126 



O. RIEPPEL AND H. ZAHER 



Fig. 4 A-C A, The left maxilla of Cylindrophis maculatus (BMNH 

 1930.5.8.48) in lateral and dorsal views; B, The left maxilla of 

 Melanophidium wynaudense (BMNH 1930.5.8.124) in lateral and dorsal 

 views; C, The left maxilla of Pseudotyphlops philippinus (BMNH 

 1978.1092) in lateral and dorsal views. 



laterally descending flange of the parietal. In Rhinophis sanguineus 

 and Uropeltis, the crista trabecularis extends further anteriorly and 

 terminates below the optic foramen that is located in the frontal. In 

 front of the ossified crista trabecularis, the cartilaginous trabecula 

 cranii is embedded in all taxa in a deep furrow located between the 

 lateral margin of the parasphenoid and the ventrally projecting margin 

 of the frontal. Tiny fontanelles may persist along the line of fusion of 

 the basisphenoid and basioccipital in Rhinophis and Uropeltis. 



THE OTICO-OCCIPITAL COMPLEX 



The otico-occipital complex is here considered to include the prootic, 

 opisthotic-exoccipital, supraoccipital, and basioccipital. These brain- 



case elements show a variable degree of fusion with each other 

 among the specimens examined (Fig. 6). All braincase elements 

 except the opisthotic and exoccipital remain separate from one 

 another in Melanophidium. All braincase elements are fused with 

 one another in Plecturus, Pseudotyphlops, Rhinophis and Uropeltis, 

 but the basioccipital remains separate from the basisphenoid in 

 Teretrurus. The exoccipitals and basioccipital are always fused in 

 the occipital condyle. The stalk of the occipital condyle is short in 

 Melanophidium, Platyplecturus, and Teretrurus, but distinctly elon- 

 gated in the other taxa investigated, such that the depression of the 

 basioccipital housing the brainstem is exposed in dorsal view (Fig. 

 5). The exoccipitals define the dorsal margin of the foramen mag- 

 num, and their posterolateral corners are either deeply notched, or 

 perforated by a foramen. 



A laterosphenoid is always present in uropeltines, but while it 

 remains a relatively narrow element in Melanophidium (Fig. 6A-B) 

 and Pseudotyphlops (Fig. 6C), it becomes distinctly broadened in 

 the other taxa investigated. 



The plesiomorphic condition of the posterior opening of the 

 Vidian canal and its relation to the facial nerve branches is exempli- 

 fied by Melanophidium among uropeltines (Fig. 6A-B). The 

 hyomandibular and palatine branches of the facial nerve exit from 

 separate foramina opening into an obliquely oriented recess located 

 on the prootic closely behind the foramen for the mandibular branch 

 of the trigeminal nerve in Melanophidium punctatum (Fig. 6A), and 

 incompletely separated from the posterior margin of the mandibular 

 branch foramen in Melanophidium wynaudense (Fig. 6B). The 

 recess housing the facialis foramina becomes deeper ventrally, as it 

 connects with the posterior opening of the Vidian canal that is 

 located on the prootic - basisphenoid suture. This condition is 

 closely comparable to that in Cylindrophis and Anomochilus (Cundall 

 & Rossman 1993), except that the posterior opening of the Vidian 

 canal is located more (Anomochilus: Cundall & Rossman 1993, Fig. 

 4) or less (Cylindrophis maculatus) below the prootic - basisphe- 

 noid suture. In Pseudotyphlops (Fig. 6C) and Rhinophis sanguineus 

 (Fig. 6F), the palatine branch of the facial nerve enters directly into 

 a canal within the prootic which connects ventrally with the Vidian 

 canal, and which opens dorsally within the posteriorly expanded 

 recess of the mandibular branch foramen. This prootic canal appears 

 to be a modification of the condition observed in Melanophidium by 

 the lateral closure of the prootic recess that houses the facialis nerve 

 foramina. In Pseudotyphlops and Rhinophis sanguineus the Vidian 

 canal retains no separate posterior opening; the internal carotid 

 enters directly into the opening of the prootic canal. In all other taxa 

 investigated (e.g., Uropeltis, Fig. 6D; Rhinophis drummondhayi. 

 Fig. 6E), the palatine branch of the facial nerve enters again a prootic 

 canal which is completely separated from the mandibular branch 

 foramen however, and which opens anteroventral to the anterior 

 corner of the juxtastapedial recess. The internal carotid enters the 

 prootic canal on its way to the sella turcica. The anterior opening of 

 the Vidian canal lies on the suture between para-basisphenoid and 

 parietal in front of the dorsolateral wings of the para-basisphenoid 

 (McDowell 1967). 



The juxtastapedial recess is well developed in uropeltines, which 

 all except Pseudotyphlops share with Anilius and Cylindrophis the 

 presence of a fenestra pseudorotunda (Rieppel 1979a). The shaft of 

 the stapes is directed posterolaterally as it connects with the elon- 

 gated suprastapedial process of the quadrate via the stylohyal (Rieppel 

 1980; see also Wever 1978). As in scolecophidians and basal 

 alethinophidians, the juxtastapedial recess is open posteriorly, and 

 the jugular foramen is exposed in lateral view (Tchernov etal. 2000; 

 Fig. 6). The posteroventral corner of the crista circumfenestralis is 

 enlarged to form a gliding surface for the quadrate ramus of the 



