Fig. 17 in A Possible Heptaxodontine and Other Caviidan Rodents from the Quaternary of Jamaica

Fig. 17. Isolated molars of Antillean heptaxodontine Amblyrhiza inundata from Pitchapple Cave, Anguilla, SEMs at low and high magnification. (A) AAHS 91253a, longitudinal section at low magnification, showing distribution of enamel, dentine and cementum (root end faces top of page; pc, pulp chamber). (B) Closeup of boxed area in A, showing appearance of dentine in crown. (C) AAHS 91253b, transverse section through root end at low magnification, showing pulp chamber (to right of box). (D) Closeup of boxed area in C, showing characteristic appearance of dentine matrix in this region. In both specimens, the root end is nearly as long as the crown, indicating that they came from aged animals. In early ontogeny each pulp chamber would have been broadly open beneath the apical ends of the enamel folds. With continuing elaboration of dentine, the chambers became constricted and progressively elongated. Since root canals must be preserved to transmit neurovascular bundles, canals mark the previous extent and line of adapical movement of pulp chamber. In Amblyrhiza, both primary and seconday dentine have an irregular appearance, with (in addition to characteristic tubules) many small vacuities that presumably housed cell bodies. There is no histologically sharp dividing line between the crown and root areas.