Guwahati: A 150-year-old mystery surrounding the identity of the Spotted Litter Skink (Sphenomorphus maculatus) has finally been resolved, thanks to a comprehensive study by a team of herpetologists from India and abroad. Through a combination of genetic analysis, historical detective work, and morphological study, the team has designated a neotype—a modern specimen to replace the long-lost holotype—providing a definitive reference for the species.
The Spotted Litter Skink, first described by Edward Blyth in 1854, was based on a specimen collected by Colonel Francis Jenkins, a British official stationed in Assam during the mid-19th century. Jenkins’ expeditions into the dense forests of Northeast India—including Guwahati, Cachar, Patkai, parts of Manipur, and areas of present-day Bangladesh—supplied numerous biological specimens to the Museum of the Asiatic Society of Bengal. However, by the time William Theobald cataloged the reptile collection in 1868, Blyth’s specimen was missing. Without a physical type specimen, the taxonomic identity of S. maculatus remained uncertain for over 150 years.
The study, led by Pranoy Kishore Borah, a PhD scholar from the National Institute of Science Education and Research (NISER), Odisha, involved collaboration with researchers from La Sierra University (USA), the Wildlife Institute of India (WII), Mizoram University, and the Zoological Survey of India (ZSI). Field sampling was conducted across Northeast India from 2021 to 2024, with efforts spearheaded by teams from NISER, Mizoram University, and WII.
The team focused their investigations on the fringe forests around Guwahati, identified as the most probable type locality for the species. Within this region, the Nilachal Hills—home to the Kamakhya Temple complex—was pinpointed as the likely site where Jenkins originally collected the specimen.
Using genetic analysis and detailed morphological comparisons, Borah’s team confirmed the neotype’s identity (ZSI–28718). They documented key features, including its snout-vent length (57.0 mm), arrangement of supraciliaries, and ventral scale patterns. The genetic data were submitted to GenBank, and the neotype specimen was deposited at the ZSI to ensure accessibility for future research.
“The genetic data suggest that what we currently call Sphenomorphus maculatus may actually represent a species complex rather than a single species,” Borah explained. “This cryptic diversity has significant implications for the taxonomy of sphenomorphine skinks across Southeast Asia.”
The study also shed light on the ecological specialization of skinks in Northeast India. Field observations revealed that these reptiles inhabit riparian forests, foraging in leaf litter along streams. The region’s dynamic geography and climate likely contributed to habitat fragmentation, leading to genetic isolation and the cryptic diversity observed.
Morphological analyses using Multiple Factor Analysis (MFA) further supported the findings. The proposed neotype, ZSI–28718, was found to be morphologically distinct from other specimens collected in Guwahati, confirming its recognition as a representative of S. maculatus sensu stricto.
This discovery is a triumph of integrative taxonomy, combining molecular, morphological, and historical data to resolve longstanding scientific puzzles. It aligns with global efforts to overcome the “taxonomic impediment”—the difficulty of cataloging Earth’s biodiversity due to incomplete or outdated species descriptions.
With this breakthrough, herpetologists now have a reliable foundation for further research on Southeast Asian Sphenomorphinae. The study demonstrates how historic collections, when paired with modern molecular tools, can resolve even century-old taxonomic mysteries.
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