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Leidy, J.


[Remarks on the teeth of Mosasaurus].

Proceedings of the Academy of Natural Sciences of Philadelphia 9:176.

Copyright 2005-2012 by Mike Everhart

ePage created 11/16/2012




LEFT: Teeth of Mosasaurus in detail from Plate XI of Leidy, 1865.

Wherein Joseph Leidy provides a description of the teeth, method of attachment and means of replacement for the teeth of Mosasaurus. A more recent study is provided by Caldwell, et. al., 2003. Click here for a picture of replacement teeth in a Leiodon specimen (Maastricht Museum).

176                                   Proceedings of the Academy of





 September 1st, 1857

Vice-President Bridges in the Chair.

     Dr. Leidy remarked that there appeared to exist a general misconception in regard to the dentition of the Mosasaurus*. The animal is almost universally called an acrodont reptile, or one in which the teeth are inserted upon, or are co-ossified with, the border of the jaws. A number of specimens of teeth and fragments of jaws, in the museum of the Academy, prove this appellation to be incorrect.

     The teeth of Mosasaurus* have a recurved pyramidal crown, and a more massive vertically oblong root, which is often twice the length of the crown. The root is inserted for three-fourths of its extent into a corresponding deep socket, with the sides of which it is co-ossified. The centre of the teeth is occupied by a fusiform pulp cavity, communicating with one or more vascular canals passing through the fang.

      In the reproduction of the teeth, it appears that new ones commence to be developed attached to the gum, on the postero-internal side of the alveoli. As they proceed, they penetrate into the latter, by exciting an absorption of the substance of the fang of the old teeth in a direction obliquely outward and forward. The cavity of the new tooth increases in size at the expense of the substance of the fang of the old one. The pulp cavity of the old tooth, in consequence of the ossification of its pulp, appears to recede before the increasing cavity of the new tooth. The latter cavity finally makes a communication with the former, thought this appears not always to be the case; and subsequently the fang of the old tooth becomes so completely excavated as to form a mere capsule, from which its crown is broken away or shed, through comparatively little violence. In further progress of the newly protruding tooth, the osseous capsule formed from the fang of the old tooth is gradually obliterated, except for a portion which remains as a partition from the next alveolus.




*- mis-spelled as Mososaurus in the original text ... corrected herein.


Caldwell, M. W., L. A. Budney, and D. O. Lamoureux. 2003. Histology of tooth attachment tissues in the Late Cretaceous mosasaurid Platecarpus. Journal of Vertebrate Paleontology, 23(3)622-630.

Leidy, J. 1858. [Remarks on the teeth of Mosasaurus]. Proceedings of the Academy of Natural Sciences of Philadelphia 9:176.

Leidy, J. 1865. Memoir on the extinct reptiles of the Cretaceous formations of the United States. Smithsonian Contributions to Knowledge14(6):1-135, pls. I-XX.

Credits: Mike Caldwell provided the copy of this somewhat obscure article by Joseph Leidy. Earl Manning provided figures from Leidy, 1865.