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Some Structural Variations in the Second Upper Premolar of the Lesser One‐horned Rhinoceros (Rhinoceros sondaicus) .
Author(s) -
POCOCK R. I.
Publication year - 1946
Publication title -
proceedings of the zoological society of london
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0370-2774
DOI - 10.1111/j.1096-3642.1946.tb00093.x
Subject(s) - rhinoceros , premolar , dentition , paleontology , geography , molar , geology
Summary. Two main conclusions may be deduced from the foregoing description:—(1) In Rh. sondaicus pm 2 of the permanent dentition, when unworn, may differ from pm 3 and pm 4 , as well as from the molars, in having the ectoloph and protoloph superficially separated and the anterior fossa opening in front between them. This at all events is the case in two youngish skulls, one without locality, the other from Lower Tenasserim. These may be set aside for the time being, pending the examination of additional skulls, if any, to prove that the newly erupted pm 2 is always so constructed. (2) In two fully adult, if not oldish, skulls from the Sanderbans, with pm 2 considerably worn, the condition above described persists, whereas in several skulls from the Sunda Islands, younger than the last, or about the same age, with pm 2 less or about equally worn, the ectoloph and protoloph are connected by a vertical crest which completely closes the anterior fossa in front. I provisionally attach racial significance to this difference and restore the name inermis for the now extinct Rhinoceros of the Sanderbans, restricting sondaicus in a racial sense to the form from the Sunda Islands.