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RE: something's wrong here: Qianosuchus phylogeny
David Peters wrote:
No wonder the authors were not able to figure out where Qianosuchus nested.
They needed the following taxa: Triassolestes, Turfanosuchus,
Just a minor quibble. _Triassolestes_ is a fossil dragonfly (Tillyard,
1918), _Trialestes_ is the fossil crocodylomorph (Bonaparte, 1982 - to
replace _Triassolestes_ Reig, 1963).
And when all the work is done, you have to step back, take a look at the
whole thing and ask yourself: "Does this make sense?" remembering that
evolution works in tiny increments.
(a) "Does this make sense?" is a question that too often is answered by
someone who believes that there own opinions have priority over analysis of
the data. This is also called "hand-waving".
(b) Evolution does not *always* work in tiny increments. Here's an example
of one hypothesis to the contrary...
Sears K.E., Behringer R.R., Rasweiler J.J. 4th, and Niswander L.A. (2006)
Development of bat flight: morphologic and molecular evolution of bat wing
digits. Proc. Natl. Acad. Sci. USA. 103: 6581-6586.
Abstract: "The earliest fossil bats resemble their modern counterparts in
possessing greatly elongated digits to support the wing membrane, which is
an anatomical hallmark of powered flight. To quantitatively confirm these
similarities, we performed a morphometric analysis of wing bones from fossil
and modern bats. We found that the lengths of the third, fourth, and fifth
digits (the primary supportive elements of the wing) have remained constant
relative to body size over the last 50 million years. This absence of
transitional forms in the fossil record led us to look elsewhere to
understand bat wing evolution. Investigating embryonic development, we found
that the digits in bats (_Carollia perspicillata_) are initially similar in
size to those of mice (_Mus musculus_) but that, subsequently, bat digits
greatly lengthen. The developmental timing of the change in wing digit
length points to a change in longitudinal cartilage growth, a process that
depends on the relative proliferation and differentiation of chondrocytes.
We found that bat forelimb digits exhibit relatively high rates of
chondrocyte proliferation and differentiation. We show that bone
morphogenetic protein 2 (Bmp2) can stimulate cartilage proliferation and
differentiation and increase digit length in the bat embryonic forelimb.
Also, we show that Bmp2 expression and Bmp signaling are increased in bat
forelimb embryonic digits relative to mouse or bat hind limb digits.
Together, our results suggest that an up-regulation of the Bmp pathway is
one of the major factors in the developmental elongation of bat forelimb
digits, and it is potentially a key mechanism in their evolutionary
elongation as well."
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