In the spirit of my habit of bringing rare, obscure dinosaurs to your attention, I’d like to introduce you to Labocania anomala, a theropod dinosaur from the peninsula of Baja California. A well-kept secret of paleontology, Baja California is rich in fossils of the Late Cretaceous period, about 70 or so million years ago. Compared with “Alta California”, a slang name often given to our own state of California, Baja contains approximately twice as many Cretaceous dinosaurs in the northern half of the peninsula than the entire state does as a whole. In addition to Labocania, the peninsula has also revealed specimens of Lambeosaurus, Albertosaurus, and even specimens of strange polyglyphanodont lizards, strange iguana-like herbivores related to skinks.
But what kind of theropod is Labocania? That’s what makes Labocania so fascinating, the fact that we don’t know. Gregory S. Paul has suggested that Labocania was an allosaur, a Late Cretaceous specimen of a group that was supposed to have died out at the End-Turonian event, along with the stegosaurs, most pterosaurs, ichthyosaurs, and much of the other Mesozoic old guard. But, seeing as Gregory S. Paul is the same guy who tried to synonymize Deinonychus and Velociraptor, a very erroneous idea (and because of which we are stuck with giant, misnamed raptors prancing around the silver screen), I really wouldn’t put much stock on “the word of Paul”. In fact, if you asked me up until a couple of years ago, I would have probably said that Labocania was most likely a dryptosaur.
What are dryptosaurs? Dryptosaurs are a sort of catch-all term, referring to the more primitive tyrannosaurids, those with long, three-fingered arms like Eotyrannus, Dilong, and others. To be technical “dryptosaurid” really only refers to those dryptosaurs that belong to the family Dryptosauridae, a group of large primitive tyrannosauroids that rampaged across Eastern North America while their short-armed, bone-crushing kin did the same in the west, including such members as Dryptosaurus and Appalachiosaurus. It is not entirely outside the realm of plausibility that Labocania was a mainland example of the group as well. Similarities in the ischium between Labocania and other tyrannosauroids seems to support this theory. Holtz also seems to think this is the case, and described Labocania as a possible tyrannosauroid in his 2004 review of the group.
However, the idea that Labocania is a primitive, three-fingered tyrannosauroid might be seriously challenged in recent years, by an old face; the idea that Labocania is a type of allosaur. For a long time, the headstone of the allosaurs basically read: R.I.P. 90 MYA. But recently findings of new allosaurs in South America changed that. Meet Aerosteon, a fascinating animal for a multitude of reasons. First off its bones show that this animal had the same sort of advanced breathing system that we see in birds, which pushes back the evolution of full-blown bird lungs down several notches on the evolutionary family tree. Secondly, it was found in sediments dating to the Santonian age, 85 MYA…five million years after the allosaurs were supposed to have kicked the bucket. Further discoveries of unusual Cretaceous allosauroids (namely Australovenator) have allowed us to identify several other species, which previously were scattered around in different groups and their relationships unknown, as belonging to the same group, the Neovenatoridae. This includes the mysterious genus Megaraptor, as well as the dinosaur Orkoraptor, previously thought to be a coelurosaur. Orkoraptor is interesting because it lived at the very end of the Mesozoic, in the Maastrictian period of the Late Cretaceous. Since we have evidence of some dinosaurs making the trip from South America to North America (Alamosaurus and possibly the alvarezsaurids), who’s to say that allosaurs could not have made the same journey.
So what is Labocania? The point is, plain and simple is that we don’t know. The material we have already is too fragmentary to make any judgments one way or the other. Unfortunately, between political strife within Mexico and arguments of bureaucracy between Mexico and other countries, it doesn’t look like there will be any new expeditions to Baja California anytime soon. But to end this tale on a bright note, Mexico is increasingly taking its place in the world of paleontology, and this country, oftentimes passed over in paleontological studies, is starting to gain attention through new discoveries in the Cohuila province (Velafrons and some other new dinosaurs that I’m really not supposed to talk about). So perhaps one day we will get a perfectly preserved skeleton of Labocania, someday…
References
Predatory Dinosaurs of the World by Gregory S. Paul
Dinosaurs and Other Mesozoic Reptiles of California by Richard P. Hilton
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003303#pone.0003303-Alcober1
http://en.wikipedia.org/wiki/Labocania
No comments:
Post a Comment