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RE: Convergence and Macelognathus, a Perspective & T-Rexapolosa

Tim Williams (twilliams_alpha@hotmail.com) wrote:

<Out of curiosity, just how strong is the case that _Hallopus_ and 
_Macelognathus_ are one and the same?>

  Well, fairly strong. Sampling limb anatomies from other sphenodontids such as
*Sphenodon,* *Terrestrisuchus,* and *Hesperisuchus,* then the sace for hindlimb
and forelimb elongation in *Hallopus* is fairly unique, implying that if any
other taxa share this feature it's pretty damn closely related. *Macelognathus*
does exhibit such similarities, but the problem is is that *Hallopus* is
preserved in a single specimen with much of the limb material poorly preserved
and impressions granting some further details. Distortion of bones and key
elements of comparison being impressions makes for a difficult to assess
comparison, so while the case is strong, the data its based on is weakened.
*Hallopus* and *Macelognathus* may be the same, but I show no confidence in
such an assignment without further data.

<Also, even though these Late Jurassic sphenosuchians had an erect posture, 
would I be correct in saying that there is no evidence that they were bipedal?>

  I would definately concur that, despite the elongated preacetabular ala of
the ilium and long limb bones, the animals were quadrupeds; several features of
the forelimb and hindlimb indicate terrestrial locomotion, including
independant forelimb anatomy and comparisons with living quadrupeds.


Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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