Re: Astrodon vs Pleurocoelous

["Timothy Williams" <twilliams_alpha@hotmail.com>]

Alan Blake Coulson wrote:

> Does anyone know the current status of these taxa? I seem to remember
> hearing that someone had consolidated the 3(?) Pleurocoelous species into
> 1 or 2, and that they were distinct from Astrodon, but I cannot remember
> the source.


If Salgado and co are correct, no less than THREE sauropod genera are 
represented from among the Lower Cretaceous North American material 
traditionally named "Pleurocoelus".  According to recent research (which is 
still in progress)...

(1) _Pleurocoelus nanus_ (type species, from the Arundel Formation of
Maryland) is a brachiosaurid (or at least outside the Titanosauria); it 
shows a few titanosauriform synapomorphs (absence of phalangeal articular 
surfaces on the distal metacarpals; transversely expanded distal tibia), but 
its anterior caudal vertebrae are amphiplatyan, not procoelous.

(2) _P. altus_ (also from the Arundel Fm) is NOT an adult _P. nanus_; it 
probably does not even belong in the same genus.  _P. altus_ "exhibits an 
anteroposteriorly expanded distal tibia, a character which is plesiomorphic 
for sauropods."

(3) The _Pleurocoelus_ material from the Comanche Series of Texas,
definitely does NOT belong in the genus _Pleurocoelus_.  Its anterior
caudals are weakly procoelous.  Based on this and other features, the 
Comanche sauropod may be a basal titanosaur, and possibly the same as 
_Cedarosaurus_.

As for _Astrodon_, its based on teeth that are considered to belong to an 
undetermined sauropod.  Thus _Pleurocoelus_ is probably not referrable to 
_Astrodon_.

Hope this helps.


Tim

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