The external and internal surfaces of the skull of the Hispaniolan solenodon, Solenodon paradoxus Brandt, 1833, are described and illustrated in detail based on five museum specimens (one from Carnegie Museum of Natural History, the remainder from American Museum of Natural History). Two of the specimens are juveniles that preserve sutural information that is lacking in the adults; one adult is bisected and exposes the interior of the nasal and cranial cavities. A sixth specimen is a serially sectioned ear region of a juvenile from the Max-Planck-Institut für Hirnforschung that provides information on soft-tissue structures.
The Hispaniolan solenodon has a peculiar skull with numerous highly unusual features among mammals. Included are: a small, oval ossification, the os proboscidis, jutting anteriorly from the ventral rim of the external nasal aperture; zygoma incomplete and jugal bone absent; exposure of the ethmoid bone in the orbit but palatine not; numerous orbital foramina accommodating veins communicating across the midline ventrally in the presphenoid and dorsally in the frontal; tiny optic foramina; venous transverse canal through basisphenoid; entoglenoid process of squamosal but no postglenoid process; abutment between the rostral process of the malleus and the crista parotica of the petrosal; rostral and caudal tympanic processes of the petrosal fused; large occipital emissary vein foramen endocranially between supraoccipital and parietal; large venous condyloid canal through exoccipital; paired interparietals; mandible with two “angles,” a true angular process and a process for the digastric muscle. Perhaps the most unexpected finding is that of a prootic canal for the lateral head vein in the petrosal bone. Prootic canals are broadly distributed in Mesozoic mammals including a few Cretaceous eutherians, but heretofore are unknown in placentals.