Sunday, January 21, 2024

[Herpetology • 2024] Dravidoseps gingeeensis, D. jawadhuensis, D. kalakadensis, etc. • A Non-adaptive Radiation of Viviparous Skinks from the Seasonal Tropics of India: Systematics of Subdoluseps (Squamata: Scincidae), with description of A New Genus and Five Cryptic New Species

Dravidoseps gingeeensisD. jawadhuensis, D. kalakadensisD. srivilliputhurensis & D. tamilnaduensis 
Agarwal, Thackeray & Khandekar, 2024

Subdoluseps is a recently described genus of Lygosomine skinks distributed in peninsular India and Southeast Asia. We conduct the first revision of Indian Subdoluseps based on range-wide sampling including 89 specimens from 33 localities. We use two mitochondrial and three nuclear markers, 58 morphological characters, and ecological data to reconstruct the evolutionary history of Indian Subdoluseps and assess their diversity and distribution, providing insights into lygosominin biogeography. We formally describe the Indian clade as a new genus, Dravidoseps gen. nov. and name five new species from Tamil Nadu, India in an integrative taxonomic framework – Dravidoseps gingeeensis sp. nov., D. jawadhuensis sp. nov., D. kalakadensis sp. nov., D. srivilliputhurensis sp. nov., and D. tamilnaduensis sp. nov.. We transfer Riopa goaensis, Subdoluseps pruthi and S. nilgiriensis to the new genus and designate neotypes for the former two. Members of Dravidoseps gen. nov. are the first known viviparous skinks from peninsular India and the only known viviparous lygosominins apart from a few species of east African Mochlus. The Lygosomini have a Southeast Asian origin and began diversifying in the Eocene with three dispersals between India and Southeast Asia. Species level diversification in Dravidoseps gen. nov. was likely driven by a combination of niche conservatism, paleoclimate and past forest distribution. The discovery of a new genus and five new species reiterates the high levels of diversity and endemism present in peninsular India and how much more remains to be discovered.

Dravidoseps gen. nov.
Type species: Lygosoma pruthi Sharma, 1977

Chresonymy: Riopa – Sharma (1976, 1978)
Lygosoma – Das (1996)
Subdoluseps – Freitas et al. (2019), Ganesh et al. (2021)

Diagnosis: Medium-sized skinks (adult SVL < 58 mm; n = 89), original tail equal to or slightly longer than body. Dorsal scales on body and tail smooth, cycloid, imbricate; ventrals similar except marginally larger on pectoral and precloacal region; scales on lateral tail base smooth or tricarinate; 62–70 scales in paravertebral rows; 26–32 scales around mid-body; 61–73 ventral scales (rarely 76, n = 1/89); 8–12 enlarged precloacal scales (rarely 13, n = 1/89); and 18–23 scales round the tail. Supranasals in contact with each other behind rostral (rarely not in contact, n = 1/89); single frontonasal; prefrontals relatively small, widely separated on midline; frontal elongate, bell-shaped; four supraoculars; three supraoculars in contact with frontoparietal (rarely two, n = 4/89); frontoparietal divided; interparietal diamond-shaped, eyespot in posterior projection; parietals large, in medial contact posterior to interparietal; 2–4 nuchals, either in contact behind parietals or separated medially by 1–3 paravertebral scales. Nasal divided; two loreals; a single pre-supraocular; two preoculars (rarely three, n = 4/89); and a single sub-preocular (rarely absent, n = 5/89); 6–8 supraciliaries (rarely nine, n = 1/89); lower eyelid with enlarged, transparent central window; a single post-supraocular and postocular; and three or four sub-postoculars (rarely five, n = 3/89); a single primary, two secondary (rarely three, n = 1/89), and three tertiary (rarely four, n = 1/89) temporals. Six or seven supralabials and infralabials; fourth or fifth supralabial elongate, below eye; one or two post-supralabials; 1–3 ear lobules; three enlarged pairs of chin shields. Pentadactyl; limbs well-developed; subdigital lamellae unpaired, smooth to weakly keeled; 4–7 lamellae under digit I of manus and pes, 9–12 lamellae under digit IV of manus and 12–17 lamellae under digit IV of pes (rarely 18, n = 1/89). Viviparous, litter size 2–4. Dorsum light coconut to dark chocolate brown; thick dark band from rostrum to tail speckled with light spots; supralabials with a white streak; males with yellow on lower parts of forebody and flanks, sometimes extending onto belly; venter white with some darker markings (Fig. 9).

ContentDravidoseps goaensis comb. nov., Dravidoseps pruthi comb. nov., Dravidoseps nilgiriensis comb. nov., and five species described below.

Etymology: A combination of the Sanskrit ‘Dravida’, referring to the original inhabitants of southern India and Sri Lanka, and the Ancient Greek ‘seps’, for a snake-like creature that has been previously used in skink generic names (e.g. Erens et al. 2017; Freitas et al. 2019). The gender of the genus is masculine and the suggested common name is Indian leaf-litter skinks.

Ishan Agarwal, Tejas Thackeray and Akshay Khandekar. 2024. A Non-adaptive Radiation of Viviparous Skinks from the Seasonal Tropics of India: Systematics of Subdoluseps (Squamata: Scincidae), with description of A New Genus and Five Cryptic New Species. Vertebrate Zoology 74: 23-83. DOI: 10.3897/vz.74.e110674