> Before examining the alleged archaeocete to modern whale
>transition, a word needs to be said about the claim that _Ambulo-
>cetus_ was an aquatic mammal. This claim is based on its alleged
>cetacean affinities, its presumed capacity to swim via dorsoventral
>undulation, and the fact it was discovered in a region in which
>whales are believed by evolutionists to have originated. While
>_Ambulocetus_ may have been an aquatic mammal, none of these
>reasons is sufficient to prove the point. <
Thewissen et al cite several pieces of data to support their contention that
the motion was dorsoventral. They state (p. 211)
"On the other hand, the foot formed a large surface that could be swung
through the water when the back was flexed and extended. Therefore, the back
muscles primarily powered the hindlimbs as in phocid seals. Unlike phocids,
however, locomotion in water did not involve mediolateral but instead
dorsoventral undulations, as in recent cetaceans; the knee and proximal ankle
joint put the foot horizontal rather than vertical when the femur was
retracted from the hip."
If these points are not sufficient to prove dorsoventral motion, what is
wrong with their analysis of the knee and ankle joint? They also note that
the lumbar vetebrate shows evidence of dorsoventral motion. What is wrong
with their analysis of the vertebrate?
Ashby wrote:
> While Thewissen, et. al., boldly declare that "_Ambulocetus_
is clearly cetacean," a more cautionary note is sounded in the
article by Berta (cited above). Regarding the characters that
Thewissen, et. al., used to establish _Ambulocetus_ as a whale, she
states: "Before these purported whale characters can be used in a
phylogenetic definition of whales, however, the possibility that
some of them may have a broader distribution (for example, in
mesonychids) needs to be examined" (p. 181). <
Berta was not at all denying that ambulocetus was transitional. She was
disagreeing that whales should be defined by the traits which Thewissen et
al were advocating. Berta might be more likely to classify Ambulocetus as a
marine mesonychid rather than cetacean. This is an argument about taxonomy,
not genealogy.
Ashby goes on to criticize the archaeocetes to modern whale transition. But
that is beyond the scope of our original disagreement. I will go no further
than the transition to the archaeocetes.
I was able to get the Paleoverbrata Asiatica articles. They are in Chinese
with only a short English summary. As I mentioned, I can speak a little
Chinese badly but read none. By looking at it, I would agree that there is
probably nothing new since the Dissacus portions are too short to have very
much info.
glenn
J.G.M.Thewissen, et al., 1994, "Fossil Evidence for the Origin of Aquatic
Locomotion in Archaeocete Whales," Science 263, Jan, 14, 1994. p. 210-212.