Fig. 13. Dinomys branickii AMNHM 46551 in Basicranial Morphology And Relationships Of Antillean Heptaxodontidae (Rodentia, Ctenohystrica, Caviomorpha)

Fig. 13. Dinomys branickii AMNHM 46551 (A); and AMNHM 70354 (B), right auditory regions (rev.), stereopair views (with key for A) in oblique ventral aspect. In A, the bullar floor and ossicles have been removed to expose the posttympanic canal; the facial canal lies more dorsally and thus is not visible. Because of the viewing angle, the posttympanic foramen, tympanic fenestra, and external acoustic meatus (asterisk and arrows) are hidden by the bullar wall. In the second specimen (B), the posttympanic ramus (suggested by pin) was conducted into the tympanic cavity along a partial septum (asterisk) rather than through a canal. The difference is not due to ontogenetic age, as AMNH 46551 is a juvenile in which cranial sutures are still widely open while AMNHM 70354 is fully adult. (The third pacarana available for osteological study, AMNHM 185372, exhibits large, possibly pathogenic exostoses in its tympanic cavity and presence of a canal could not be determined.)