Re: Arctometatarsalia condition

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

At 01:32 PM 9/12/98 +0200, you wrote:
>Does someone tell me what's means that the Arctometatarsalian condition is
>reversed in Archaeopteryx, Ornithurine and Enanthiornithine birds?

To be fair, the arctometatarsalian (fully pinched metatarsal III) condition
is *absent* in Archaeopteryx, enantiornithines, and all other bird taxa
(with the exception of the derived alvarezsaurids Mononykus, Parvicursor,
and Shuvuuia).

To say that it is "reversed" in most birds would mean that this condition
was the ancestral condition for Aves.  To my knowledge, no numerical
cladistic analysis has placed birds unambiguously within a clade of
arctometatarsalian forms (tyrannosaurids, ornihomimosaurs, troodontids,
caenagnathids, etc.).

For the scoop on the arctometatarsalian condition, see:
Holtz, T.R., Jr. 1995. The arctometatarsalian pes, an unusual structure of
the metatarsus of Cretaceous Theropoda (Dinosauria: Saurischia).  JVP 14:
480-519.

(Although this is the "December 1994" issue, it was printed on 15 February
1995, so it is technically a 1995 publication).

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