New information on the braincase of the North American therizinosaurian (Theropoda, Maniraptora) Falcarius utahensis

Journal of Vertebrate Paleontology
By: , and 



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 ofFalcarius 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.

Study Area

Publication type Article
Publication Subtype Journal Article
Title New information on the braincase of the North American therizinosaurian (Theropoda, Maniraptora) Falcarius utahensis
Series title Journal of Vertebrate Paleontology
DOI 10.1080/02724634.2011.549442
Volume 31
Issue 2
Year Published 2011
Language English
Publisher University of Oklahoma
Description 18 p.
First page 387
Last page 404
Country United States
State Utah
Online Only (Y/N) N
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details