Trituberculy : a review dedicated to the late Professor Cope / by Henry Fairfield Osborn.

  • Osborn, Henry Fairfield, 1857-1935.
Date:
[1897]
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Licence: Public Domain Mark

Credit: Trituberculy : a review dedicated to the late Professor Cope / by Henry Fairfield Osborn. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    1897.] accompanying table of terms used among the rhinoceroses and horses alone. It could not have been anticipated that the Fig. 2.—Rhinoceros Molar. Unde- that you see the simple termined species, showing secondary folds. bunodont molar of such a form as Owen’s Hyracotherium vulpiceps, underlying these diverse crests and crescents. Consult Taeker’s “ Zur Kenntniss der Odontogenese bei Ungulaten ” and you will find that this sexitubercular archetype is not imaginary, but is a constantly recurring fact of embryonic development—all the crests and crescents being preceded in the embryo by simple cones. Then compare carefully the variations in the two teeth as follows : The two “ cement lakes ” of Merycliippus with the two “ fos- settes ” of Aceratherium, enclosed in the former by crescentic spurs, and in the latter by the “ antecrochet” and “ crochet;” Fig. 3.—Simple Bunodont Molar.—Hyracotherium vulpiceps, after Owen. the posterior “lake” and “fossette” similarly enclosed by an upgrowth of the posterior basal cingulum. Can any one question the homologies between these secondary adaptations to a diet of grasses when it is seen that they spring from the diverse molars of the horse and of the rhinoceros, for example, would be limited in their variations, in a late geological period, by their -pre/ossette unity of origin in an ex- tremely early geological • QDt&croohet _J J G ° period. Yet such is un- doubtedly the case. Com- pare the accompanying figures of Merycliippus and of Aceratherium. Imagine crochet