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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 (a1), Biren A. Patel (a1) and Mark N. Coleman (a2)

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.

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Andrews, C. W. and Beadnell, H. J. L. 1902. A preliminary note on some new mammals from the upper Eocene of Egypt. Survey Department, Public Works Ministry, Cairo, p. 19.
Barklow, W. E. 2004. Amphibious communication with sound in hippos, Hippopotamus amphibius. Animal Behavior, 68:11251132.
Bown, T. M. and Kraus, M. J. 1988. Geology and paleoenvironment of the Oligocene Jebel Qatrani Formation and adjacent rocks, Fayum Depression, Egypt. U.S. Geological Survey Professional Papers, 1452:160.
Ciarelli, M. J., Goldstein, S. A., Kuhn, J. L., Cody, D. D., and Brown, M. B. 1991. Evaluation of orthogonal mechanical properties and density of human trabecular bone from the major metaphyseal regions with materials testing and computed tomography. Journal of Orthopaedic Research, 9:674682.
Clementz, M. T., Holroyd, P. A., and Koch, P. L. 2008. Identifying aquatic habitats of herbivorous mammals through stable isotope analysis. Palaios, 23:574585.
Drum, M. G., Les, C. M., Park, R. D., Norrdin, R. W., Mcilwraith, C. W., and Kawcak, C. E. 2009. Correlation of quantitative computed tomographic subchondral bone density and ash density in horses. Bone, 44:316319.
Ducrocq, S. 1997. The anthracotheriid genus Bothriogenys (Mammalia, Artiodactyla) in Africa and Asia during the Paleogene: Phylogenetical and paleobiographical relationship. Stuttgarter Beitrage zur Naturkunde. Series B, 250:144.
Holroyd, P. A., Simons, E. L., Bown, T. M., Polly, P. D., and Kraus, M. J. 1996. New records of terrestrial mammals from the upper Eocene Qasr El Sagha Formation, Fayum Depression, Egypt. Palaeovertebrata, 25:175192.
Holroyd, P. A., Lihoreau, F., Gunnell, G. F., and Miller, E. R. 2010. Anthracotheriidae, p. 843851. InWerdelin, L. and Sanders, W. J.(eds.), Cenozoic Mammals of Africa. University of California Press, Berkeley.
Ketten, D. R. 1994. Functional analysis of whale ears: Adaptations for underwater hearing. I.E.E.E. Proceedings in Underwater Acoustics, 1:264270.
Ketten, D. R. 1997. Structure and function in whale ears. Bioacoustics, 8:103135.
Leidy, J. 1869. Notice of some extinct vertebrates from Wyoming and North Dakota. Proceedings of the Academy of Natural Sciences of Philadelphia, 21:6367.
Luo, Z. and Gingerich, P. D. 1999. Terrestrial Mesonychia to aquatic Cetacea: transformation of the basicranium and evolution of hearing in whales. University of Michigan Papers on Paleontology, 31:198.
McKenna, M. C. and Bell, S. K. 1997. Classification of mammals above the species level Columbia University Press, New York.
Nachtigall, P. E., Lemonds, D. W., and Roitblat, H. L. 2000. Psychoacoustic studies of dolphin and whale hearing, p. 330363. InAu, W. W. L., Popper, A. N., and Fay, R. R.(eds.), Hearing in whales and dolphins. Springer-Verlag, New York.
Nummela, S. 1999. Scaling and modeling of the mammalian middle ear. Ph.D. dissertation, University of Helsinki, Finland.
Nummela, S., Thewissen, J. G. M., Bajpai, S., Hussain, S. T., and Kumar, K. 2004. Eocene evolution of whale hearing. Nature, 430:776778.
O'Leary, M. A. 2010. Anatomical and phylogenetic study of the osteology of the petrosal of extant and extinct artiodactylans (Mammalia) and relatives. Bulletin of the American Museum of Natural History, 335:1206.
Owen, R. 1848. Description of teeth and portions of jaws of two extinct anthracotherioid quadrupeds discovered in the Eocene deposits on the N.W. coast of the Isle of Wight. Quarterly Journal of the Geological Society of London, 4:103141.
Patel, B. A. and Carlson, K. J. 2007. Bone density spatial patterns in the distal radius reflect habitual hand postures adopted by quadrupedal primates. Journal of Human Evolution, 52:130141.
Reysenbach de Haan, F. W. 1960. Some aspects of mammalian hearing under water. Proceedings of the Royal Society of London, B, 152B:5462.
Schmidt, M. 1913. Uber Paarhufer der fluviomarinen Schichten des Fajum: Odontographisches und osteologisches Material. Geologische und Palaeontologische Abhandlungen, 11:153264.
Seiffert, E. R. 2006. Revised age estimates for the later Paleogene mammal faunas of Egypt and Oman. Proceedings of the Academy of Natural Sciences, Philadelphia, 103:50005005.
Smith, P. F. 1969. Underwater hearing in man: I. Sensitivity. Navy Submarine Medical Center Report, 659:123.
Snyder, M. S. and Schneider, E. 1991. Estimation of mechanical properties of cortical bone by computed tomography. Journal of Orthopaedic Research, 9:422431.
Spaulding, M., O'Leary, M. A., and Gatesy, J. 2009. Relationships of Cetacea (Artiodactyla) among mammals: Increased taxon sampling alters interpretations of key fossils and character evolution. PloS One, 4:114.
Thewissen, J. G. M., Cooper, L. N., Clementz, M. T., Bajpai, S., and Tiwari, B. N. 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature, 450:11901194.
Tonndorf, J. 1968. A new concept of bone conduction. Archives of Otolaryngology — Hand and Neck Surgery, 87:595600.
Wainright, W. N. 1958. Comparison of hearing thresholds in air and water. Journal of the Acoustical Society of America, 30:10251029.
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Journal of Paleontology
  • ISSN: 0022-3360
  • EISSN: 1937-2337
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