RE: Requiem for Diatryma (birdwalk)

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> NJPharris@aol.com
> In a message dated 9/22/99 8:12:18 AM Pacific Daylight Time,
> cfkammer@midway.uchicago.edu writes:
>
> > Hyracotherium (another name, albeit
> >  much less beloved, whose meaning has been dramatically altered
> of late).
>
> I remember some posts about this over the last couple years, but I never
> heard it resolved.  Just what *is* _Hyracotherium_ believed to be
> these days,
> and what is the proper name for the early horse material?
>
Check out:
Froehlich, D. J.  1999.  Phylogenetic systematics of basal perrissodactlys.
JVP 19:140-159.

Basically, the type of _Hyracotherium_, _H. leporinum_, is palaeothere (the
group which was the extinct sister taxon to Equidae, and incidentally one of
the (human historically) oldest named groups of Tertiary mammals!);
_Eohippus_ is very likely a junior synonym of either _Systemodon_ (a basal
tapiromorph) or the aberrant basal equid _Xenicohippus_.  Several of species
traditionally placed in _Hyracotherium_ (_H. sandrae_, _H. grangeri_, _H.
craspedotum_, _H. montanum_, _H. venticolum_) represent a paraphyletic
series of basal equids.  Interspersed among these are the genera
_Xenicohippus_, _Pliolophus_, _Orohippus_, and _Epihippus_.

So, there is a paraphyletic smear of basal equids, for which no good name is
available (or necessarily appropriate).

C'est la vie.

> And to legitimize this post on a dinosaur mailing list, what's
> the deal with
> _Ammosaurus_ and _Anchisaurus_?
>

Lurking in the supplementary material (downloadable from the web) of
Sereno's recent Evolution of Dinosaurs paper (Science 284:2137-2147) is the
statement that _Ammo._ and _Anchi._ are synonyms.  No detailed description
as to the reasons for the synonymy at this date, and I will be interested to
see what other prosauropod workers (e.g., Upchurch) find with the
relationship of these two critters.

                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