PHALLUS MORPHOLOGY IN CAECILIANS 



147 



Fig. 4 Uraeotyphlus cf. narayani ( Held tag MW 207). Views of (a) right lateral, (b) dorsal, (c) distal and slightly ventral, and (b) ventral surfaces of 

 phallus (everted cloaca). Scale bar for Fig. 4b = 3 mm. 



considered to be closely related, have blind sacs in a similar con- 

 dition, suggesting relatively stable and systematically informative 

 interspecific variation. Blind sacs are well developed in ichthyophiids 

 and uraeotyphlids, caecilians that Wake (1972) considered 'primi- 

 tive' in other reproductive characters, leading her to suggest that 

 well developed blind sacs are a general caecilian feature, with 

 reduction and loss being derived. In contrast, Tonutti (1931. 1933) 

 considered well developed blind sacs derived. Rhinatrematids are 

 believed to be the sister group of other extant caecilians on the basis 

 of a wide variety of evidence (e.g. Nussbaum, 1977; Hedges et <//., 

 1993; Wilkinson, 1996). Spengel (1876) and Wake (1972) docu- 

 mented blind sacs in the rhinatrematids Rhinatrema bivittatum 

 (Cuvier, 1829) and Epicrionops petersi Taylor, 1968 respectively, 

 but we note their absence (or minimal development) in mature 

 Epicrionops marmoratus Taylor, 1968 (MW, pers. obs.). This sug- 

 gests homoplasy and may complicate the interpretation of polarity. 



Anterior phallodeum. The lumenal surface of the anterior 

 phallodeum bears the distinctive structures seen on the external 

 surface of the more distal part of the fully everted phallus (Figs. 1,4 

 to 9). Much variation occurs here, but we discern a presumably 

 homologous pattern anteriorly that is common to almost all caecilians. 

 In this region there is a pair of deep dorsolateral grooves, one on 

 either side. Each of these sulci (Figs. 4 to 9) are bordered by a pair 



of well developed, parallel dorsolateral longitudinal or oblique 

 ridges. A median mid-dorsal longitudinal ridge may or may not also 

 be present, a variation that appears to be species specific. In species 

 with blind sacs, the sulci and their bordering ridges run into the blind 

 sacs, extending to their distal tips. In species lacking blind sacs, the 

 ridges fade out and the sulci open out at the anterior of the phallodeum, 

 either side of the colliculus. In Hypogeophis rostratus. the sulci run 

 posteriorly and terminate blindly with the fusion of their associated 

 ridges (Tonutti, 193 1 : Fig. 20; pers. obs.), a pattern that is consistent 

 in the 1 1 specimens of this species examined by one of us (MW). 

 Similar 'fusion' of the dorsolateral longitudinal ridges occurs in 

 many caecilians (e.g. Uraeotyphlus, Figs. 6 to 9). Less commonly, 

 the posterior end of each sulcus is open, with the more medial 

 bordering ridge fading out or fusing with its antimere along the 

 dorsal midline (e.g. Grandisonia alternans (Stejneger, 1893), 

 Gegeneophis ramaswamii, Boulengeritla boulengeri Tornier, 1896, 

 MW, pers. obs.). Additional major longitudinal ridges may or may 

 not be present lateral and/or ventral to those forming the sulci. In 

 uraeotyphlids (Figs. 4 to 9) and ichthyophiids, major longitudinal 

 ridges are broadly distributed, whereas in some caeciliids (pers. obs. 

 of e.g. Grandisonia Taylor, 1 968 and Schistometopum Parker, 1941; 

 this paper; Fig. 10) the ridges are more restricted to the dorsal 

 surface of the phallodeum. Although we have discussed a single 

 main pair of sulci, there may be other, smaller, more or less 



