SKULL OF UROPELTINAE 



129 



are informative for the analysis of uropeltine interrelationships 

 (unfortunately. Melanophidium was not included in the analysis 

 performed by Cadle et al. [1990]). 



The genera Teret runts. Platyplecturus, Pseudotyphlops, Plecturus, 

 Uropeltis. and Rhinophis form a monophyletic clade that is very 

 strongly supported on the basis of 7 characters (decay index: +6). 

 This represents a strong corroboration of the basal position of the 

 genus Melanophidium (unequivocal synapomorphies are designated 

 with an asterisk): *8(1), supraoccipital fused to opisthotic - 

 exoccipital; *9(1) prootic fused to opisthotic - exoccipital; 11(1) 

 laterosphenoid broad (reversal implied); 12(2) palatine branch of 

 facial nerve enclosed in prootic canal which is separate from man- 

 dibular branch foramen; 15(1) jugular foramen single (reversals 

 implied); 18(2) posteroventral process of dentary absent (reversal 

 implied); 29(2) gliding surface for pterygoid posteroventral to 

 juxtastapedial recess 'rounded off (reversal implied). The 

 monophyly of all uropeltines except Melanophidium is the most 

 strongly supported clade on the basis of this data set. 



Within that clade, Platyplecturus is the sister-taxon of a clade that 

 includes (Pseudotyphlops (Plecturus (Rhinophis, Uropeltis))) on 

 the basis of 2 characters (decay index: +1): *2(1) nasals narrow 

 anteriorly, gradually tapering to pointed tip; *10(1) basioccipital 

 fused to basisphenoid. Pseudotyphlops is the sister-taxon of a clade 

 that includes (Plecturus (Rhinophis, Uropeltis)) on the basis of three 

 characters (decay index: + 1 ): 1(1) transverse process of the premax- 

 illa points posterolaterally, and meets the straight maxilla in a 

 shizarthrosis (convergent in Teretrurus); * 1 3( 1 ) narrow lateral open- 

 ing of the juxtastapedial recess; * 17(1) stalk of the occipital condyle 

 elongated. Plecturus shares with the (Rhinophis. Uropeltis) - clade 

 three characters (decay index: +2): 5( 1 ) optic foramen fully enclosed 

 by frontal; 14(1) jugular foramen recessed within posteroventral 

 corner of juxtastapedial recess; 15(0), jugular foramen internally 

 subdivided (reversal). 



The clade that includes Rhinophis and Uropeltis (decay index: 

 + 1) is diagnosed by a well-defined buttressing contact between the 

 processus medialis anterior of the maxilla and an anterior lateral 

 process of the vomer (*4 [1]). Interestingly, there is a signal for the 

 paraphyly of the genus Rhinophis, because Rhinophis sanguineus 

 appears to be more closely related to Uropeltis than to Rhinophis 

 drummondhayi on the basis of two characters (decay index: +1): 

 6(2) crista trabecularis ends in front of lateral fronto-parietal suture; 

 7(0) supraorbital process of parietal does not contact prefrontal 

 (reversal). 



1990) is not supported here. By contrast, the possible paraphyly of 

 the genus Rhinophis indicated by molecular data (Cadle et al. 1990) 

 is also found here, although far less species were included in the 

 morphological analysis. 



Pseudotyphlops is larger that all other uropeltines included in the 

 analysis, and it shows characters of cranial anatomy that appear in 

 outgroup taxa such as Anilius and Cylindrophis, but not in other 

 uropeltines. In the adult skull of Anilius and Cylindrophis, the part of 

 the para-basisphenoid located behind the optic foramen has a con- 

 cave ventral surface, which results in the formation of distinct lateral 

 ventral ridges (Tchernov etal. 2000). This character is also observed 

 in the relatively large skull of adult Pseudotyphlops. In the much 

 smaller skull of other uropeltines, the ventral surface of the para- 

 basisphenoid is at best very weakly concave, flat, or even slightly 

 convex, and ventral lateral ridges are very faintly indicated 

 (Melanophidium. Platyplecturus. Plecturus. Uropeltis. Rhinophis), 

 or absent (Teretrurus; also in Anomochilus: Cundall & Rossman 

 1993). The same observation relates to the presence of a sagittal 

 ridge on the parietal, well expressed in adult Anilius, Cylindrophis, 

 and in Pseudotyphlops among uropeltines, much reduced and re- 

 stricted to the posterior part of the parietal or absent in Anomochilus 

 and smaller uropeltines. Given its relative size, and the presence of 

 relatively plesiomorphic features in the skull, a basal position of 

 Pseudotyphlops relative to other uropeltines might have been 

 expected, but was not corroborated by cladistic analysis, although 

 the genus is still outside the (Plecturus (Rhinophis. Uropeltis)) 

 clade. 



The morphological transformation that is implied in the descrip- 

 tion of the Vidian canal in uropeltines (and in its coding; the 

 character was used unordered) is also contradicted by the cladistic 

 analysis discussed above. The description suggests that the indi- 

 vidualization of the prootic canal (which receives the palatine 

 branch of the facial nerve and into which enters the internal carotid) 

 follows its formation in association with the recess of the mandibu- 

 lar branch foramen, the cladistic analysis suggests otherwise. The 

 incorporation of the opening of the prootic canal into the recess of 

 the mandibular branch foramen is a secondary development that 

 occurred convergently in Pseudotyphlops and Rhinophis sanguineus. 



Acknowledgements. We would like to thank E.N. Arnold and C. 

 McCarthy (BMNH), as well as Harold Voris and Alan Resetar (FMNH) for 

 permission to study the collections under their care. D. Cundall and two 

 anonymous reviewers offered helpful criticism on earlier drafts of this paper. 



DISCUSSION AND CONCLUSIONS 



The monophyly of Uropeltinae has not previously been questioned 

 (Rieppel 1977; Cadle et al. 1990; Cundall et al. 1993;Scanlon&Lee 

 2000; Tchernov et al. 2000) and is here corroborated by six un- 

 equivocal synapomorphies (decay index: +3): *19(2), exoccipitals 

 and basioccipital fused in occipital condyle; *20(2), anterior denti- 

 gerous process of palatine modified into expanded lamina; *30(1), 

 occipital condyle modified as described by Williams (1959) and 

 Hoffstetter & Gasc ( 1 969); *3 1 ( 1 ), the superior alveolar nerve canal 

 in the maxilla is open dorsally ; *32( 1 ), frontals at least twice as long 

 as broad; *33( 1 ), supratemporal absent. 



The phylogenetic analysis of the interrelationships among 

 Uropeltinae corroborates the hypothesized basal position of the 

 genus Melanophidium, the latter possibly paraphyletic. The clade 

 comprising Teretrurus and the Indian species of Uropeltis that is 

 consistently obtained on the basis of allozyme data (Cadle et al. 



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