Sunday, July 13, 2014

A new arrangement for the blind snake superfamily Typhlopoidea

The blindsnake superfamily Typhlopoidea is a diverse and widespread part of the global snake fauna. The superfamily Typhlopoidea now contains three families: Gerrhopilidae, Typhlopidae, and Xenotyphlopidae. Gerrhopilidae inhabits South and Southeast Asia and the East Indies. Xenotyphlopidae occurs only in northeastern Madagascar. But, Typhlopidae is widespread, containing at least 257 species. Typhlopids have major radiations in the New World tropics, Africa, Madagascar, South Asia, Southeast Asia, and Australia and new species are commonly reported from all of these areas. The true diversity of the group is probably much higher, as evidenced by a recent molecular study of Australian Ramphotyphlops, which showed that the actual number of species is 200–340% greater than currently recognized.

The discovery and description of new species is limited by their fossorial life styles (making them difficult to encounter), and relatively conserved morphology (making them difficult to diagnose and delimit). As a result, there has been little in-depth phylogenetic analysis or systematic investigation of the group, usually restricted primarily to single geographic areas and relatively few characters. Throughout most of their recent history, all blindsnakes were included in the genus Typhlops. In the mid-20th century, solid coiled hemipenes and paired retrocloacal sacs were discovered in the Australasian radiation, leading these species to be separated into Ramphotyphlops. The name Typhlina was also applied to this group, but was found to be in the synonymy of both Ramphotyphlops and Leptotyphlops, and was thus later suppressed by the International Commission on Zoological Nomenclature on appeal. Until very recently, most species were placed in Typhlops and Ramphotyphlops. Other genera were erected or resurrected and species moved between them on the basis of morphological characters, but rarely, if ever, from phylogenetic analysis of either morphological or molecular data. These include the African radiation, and two morphologically divergent groups from Oceania. The genus Cathetorhinus was resurrected for the morphologically divergent Typhlops melanocephalus, which was previously considered incertae sedis. The genus Grypotyphlops was resurrected for Rh. acutus, the only Indian member of a group otherwise found solely in Africa. Multiple species groups were identified within these larger genera (particularly Typhlops), based on shared morphological features such as the number of lateral and transverse scale rows, supralabial imbrication patterns, hemipenial morphology, and lung architecture. The differences between these groups suggested that current taxonomic arrangements did not describe monophyletic genera. This suspicion was confirmed by recent molecular phylogenetic analyses, which revealed that numerous taxonomic problems existed within Typhlopidae, and that previous nomenclature did not reflect monophyletic groups revealed in the available phylogenies. The morphological distinction between Ramphotyphlops and Typhlops was not corroborated by molecular evidence, and species from these and other genera interdigitated with each other in molecular phylogenies.

In a new paper Pyron et al. (2014) provide a systematic revision based on molecular phylogenetic analyses and some morphology and present a preliminary solution to the non-monophyly of many previously recognized genera. They also found additional clarification is needed regarding the recognition of some species and genera. They rectify these problems in a new paper with a new molecular phylogenetic analysis that includes 95 of the 275 currently recognized, extant typhlopoids, incorporating both nuclear and mitochondrial loci. They supplement this with data on the external, visceral, and hemipenial morphology of nearly all species to generate a revised classification for Typhlopoidea. Based on morphological data, the re-assign Cathetorhinus from Typhlopidae to Gerrhopilidae. Xenotyphlopidae maintains its current contents (Xenotyphlops). In Typhlopidae, one monotypic genus is synonymized with its larger sister-group as it cannot be unambiguously diagnosed morphologically (Sundatyphlops with Anilios), and two genera are synonymized with Typhlops (Antillotyphlops and Cubatyphlops), as they are not reciprocally monophyletic. The genus Asiatyphylops is renamed Argyrophis, the senior synonym for the group. They also erect one new genus (Lemuriatyphlops) for a phylogenetically distinct species-group in Asiatyphlopinae. Fourteen of eighteen recognized typhlopid genera are maintained in four subfamilies: Afrotyphlopinae (Afrotyphlops, Grypotyphlops [re-assigned from Asiatyphlopinae], Letheobia, and Rhinotyphlops), Asiatyphlopinae (Acutotyphlops, Anilios, Cyclotyphlops, Indotyphlops, Malayotyphlops, Ramphotyphlops, and Xerotyphlops), Madatyphlopinae (Madatyphlops), and Typhlopinae (Amerotyphlops and Typhlops), some with altered contents. Diagnoses based on morphology are provided for all 19 typhlopoid genera, accounting for all 275 species. This taxonomy provides a robust platform for future revisions and description of new species.

Pyron, R. A., Wallach, V., & Press, M. (2014). Systematics of the blindsnakes (Serpentes: Scolecophidia: Typhlopoidea) based on molecular and morphological evidence. Zootaxa3829(1), 001-081.

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