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Re: 190 million year old mammal footprints found



Dora Smith wrote:
> Yeah, I realized that, but it was kind of obvious, so I decided not to say
> it.   I believe it was alot more primitive as well.   I think that the
> critter from 190 million years ago was a full fledged mammal.
>
> Well, it pays to have a full timeline of mammalian evolution.

I was going to point you to the Synapsida and Mammaliformes phylogenies on
my Principles of Paleo website, but the server is down...

> Wikipedia says that the critter from the end of the Permian was probably
> already warm blooded and covered with fur.
>
Well, maaayyyybbbeee... At present the most primitive member with fur
homologous to modern mammals are the docodonts. Depending on whether
certain Triassic forms are docodonts are not, we might be pretty secure in
Late Triassic fur.

Some have argued that Thrinaxodon and related forms may have had fur, but
we don't have direct evidence of it yet. (I wouldn't be surprised at all,
though!)

And as for warm-bloodedness: we still do not have a secure way of
demonstrating when a lineage became warm-blooded, or to what degree. So
maybe some of the Late Permian forms were warm-blooded, but we can't tell
at present.
-- 
Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661

Faculty Director, Earth, Life & Time Program, College Park Scholars
http://www.geol.umd.edu/~jmerck/eltsite/
Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA