Evidence for Early Mesozoic diversification of Hypsimetopidae Nicholls, 1943 (Isopoda), with the description of a new genus from Andhra Pradesh and notes on threats to Indian cave environments

Abstract

AbstractA new phreatoicidean isopod, Speonastes venkataramanigen., sp. nov. is described from Borra Cave in northeastern Andhra Pradesh, India. This new taxon has features seen in most phreatoicideans such as ventrally projecting pleonal pleurae, but also has features characteristic of the hypogean family Hypsimetopidae, such as an elongated pleotelson with a medially rotating uropod that has protopodal denticles or denticulate setae opposing the denticulate margin of the pleotelson, as well as the distal article of the antennula being minute and the penultimate article elongated and somewhat inflated. Robustness-tested phylogenetic analyses of character data from exemplars from nearly all phreatoicidean genera and four non-phreatoicidean outgroups finds that this species is the earliest derived member of Hypsimetopidae. These analyses have substantial implications for both relationships among Phreatoicidea, but within the family as well. The body form of the Phreatoicidea basal to the hypsimetopid clade resembles the form seen in fossils or by recent taxa such as CrenisopusWilson & Keable, 1999. Ancestors of Speonastesgen. nov. may have independently colonized India from those of the Nichollsia-Andhracoides clade. An early Mesozoic diversification of Hypsimetopidae and related taxa along continental rifts in eastern Gondwana between Antarctica, India, and Australia is one implication of the phylogeny. Although the caves of Andhra Pradesh and other Indian states have biologically unique and scientifically important taxa, India provides no protection for any cave. This exposes the fauna to negative impacts such as quarrying or illegal mining, over-exploitation of water resources, and damage from unconstrained tourist visitation.