Paraquanothrus n. gen. from freshwater rock pools in the USA, with new diagnoses of Aquanothrus, Aquanothrinae, and Ameronothridae (Acari, Oribatida)

Abstract

Many taxa of mites inhabit long-lived freshwater environments, but the few known to live in small, ephemeral rock pools (lithotelmata) are brachypyline Oribatida. One of these is in the South African genus Aquanothrus (Ameronothridae). We describe adults and juveniles of two new rock-pool species from the USA and propose the sister-genus Paraquanothrus n. gen. to include them. The type-species, Paraquanothrus grahami n. sp., inhabits shallow weathering-depressions (‘pans’) on barren sandstone in the Colorado Plateau, especially southeastern Utah, where it seems to be an opportunistic grazer on microflora and rotifers. Paraquanothrus spooneri n. sp. inhabits rock pools on granite outcrops, is known only from the type-locality in eastern Georgia and appears to ingest mostly plant fragments. Like Aquanothrus, these mites are active only when free water exists. Paraquanothrus shares multiple apomorphic traits with Aquanothrus, for which a new diagnosis is based on corrected information on the type-species, A. montanus, and two undescribed species (one of which is represented in the paratype series). After reviewing historical concepts of Ameronothridae, we propose a new diagnosis (excluding Podacaridae) and propose a new rank and diagnosis for the subfamily Aquanothrinae, which includes Aquanothrus and Paraquanothrus. Molecular studies that have revealed links among Ameronothroidea, Cymbaeremaeoidea and Licneremaeoidea—in ways that question the monophyly of all three superfamilies—are reviewed, and a preliminary evaluation shows morphology to have a modest level of congruence with these results.