the contemporary Allosaurus fragilis. Despite its scantiness, the coelurus has had a great historical relevance. As soon as the XIX century, Coelurus gave its name to the Coelurosaurs, aka all small/slender theropods, countered against the Carnosaurs aka large/robust theropods such as Tyrannosaurus rex. "-coelurus" has even become a suffix itself for a bunch of small theropods like Sinocoelurus, Thecocoelurus, and Chuandongocoelurus, or even a prefix: Coeluroides and the non-dinosaur Coelurosauravus (meaning "ancestor of coelurosaurs")! In the very first classifications carnosaurs & coelurosaurs were not originally thought to be closely related (with carnosaurs being closer to sauropods), but most later studies indeed believed distinct lineages of theropods, arisen independently in the Triassic and evolved through the epochs until the end of the Cretaceous with a succession of animals like these: COELUROSAURS: Coelophysis —> Compsognathus —> Dromeosaurids & Ornithomimids; CARNOSAURS: Ornithosuchus note —> Megalosaurus —> Allosaurus —> Tyrannosaurus. Then, in the 1970s, "coelurosaurs" was restricted to the most generic & primitive small theropods (the subject of this page), while the most recent & specialized sickle-clawed and toothless coelurosaurs were separated in three new groups: Deinonychosaurs (dromaeosaurids + troodontids), Oviraptorosaurs (oviraptorids & relatives), and Ornithomimosaurs (ornithomimids & relatives). The modern meaning of "coelurosaur" was created only in the 1980s after the rise of the new cladistic method of classification; since then, coelurosaurian dinosaurs have re-included deinonychosaurs, ornithomimosaurs & oviraptorosaurus and (ironically) exclude several traditional members of the group like Coelophysis as well as the ceratosaurians Elaphrosaurus and Noasaurus (see the next paragraph). But the most revolutionary change is another: the former carnosaur Tyrannosaurus rex has been reclassified as an overgrown coelurosaur. In short, big & small theropods were not distinct lineages: big meat-eaters originated indipendently across the Mesozoic from several distinct small-sized ancestors, and are too different among each other to make a natural lineage. A 2007 analysis seems to indicate Coelurus may have been a basal tyrannosauroid, along with a recently discovered larger-sized relative from the same habitat, Tanycolagreus. These two may form to form the group Coeluridae, which was once treated as a "wastebasket" family including Coelurus, Ornitholestes, and dozens of undetermined small theropods (Calamospondylus, Inosaurus, Jubbulpuria, Kakuru, Ngexisaurus, Ornithomimoides, Teinurosaurus, Tugulusaurus etc.). However, even this reduced Coeluridae may not exist; instead, Coelurus may be closer to maniraptorans, with Tanycolagreus as a very primitive coelurosaur or staying with tyrannosauroids. Several other possibly non-maniraptoran coelurosaurs have been described since the 1990s, such as Bagaraatan from Late Cretaceous Mongolia (possibly a late-surviving primitive tyrannosaur), Nedcolbertia from the Early Cretaceous of the U.S. (an unusually long-legged form), Lourinhanosaurus from Late Jurassic Portugal (long thought to be a megalosaur or allosaur), and Xinjiangovenator from Early Cretaceous China (maybe the same animal as "Phaedrolosaurus", known only from a tooth).


Deceptive relationships: Elaphrosaurus & Noasaurus

  • Few other dinosaurs have had such an intricated Science Marches On story than Elaphrosaurus. This medium-sized, slender-framed theropod (meaning “light lizard”) is known from one skeleton found in the famous Jurassic Tendaguru site in which Giraffatitan (the universally-known “Brachiosaurus”) has been discovered, while other poor remains found in North America and Cretaceous Northern Africa formerly classified as Elaphrosaurus actually don't belong to it — the African ones are now called Spinostropheus. The problem is, the skull of the original proper elaphrosaur is not preserved, and we don’t know if it was toothed or toothless. In old paintings, it was depicted Coelophysis-like and toothed. Then, scientists proposed Elaphrosaurus was the ancestor of the ornithomimosaurs, and often depicted it toothless. In the nineties, when theropod classification was strongly improved, Elaphrosaurus was recognized as a much more primitive animal related with Ceratosaurus, and still is today: this caused its mouth to return toothed. However, the very recent discovery of Limusaurus, a close relative from China whose skull is quite reminescent of an ornithomimid's, has shuffled the cards again: now it’s possible Elaphrosaurus really looked like an ostrich-dinosaur, in spite of not being closely related at all. In 2015 a theropod very similar to Limusaurus was found, Chilesaurus, but has revealed was closer to the great megalosaurs & allosaurs. A possible true ornithomimosaur was found in 2000 in the same continent of Elaphrosaurus, but was initially believed a generic toothed small theropod: the African-sounding Nqwebasaurus, which is also considered the oldest known coelurosaur from the southern continents. Unusually found in Early Cretaceous South Africa (dinosaurs from southern Africa are usually Triassic or Early Jurassic), Nqwebasaurus is interesting because the specimen (a juvenile 3 ft long) shows some traits carnivorous and other herbivorous: it had an opposable thumbclaw on each hand, reduced teeth, and the stomach cavity contains gastrolithes (aka small stones), a trait usually associated with plant-eaters; all this means it could be an intermediate form between early typical theropods and the toothless ornithomimids living in Late Cretaceous (see also Birdlike Theropods). Science Marches On has also involved still another small basal theropod, Noasaurus from Late Cretaceous South America. Discovered in 1980, Noasaurus ("lizard from North-Western Argentina": N=north, O=west A=Argentina) was initially thought similar to dromaeosaurids and depicted with sickle-claws on its feet, making it the “southern dromeosaur”. However, more careful researches showed Noasaurus was far more archaic than a “raptor”: even though hard to believe, it was closely related with its neighbour Carnotaurus (which was found 5 years later). One scientist suggested that both were late megalosaurs, but they are more likely ceratosaurs. The alleged Hook Foot of the noasaur has revealed a Hook Hand, almost like a miniaturized Megaraptor. One close Noasaurus relative described in 2001, Masiakasaurus from Madagascar, has revealed its unique protruding teeth, whose purpose remains uncertain - some think it used them to catch fish or insects. Other noasaurids include Velocisaurus (not that Veloci) and tiny Ligabueino, both from South America, as well as the Indian Compsosuchus (known only from neck vertebrae once thought to come from a giant allosauroid), the Madagascan Dahalokely (an unusually robust form) and the Patagonian Austrocheirus (which had larger hands than most other ceratosaurs). From India comes Jubbulpuria, a late-surviving small ceratosaur of uncertain classification. From Australia comes Kakuru, another small theropod whose one remain, a shin, was transformed in opal (a kind of gemstone) during the fossilization. Laevisuchus from India is known from a single vertebra, and was originally believed an oviraptorosaur.


Tyrannosaurs went a long way: Guanlong & Dilong

  • Well, it’s true: the undisputable charm of T. rex is also due to the long travel it made to become the Ultimate-King. Tyrannosaurs were already around in the Jurassic, but were still small, uncospicuous animals similar to Ornitholestes. But this is an extremely recent knowledge, confirmed as recently as in 2006. The merit belongs to a very undinosaur-sounding dinosaur: Guanlong. Today, Guanlong may be the most famed dinosaur with “long” (in Chinese means dragon). The trend to call Chinese dinosaurs with this suffix has started only in the early 2000s; since then “dino-long”s have become more and more common, with at least one new-entry for every year. Easily recognizable thanks to its bizarre helmet-like crest pointing backwards, the 10-ft-long Guanlong lived in Late Jurassic; despite its vaguely Coelophysis-like look, Guanlong was the most ancient tyrannosaur known in 2006. Another "dino-long" Dilong paradoxus, was found some year earlier in the famed Liaoning fossil site, was about the same size but lacking any known crest, and lived later, in Early Cretaceous. However, in the last years Guanlong has lost the record in favor of Proceratosaurus. This was a Middle Jurassic European theropod found at the beginning of the XX century; as its only-known remain is a partial skull with a horn on the nose similar to the younger Ceratosaurus (hence its name, "before Ceratosaurus"), it was reclassified as a basal tyrannosaur only in the latest part of 2009. Another basal tyrannosauroid (possibly a relative of Proceratosaurus) was the Late Jurassic Stokesosaurus (see just below for these two), known from North American remains since the 1970s. note  But it was too late: the sensationalism which surrounded Guanlong as “The First Tyrannosaur!” soon gave it the general attention in media, to the point that it appeared as the protagonist of one documentary appositely dedicated to it: a very rare honor for every dinosaur that is not T.rex. And then, Guanlong was also portrayed in the third movie within the Ice Age series in place of the stock dromaeosaurids. Could it become a stock dinosaur in the future?


The first Rex's ancestors?: Stokesosaurus & Proceratosaurus

  • Before the Early Cretaceous Yutyrannus Eotyrannus & Dilong, there were Proceratosaurus and Stokesosaurus other than Guanlong among Jurassic tyrannosaurs. Both the european Proceratosaurus and the north american Stokesosaurus were primitive tyrannosaurs named years before all their chinese relatives. Discovered in Utah in 1974 by William Lee Stokes (for whom the genus was named) and his assistant James Madsen, Stokesosaurus was one of the first of the Jurassic tyrannosauroids to be found; it's only known from hip elements, but those hip elements have enough to distinct it from other Late Jurassic theropods from the same fauna. Interestingly, Stokesosaurus was found in the Cleveland-Lloyd Dinosaur Quarry in Utah, the same place in which the huge Allosaurus graveyard comes from. Proceratosaurus and Stokesosaurus are today classified in the Proceratosaurid family of tyrannosaurs: because of their scrappy remains, it's hard to get a clear image of what they looked like. Proceratosaurids likely differed from more evolved tyrannosaurs in a plethora of ways: for one, their skull would not be as large or tall. For another, their arms would have been fairly elongate with three funtional fingers, each tipped with a claw. Their legs would probably have been quite elongate and gracile, unlike those of later tyrannosaurids, and their neck was longer than other tyrannosaurs. And, considering their relative Guanlong, they may have sported some kind of cranial crest (though the fact that the former "Stokesosaurus" species Juratyrant lacks a cranial crest could point to it not existing in Stokesosaurus, either). Stokesosaurus likely wasn't the most powerful predator on the block in it's time; as it lived in the Morrison Formation, it was living alongside Ceratosaurus, Marshosaurus,note  Torvosaurus and Allosaurus; all of whom were at least slightly bigger than Stokesosaurus. Even though the earliest tyrannosauroids got eclipsed, their lineage would have the last laugh in the predatory dinosaur rush; the descendants, tyrannosaurids, became the top predator in North America and Asia for most of the Cretaceous Period, pushing out the other large predators before being wiped out in the Cretaceous/Palaeogene extinction 66 million years ago.


A dinosaur with plenty of guts: Scipionyx

  • When talking about dinosaur fossils, our mind immediately thinks “bones”. Sometimes, also skin prints, footprints, and petrified eggs. And then, the rare “mummies” with hardened muscles like the famous hadrosaurian ones. But things such as hearts, guts, livers, lungs, kidneys, are not usually heard about; this because the preservation of soft tissues and internal organs in vertebrates in an extremely rare event. So, the Early Cretaceous Scipionyx samniticus from Italy made sensation when was discovered in 1995, and with reason. This tiny theropod (still a juvenile when it died), long believed unclassifiable but now known to be a compsognathid, was the very first dinosaur ever found with fossilized internal organs. The windpipe, intestines, liver, and muscles, all these were preserved in the fine limestone which has preserved the usual bones as well. Since the relative positions of dinosaurian organs could only be guessed before Scipionyx, this has been rightly celebrated as one of the most important discoveries within the whole paleontological science. As for now, no other prehistoric dinosaur has left such complete remains of internal organs. Like many other compsognathid specimens, Scipionyx also preserves evidence of its last meals: in this case several smaller reptiles and some fish. It's worthy of note that before the 1990s the compsognathids included only one member, Compsognathus indeed — Procompsognathus, despite the name, has always been considered a member of the much more archaic coelophysoids. Other real or putative compsognathids include English Aristosuchus ("noble croc", known since the start of the XX century), and the more-recently-discovered Huaxiagnathus (a chinese kind from Early Cretaceous), Mirischia (whose pelvis was unusually asymmetrical), and two Liaoning theropods, Sinosauropteryx and the similarly-named Sinocalliopteryx. The latest one when discovered was the biggest (9 ft long) dinosaur found with feathers, beating the traditional record holder Beipiaosaurus, before Yutyrannus was discovered in 2011.


Squirrel-dinosaurs?: Sciurumimus & Juravenator

  • Recently, the famous Late Jurassic Germany fossil sites (the same from which Archaeopteryx and the original Compsognathus come from) gave us two exquisitely preserved animals that may be juvenile megalosauroids, but are placed in this page because of the size of the specimens (only few feet long from nose to tail), as well as the uncertainty surrounding their true affinities. The best-preserved one was announced in 2011 — incidentally, the same year of Yutyrannus: named Sciurumimus ("squirrel mimic": "Sciurus" is Latin for squirrel), this is a reference to its bushy tail covered in filamentous structures which recalls a bit that of the eponymous rodent. The interesting this is: if Sciurumimus is a megalosauroid, it pushes the origin of feathers very far back, if not as far back as Tianyulong. Juravenator ("Jurassic hunter") was first described as a compsognathid in 2006, but may be close to Sciurumimus instead. Despite the recentness of its finding, it has already had a complex Science Marches On story. As its tail seems showing signs of scales, it was initially described as a traditionally-scaly theropod, giving fuel to those that still are doubtful about the dinosaurian origins of birds. But recent research has shown that true proto-feathers are also present. The most surprising thing is, this was only revealed under ultraviolet light.


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    From Early Jurassic to Triassic 


Feathers and wishbones: Coelophysis rhodesiensis (once called "Syntarsus" or "Megapnosaurus") & Segisaurus

  • Scientific names are a route full of hurdles. It’s almost unbelievable how many living or extinct animals have been described so far (more than 100,000 genera, 90% of which are insects!). Thus, it's not surprising that sometimes scientists make the mistake of giving their newly described animals already used names. This is what happened to Syntarsus rhodesiensis, a coelophysid that lived in Early Jurassic Southern Africa — some questionable remains found in North America showing a small double-crest similarly to Dilophosaurus were labeled as a distinct species, Syntarsus kayentakatae. In the 2000s, an entomologist discovered the name “Syntarsus” was preoccupied by a living insect (more precisely a beetle), and changed it to Megapnosaurus: “big unbreathing lizard”, under the mistaken impression that the dinosaur's original discoverer had died. Science Marches On however, and now most scientists consider "Megapnosaurus" just a late surviving, Early Jurassic species of Coelophysis, thus making this name invalid as well. Whatever the name, this dinosaur has the distinction to be the first non-avian dinosaur ever depicted with feathers (in 1975, few years before the description of Avimimus), in a time when this hypothesis was only speculation. Ironically, we don't know if this animal was really feathered; if it was, certainly it didn't have true feathers as shown in the depiction of the 1975, but simple downlike fibers or something else. Other examples of much smaller coelophysids were the Early Jurassic Segisaurus and Podokesaurus, and the Late Triassic Camposaurus, all from North America — at present, the latter is the oldest named dinosaur from that continent. Segisaurus is interesting because, together with Archaeopteryx and Oviraptor, was one of the first non-bird dinosaurs to have revealed a wishbone (a typical bird trait), in a time dinosaurs and birds were still thought not related at all. Later, remnant of wishbones were found in other theropods, Coelophysis among them. Podokesaurus holyokensis was described in Eastern North America at the start of the XX century by Mignon Talbot (making it the first non-bird dinosaur officially named by a woman-researcher), but sadly its skeleton got destroyed by fire; some think it's a juvenile Coelophysis. Camposaurus (maybe an early specimen of Coelophysis as well) has not to be confused with the Iguanodon relative Camptosaurus, which was much larger and lived well after it.


The other compies: Procompsognathus & Saltopus

  • One of the very first theropods ever lived (but only if herrerasaurians were not proper theropods), Procompsognathus lived in the Triassic Period in Europe together with Plateosaurus. It shared with Compsognathus the same overall shape, the same size (about 4 ft long), the same country (Germany) and a very similar name (“before Compsognathus”). Despite all this, Procompsognathus was not related to its Late Jurassic namesake, nor was it its direct ancestor at all as one might believe: it was a small coelophysoid, maybe more primitive than Coelophysis itself. A skull once assigned to it likely came from a non-dinosaurian archosaur. In 1990, Procompsognathus has gained notoriety thanks to its apparition in the first Jurassic Park novel, depicted as a scavenger which paralyzed its victims with a totally speculative venomous bite. This is indeed the original "Compy" in the Jurassic Park world. Before, Procompsognathus was an obscure animal, as is lampshaded in the novel itself – with Alan Grant thinking the drawing made by the child who saw the “compy” alive was not fake, just because “even dino-lovers don’t know Procompsognathus”. However, seven years later, Spielberg decided to play straight Stock Dinosaurs and chose the more familiar Compsognathus in the same role in The Lost World: Jurassic Park. Considering that the “procompy” is known from much scantier remains than the usual 'Compy', this might be justified. Another alleged theropod from Triassic Europe was once believed the most ancient dinosaur of this landmass, and was smaller than Procompsognathus both in its size and in its name: Saltopus. A rare Scottish speciality (almost all British dinosaurs have been found in southern England), being merely 2 ft long, Saltopus was sometimes referred as “the smallest dinosaur” in old books (when Compsognathus wasn't already), but now it seems to be only a non-dinosaurian dinosauromorph. Both Procompsognathus and Saltopus were found at the start of the twentieth century. Saltopus was often confounded with Saltoposuchus, a tiny crocodilomorph from Triassic Europe also common in old books because was once thought the common ancestor of dinos, birds and crocs.


The other first-birds: Protoavis and "Proavis"

  • Yes, Archaeopteryx was not alone. There was also "Protoavis". Discovered in 1990, this very incomplete Triassic fossil from Texas has originated much discussion among paleontologists: its describer thought that it, and not Archaeopteryx, was the true "first bird", basing this upon some skeletal features (he thought it was older but more advanced than Archaeopteryx). He chose to name its “sensational” find Protoavis, which just means “first bird”. Not surprisingly, our animal has often been mentioned in books and documentaries in those years, even portrayed with small imaginary “wings” on its forearms. However, its legacy with birds is now heavily contested if not totally discredited. This alleged “protobird” is more probably a primitive theropod, a basal saurischian, or a non-dino archosaur, and it was likely described from a mixup of dinosaurian and non-dinosaurian bones, thus not even a real animal. But others still think "Protoavis" really contains the bones of an early bird-relative, perhaps the most ancient coelurosaur known (nonetheless, it almost certainly wasn't an actual bird). There is also a Hilarious in Hindsight detail about the “first-bird” argument. Many decades before the discovery of "Protoavis", in a time when birds were still thought to have directly descended from a bipedal archosaur (thecodonts like Euparkeria or Saltoposuchus), the similar name “Proavis” (“before birds”) was invented for an imaginative missing-link between thecodonts and Archaeopteryx. This critter was depicted as a tree-climbing animal with small wings and capable to glide from a tree to another, but still not capable to fly actively. Then, in year 2000, somewhere in the Chinese province of Liaoning, the "proavis" was really found... in the shape of the four-winged Microraptor.


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