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Velociraptor wrists

Posted by tigerhawkvok on February 19, 2009 02:49 in biomechanics , dinosaurs , biology , paleontology

The promised science post!

Rewatching Jurassic Park, I wanted to correct a rather small, but important and understated error.

There's a hint in the URL, of course. The answer? The claws — they're held horribly, horribly wrong.

Jurassic Park Velociraptors are named after Velociraptor mongoliensis, and modeled after a hybrid between the genera Deinonychus and Utahraptor. At the time the novel was written, there was some talk of moving Deinonychus into the genus Velociraptor, which was the convention followed by Micheal Crichton, though this didn't play out. However, all of these were dromaeosaurids, which are eumaniraptorans. In fact, Dromaeosauridae is the group closest to but outside of Aves. So, all members of eumaniraptora have a synapomorphy list that includes a "semilunate carpal".

Sinoris manus

Sinornis santensis manus

Tanycolagreus manus

Tanycolagreus topwilsoni manus. Scale in cm.

Cathayornis manus

Cathayornis sanctis manus.

All three of the pictures above show this semilunate carpal in other maniraptorans. Unlike most mammalian wrists, it cannot flex perpendicular to the radius-ulna plane (ie, what we would most commonly accept as perpendicular to the groud). Instead, its motions were restricted to that plane, giving a jacknifing motion, much like a flight stroke. This was an optimal grasping motion for prey, and good for grappling large prey, and was easy to adapt into a flight stroke (particularly given the presence of primary feathers on some dromaeosaurids).

Sadly, this does mean that the raptors couldn't open doors. They would have broken their wrists trying to make the motion!

Image citations:

  • Carpenter K., Miles C., Cloward K. New Small Theropod from the Upper Jurassic Morrison Formation of Wyoming. In "The Carnivorous Dinosaurs" (ed. Kenneth Carpenter), 2005.
  • Sereno PC., Chenggang R., Jianjun L. Sinornis santensis (Aves: Enantiornithes) from the Early Cretaceous of Northeastern China. In "Mesozoic Birds: Above the Heads of Dinosaurs" (ed. Luis M. Chiappe and Lawrence M. Witmer), 2002.
  • Zhonghe Z. and Lianhai H. Mesozoic Birds in China. In "Mesozoic Birds: Above the Heads of Dinosaurs" (ed. Luis M. Chiappe and Lawrence M. Witmer), 2002.

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