Description and Phylogenetic Position of Thermocypris isabella gen. et sp. nov. (Ostracoda: Cyprididae: Cyprinotinae) from a Hot Spring in Peru.

During a faunal survey in Baños del Inca hot spring (40-50°C), Cajamarca, Peru, we collected a cyprinotine ostracod species, the sixth example of a thermophilic ostracod inhabiting freshwater in temperatures above 40°C. Because this could not be assigned to any of nine genera in Cyprinotinae, we established the new genus Thermocypris for it and described it as Thermocypris isabella gen. et sp. nov., defined by the following combination of characters: (1) no dorsal hump on carapace, (2) no tubercles on either valve, (3) left valve slightly overlapping right valve along all margins, (4) no selvage on anterior part of right valve, (5) only seta d1 on first podomere of 6th limb, (6) only two shields (medial and lateral) on hemipenis, and (7) medial shield unilobed and lateral shield tooth-shaped. We determined partial sequences for the mitochondrial cytochrome c oxidase subunit I (COI) and nuclear 18S and 28S rRNA genes from a specimen of the new species. In a maximum likelihood tree based on 18S + 28S, T. isabella was the sister taxon to Heterocypris chetumalensis (Yoo, Cohuo, Macario-Gonzalez, and Karanovic, 2017), with high branchial support. A clade including Cyprinotinae (Cyprinotus Brady, 1868 + Heterocypris Claus, 1892 + Thermocypris) and Eucypridinae (Eucypris Vavra, 1891) was fully supported; our phylogeny showed Heterocypris not to be monophyletic.