Zupaysaurus

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

I have the description of _Zupaysaurus rougieri_ (Arcucci and Coria, 2003).  
Some interesting points from the paper:

Holotype: PULR-076, including a nearly complete skull (estimated total 
length: 45cm), several vertebrae (representing presacral and sacral series), 
and fragmentary limb material.  The specimen was found in the upper part of 
the Los Colorados Formation (Late Triassic; Rhaetian or Norian), La Rioja 
Province, Argentina.  The _Zupaysaurus_ holotype was found associated with 
other elements, from a smaller individual, including a fused 
scapulo-coracoid (it seems to be unfused in _Zupaysauyrus_), ilium, and 
distal femur.  The affinities of this second critter are unclear, and the 
material is not discussed further.

The _Zupaysaurus_ name derives from 'zupay', meaning 'devil' in the Quechua 
native language.  The species name honors Dr Guillermo Rougier.

The most prominent feature of the skull is the paired parasagittal crests, 
formed exclusively from the nasals (not the nasals and lacrimals, as in 
coelophysoids).  These were very thin.  Additional cranial ornamentation is 
expressed in the form of a rugose, laterally-projecting lacrimal ridge.  The 
premaxilla is not known, but the maxilla has a conspicuous step at its 
anterior edge.  The maxilla bears an alveolar ridge (apparently a primitive 
theropod feature; it is also seen in _Eoraptor_ and coelophysids).  The 
antorbital fenestra is oval-shaped, and the fossa very large (> 25%), and 
the maxilla tooth row ends in front of the orbit.  The dentition is poorly 
preserved, though the fourth maxilary tooth is the largest.  The authors 
estimate up to 24 four teeth in the jaws (15 in the maxilla).  The lower jaw 
shows an intramandibular hinge.

The neck of _Zupaysaurus_ was rather long, based on the length of the 
cervical centra.  The tibia is trasversely expanded distally, as in 
tetanurans.  The astragalus and calcaneum are fused to each other, but not 
to the tibia; and the astragalus has an anteriorly positioned ascending 
process.  Arcucci and Coria propose _Zupaysaurus_ as the most primitive 
known tetanuran theropod.



Tim

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