We here describe a new species of Isometrus Ehrenberg, 1828 from the southeastern plains of Tamil Nadu, India, which is known only from its type locality, Chengalpattu. The new species was recovered as sister to Isometrus nakshatra based on a molecular phylogeny inferred from COI and 16S mitochondrial genes. Sequence divergence between the new species and all the Indian congeners was 12.6–15.7 % for COI and 12.2–14.4 % for 16S. The new species can also be differentiated from all the Indian congeners based on the following set of characters: surface of carapace with mixed (coarse and fine) and dense granulation; telson vesicle length to depth ratio in males 3.5–3.7; chela length to width ratio in males 5.0–5.4; metasomal length to carapace length ratio in males 8.2–8.9; coarse granulation on mesosomal tergites V and VI along the margins; lateral supramedian and ventral lateral carinae on metasomal segments II–IV moderately to weakly granular; ventral median carina of telson vesicle weakly granular; spiniform granules of promedian carina of the pedipalp patella strongly developed. This is the ninth species of Isometrus described from India and the first species from southeastern peninsular India. This discovery highlights the need for more surveys from the eastern peninsular region.
Deshpande, S., Gowande, G., Bastawade, D., & Sulakhe, S. 2022 . A new species of Isometrus Ehrenberg, 1828 (Scorpiones: Buthidae) from southeastern plains of Tamil Nadu, India. Euscorpius, No. 353: 1-19.