Arunachal: Two new lizard species discovered solve century-old puzzle

In a remarkable discovery that deepens our understanding of biodiversity in India’s Eastern Himalayas, scientists from the Wildlife Institute of India (WII) have described two new species of forest lizards from Arunachal Pradesh — Ptyctolaemus siangensis and Ptyctolaemus namdaphaensis.

The study, published in the latest issue of the journal Vertebrate Zoology, combines DNA sequencing with detailed morphological analysis to reveal that these previously unrecognized species had long been hidden under what was thought to be a single widespread species, Ptyctolaemus gularis.

For over a century, Ptyctolaemus gularis — commonly known as the green fan-throated lizard of Northeast India — was believed to range widely across India, Bangladesh, Myanmar, and parts of China. However, new genetic evidence based on the mitochondrial ND2 gene has shown that populations in different parts of Northeast India are, in fact, genetically distinct.

Lead authors Amirtha Balan, Abhijit Das, and Bitupan Boruah from WII, along with collaborators from Germany and the UK, collected specimens from 29 locations across Arunachal Pradesh, Meghalaya, Mizoram, and Assam. Their analyses revealed three genetically separate lineages, two of which are new to science.

The two newly named species — Ptyctolaemus siangensis, found west of the Siang River, and Ptyctolaemus namdaphaensis, found in Namdapha Tiger Reserve in Changlang district — are each restricted to distinct ecological zones.

Fieldwork for the study spanned dense tropical forests, river valleys, and hill slopes, including protected areas such as Namdapha Tiger Reserve, Mehao Wildlife Sanctuary, and Kamlang Tiger Reserve in Arunachal Pradesh.

In Namdapha, P. namdaphaensis was found in multiple sites — Deban, Haldibari, and Kamala Valley — thriving in humid, shaded forests at elevations between 400 and 700 metres. Meanwhile, P. siangensis was discovered around Rottung, Pittung, and Potin in the Siang Valley, where it prefers mixed evergreen forests and riparian habitats.

Green fan-throated lizards, long thought to be a single species across Northeast India, have finally been correctly identified — thanks to an integrated taxonomic study that combines morphology, genetics, and natural history observations.

“For decades, this species was referred to as Ptyctolaemus gularis, a name dating back to a historical specimen originally purchased in Kolkata,” the study notes. “However, the species is actually found only in the hills of Northeast India. Because of the ambiguous collection locality of the type specimen, researchers struggled to confirm the true identity of P. gularis.”

As a result, multiple similar-looking populations across the Northeast were lumped together under a single name — masking the region’s true reptile diversity.

The new study resolves this long-standing taxonomic puzzle. Researchers have now confirmed the true identity of P. gularis and, in the process, described two entirely new species — P. siangensis and P. namdaphaensis.

“These findings highlight the remarkable hidden reptile diversity of India’s Northeast — and underscore the importance of revisiting old museum records, field surveys, and genetic data to clarify species boundaries,” the authors said.

This taxonomic clarification, experts say, could have major implications for conservation, particularly for future IUCN Red List assessments, where precise species identification is vital for evaluating threat status and planning protection measures.

“As the biodiversity of Arunachal Pradesh continues to surprise and inspire, the discovery and recognition of these distinct green fan-throated lizards adds yet another reason to celebrate the region’s role as a hotspot for herpetofaunal diversity,” said Dr. Abhijit Das of the Wildlife Institute of India.

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