Re: FEET OF EARLY BIRDS

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

At 06:14 AM 9/15/98 -0400, Larry Febo wrote:

>     So, I assume that the original statement,.. that the
arctometatarsalian condition is " reversed " in archaeopteryx, and
enantiornithine (sp),.. dosen`t imply that it is in the process of being
undone, but that the condition, unlike the arctometatarsalian, has the bones
fused principally at the proximal end. The Ornithurae would, as implied by
Feduccia, have the arctometatarsalian condition, and therefore shouldn`t be
grouped with the other two.
>

NONE of these birds shows the arctometatarsalian condition, which doesn't
have anything to do with fusion of the bones.

In the arctometatarsalian condition, the central metatarsal (III) is
wedge-shaped distally, and becomes a thing solid splint proximally.  The
sides of the wedge meet buttressing surfaces of metatarsals II and IV.

Now a few theropods with arctometatarsi DO have fusion (proximal -
Elmisaurus and Avimimus), but so do some theropods without an
arctometatarsus (Syntarsus, for example).

In the case of birds, there is actual fusion of the bones, but not an
arctometatarsus.

Hope this helps.

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