Isometrus Ehrenberg, 1828

Sulakhe, Shauri, Deshpande, Shubhankar, Gowande, Gaurang, Dandekar, Nikhil & Ketkar, Makarand, 2022, Arboreal gems: resurrection of Isometrus sankeriensis Tikader & Bastawade, 1983 and descriptions of two new species of Isometrus Ehrenberg, 1828 (Scorpiones: Buthidae) from the Western Ghats, India, European Journal of Taxonomy 811 (1), pp. 1-50 : 14

Genus Isometrus Ehrenberg, 1828

Figs 1–26 ; Tables 1–8

Type species

Scorpio maculatus (DeGeer, 1778) .

Diagnosis (♂ ♀)

Carapace without carinae. Lateral ocular tubercle with type 5 ocelli and median ocular tubercle with one pair of ocelli. Sternum type 1, triangular in shape. Ventral aspect of tarsomere II of leg IV with two dense rows of setae. Pedipalps orthobothriotaxic, type Aβ. Trichobothrium db of fixed finger of chela located between dt and et. Legs without tibial spurs on tibiae III and IV. Movable finger and fixed finger of chela with six rows of prolateral and retrolateral denticles in pairs and one additional single retrolateral denticle on proximal portion. Mesosoma I–VI tergites each with single median carina. All metasomal segments longer than wide. Telson vesicle always longer than wide, with subaculear nodule.

Sexual dimorphism

All species of Isometrus in India exhibit similar sexual dimorphism. Males have longer and more slender pedipalps as opposed to females. Males have a slightly more elongated telson vesicle than females. The aculeus of the telson in females is more curved and elongated than in males. The male genital operculum bears a pair of small genital papillae posteriorly. In females the genital operculum is divided by a median suture covering the female genital orifice.

Figures

Fig. 1. Ultrametric tree showing phylogenetic relationships. Values along the nodes indicate Bayesian posterior probabilities and divergence dates in MY (PP/DD). Bars at the nodes indicate 95% HPD. Vertical bars represent delimitation analysis results.

Fig. 2. Maximum Likehood phylogenetic tree (ML) for Isometrus Ehrenberg, 1828. Values along the nodes are bootstraps for 1000 iterations.

Fig. 3. Projection of first two Principle Component factors explaining 91.06% of the variation among the seven species of the genus Isometrus Ehrenberg, 1828.

Fig. 4. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). A. Dorsal view. B. Ventral view. C. Sternopectinal area, dorsal view. D. Chelicerae, dorsal view.

Fig. 5. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). A. Dorsal view, UV light. B. Ventral view, UV light. C. Carapace, white light.

Fig. 6. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). A–B. Pedipalp chela. A. Dorsal view. B. Ventral view. C–D. Patella. C. Dorsal view. D. External view. E–F. Femur. E. Dorsal view. F. Internal view. Trichobothrial pattern indicated by yellow dots.

Fig. 7. Type locality of Isometrus sankeriensis Tikader & Bastawade, 1983. A. View of Sunkeri Road. B. View of semi-evergreen disturbed forest at the type locality.

Fig. 8. Isometrus nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). A. Dorsal view. B. Ventral view. C. Sternopectinal area. D. Chelicera, dorsal view.

Fig. 9. Isometrus nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). A. Dorsal view, UV light. B. Ventral view, UV light. C. Carapace, white light.

Fig. 10. Isometrus nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). A–B. Pedipalp chela. A. Dorsal view. B. Ventral view. C–D. Patella. C. Dorsal view. D. External view. E–F. Femur. E. Dorsal view. F. Internal view. Trichobothrial pattern indicated by yellow dots.

Fig. 11. Isometrus nakshatra sp. nov., paratype, adult ♀ (BNHS SC 196). A. Dorsal view. B. Ventral view. C. Carapace, dorsal view. D. Sternopectinal area. E. Telson, lateral view.

Fig. 12. Type locality of Isometrus nakshatra sp. nov. A. View of dense evergreen forest along road at the type locality. B. View of Kadmane Tea Estate with mountain range in southern Western Ghats, India.

Fig. 13. Isometrus wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190). A. Dorsal view. B. Ventral view. C. Sternopectinal area. D. Chelicera, dorsal view.

Fig. 14. Isometrus wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190). A. Dorsal view, UV light. B. Ventral view, UV light. C. Carapace, white light.

Fig. 15. Isometrus wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190). A–B. Pedipalp chela. A. Dorsal view. B. Ventral view. C–D. Patella. C. Dorsal view. D. External view. E–F. Femur. E. Dorsal view. F. Internal view. Trichobothrial pattern indicated by yellow dots.

Fig. 16. Isometrus wayanadensis sp. nov., paratype, adult ♀ (BNHS SC 191). A. Dorsal view. B. Ventral view. C. Carapace, dorsal view. D. Sternopectinal area. E. Telson, lateral view.

Fig. 17. Type locality of Isometrus wayanadensis sp. nov. Views of tall evergreen forest along road at the type locality.

Fig. 18. Carapace under UV light. A. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 19. A–C. Telson in lateral view. D–F. Telson in ventral view. A, D. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B, E. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C, F. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 20. Mesosomal tergites V and VI in dorsal view under UV light. A. Isometrus thurstoni Pocock, 1983, topotype, adult ♂ (INHER-139). B. I. tamhini Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 155). C. I. amboli Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 157). D. I. kovariki Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 161).

Fig. 21. Mesosomal tergites V and VI in dorsal view under UV light. A. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 22. Metasoma in lateral view under UV light. A. Isometrus thurstoni Pocock, 1983, topotype, adult ♂ (INHER 139). B. I. tamhini Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 155). C. I. amboli Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 157). D. I. kovariki Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 161).

Fig. 23. Metasoma in lateral view under UV light. A. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 24. Comparison of left pedipalps. A. Isometrus thurstoni Pocock, 1983, topotype, adult ♂ (INHER 139). B. I. tamhini Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 155). C. I. amboli Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 157). D. I. kovariki Sulakhe et al., 2020, holotype, adult ♂ (BNHS SC 161).

Fig. 25. Comparison of left pedipalps. A. Isometrus sankeriensis Tikader & Bastawade, 1983, neotype, adult ♂ (BNHS SC 194). B. I. nakshatra sp. nov., holotype, adult ♂ (BNHS SC 195). C. I. wayanadensis sp. nov., holotype, adult ♂ (BNHS SC 190).

Fig. 26. Distribution of Indian species of Isometrus Ehrenberg, 1828 with elevation data. Stars represent type localities and circles represent additional sampled localities.