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New insights into the brain, braincase, and ear region of tyrannosaurs (Dinosauria, Theropoda), with implications for sensory organization and behavior.
Anat Rec (Hoboken). 2009 Sep; 292(9):1266-96.AR

Abstract

The braincase region of tyrannosaurs was investigated to provide insights on anatomical attributes relevant to inferences of sensory biology and behavior. CT scanning focused on three specimens of Tyrannosaurus rex, a juvenile Gorgosaurus, and the controversial Cleveland skull (CMNH 7541). Analysis shows that the cerebral hemispheres were enlarged, but conflicting information on the optic lobes suggests that brain conformation was not fully avian. Previous estimates of olfactory bulb size for T. rex were much too large, but even the corrected sizes are relatively larger than other theropods, suggesting that odor detection was indeed of particular importance to tyrannosaurs. The inner ears show a number of coelurosaurian traits, such as elongate and rounded and rostral, lateral semicircular canals, and incipient twisting of the common crus, which we interpret to be related to enhanced reflexes coordinating rapid eye and head movements. The cochlea is elongate, which, coupled with the finding of extensive tympanic pneumaticity, supports the inference of behavioral emphasis of low-frequency sounds. Three main groups of sinuses pneumatized the braincase, and there are a number of perhaps systematically relevant differences. Orientation of the endosseous labyrinth reveals that alert head postures of T. rex and Gorgosaurus were somewhat depressed below the horizontal, but the Cleveland skull had a very strongly down-turned posture. It is concluded that tyrannosaur sensory biology is consistent with their predatory coelurosaurian heritage, with emphasis on relatively quick, coordinated eye and head movements, and probably sensitive low-frequency hearing; tyrannosaurs apomorphically enhanced their olfactory apparatus. The taxonomic status of the Cleveland skull remains unresolved.

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Publisher Full Text (DOI)

Authors+Show Affiliations

Witmer LM
Department of Biomedical Sciences, College of Osteopathic Medicine, Ohio University, Athens, Ohio 45701, USA. witmerL@ohio.edu
Ridgely RC
No affiliation info available

MeSH

AnimalsBrainCochleaDinosaursEar, InnerOlfactory BulbPostural BalancePsychomotor PerformanceSkullSmellVestibule, Labyrinth

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.
Review

Language

eng

PubMed ID

19711459

Citation

Witmer, Lawrence M., and Ryan C. Ridgely. "New Insights Into the Brain, Braincase, and Ear Region of Tyrannosaurs (Dinosauria, Theropoda), With Implications for Sensory Organization and Behavior." Anatomical Record (Hoboken, N.J. : 2007), vol. 292, no. 9, 2009, pp. 1266-96.
Witmer LM, Ridgely RC. New insights into the brain, braincase, and ear region of tyrannosaurs (Dinosauria, Theropoda), with implications for sensory organization and behavior. Anat Rec (Hoboken). 2009;292(9):1266-96.
Witmer, L. M., & Ridgely, R. C. (2009). New insights into the brain, braincase, and ear region of tyrannosaurs (Dinosauria, Theropoda), with implications for sensory organization and behavior. Anatomical Record (Hoboken, N.J. : 2007), 292(9), 1266-96. https://doi.org/10.1002/ar.20983
Witmer LM, Ridgely RC. New Insights Into the Brain, Braincase, and Ear Region of Tyrannosaurs (Dinosauria, Theropoda), With Implications for Sensory Organization and Behavior. Anat Rec (Hoboken). 2009;292(9):1266-96. PubMed PMID: 19711459.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - New insights into the brain, braincase, and ear region of tyrannosaurs (Dinosauria, Theropoda), with implications for sensory organization and behavior. AU - Witmer,Lawrence M, AU - Ridgely,Ryan C, PY - 2009/8/28/entrez PY - 2009/8/28/pubmed PY - 2009/12/16/medline SP - 1266 EP - 96 JF - Anatomical record (Hoboken, N.J. : 2007) JO - Anat Rec (Hoboken) VL - 292 IS - 9 N2 - The braincase region of tyrannosaurs was investigated to provide insights on anatomical attributes relevant to inferences of sensory biology and behavior. CT scanning focused on three specimens of Tyrannosaurus rex, a juvenile Gorgosaurus, and the controversial Cleveland skull (CMNH 7541). Analysis shows that the cerebral hemispheres were enlarged, but conflicting information on the optic lobes suggests that brain conformation was not fully avian. Previous estimates of olfactory bulb size for T. rex were much too large, but even the corrected sizes are relatively larger than other theropods, suggesting that odor detection was indeed of particular importance to tyrannosaurs. The inner ears show a number of coelurosaurian traits, such as elongate and rounded and rostral, lateral semicircular canals, and incipient twisting of the common crus, which we interpret to be related to enhanced reflexes coordinating rapid eye and head movements. The cochlea is elongate, which, coupled with the finding of extensive tympanic pneumaticity, supports the inference of behavioral emphasis of low-frequency sounds. Three main groups of sinuses pneumatized the braincase, and there are a number of perhaps systematically relevant differences. Orientation of the endosseous labyrinth reveals that alert head postures of T. rex and Gorgosaurus were somewhat depressed below the horizontal, but the Cleveland skull had a very strongly down-turned posture. It is concluded that tyrannosaur sensory biology is consistent with their predatory coelurosaurian heritage, with emphasis on relatively quick, coordinated eye and head movements, and probably sensitive low-frequency hearing; tyrannosaurs apomorphically enhanced their olfactory apparatus. The taxonomic status of the Cleveland skull remains unresolved. SN - 1932-8494 UR - https://www.unboundmedicine.com/medline/citation/19711459/New_insights_into_the_brain_braincase_and_ear_region_of_tyrannosaurs__Dinosauria_Theropoda__with_implications_for_sensory_organization_and_behavior_ L2 - https://doi.org/10.1002/ar.20983 DB - PRIME DP - Unbound Medicine ER -