Additional holotype remains of Ambulocetus natans (Cetacea, Ambulocetidae), and their implications for locomotion in early whales

Continued excavation at the type locality of Ambulocetus natans led to the recovery of a majority of the axial skeleton of the holotype of this early Eocene cetacean, including both innominates, the sacrum, and most of the thoracic cage and thoracolumbar vertebral column. Additional appendicular, ca...

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Bibliographic Details
Published in:Journal of vertebrate paleontology 2002-07, Vol.22 (2), p.405-422
Main Authors: MADAR, S. I, THEWISSEN, J. G. M, HUSSAIN, S. T
Format: Article
Language:English
Subjects:
Animal morphology
Cetaceans
Mammals
Pelvic bones
Ribs
Sacral spine
Sacrum
Spine
Vertebrae
Whales
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Summary:Continued excavation at the type locality of Ambulocetus natans led to the recovery of a majority of the axial skeleton of the holotype of this early Eocene cetacean, including both innominates, the sacrum, and most of the thoracic cage and thoracolumbar vertebral column. Additional appendicular, caudal, and cranial materials were also recovered, resulting in a specimen that is now approximately 80 percent complete. This new material allows refined interpretations of its functional morphology. Ambulocetus has a longer thoracolumbar column than that reported for later remingtonocetid and protocetid genera, suggesting that previous estimates of spinal length derived from models of mesonychid ancestry may be inaccurate. Ambulocetus also possesses a co-ossified ecto–mesocuneiform, a character found in some early and middle Eocene artiodactyls, but not mesonychids. New postcranial material provides further evidence of a systemic shift to aquatic locomotion.
ISSN:0272-4634
1937-2809
DOI:10.1671/0272-4634%282002%29022%5B0405%3AAHROAN%5D2.0.CO%3B2