Re: So-called Sickle Claws

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

At 09:37 AM 8/21/97 -0700, <vonrex@gte.net> wrote:
>Speaking, and I am, of things to be objected to; the term "sickle claw" is
>a misnomer that should be discarded.  The claw may be crescent shaped like
>a sickle but a sickle has a cutting edge along one side like a razor,
>central to its very function.  "Raptor" claws have sharp tips for piercing
>and grasping, not slicing like a knife or razor.

In terms of morphometrics, there are no theropod claws more highly curved
nor flat side-to-side as dromaeosaurid second toe claws, especially
_Deinonychus_.  They are very blade-like in cross-section.  Some
dromaeosaurid claws actually have a sharp ridge along the inside of the curve.

On top of this, the bone is not the true external surface.  These things
were covered with keratinous sheaths, which may (or may not) have supported
a sharp edge.

The claws of dromaeosaurids are NOT morphometrically like those of modern
"raptors" (falconiforms such as hawks, eagles, falcons).  Those claws have a
lower angle of curvature, and a more oval cross-section.  The nonavian
theropod claws closest to eagle talons are the manual claws of allosaurids,
_Dryptosaurus_, and the like: the true analogs to raptor-birds among the
nonavians.

The claws of dromaeosaurids are closest to those of big cats, which do use
slashing/slicing as well as piercing.

>The
>exaggeration of this "sickle" claw's size and importance, I restate, is
>merely for publicity and to make the animals seem more spectacular.

The claw of _Deinonychus_ is still pretty damn big compared to the rest of
the animal.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661