Amphiesma

Cadle, John E., 2011, Hemipenial morphology in the North American snake genus Phyllorhynchus (Serpentes: Colubridae), with a review of and comparisons with natricid hemipenes, Zootaxa 3092 (1), pp. 1-25 : 8-9

Amphiesma

Amphiesma bitaeniatum (Wall) (CAS 215037; Figs. 4B and 5A ). Hemipenis with a pair of very short lobes, which are entirely spinose all around; left lobe slightly smaller than right. Apex between the lobes very broad and nude; nude area not extending to medial surface of the lobes and not demarcated by a distinct border from the spinose body (e.g., as in A. stolatum or Afronatrix ). Sulcus spermaticus simple, terminally expanded, and sinistral, gradually deviating left from a point well proximal to the apex. Sulcus lips slightly divergent distally, the divergence starting within the distal spinose area of the body and the widest part of the divergence at the border between the spines and the apical nude area, and just within the nude area. The left sulcus lip extends toward the left lobe, merging with the small spines on the medial surface of that lobe; the right lip essentially disappears at the edge of the nude apex, with a very fine extending ridge continuing into the nude area, deviating left and continuing toward the left lobe as well (this fine ridge is not clearly part of the sulcus lip, but it might be).

Amphiesma stolatum (Linnaeus) (CAS 215361; Fig. 5B ). Hemipenis bilobed, the lobes relatively slender, narrowing distally, and asymmetrical (left lobe shorter and narrower than the right). Sulcus spermaticus extends to the crotch in centrolineal position. Just before reaching the edge of the crotch the sulcus lips diverge slightly; at the sulcate edge of the crotch the sulcus lips diverge broadly, each lip following the sulcate edge of its lobe laterally for about two-thirds the length of the lobe before petering out. Another prominent transverse ridge extends across the asulcate edge of the crotch (arrow in Fig. 5B ), strongly demarcating that side. The asulcate ridge appears superficially similar to the tissue comprising the lips of the sulcus, i.e., smooth and thick; it peters out just short of half way up the asulcate edge of each lobe. The proximal single part of the sulcus is typically simple but the distal widely divergent sulcus lips are atypical outside natricids. Crotch itself entirely nude, the broad nude area extending nearly to the tip of each lobe, where small spines take over. Although this tissue is nude, it has many transverse (perpendicular to axis of the lobes) rounded ridges, giving a rugose appearance. The single part of the sulcus is continuous with this broad nude area but at the sulcate edge of the crotch is a very slight expansion and depression. In contrast to the specimen of A. stolatum examined by Rossman & Eberle (1977: 40 and Fig. 4F ), CAS 215361 and several others I examined have distinctly asymmetrical lobes. Additional specimens also suggest some variation in the prominence of the asulcate ridge (CAS 215361 was more prominent than some others).

Amphiesma venningi (Wall) (CAS 238902) and Amphiesma xenura (Wall) (CAS 220368). These two hemipenes are very similar and have short asymmetrical lobes that narrow distally like those of A. stolatum ; the very short lobes in A. venningi are more symmetrical than either A. xenura or A. stolatum . Crotch and medial surfaces of lobes nude (nude area extending proximally a short distance onto the asulcate surface in A. venningi ) but the very tips of the lobes are spinose. Sulcus spermaticus in both species extends to the sulcate edge of the crotch, where there is a slightly broadened tip. At this point, the lips of the sulcus diverge and extend one-half to three-quarters of the way up the sulcate side of the lobes as thick, rounded ridges. In A. xenura there was also a low ridge extending longitudinally up the middle of the nude area in each lobe but it was unclear whether this ridge was associated with the sulcus spermaticus proper.

Figures

FIGURE 4. Everted hemipenes of natricids in sulcate view. A, Afronatrix anoscopus (CAS 230205). B, Amphiesma bitaeniatum (CAS 215037) (detail of apex shown in Fig. 5A). C, Natrix tessellata (CAS 183115) (detail of apex shown in Fig. 5D).

FIGURE 5. Details of apical morphology of natricid hemipenes. A, Amphiesma bitaeniatum (CAS 215037). B, Amphiesma stolatum (CAS 215361). C, Natrix maura (CAS 138733). D, Natrix tessellata (CAS 183115). Arrow in B indicates the asulcate ridge delimiting the apical nude area (see text).