Rhinoceros unicornis, Kaziranga, Assam, India. The mandible is the largest bone of the skull. It consists of two symmetrical halves which ossified at the body, both in adult and in young. The two halves ossified at the symphysis mandible. The lingual surface was wide, smooth and lightly concave, presenting a median line indicating the line of fusion of the originally distinct two halves of the body. The alveolor border was thick and slightly convex and continuous with the alveolar border of the body. There were 4 alveoli for lower incisor teeth. The two alveoli in the middle and smaller than those on the outside. The outer alveoli contained two large incisors. The inter-alveolar septum was massive. The lateral border was thick and slightly convex and continuous with the alveolar border. It formed a sharp ridge, extending from the large incisor teeth to the alveolar border of the rami and terminated at the cheek tooth. The rami, left and right, diverged laterally, forming a ?V' shaped intermandibular space. They were massive amd flattened from side to side. Each ramus was bent upwards and forward. The horizontal part was perforated by 6 alveoli for the cheek teeth, the first alveolus was the smallest and the rest were gradually larger in size towards the back. The posterior border of the horizontal part was thick, convex and smooth posteriorly while the vertical part was convex and rough. The lateral surface of the ramus was widest at the angle of the mandible. It was concave at the vertical part and convex at horizontal part. The horizontal part was gradually narrow towards the body of the mandible. The vertical part was wide throughout its length. It presented few rough lines at its lateral surface for the muscular attachment. The mental foramen was present at the level of the second cheek tooth. The horizontal part was convex dorsoventrally. The medial surface at the vertical part was concave with a prominent rough line towards the posterior part. Numerous faint impressions for nerves and blood vessels could be noticed. The mandibular foramen was closer to the alveolar border of the vertical part. The cornoid process projected upwards and then slightly backwards and inwards. It was pointed at the extremity and wide at the base. The mandibular notch was wide. The articular surface of the condyle situated below and behind the coronoid process. It was elongated transversely and projected inwards. Laterally, the surface was higher in position and thicker than the medial part. The condyle was convex antero-posteriorly. The neck of the condyle was thick, short and constricated. The posterior part behind and below the condyle revealed a triangular tuberosity. The labial surface was flat and quadrilateral in outline. A median faint ridge was found in some cases. On either side of the median ridge, a series of foramina was present obliquely which continued into the spongy part within the rami of the mandible. The number of formaina varied on either side. In addition, some minute foramina were also seen scattered throughout this surface. It was continuous with the lateral surface of the horizontal part of the ramus.
Rhinoceros unicornis, Kaziranga, Assam, India (n=7). The skull has the form of an irregular triangle, the base of which is caudal. Dorsal surface, is formed by occipital, interparietal, parietal, frontal and nasal bones. Interparietal bone was fused in adults. The dorsal surface wasdivided in three regions: parietal, frontal and nsal. The parietal region extends from the squamous part of the ocvcipital bone to the parietofrontal suture. This region ws located in between the external sagittal crist. The frontal region was the most extensive. The paired frontal bones were interposed between the parietal bones caudally and nasal bones rostrally. The profile of the frontal regionm is triangular and slightly concave. On either side of naso-frontal suture, two tuverosities can be noticed. The zygomatic process of the frontal bone is completely absent. However, the tuberosity mentioned before might be the rudimentary zygomatic process. The supra-orbital foramen is absent. The supra-orbital groove is absent. The nasal region is sharply concave due to the presence of a rough bony protuberance at the centre of the nasal bone which formed the highest point of the skull. Such protuberance on the nasal sutue was represented by a shallow groove. Nuchal or occipital surface. This is formed mainly by squamous and lateral parts of the occipital bone, together witha narrow strip of temporal bone on either side. The nuchal surface is separated from the dorsal surface by the nuchal crest. Just below the nuchal crest, squamous part of the occipital bone presents external occipital protuberance, on either side of which was a deep fossa. Between the protuberance and the foramen magnum was the external occipital crest which could be considered as the downward continuation of the external occipital protuberance. In the lateral part of the occipital bone, massive occipital condyles are found, one on either side of the foramen magnum. The dorsal and ventral margins of the foramen magnum were notched. Both the width and height of the foramen measured 6 to 7 cm. Lateral to the occipital condyle there was a paracondylar process.
