Re: Dinofest 1999 in Baltimore!!!!!! <maybe>

[Tompaleo@aol.com]

In a message dated 2/3/99 5:02:50 PM Eastern Standard Time, pharrinj@plu.edu
writes:

> 
>  Regarding Maryland dinos, I apologize if this subject has already been
>  beaten to death,

This subject will never be beaten to death!



 but regarding large, _Brachiosaurus_-like sauropods from
>  eastern North America:
>  
>  Is it _Pleurocoelus_ or _Astrodon_?  How many species?

Well that depends on who you talk to. The taxonomic affinities of this
sauropod are far from clear. Many of those on the east coast who are familiar
with this ( Dave Weishampel for one, me , and I _think_ Tom Holtz and Greg
Paul among them, tend to accept  _Astronon_johnstoni_ as having priority over
any Pleurocoelus. There are those however such as Wann Langston who
steadfastly insisted to me one occasion that it's Pleurocoelus . I have
noticed that the western folks prefer the latter  whereas easterners prefer
the former (something to think about).
Leidy (1865) officially described _Astrodon_ johnstoni _based on some teeth
with no crania or postcranial material. Marsh (1888) described sauropod
postcrania, exclusive of teeth of apparently different intividuals thus
leading him to erect two species of _Pleurocoelus_. Incidentally, at that time
the only sauropods known were from the Jurassic so Marsh incorrectly thought
the Arundel was Jurassic in age and comparable to the western form of
_Pleurocoelus_. 

We need a damn skull to settle this once and for all!!!!!

Finally, Mike Brett-Surman has told me on a couple occasions that if the issue
is ever settled by addition of describable material that the rules of
nomenclature dictate that both genera will be sunk! ARGH!


The 'few" species named by Marsh, P. Altus and P. nanus are ontogenetic
variants on the same theme, Astrodon.


>  
>  Just how well-known is/are this/these species?  I.e. what material is
>  known?
>  

Mostly postcrania such as parts of long bones, including a 4 foot section of a
large femur, tibia/fibula, verts, mostly caudals with some dorsals and
sacrals, carpels etc. I have seen some small skull elements such as a partial
dentary of a small individual. These are described in Lull (1911) and
subsequent papers. 


>  Do these species show specific affinities with _Brachiosaurus_, or do they
>  simply resemble it in a general way?  <snip>

Originally, Astrodon was thouhght to be a Brachiosaurid  based on general
similarities of the available material but recently it had been speculated to
be a basal titanosaur. I honestly don't know enough about the material at hand
to even speculate. Perhaps Tom or Greg can...

Cheers,

Thomas R. Lipka
Paleontological/Geological Studies