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ABSTRACT
Endocranial cavities preserve a record of neural anatomy often used for hypotheses of behavior in extinct organisms. Two reconstructions of cranial endocasts of Allosaurus fragilis and A. jimmadseni from computed tomography data expand understanding of theropod endocranial anatomy including endocranial volume, inner ear shape, and trigeminal ganglion size. Endocranial and trigeminal ganglion volumes are compared with a sample of birds, crocodylians, and non-avian theropod dinosaurs. Allosaurus is found to have a relatively small trigeminal foramen for its body size when compared with foramina of birds and crocodylians. The inner ear is fragmentary but similar in shape to semicircular canals of other large-bodied theropod dinosaurs. These findings suggest Allosaurus had generalist neural structures relative to other non-avian theropod dinosaurs. Like other large-bodied theropod dinosaurs, Allosaurus likely had a large dural venous sinus, potentially important for brain cooling. Allosaurus did not have a derived sense of facial somatosensation akin to that found in crocodylians or some birds. Additional data like these, collected from other tetanuran dinosaurs, will help clarify the evolution of neurosensory systems in the lineage.
ACKNOWLEDGMENTS
We thank The Jurassic Foundation (to EJL) and the National Science Foundation (to CMH; NSF EAR 1631684, IOS 1457319) for funding. Also thanks to C. Levitt-Bussian, Morphosource, the Ashley Regional Medical Center Staff including A. Batty, J. Nickells, and J. Hanberg, and the University of Texas High-Resolution X-Ray CT Facility, M. Colbert, and J. Maisano (NSF EAR 1762458). The conclusions presented here are those of the authors and do not represent the views of the United States Government.
DATA AVAILABILITY
The data that support the findings of this study are openly available in the digital repository Morphosource at https://www.morphosource.org/projects/000498875?locale=en.
AUTHOR CONTRIBUTIONS
EJL designed the project, gathered and analyzed data, and drafted the manuscript, CC gathered and analyzed data, RHF gathered data, and CMH analyzed data and drafted the manuscript. All authors edited the manuscript.