Re: Beipiaosaurus and sauropod ancestry

["Jaime A. Headden" <qilongia@yahoo.com>]

Heinz Peter Bredow wrote:

<Now I wonder if such a redevelopment of the fifth toe
in therizinosauroids took really place, shouldn't it
also be possible for sauropods to do the same? So this
single character wouldn't preclude a prosauropod
ancestry of sauropods?>

  Not the fifth toe, the first. In advanced
prosauropods (everything above *Thecodontosaurus*, in
fact) the first metacarpal is in line with the first
at the ankle-hinge. As in advanced therizinosaurs, or
what have been interpreted as therizinosaurs (see Jack
Conrad's short article in Berislav's DIM for a
perspective he's advocated on his site). The
development of a tall mtI in late therizinosaurs and
late prosauropods only shows that the ankle format in
both is convergent, not evidence for closer
relationship. Once that's out of the way, being a less
diagnostic character, the other characters can be
analyzed more keenly. The wrist, for example, or the
hip. Or the teeth, or the "beak", or the .... Posts to
the list in the last two years and earlier this one
break down the characters and distributions, plus
check out Paul's 1984 paper in _JVP_, Maryanska's in
_the Complete Dinosaur_, and Barsbold and Osmolska's
in _Dinosauria_ for a more or less complete listing as
of 1997. Dong and Russell, 993, and Norell, Perle, and
Clark, 1997, listed more complete cranial evidence
that better focuses on some of the skull material in
relationships.

  Otherwise, the foot characters can be interpreted on
a functional basis: greater weight, shorter the foot
and metatarsals, more robust mtI (if present), and
longer femur than tibia ... you can compere these with
thyreophores, sauropods, iguanodont ornithschians
spending much of their time on four limbs, and even
several very large mammals. Really, it appears to be a
weight-related feature, but hopefully this can be
clarfied by further study, and a chance by me to cathc
the paper next time I manage to get to the college
library.

  Comments, fire?

  Spitwads?

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