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RE: dinosaur nail-hooves??




Tom,
Thanks for that information. So if some small sauropods or ornithischians had survived K-T, the expanding grasslands of the Cenozoic could have seen the evolution of ruminant-like or perissodactyl-like dinosaurs with convergently similar "dino-hooves" for faster running ("dino-ungulates"). Cool.
I can just hear Stephen Gould crying out--- "historical contingency" and "let's rerun that Cenozoic tape again starting with a few minor changes".
Very cool,
Ken
********************************************************
From: "Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>
To: <kinman@hotmail.com>, <dinosaur@usc.edu>
Subject: RE: dinosaur nail-hooves??
Date: Mon, 21 May 2001 10:44:49 -0400

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Ken Kinman
>
> Dear All,
>      I am wondering if any of the big non-theropod dinosaurs
> might have had
> evolved something like the nail-hooves of elephants.  Or are
> nail-hooves and
> true hooves unique to mammals which evolved faster runners in the
> grasslands
> of the Cenozoic?

The flattened unguals in big sauropodomorphs and ornithopods and
thyreophorans look like they would have supported "nail-hooves" rather than
the hooves of, inter alia, ruminants, horses, and lipoterns.  Furthermore,
the big plant eating dinos never reached an unguligrade stance as seen in
some of those mammals: the non-ungual phalanges touched the ground, as well
as (in many cases) a metatarsal pad.

> And also a question about the number of toes. At least some of the
> mammalian pseudoungulates have a different number of toes on the
> front and
> back legs. Does this occur in any of the big non-theropods? Maybe these
> are dumb questions, but I'm not normally very interested in the
> non-theropods.


In big ornithopods there were three digits in the feet and five (primitive)
or four (hadrosaurids) in the hand, but it should be said that of the latter
only II-IV were weight-bearers. In neoceratopsians, five manual digits
(with IV & V rather small) and four pedal. In ankylosaurs, 5-4 manual
digits and 3-4 pedal. In stegosaurs, 5 manual digits (or at least 5
metacarpals) and 3 weight-bearing pedal digits.


In sauropods, five metacarpals and five metatarsals, but as for which
exactly had weight-bearing digits (and which may have been weight-bearing
metapodials lacking digits!) varies from group to group.

              Thomas R. Holtz, Jr.
              Vertebrate Paleontologist
Department of Geology          Director, Earth, Life & Time Program
University of Maryland         College Park Scholars
              College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone: 301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661      Fax (CPS-ELT): 301-405-0796

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