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Re: Pleurocoelus question
In a message dated 6/12/01 9:00:51 PM Eastern Daylight Time,
> Okay, fine, but who is to say that Astrodon is a nomen dubium. I was just
> talking about this with Ray Stanford off list (feel free to jump in, Ray
> I've done a lot of reading on the early discoveries of this dinosaur for a
> project during the past week or so.
So have I and many others, both on and off this list, and over a
considerably longer time ;-)
From what I have read, the first
> Astrodon specimens were discovered by a chemist, who showed the specimens
> few teeth) to a dentist. This dentist, Christopher Johnson, named the
> diagnosing it as having a "star shape" when cross cut. Leidy officially
> named the species and described it in 1865, keeping Johnson's diagnosis.
Right. Good research!
> To me, the species is diagnostic, unless tooth evidence does not count...
BINGO! In the case of sauropods, it does not! Sauropod teeth in general are
not distinct enough for taxonomic distinction. The "Astrodon" form is a
general form expressed by other genera not necessarily related to it. Though
star shaped in x-section, it is still a peg like in overall shape which
might indicate basal titanosaur or brachiosaur. Matt Wedel refers to the
"Astrodon" morph as a "form genus" . I can see why, I have also seen and
recovered these _exact_ shaped_teeth from the Antlers Fm. of Oklahoma (home
of _Sauroposeidon_) and in the Cloverly Fm. of MT (along with a considerable
number of postcrania and verrts of a yet to be described sauropod that are
NOT pleurocoelus sensu Pleurocoelus sp.) If the teeth from these localities
were mixed in with my Arundel material, it would be impossible to distinguish
them! But it is a near certainty that they belong to entirely different
Additionally, regarding the Maryland taxon, _P. altus _ (Marsh) was named for
the material belonging to a larger (ie. more adult) sauropod than that which
belonged to the smaller (more juvenile)_P. nanus_. Virtually all who have
seen the material, including myself, recognize the likelhood that the two
represent ontogenetic variants on the same Pleurocoelus sp.(?) theme. Alas,
the teeth we now refer to as Astrodon, likely belonged to Pleurocoelus
(likely _altus__ ) INMHO.
Conclusion: All sauropod material from the Arundel should now be referred to
Pleurocoelus, and _P._altus_ at that - the more valid nomen.
And just because Leidy named it just doesn't make it so! Ditto for O. C.
Marsh. Where the Arundel is concerned, Marsh's nomenclature leaves much to be
desired! I am having a ball with his theropoda! ;-)
He even believed the Arundel to be of Jurassic age because of the presence of
this sauropod. The Arundel is firmly dated to late-early K (Aptian) age. And,
we all now know that sauropods survived into the Late-K.
At least Marsh gave us a framework from which to build upon.
Finally, all of the above represents a turn around in my thinking regarding
Astrodon. I used to regard the "Astrodon" problem much the same way you do
now Steve. But with recent discoveries, and work by Salgado, Wedel and
others, and my own pers. obs., I have seen the light. My "Maryland Pride"
has been humbled!
Well, it's past my bedtime so I'll close before I really step on a mine!
Thomas R. Lipka