Fig. 25 in New Taxa And Cryptic Species Of Neotropical Snakes (Xenodontinae), With Commentary On Hemipenes As Generic And Specific Characters

Fig. 25. Evolutionary loss of a bilobed hemipenis and a forked sulcus spermaticus, demonstrated by apparent sister species. A. Taeniophallus brevirostris (W. Peters) showing retention of weak bilobation (right lobe incompletely everted) and shortening of the left branch of the sulcus spermaticus (MZUSP 8484, left organ). B. T. brevirostris showing complete loss of bilobation and similar shortening of the left branch of the sulcus spermaticus (AMNH R-28799, right organ). C. Taeniophallus nicagus (Cope) showing complete loss of bilobation and complete loss of bifurcation in the now-single sulcus spermaticus, which extends from the base to one side of the apex (AMNH R-138683, right organ). D. T. nicagus, an uneverted hemipenis, showing the unbifurcated sulcus spermaticus that extends to the apex, where it is largely concealed by the close-pressed sulcus lips (MCZ 149545, left organ). The first three hemipenes were manually and fully everted (except for one resistant lobe in A), but they probably are not completely expanded as is commonplace with eversions made from preserved specimens. Not to same scale.