Lankascincus, a New Genus of Scincid Lizards from Sri Lanka, with Descriptions of Three New Species

Abstract

-A lineage of lygosomine skinks endemic to Sri Lanka is diagnosed and given generic rank with the name of Lankascincus. The group consists of six species, three of which are described as new. Brief accounts are provided for each species, and there is a key to aid their identification. As part of an ongoing review of the lygosomine scincid lizard assemblage it has become clear that amongst the Sphenomorphus of Sri Lanka there is an easily diagnosable, monophyletic group of six species, among which are three undescribed species. In this paper I diagnose this endemic Sri Lankan supraspecific group, give it generic rank, discuss its relationships, and describe the new species in the context of a brief review of all the species in the taxon. Collection abbreviations throughout follow Leviton et al. (1985), with the exception of the Australian Museum (AM, not AMS) and the addition of the E. H. TaylorH. M. Smith collection (EHT-HMS), now dispersed. Lankascincus new genus Type Species.-Lygosoma fallax Peters, 1860:184; designated herein. Diagnosis.-Compared to other lygosomine skinks, the skinks of this genus share the following combination of derived character states: size small (maximum SVL, 58 mm); nuchals undifferentiated; subocular scale row complete and non-interdigitating with supralabials; external ear opening reduced, approximately three times size of narial opening; postmental contacts first infralabial only; third pair of chin scales separated from infralabial row; outer preanals overlap inner; scales perfectly smooth; subdigital lamellae with postaxial groove basally; premaxillary teeth >11; palatal rami of pterygoids slightly expanded posteromedially; fat bodies absent; clutch size constant, two or one, depending on species. For a general description of the species in the taxon see Taylor (1950) and Deraniyagala (1953), and for some general morphometrics see Table 1. Referred Species (6).-Sphenomorphus deignani Taylor, 1950; Lankascincus deraniyagalae, new species; Lygosoma fallax Peters, 1861; Lankascincus gansi, new species; Eumeces taprobanense Kelaart, 1854; Lankascincus taylori, new species. Distribution and Life History.--The genus is endemic to Sri Lanka, occurring in both the lowlands and the highlands. It is diurnal and terrestrial. It is oviparous, and the clutch size is a constant one or two, depending on species. Relationships. -Although the skinks discussed here have previously been placed in the genus Sphenomorphus, it is uncertain whether they belong to this major group of lygosomines or to the Eugongylus group (Greer, 1979). Of the group characters that can be assessed in Lankascincus, it possesses three of the Eugongylus group characters (premaxillary teeth 11; inner preanals overlapped by outer-Greer, 1990; scales on dorsal surface of digits mostly in single row), and none of the group characters. However, the hemipenis character that is the single most important feature of the group (deeply bifurcate) has not yet been examined in Lankascincus due to lack of suitable material. Needless to say it would be highly desirable to know the morphology of the hemipenis of Lankascincus. Regardless of its major group relationships, Lankascincus may be most closely related to the southern Indian genus Ristella, a group whose own major group relationships are also unclear for the same reasons as apply to Lankascincus. Both taxa share a larger number of derived character states with each other than with any other lygosomine, including small size, undifferentiated nuchals, a complete subocular scale row, reduced external ear opening, postmental in contact with only one infralabial on each side, and slightly posteromedially expanded palatal rami of the pterygoids. Lankascincus differs from Ristella in having the derived character states: scales smooth, lower secondary temporal bordered posteriorly by two tertiary temporals instead of one, third pair of chin scales separated from infralabials, and clutch size a constant two or one. Ristella differs from Lankascincus in having the derived character states: supraoculars contacted by frontal three instead of two, digits on the manus four, and claws retractile. The This content downloaded from 157.55.39.45 on Thu, 01 Sep 2016 05:28:41 UTC All use subject to http://about.jstor.org/terms