Chatterjee,   Sankar.    (The  Museum,  Texas  Tech 
University,  Lubbock, TX 79409)  Skull of Protoavis 
and   Early   Evolution  of  Birds.    Journal   of 
Vertebrate Paleontology,  7 (Supplement to no.  3), 
16 September l987: Abstracts of Papers, 47th Annual 
Meeting,   Society   of  Vertebrate   Paleontology, 
October 22-24, l987.

Protoavis,  the oldest known bird from the Triassic 
of Texas is united with the ornithurine birds by 30 
postulated cranial synapomorphies which are grouped 
as follows: 1) loss of diapsid arch and postorbital 
bar   resulting   in   confluence   of   supra- and 
infratemporal fenestrae and orbit;  2) formation of 
postorbital  and zygomatic processes;  3)  external 
naris   bounded  by  premaxilla   and   nasal;   4) 
streptostylic quadrate with developments of orbital 
process,  condylar articulation with pterygoid, and 
lateral  cotylus  for  quadratojugal;  5)  loss  of 
postorbital  and ectopterygoid,  formation of jugal 
bar  and  prokinesis;  6)  highly  enlarged  brain, 
cerebrum contacts cerebellum  dorsally,  displacing 
optic  lobes  ventrally;  7) presence of  all  five 
tympanic   diverticula   with  the   formation   of 
squamosal  roof over the superior tympanic  recess; 
both    ATR   and   STR   developed   contralateral 
communications;  8) bony eustachian tubes;  9) bony 
mandibular  symphysis;  mandibular  elements  fused 
posteriorly and compressed laterally,  obliterating 
Meckelian  canal;  10)  horizontal  braincase  with 
well-developed metotic process and cochlear recess.

Most of these ornithurine apomorphies are absent or 
unknown  in  Archaeopteryx,   indicating  a   basal 
dichotomy   in   the  early  lineages   of   birds.  
Archaeopteryx  seems to be on a separate line  from 
modern  birds.   Protoavis  is the ancestor of  the 
Ornithurae to which all modern birds belong.

The  architectures  of the brain and inner  ear  of 
Protoavis  indicate  neurosensory   specializations 
associated with flight.


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