Look At That Manicure

The claw at lower right belongs to Dryptosaurus aquilunguis. The photo is courtesy of the Academy of Natural Sciences of Drexel University, Philadelphia, PA.

Typically when we think of large claws, at least for me, on a large theropod a few dinosaurs come to mind. On the foot the claw evokes images of dromaeosaurs of the "raptor" persuasion. On the hands large claws remind us of Baryonyx, Allosaurus, and other earlier theropods. Rarely do we think of tyrannosauroid dinosaurs having large three fingered hands on adequately long arms for using large 8 inch claws as weapons against their prey (or intra-specific heated discussions). This, for me, brings about an interesting question; How related are Tyrannosaurs to Allosaurs? If the last large clawed theropod we happen to see on our continent, other than Therizinosaurs, that was a prominent predator was way back in the Jurassic and named Allosaurus, could there be some sort of long ancestral line linking Tyrannosaurs directly with Allosaurs? I know this line of questioning is making someone somewhere cringe, but remember, we are leading an academic adventure here, we have to explore a lot of questions that seem out there or totally wrong!

E.D. Cope's figure drawings

Using Thomas Holtz's complete phylogenetic tree (I am borrowing from his class handouts online as a road map) we can see that Allosaurs and Tyrannosaurs are related somewhere in the past, but not directly related as Allosaurs branch off the theropod family tree prior to the incorporation of adaptations which created the Coelurosauria, of which the Tyrannosaurs are a subgroup. Powerful arms, though, existed before the Allosauroids and large hands even before that as diagnostic characters; perhaps Allosaurus and its family were not far enough back. Then again, we have evidence of traits in animals being redesigned and emphasized eons after their ancestors adapted in different ways to erase those traits. As an example of this consider Mosasaurs; predatory reptiles thought to be related to existing snakes and monitor lizards were related to land reptiles and, at some point in their development as a family, re-expressed traits conducive to living in marine environments which had been lost to reptiles since they had adapted to terrestrial living, namely the development of highly successful extremities designed to move through the water and not on land. If Mosasaurs could become successful and basically repurpose the legs of a terrestrial animal as paddles akin to a fish's fins (fish to land reptile to fish-like, in some ways, reptile is a minor miracle of evolution I would say!) then certainly a basal Tyrannosauroid dinosaur could develop large hands with long powerful claws. If Allosaurs were not their direct ancestors, nor were Baryonyx or Megalosaurus with their large claws and powerful arms, than what was the direct ancestor of Dryptosaurus and how does that ancestor explain these enormous claws?

From the Eyewitness Visual Dictionary of Dinosaurs

The use of claws like that is typically fairly easy to infer (or at least to make some kind of educated guess and paint an interesting scenario with) and they lend themselves to two scenarios of use, one of which we cannot prove with the tiny fragments of jaw that have been thus far collected. One is that they were purely for slashing at victims; disembowling and the like. The second is that they were for grasping while the mouth, a typically Tyrannosaur weapon of mass destruction, inflicted serious injury with large teeth and a powerful bite. We are missing almost the entire skull, so proving number two would be rather difficult. Having only one claw makes both theories difficult to prove; what if that claw was singular on each hand, like in Baryonyx for example? What if the writer over at Animal Planet is correct and Dryptosaurus "may have been like the African lion that feeds on a carcass rather than chasing an antelope."? I rather hope not. I like the majority of my Tyrannosaurs to be active predators rather than scavengers, unless forced to scavenge.