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Endocranial petrosal anatomy of Bothriogenys (Mammalia, Artiodactyla, Anthracotheriidae), and petrosal volume and density comparisons among aquatic and terrestrial artiodactyls and outgroups

Maureen A. O'Leary, Biren A. Patel and Mark N. Coleman
Endocranial petrosal anatomy of Bothriogenys (Mammalia, Artiodactyla, Anthracotheriidae), and petrosal volume and density comparisons among aquatic and terrestrial artiodactyls and outgroups
Journal of Paleontology (January 2012) 86 (1): 44-50

Abstract

We provide the first detailed endocranial description of the petrosal bone of the ear region of the anthracotheriid artiodactyl Bothriogenys, based on two new specimens from the early Oligocene of the Jebel Qatrani Formation, Fayum, Egypt. The new fossils have petrosals with a hyperinflated (pachyostotic) tegmen tympani (the roof over the middle ear), resembling the condition in certain cetancodontans such as hippopotamids and basal cetaceamorphans (fossil stem taxa to extant Cetacea). The morphology of the petrosal, particularly its relative size and density, has been considered an important indicator of the ability of a marine mammal to localize sound transmitted in water, yet petrosal size (pachyostosis) and density (osteosclerosis) have not previously been quantified independent of each other. We examine the new fossils in the context of a preliminary CT-based study of petrosal density (extant taxa only) and petrosal volume (extant and extinct taxa) in a sample of artiodactyls and outgroups. In our extant comparative sample, the petrosals of cetaceans are both dense and voluminous as has been previously stated. We find, however, that the tegmen tympani is relatively voluminous (pachyostotic) without being particularly dense (osteosclerotic) in Hippopotamus amphibius, an extant taxon that has been documented to show some aquatic hearing behaviors, albeit less derived ones than those seen in cetaceans. A voluminous tegmen tympani, which is present in Bothriogenys, may have specific implications for behavior that are distinct from increases in petrosal density.


ISSN: 0022-3360
EISSN: 1937-2337
Coden: JPALAZ
Serial Title: Journal of Paleontology
Serial Volume: 86
Serial Issue: 1
Title: Endocranial petrosal anatomy of Bothriogenys (Mammalia, Artiodactyla, Anthracotheriidae), and petrosal volume and density comparisons among aquatic and terrestrial artiodactyls and outgroups
Affiliation: State University of New York at Stony Brook, Department of Anatomical Sciences, Stony Brook, NY, United States
Pages: 44-50
Published: 201201
Text Language: English
Publisher: Paleontological Society, Lawrence, KS, United States
References: 29
Accession Number: 2012-016443
Categories: Vertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: NSF grants IIS-9874781, IIS-0208675, IOB 0517748, DEB-9903964, EAR 0116517, and DEB 0629836
Illustration Description: illus. incl. 1 table
N29°00'00" - N29°30'00", E30°30'00" - E31°15'00"
Secondary Affiliation: Midwestern University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201209
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