[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Avimimus!!

Tim Donovan wrote-

>    Do you mean at Iren Dabasu? When was Avimimus found
> there?

Ryan, Currie and Russell, 2001. New material of Avimimus portentosus
(Theropoda) from the Iren Debasu Formation (Upper Cretaceous) of the Erenhot
Region of Inner Mongolia. JVP 21(3) 95A.

This describes several avimimid elements from the Iren Debasu Formation
(Campanian?) of China.  The orbital margin of a frontal (TMP 92.302.104) is
difficult to compare to A. portentosus, but is similarily bulbous over the
orbits.  There is an anterior dorsal (TMP 92.302.140) that resembles the
second of Avimimus, but has a shorter hypapophysis and more ventrally placed
parapophyses.  Another vertebra (TMP 92.302.344) was not identified
specifically, but appears to be a mid caudal.  There seem to be two small
lateral foramina, the centrum is not quadrangular in section and a low
neural spine is present.  A partial fused scapulocoracoid (TMP 92.302.116)
is shown, with a ventrally directed glenoid and low coracoid tubercle.  It
is very comparable to the holotype, but more incomplete, lacking the ventral
coracoid tip, most of the anterior edge and all but the base of the scapular
shaft.  A proximal humerus (TMP 92.302.117) is extremely similar to the
holotype, differing only in minor proportional details.  Both proximal (TMP
92.302.149) and distal (TMP 92.302.110) femoral ends are known.  The former
differs from the holotype in the more lateromedially compressed greater
trochantor and less prominent anterior trochantor in proximal view.  The
distal femur has less extensive articular surfaces in anterior view and a
less prominent lateral condyle.  In distal view, it is less convex
anteriorly.  A proximal tibia (TMP 92.302.150) is quite different from A.
portentosus, having a bulbous lateral condyle, less dorsally projected
cnemial crest, and small posterior process in proximal view.  The proximal
metatarsus (TMP 92.302.102) is very similar anteriorly and posteriorly, but
is differently shaped proximally, being parallelagram-like.  Another
metatarsus (AMNH 6755), this one complete except for the proximal portion of
metatarsal III, is quite unique.  It was found in the Central Asiatic
Expeditions of 1923 along with another third metatarsal (AMNH 6764).  This
metatarsus is arctometatarsalian, but the third metatarsal extends up 90% of
the metatarsal length in anterior view (and almost as much posteriorly).
This contrasts with 45% in A. portentosus.  This metatarsus is less slender
than the latter, with a more reduced fourth metatarsal and no fifth
metatarsal fused to it.  I'm not altogether convinced this is an avimimid
and not a caenagnathid, for instance.  Two pedal unguals (TMP 92.302.119A
and B) are quite odd.  They are markedly asymmetrical, having smaller
lateral halves with much higher grooves on that side.

Mickey Mortimer
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html