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Braincases of Carnotaurus and Falcarius (new JVP)



From: Ben Creisler
bh480@scn.org

A couple of new articles on theropod braincases in the 
March 2011 Journal of Vertebrate Paleontology:


Carabajal, Ariana Paulina, 2011
The braincase anatomy of Carnotaurus sastrei (Theropoda: 
Abelisauridae) from the Upper Cretaceous of Patagonia  
Journal of Vertebrate Paleontology 31(2): 378 - 386 
DOI: 10.1080/02724634.2011.550354 
http://www.informaworld.com/smpp/content~db=all~content=a9
35220610~frm=titlelink

Abstract 
Carnotaurus sastrei is a large abelisaurid dinosaur from 
the Upper Cretaceous of Patagonia. Its remains include an 
almost complete skeleton with a well-preserved skull and 
braincase. Because relatively few abelisaurid braincases 
are known, the description of the Carnotaurus braincase 
is important for understanding the variability of this 
complex structure within the clade. Carnotaurus exhibits 
traits that characterize the abelisaurid basicranium, 
such as a well-developed preotic pendant, solid 
basipterygoid processes, and pneumatic basisphenoid, 
subsellar, and lateral tympanic recesses. The 
basipterygoid processes do not project laterally, unlike 
the divergent processes observed in other abelisaurids. 
Carnotaurus shares with the Malagasy abelisaurid 
Majungasaurus crenatissimus caudodorsally oriented 
paroccipital processes and a maxillomandibular foramen 
for the trigeminal nerve that in lateral view is aligned 
with the nuchal crest. The detailed description of the 
braincase of Carnotaurus presented here provides a better 
cranial anatomical record of this Patagonian abelisaurid 
and preliminary insights to the neurocranial morphology 
within the group.  


Smith, David K.; Lindsay E. Zanno; R. Kent Sanders; 
Donald D. Deblieux; James I. Kirkland, 2011 
New information on the braincase of the North American 
therizinosaurian (Theropoda, Maniraptora) Falcarius 
utahensis.  
Journal of Vertebrate Paleontology 31(2): 387 - 404 
DOI: 10.1080/02724634.2011.549442 
http://www.informaworld.com/smpp/content~db=all~content=a9
35221232~frm=titlelink


Abstract 
Many disarticulated bones from multiple individuals of a 
primitive therizinosaurian, referred to Falcarius 
utahensis, were found in the paucispecific Crystal Geyser 
bonebed in the Lower Cretaceous Cedar Mountain Formation 
of eastern Utah. To date, more than 2000 specimens from 
this species have been excavated. Included in this 
collection are two partial braincases, one of which is 
designated the holotype. Here we describe the braincase 
morphology of Falcarius utahensis. These specimens help 
establish the primitive cranial condition for the 
Therizinosauria and further substantiate intraspecific 
and contralateral braincase pneumatic variation in 
theropods. When combined with new observations on the 
cranial remains of the therizinosaurid Nothronychus 
mckinleyi derived from computed tomographic (CT) scans, 
the braincase morphology of Falcarius clarifies several 
evolutionary trends within the Therizinosauria and 
establishes a suite of synapomorphies for the 
Therizinosauridae. Trends within the clade include 
increased basicranial pneumatization (the development of 
a basisphenoid bulla and loss of external subcondylar 
recesses), anterior deflection of the supraoccipital, and 
the reduction of points of origin of the craniocervical 
musculature, associated with the loss of discrete 
basipterygoid processes, probably due to incorporation of 
these structures into the expanded hyperpneumatic bone. 
Finally, CT scans reveal a complete, nearly avian, inner 
ear with bird-like semicircular canals and a long cochlea 
indicating broad frequency discrimination.