Whales, not whippos, part I: Nature

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

Greetings,

Taking a break from last minute SVP preparations to say a few things about
TODAY'S new information on whale origins. (I say "today's" because
tomorrow's Science is supposed to have another important paleo-whale paper).

Thewissen, J.G.M., E.M. Williams, L.J. Roe & S.T. Hussain.  2001.  Skeletons
of terrestrial cetaceans and the relationship of whales to artiodactyls.
Nature 413: 277-281.

Describes new fossils of _Pakicetus_ and little _Ichthyolestes_, both with
substantial portions of their postcrania.  They have relatively long and
slender fore- and hindlimbs, and good old fashioned artiodactyl-style
double-pulley astragali.

The addition of this good skeletal material allows for a more substantial
phylogenetic analysis of mesoychian, cetacean, and artiodactyl
relationships.  Thewissen et al. find:
        *"Mesonychia" broadly defined is paraphyletic, with _Andrewsarchus_,
_Eoconodon_, a monophyletic Mesonychia, and a monophyletic Cetartiodactyla
forming a polytomy relative to basal ungualates;
        *Cetacea is the sister group to Artiodactyla;
        *There is no particular association of Cetacea with hippos (which are
relatively derived members of Suina, the traditional position for those
guys).

So, based on the new morphological information, whales are NOT descendants
nor the sister group of Mesonychia proper (although they and artiodactyls
share a common ancestor among "mesonychian-grade" ungulates).  However,
neither is Whippomorpha as concieved of by the gel-jocks a monophyletic
grouping.  Finally, the supposed dental synapomorphies of Cete (whales plus
mesonychians) are homoplastic.

According to Henry Gee's notes on Christian de Muizon's News & Views article
(p. 259-260), Gingerich et al.'s paper tomorrow includes a new protocetid
genus as well as a new species of _Rodhocetus_.

Later,

                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