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RE: Of Tarbosaurs and tabbies



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> zone65@bigpond.com
>
> I should know this already, but when did the lion and tiger diverge?
> Would it be accurate to say they are each branches of the same species
> on the path to distinct speciation? If so, do they therefore represent
> transitional forms, of the type so coveted in the fossil record?

No, lions and tigers are about as secure as species as any two taxa are. It
is fairer to say that these are two distinct species in which genetic or
morphological features to prevent interbreeding have not evolved. As Darwin
showed, regional varieties grade into subspecies which grade into species:
there aren't distinct breaks between these "ranks".

As for divergence dates: I believe there are Early Pleistocene
representatives of both P. tigris and P. leo, but I'm not certain if there
are any older.

Incidentally, leopards are part of this clade, too, and may be nested within
the lion-tiger clade.

                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