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Re: Re: dino dna



>
>Mammals presumeably arose during the Triassic from mammal like reptiles, of
>which little is known. There are few if any Triassic fossils which can be
>identified as mammals. Mammals appear suddenly in the Jurassis, but who know
>what ancestors led to this Jurassic radiation.  It has been suggested(Romer,
>Vert. Paleon.) that Synapsids led to mammals.  During those mysterious
>Triassic days, along with the mammal-like reptiles, theropod like dinosaurs
>appeared.

These statements, if nothing else, shows that Chip needs to get up to date
(like, about the 1960s, at least!) on vetebrate paleontology.  A VAST amount
of data, especially from southern Africa, Russia, China, southwestern U.S.,
South America, and western Europe, documents the lineages of the Synapsida
from the upper Pennsylvannian to the early Mesozoic (with the rise of the
Mammaliformes).  Synapsids are no longer considered members of the
Sauropsida ("Reptilia"), but are the sister taxon of such.  The Synapsid
fossil record is extraordinarily well documented (better than most of the
dinosaur or pterosaur record, unfortunately).

> The Archosauria probably gave rise to lines leading 1) to
>mammals, 2) to dinosaurs, 3) to modern day reptiles, and, as I suggested 4)
>to a line culminating in modern day birds.  Where and exactly when these
>branches appeared from the arcosaurian stem, remains to be elucidated.
>Correct me if I am wrong, but I can find no trees that don't have dotted
>lines during the Triassic, that is, back then, it's just speculation.  If
>there are recent fossil discoveries that further resolve this issue, please,
>please let me know.  My analysis of the sequence data, so far, sheds some
>light on the branching points in the early to middle triassic, and it is
>here that the birds branch off separately from the dinos and mammals.  I am
>estimating the 40 MYA, and that estimate will be fine tuned when, and if
>(that's a big if), I get more data.

You are wrong.

Try reading some recent texts (technical for once, since I can't see how you
could misunderstand these basic aspects of vertebrate paleontology unless
you've only been reading textbooks from the 1950s or popular books of today
[although even BAKKER deals with this!]).  Carroll 1988 is a fairly good
start, although the GSA short course of Major Events in Vertebrate Evolution
(from the 1994 Seattle meeting) is a good modern reference.

The Permian and Triassic have fantastic fossil records, which support a long
separation of the synapsid clade (including the mammals) and the sauropsid
clade (turtles, lepidosaurs, crocs, birds, and their extinct kin, including
the dinosaurs).

To turn this into a constructive comment, perhaps you can test your very
unconvential phylogenetic hypothesis with DNA fragments from extinct (or
living) pseudosuchians, lepidosauromorphs, anapsids, and nonmammalian
synapsids.  At least this has the potential to compare these different
lineages with mammals, dinos, and birds.  I can direct you to abundant
sources of all of these.  In fact, the results of such a study might well be
worth a presentation at the North American Paleontological Convention
symposium on preserved biomolecules!


Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084