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RE: dinosaur nail-hooves??



> 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