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Useful Notes: Prehistoric Life Other Small Theropods
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 narrower 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.

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

Proto-raptor and Proto-rex?: Ornitholestes & 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.

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. In the “Time of the Titans” episode of Walking with Dinosaurs we can see some Ornitholestes behaving in such a way. In many paleo-artistic works Ornitholestes has been shown behaving like a jackal, tearing chunks of flesh from the kills of Allosaurus or Ceratosaurus and fleeing safely from these larger predators.

Coelurus was often confused with Ornitholestes in the past, and arguably behaved in a similar way above. First found during the Bone Wars, Coelurus was the first small theropod discovered in USA, and 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. Then, in the 1970s, "coelurosaurs" was restricted to the most generic & primitive small theropods (the subject of this page), while the 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.

Ornitholestes was found a bit later, at the beginning of the 20th century. Its name, “bird thief”, was given because it was though a specialist predator well-adapted to grasp “first bird” Archaeopteryx with its prehensile hands. Such a thing would not technically be impossible, the two being contemporaries… only, the “proto-bird” lived in Europe. In many modern portraits, Ornitholestes used to be shown with a horn-like crest on its nose, seen even in Walking with Dinosaurs; however, we know now that it didn’t have this feature. Walking With also added some speculative erectile quills on its neck: though not demonstrated, these might be possible, especially as Ornitholestes has recently been classified as a bird-like maniraptoran in some analyses (albeit still of uncertain placement within the clade: maybe a distant relatives of dromaeosaurids and troodontids). The link with maniraptors is further reinforced by one detail: Ornitholestes had a retractable toe similar to that of deinonychosaurs and early birds, even though almost-every pictures (WWD included) show it with generic bird-like three-toed feet.

About Coelurus, a 2007 analysis seems to indicate it 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. However, even this reduced Coeluridae may not exist; instead, Coelurus may be a compsognathid, with Tanycolagreus as a very primitive coelurosaur. 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) and Lourinhanosaurus from Late Jurassic Portugal (long thought to be a megalosaur or allosaur).

False 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”). note 

The problem is, its skull 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 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 whose skull is quite reminescent of an ornithomimid's, has shuffled the cards again: now it’s possible Elaphrosaurus really looked like an ostrich-mimic dinosaur, in spite of not being closely related at all.

Ironically, 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 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),note  while its alleged Hook Foot has revealed a Hook Hand, 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).

Tyrannosaurs went a long way: Guanlong

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, the 10-ft-long Guanlong lived in Late Jurassic; despite its vaguely Coelophysis-like look, Guanlong was the most ancient tyrannosaur known in 2006. 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 classified as a basal tyrannosaur in the latest part of 2009. Another basal tyrannosauroid (possibly a relative of Proceratosaurus) was the Late Jurassic Stokesosaurus, known from North American remains since the 1970s. Some thought that Stokesosaurus was the same as the mysterious small theropod Iliosuchus; in turn, the European Juratyrant was long thought to be a species of Stokesosaurus.

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 next future?

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 from Italy made sensation when was discovered in 1995, and with reason. This tiny theropod (still a juvenile when it died), 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 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. Other compsognathids include Aristosuchus, Huaxiagnathus, Mirischia, Sinosauropteryx, and Sinocalliopteryx (the latest two were found with proto-feathers, see Bird-like theropods).

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: named Sciurumimus ("squirrel mimic"), this is a reference to its bushy tail covered in filamentous structures. The interesting this is: if it is a megalosauroid, it pushes the origin of feathers very far back, if not as far back as Tianyulong, or even further.

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. Interestingly, this was only revealed under ultraviolet light.

Big dead lizard: Megapnosaurus (once called "Syntarsus")

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 10,000 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, a close relative of Coelophysis that lived in Early Jurassic Southern Africa, with some questionable remains also found in North America (the latter show a small double-crest similarly to Dilophosaurus). In the 2000s, an entomologist discovered the name “Syntarsus” was preoccupied by a living insect, and changed it to Megapnosaurus (“big dead lizard”) under the mistaken impression that the dinosaur's original discoverer had died. Some dino-fans complain about this change, to the point where Megapnosaurus has become one of the least-beloved dinosaurian names… Science Marches On however, and if Megapnosaurus is just a late surviving, Early Jurassic species of Coelophysis, this name will become invalid as well.

Whatever the name you prefer, this dinosaur has the distinction to be the first non-avian dinosaur ever depicted with feathers (in 1975), in a time when this hypothesis was only speculation. Ironically, we don't know if this animal was really feathered; the closer to birds Ceratosaurus and Carnotaurus show extensive areas of scales and/or bony scutes in the back, so it may be unlikely. Other examples of much smaller coelophysoids were the Early Jurassic Segisaurus and Podokesaurus, and the Late Triassic Camposaurus (don't confound it with the large ornithopod Camptosaurus), all from North America — at present, the latter is the oldest named dinosaur from that continent. Segisaurus is interesting because was one of the first dinosaurs to have revealed a wishbone (a typical bird trait), in a time dinosaurs and birds were still thought not related at all. Podokesaurus was found in Eastern North America at the start of the XX century, but sadly its skeleton got destroyed by fire.

The other compies: Procompsognathus & Saltopus

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: it is a small coelophysoid, but 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 is 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. Not to be 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-bird: Protoavis

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 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 (the aforementioned Saltoposuchus), the similar name “Proavis” (“before birds”) was invented for an imaginative missing-link between Saltoposuchus 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.

Stokes' lizard: the first Jurassic tyrannosauroid (Stokesosaurus)

Before Yutyrannus, Guanlong or Dilong, there was Stokesosaurus clevelandi.

This primitive tyrannosaur, discovered in Utah by William Lee Stokes (for whom the genus was named) and his assistant James Madsen, was named in 1974; years before those other tyrannosauroids. Stokesosaurus was also 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 Jurassic theropods, and other material once reffered to as Stokesosaurus langhami was risen into the genus Juratyrant later. Stokesosaurus was found in the Cleveland-Lloyd Dinosaur Quarry in Utah, and thus is a genus from the Morrison Formation. Stokesosaurus was a proceratosaurid, and thus one of the earliest of the tyrannosaur radiation.

Because of it's scrappy remains, it's hard to get a clear image of what Stokesosaurus looked like; though closer relatives like Guanlong or Proceratosaurus can aid in piecing together what this Morrison forebear looked like.

Stokesosaurus likely differed from more traditonal tyrannosaurs in a plethora of ways, if we take that into account; for one, it's skull would not be as large or tall. For another, it's arms would have been fairly elongate with three funtional fingers, each tipped with a claw. It's legs would probably have been quite elongate and gracile, unlike those of later tyrannosaurids, and it's neck was longer than other tyrannosaurs. And, considering it's relatives, Stokesosaurus may have sported some kind of cranial crest (though the fact that Juratyrant lacks a cranial crest could point to it not existing in Stokesosaurus, either).

Stokesosaurus likely wasn't the biggest, baddest predator on the block in it's time; as it lived in the Morrison Formation, it was living alongside Ceratosaurus, Marshosaurus, Torvosaurus and Allosaurus; all of whom were at least slightly bigger than Stokesosaurus.

Even though Stokesosaurus itself was eclipsed, it's lineage would have the last laugh in the predatory dinosaur rush; the descendants of Stokesosaurus, 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.

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