New Supple Skink, Genus Lygosoma (Reptilia: Squamata: Scincidae), from Indochina and Redescription of Lygosoma quadrupes (Linnaeus, 1766)
Based on molecular and morphological data sets, we describe a new species of scincid lizard of the genus Lygosoma from Indochina, and redescribe true Lygosoma quadrupes (Linnaeus, 1766). The new species is small and slender, and represents the third member of the L. quadrupes complex, increasing the diversity of Lygosoma species recognized in Southeast Asia to 24. Based on the reevaluation of vouchered specimens from the type locality of L. quadrupes sensu Linnaeus (1766), the recognized geographic distribution of true L. quadrupes is restricted to the island of Java in Indonesia. With 10 species of Lygosoma recognized in Thailand, the country possesses considerable species-level diversity of these enigmatic, semifossorial skinks. In addition to being one of the smallest species in the genus, the new species can be distinguished from all congeners by features of its external morphology, including having small relative limb lengths, longer trunk length, and greater numbers of axilla–groin and paravertebral scale rows. Phylogenetic analyses support three divergent lineages corresponding to recognized and newly described members of the L. quadrupes complex. The descriptions underscore the need for continued and comprehensive biodiversity survey work throughout much of Southeast Asia, particularly in Indochina, where scincid diversity remains poorly understood.Abstract
Map of Southeast Asia showing the distribution of focal lineages of the Lygosoma quadrupes complex. The distribution of the Sunda Shelf is represented by 120-m submarine bathymetric contour lines and light grey shading.
(A) Results of DAPC analysis based on the first four component scores showing the greatest between-group and smallest within-group variance illustrated by the 95% confidence ellipses. (B) PCA plot showing complete separation of Lygosoma quadrupes, Lygosoma siamensis, and Lygosoma tabonorum in morphospace. Mensural and meristic characters used in the PCA include AGD, MBW, MBD, TW, TD, HL, HW, HD, ED, END, SNL, IND, FLL, HLL, MBSRC, AGSRC, PVSRC, F3lam, SL, IFL, SO, and SC (see text for definitions).
(Inset) Map of Southeast Asia showing the distribution of Lygosoma siamensis across Indochina shaded in black. (Right) Map of Thailand showing known provincial distribution of Lygosoma siamensis based on vouchered museum specimens (black and grey provinces), with focal provincial names shown for reference. Close-up view of provinces in grey shown within box A. (Bottom left) Hypothesized relationships among species of the Lygosoma quadrupes complex illustrated by the maximum clade credibility tree resulting from Bayesian analyses of 16S. Nodes supported by ≥95% Bayesian posterior probability and P ≥ 70% Maximum–likelihood bootstrap support were considered significantly supported.
Illustrations of the heads of male holotype of Lygosoma siamensis (FMNH 177496) and subadult specimen of Lygosoma quadrupes (USNM 43578) in dorsal, lateral, and ventral views. Taxonomically useful head scales within Lygosoma are labeled as follows: C, chin shield; F, frontal; FN, frontonasal; FP, frontoparietal; IL, infralabial; IP, interparietal; L, loreal; M, mental; N, nasal; P, parietal; PF, prefrontal; PM, postmental; PN, postnasal; PreOc, preocular; PostOc, postocular; R, rostral; SC, superciliary; SL, supralabial; SN, supranasal; SO, supraocular; 1°, primary temporal; 2°, secondary temporal. Roman numerals indicate scales in the supraocular series, with arabic numerals indicating scales in the superciliary series. Temporal scales highlighted in gray. Illustrations by CDS and BBH.
Illustration of left hand and foot of male holotype of Lygosoma siamensis (FMNH 177496) in ventral view. Digit identities labeled with Roman numerals, subdigital lamellae labeled with arabic numerals. Illustrations by CDS and BBH.
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