On Saturday it was announced that Polish paleontologists have uncovered the remains of an ancient predatory animal, heralded as an ancestor to Tyrannosaurus in the mass media accounts. Nicknamed "the Dragon" the fossil remains were recovered from Lisowice and are of Triassic age, the large size of the animal (~16 feet) suggesting that it ate almost anything it wanted. Yet there are some questions about this fossil, especially since it has not yet been published in the technical literature. Is it really a Triassic representative of the Tyrannosaurus family tree?
If you take a look at the latest update to Thomas Holtz's dinosaur genus appendix you'll see that there have been some significant discoveries of Tyrannosaurus relatives over the past few years, particularly older forms like Dilong and Guanlong from China. The oldest of these reaches only into the Late Jurassic, however, making the jump between "the Dragon" and Dilong/Guanlong a pretty substantial one. If the new fossil is a member of the Tyrannosaurus family tree the traits that identify the group evolved very early on and will allow for hypotheses to be formed about where the annectant forms between the Triassic fossil and creatures like Dilong might be found. Such a claim requires substantial evidence, however, and this new case reminds me of a paper that came out more than 20 years ago.
In 1985 paleontologist Sankar Chatterjee published a paper titled "Postosuchus, a New Thecodontian Reptile from the Triassic of Texas and the Origin of Tyrannosaurs." A very large Triassic rauisuchid Postosuchus was something like a giant terrestrial crocodile, carrying its legs beneath their body like dinosaurs. It must have been a fearsome creature, and Chatterjee thought that Postosuchus shared enough similarities with Tyrannosaurus that it was "close to the ancestry of tyrannosaurs." This is not held up by the evidence (Postosuchus being the ancestor of tyrannosaurs making Tyrannosaurus a derived rauisuchid and not a dinosaur, which we know is not true, for one thing), particularly since creatures like Dilong have been discovered.
Chatterjee's paper raises the question of whether the tyrannosaur traits mentioned in the mass media reports belie that the "Dragon" is a rauisuchian rather than a dinosaur. Then again, it could be an entirely different type of predatory dinosaur, but whatever it is we will have to wait for a description before it can be deemed relevant to the evolution of tyrannosaurs. Even if it does turn out to be some very early tyrannosauroid, though, we can't say that it is an ancestor of Tyrannosaurus. Evolution is a branching process and there was no direct line leading from small predatory dinosaurs to the "tyrant king."
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There has been some discussion of this specimen on both the dinosaur and VRTPALEO mailing lists. Work is in progress on this carnivore and on the very large dicynodont species associated with it.
I have to admit that the maxilla in the drawing, at least, looks very much like a rauisuchian. However, I do know that members of the team examining it are pretty familiar with those crurotarans.
I have also heard that what the researchers ACTUALLY consider the specimen to be is a basal tetanurine. So yes, a possible T. rex ancestor, but in the same fashion also an ancestor for Spinosaurus, Allosaurus, Ornithomimus, and hummingbirds...
Seeing into the drawing of this fossil I've thought that it could be a basal tetanurine closely related with Spinosauroidea...
I think that particularly meaningful is the dorso-ventral extension of the dental that resembles a feature of spinosauroidea.
For more details: http://theropoda.blogspot.com/2008/08/un-misterioso-arcosauro-polacco-u…
This reminds me of *Teratosaurus*, wich was thought to be a giant Triassic theropod, and perhaps even an early carnosaur, for a long time, and was often depicted in popular books as an *Allosaurus*-like creature. It turned out to be a rauisuchian, either a rauisuchid or a poposaurid.
There are so many clades of Triassic hellasaurs - erythrosuchians, rauisuchians, ornithosuchians - and all of them are quite similar in the adaptions of their jaws and teeth, and, as a result, easy to confuse with each other, or even with their archosurian cousins, the theropods. To confuse matters even more, they are also quite similar to the synapsid sphenacodonts of the lower Permian, and, as a result, it has been claimed (by Reig, in the sixties) that archosaurians were no eureptilians at all, but highly derived pelycosaurs! Needless to say, this theory was shredded into very fine pieces by the greatest contemporary authority in vert pal, Romer himself - all the similarities are adaptions for dealing with large, terrestrial prey, and are the result of convergent evolution.
"Teratosaurus 2 - Back with vengeance" XD
Rauisuchians are often mistaken as dinosaurs because of their dinosaur-like appearance. I remember Teratosaurus being mistaken as an early carnivorous dinosaur before being identified as a Raurisuchian. The discovery of "The Dragon" could likely be another case of mistaken identity similar to that of Teratosaurus.
Could this be a chimaera? It's happened before with big, Triassic-aged purported theropods (like Aliwalia.) Though the proportions look good for a basal theropod, could it be that the skull belong to a crurotaran while the postcranial material belongs to a basal saurischian/basal sauropodomorph/basal theropod/silesaur-like dinosauromorph?
So if this sucker really is a tetanurine theropod, wouldn't that make it the earliest representative of the group? I'm doubting that it really IS a tetanurine, but if it turned out to be one, that would be pretty awesome.
wait! must be patient!
Piltdown's fake association is around the corner!
We could not tell the diff'rence between a crutotarsan or a (very/very!) supposed basal tetanurine judging by a couple of photos...
we are just involved (as bloggers and blogger-commenters) in the Katz-Lazarsfeld's 2-step flow of communication(1. 'source'-2.'mass media'-3.'audience'...we're just "mass-media" for the audience), and as good habit, we must wait until new researches are published.
Until then, I do believe that every possible way out there was considered.
A) rauisuchian
B) chimera: association of crurotarsan/silesaur-like + saurischian?
c) (the most incredible, for now) a basal tetanurine
and after all, don't you ever forget ...
Be aware of the Chatterjee'legacy! (Protoavis+Postosuchus...)
Leo
If a tetanurine, than yes: it would be the oldest. Averostra (Ceratosauria + Tetanurae) is not definitely present until the late Early Jurassic.
This actually doesn't seem that revolutionary provided the discoverers believe the fossil was a basal Tetanurine.
The fossil is definitely Rhaetian. This is very late Triassic, late enough that some dinosaur genera were already extinct, and at least fifteen could have been contemporaries, including several species of Coelophysidae. By definition, the ancestors of Averostra must have been around by then. The gap was only 20 million years between this and the first Ceratosaur (which again, given cladistics, means a basal Tetanurine would have to exist at that time).
Basically, it pushes one more split of the Theropod family tree 20 million years further back. This could be a big find, but not as big of a deal as, say if Eshanosaurus is found to be a real Therizinosaur, or the purported Cretaceous Dicynodont. It will be interesting to see what comes of it though.