×

Takydromus sikkimensis was named in 1888 by A. Günther on the basis of an 1872 description of grass lizards from Sikkim by F. Stoliczka. Subsequent workers have not considered this species valid and have even doubted the occurrence of Takydromus in Sikkim. We confirm the occurrence of grass lizards in the lower Teesta valley of Sikkim. These are consistent with the description of T. sikkimensis and are distinguishable from all other congeners on the basis of having 12 rows of enlarged ventral scales across midbody, three pairs of chin shields, 3–6 femoral pores on each thigh, and color pattern lacking stripes, spots, or ocelli. Because the type specimens are lost, and because there has been a persistent confusion regarding the identity, and even the existence, of the taxon described by A. Günther as T. sikkimensis, we designate a neotype to stabilize the use of the revalidated name.

×

We report the first record of Sikkim grass lizard, Takydromus sikkimensis Günther, 1888 in Nepal based on morphological characters such as the presence of four pairs of femoral pores, 12 rows of ventral scales, tail more than 3.6 times longer than snout-vent length. Our record of T. sikkimensis at Miklajung, Morang district represents the western-most observation of the species, ca. 94 km west of its type locality, Sikkim, India and is the first in Nepal for this species, genus, and family. This record is from Chure/Siwalik hill range which lies outside of Nepal’s protected area network. This species is listed as Endangered by the International Union for Conservation of Nature and Natural Resources and warrants detailed inventory and immediate conservation interventions.

×

Aim: Small geographic ranges make species especially prone to extinction from an- thropogenic disturbances or natural stochastic events. We assemble and analyse a comprehensive dataset of all the world’s lizard species and identify the species with the smallest ranges—those known only from their type localities. We compare them to wide-ranging species to infer whether specific geographic regions or biological traits predispose species to have small ranges. Location: Global. Methods: We extensively surveyed museum collections, the primary literature and our own field records to identify all the species of lizards with a maximum linear geo- graphic extent of <10 km. We compared their biogeography, key biological traits and threat status to those of all other lizards. Results: One in seven lizards (927 of the 6,568 currently recognized species) are known only from their type localities. These include 213 species known only from a single specimen. Compared to more wide-ranging taxa, they mostly inhabit relatively inaccessible regions at lower, mostly tropical, latitudes. Surprisingly, we found that burrowing lifestyle is a relatively unimportant driver of small range size. Geckos are especially prone to having tiny ranges, and skinks dominate lists of such species not seen for over 50 years, as well as of species known only from their holotype. Two- thirds of these species have no IUCN assessments, and at least 20 are extinct. Main conclusions: Fourteen per cent of lizard diversity is restricted to a single location, often in inaccessible regions. These species are elusive, usually poorly known and little studied. Many face severe extinction risk, but current knowledge is inadequate to properly assess this for all of them. We recommend that such species become the focus of taxonomic, ecological and survey efforts.

×

Sexual dimorphism is widespread among lizards and may cause variation in morphology or color between sexes. These variations are determined by ecological, environmental, and genetic factors. In this study, we examined sexual dimorphism in Sikkim Grass Lizards (Takydromus sikkimensis) of Sikkim-Darjeeling Himalaya, India. We investigated whether differences exist in morphology and colors between sexes, and we also explored the breeding biology of this lizard in both captivity and under natural conditions. We observed female-biased sexual dimorphism in size and shape with females having greater snout vent length (SVL), forelimb length (FLL), hindlimb length (HLL), length of fourth finger (LFF), and snout to arm length (SAL) than males. Males had larger head length (HL) and head width (HW) compared to females. Our findings showed female-biased sexual dimorphism to fecundity selection, where larger females have higher fecundity than smaller females. Additionally, male-biased sexual dichromatism was observed during the breeding season. The primary habitat of Sikkim Grass Lizard in the study region is agro-ecosystems mostly below 1,000 m elevation. These ecosystems are undergoing rapid changes due to developmental projects, which could jeopardize the long-term survival of this species. Therefore, conservation efforts are needed and should focus on preserving a mosaic of agro-ecosystems, especially in the lower middle hills in Sikkim-Darjeeling region of the Eastern Himalaya.