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D.J. GOWER AND M. WILKINSON 



among individuals, but whether this variation is correlated with 

 taxonomy, ontogeny, and/or temporally within any possible repro- 

 ductive cycles is as yet unknown. Occasionally, minor variations in 

 the ornamentation are seen. For example, the individual shown in 

 Fig. 4 also has a single, poorly formed, transverse thickening 

 ventrally. In the individual shown in Fig. 6, the posteriormost 

 transverse thickening on the right dorsolateral longitudinal ridge 

 extends posterior to the posteriormost transverse thickening on the 

 mid-dorsal longitudinal ridge, whereas the reverse of this pattern (as 

 seen on the left of this individual) is more commonly encountered. 

 Finally, the transverse thickenings or tuberosities are sometimes 

 multipartite. 



Figure 9 depicts the phallodeum of an individual identified as U. 

 cf. oxyurus (Dumeril and Bibron, 1841). Although the precise 

 specific identity of this individual also is not entirely clear, we are 

 confident that it is referable to a species distinct from that (or those) 

 represented in Figs. 4 to 8. For example, the U. cf. oxyurus indi- 

 vidual comes from a population with substantially more vertebrae 

 (112-115, n = 18) than the populations represented by the other 

 figured specimens (93-1 10, n > 100). Despite their apparent specific 

 distinctness, the phallodea of U. cf. narayani (Figs. 4 to 8) and U. cf. 

 oxyurus (Fig. 9) share the same number and pattern of longitudinal 

 ridges and transverse ornamentation. Thus Wake's (1972: 353) 

 claim that the phallodeal ridges and 'cloacal accessory structures is 

 species-specific' does not appear to hold - at least not at the level of 

 the presence, number, or topographical relations of major features. It 

 might yet hold for morphometric variations of phallodeal features 

 and/or for fine morphological details of the longitudinal ridges and 

 their ornamentation, but this needs further assessment. 



That not all species of Uraeotyphlus share the same basic 

 phallodeal morphology is revealed by observation of U. cf. 

 malabaricus (Beddome, 1870), in which the number and arrange- 

 ment of longitudinal ridges and their ornamentation is markedly 

 different. Interestingly, analysis of mitochondrial DNA sequence 

 data strongly indicates that U. narayani and U. cf. oxyurus share a 

 more recent common ancestor with each other than either does with 

 U. cf. malabaricus (Gower et al, 2002). 



Species' differentiation and generic identity. Nussbaum & 

 Pfrender's (1998) recent revision of the caeciliid genus 

 Schistometopum recognised two species occurring on opposite sides 

 of the African continent. S. thomense (Barboza du Bocage, 1873) is 

 known from Sao Tome island in the Gulf of Guinea, and S. gregorii 

 (Boulenger, 1894) from lowland coastal regions of Kenya and 

 Tanzania. The validity of the genus has not been seriously ques- 

 tioned, but it is currently diagnosed on a combination of characters, 

 with no known unique synapomorphies. 



Wake (1972: 358) described the male cloaca of S. thomense as 

 having 'four regularly spaced muscle bands on each side of the 

 cloaca', presumably features of the urodeum, and that 'the posterior 

 part of the cloaca [more the central region, as can be seen when the 

 cloaca is fully dissected] is arranged in three sets of transverse, 

 crescent-shaped muscles, one mid-dorsal, the other two ventro- 

 lateral.' Tonutti (1933) described longitudinal phallodeal ridges as 

 dorsal rather than ventrolateral in 5. thomense and we concur with 

 his assessment (see Fig. 10). Wake found the cloaca of S. gregorii to 

 have a similar morphology to that of S. thomense. Although we are 

 not convinced that the transverse ridges comprise muscle, we agree 

 that the two species share a similar morphology, and consider the 

 presence of three (though see discussion of S. gregorii below) 

 narrow and long longitudinal ridges with a characteristic ornamen- 

 tation of regularly spaced, scalloped transverse ridges and grooves 

 to be restricted to these two species among material we have 



a 



Fig. 11 Sketches showing disposition of major longitudinal ridges and 

 their ornamentation in the dorsal lumenal wall of the anterior part of the 

 phallodeum of (a) Schistometopum thomense (UMMZ 188027), and (b) 

 S. gregorii (UMMZ 14701 1 ) from Kenya. Compare with Tanzanian 5. 

 gregorii shown in Fig. 10. Not drawn to scale. 



observed. Thus, this phallodeal structure is potentially a unique 

 diagnostic character of Schistometopum. 



Wake (1972) considered the phallodeal ridges of Schistometopum 

 to resemble the condition in Geotnpetes. However, the part of the 

 mid-dorsal longitudinal ridge that bears ornamentation in both S. 

 thomense (Fig. 1 la) and S. gregorii (Figs. 10, lib) is relatively much 

 longer than the comparable ornamented area in Geotrypetes 

 seraphini, which is instead restricted to a small nubbin that lies at, or 

 slightly beyond, the level of the posterior end of the ornamented part 

 of the longitudinal ridges lateral to it (pers. obs. of e.g. UMMZ 

 172648). In addition, the ornamentation appears to be somewhat 

 different in the two genera, which otherwise also have quite differ- 

 ently organised cloaca (for example, Schistometopum lacks blind 

 sacs). 



The phallodeum of a single specimen (UMMZ 147011) of S. 

 gregorii from Northern Kenya has been examined and a sketch of 

 the ornamented part of the longitudinal ridges is shown in Fig. 1 lb. 

 The figured morphology is largely similar to that seen in several 

 specimens of S. thomense (e.g. Fig. 11a), except that, in UMMZ 

 147011, there is not a single mid-dorsal ridge, but instead two 

 paramedian longitudinal ridges, one longer than the other. Both of 

 these ridges bear transverse crests, but they are shorter relative to the 

 dorsolateral longitudinal ridges than in the observed specimens of S. 

 thomense. The morphology of the mid-dorsal region of the phallo- 

 deum in two Tanzanian specimens of S. gregorii observed for this 

 study (Fig. 10) both bear a greater resemblance to the condition in S. 

 thomense (Fig. 11a) than to the single Kenyan 5. gregorii (Fig. 1 lb) 

 examined. The sample size is small, but the observed morphological 

 variation is intriguing in light of Taylor's (1968: 677) suggestion 

 that, based on differences in annulation, the Tanzanian and Kenyan 

 populations of S. gregorii might be specifically distinct. 



DISCUSSION 



The complex structure of the caecilian phallus offers great potential 

 for caecilian systematics, both as a source of diagnostic features for 

 species, and of characters for phylogenetics. However, to fully 

 exploit this potential requires a better understanding of the extent of 

 intraspecific variation that occurs within features that appear to vary 

 interspecifically. Of course, in this regard there is no difference 

 between the caecilian phallus and any other structure employed in 

 systematics, and we suggest that incomplete understanding of vari- 

 ation should temper but not discourage the use of cloacal characters 



