THE DEVELOPMENT OF THE SKULL IN THE SLENDER LORIS, LORIS TARDIGRADUS LYDEKKERIANUS CABR.

Abstract

In the fully formed chondrocranium of the basal plate shows a steep incline towards the foramen magnum and orbitoparietal arches are united posteriorly with the basal plate, showing a prominent ridge. A tectum posterius connects the arches dorsally. The otic capsules are surmounted by the parietal cartilages and these are not connected with the planum supraseptale by the orbitoparietal commissures. The otic capsule is connected mesially with the basal plate by the basivestibular and sphenocochlear commissures. A prominent dorsum sellae is seen; in front of this in early stages (6.5 mm), a hypophysial fenestra is noticed. The hypophysial fenestra is obliterated later. A processus alaris, a processus petrygoideus and a broad ala temporalis are noticed; the latter is imperforate. The pilae metopticae and prooticae are broad and the orbital cartilage is connected with the nasal capsule by the sphenethmoid commissure. Sulci are noticed on the olfactory capsule and the epiphanial foramen is fissure-like. The lamina transversalis is incomplete and there is no complete zona annularis. The lamina transversalis posterior is broad and encloses Jacobson's organ. The posterior paraseptal cartilages are unconnected with the median septum nasi and also with the anterior paraseptal cartilage. At the region where the sulcus anterior separates the anterior and middle portions of the nasal capsule there is an independent piece of cartilage lateral to the cranial wall. There are 5 sets of turbinals. In the osteocranium, the successional appearance and fusion of the various membrane and cartilage bones are described. The study discloses that the chondrocranium of Loris resembles that of Nycticebus and differs from that of Tarsius.