New taxa and cryptic species of neotropical snakes (Xenodontinae), with commentary on hemipenes as generic and specific characters / Charles W. Myers, Samuel B. McDowell

• Superior document: Bulletin of the American Museum of Natural History 385
• VerfasserIn: Myers, Charles W. 1936-2018; MacDowell, Samuel Booker
• Place / Publishing House: New York, NY : American Museum of Natural History, 2014
• Year of Publication: 2014
• Language: English
• Series: Bulletin of the American Museum of Natural History 385
• Physical Description: 112 S.; Ill., Kt.; 26 cm
• Notes: Literaturverz. S. 104 - 112

Eutrachelophis, new genus is established to accommodate E. bassleri, new species, and E. steinbachi (Boulenger), new combination; a third species close to E. bassleri awaits naming. These taxa are placed in the Eutrachelophiini, new tribe, to express hypothesized relationship with the Xenodontini, which are defined by presence of hemipenial apical discs (a character lost in several species). The acalyculate spiny hemipenis of Eutrachelophis bassleri is unique among "xenodontines" in having a noncapitate, well-formed capitulum in the form of a nude dome; bifurcation is lacking even in the insertion of the major retractor muscle; the sulcus spermaticus is centrolineal in the retracted organ but becomes centrifugal during eversion. The hemipenis of Eutrachelophis steinbachi is strikingly different in being deeply divided, with long spiny lobes tipped with tufts of sender spines, but it resembles those of some other colubrids (e.g., South American Xenodon suspectus; African Mehelya poensis). Based on hemipenial comparisons, E. bassleri and E. steinbachi seem unlikely congeners. Nonetheless, global comparisons of viscera, head glands, head muscles, color pattern, skull, and dentition indicate that they are congeneric despite hemipenial differences. Neither E. bassleri nor E. steinbachi shows sufficient resemblance to any other "xenodontine" that would suggest an alternative phylogeny. Overall resemblance in so many details, especially of the skull, is not reasonably explained by convergence. Therefore, contrary to dogma, the hemipenes in this case provide no clues to generic affinity. An explanatory hypothesis has Eutrachelophis bassleri and E. steinbachi derived from common stock, but with hemipenial lobes in the bassleri lineage suppressed during embryonic development. It further suggests that the unusual broad, hemispherical nude apex in E. bassleri is homologous with the interlobular smooth, expandable terminal basin in E. steinbachi. The hemipenial differ