The Puzzling Falcomurus Mandal (Collembola, Orchesellidae, Heteromurinae): A Review

Falcomurus Mandal is currently a monotypic genus of Heteromurinae described from India in 2018. Its key characters are the first antennal segment subdivided, the second undivided and the third annulated; the first abdominal segment lacking macrochaetae; and the presence of a sinuous modified macrochaeta on the proximal dens. Some details of its morphology were recently put in doubt, and so its genus status and affinities remain uncertain. Here, we revise the genus based on the type material of Dicranocentrus litoreus Mari-Mutt, as well as provide the description of two new species from Australian archipelagos and a reinterpretation of the chaetotaxy of Falcomurus chilikaensis Mandal and D. halophilus Mari-Mutt. After our revision, Falcomurus shows a well-conserved chaetotaxy and overall morphology, which allowed us to provide an updated generic diagnosis. While the antennae morphology of Falcomurus resembles that of Dicranocentrus Schött, its dorsal sensillar and macrochaetotaxy suggest it is closely related to Heteromurus Wankel, as originally stated by Mandal. The main features useful to separate Falcomurus species are the head, mesothorax and fourth abdominal segment chaetotaxy. We also provide a key to its five species, a comparative table and notes on the affinities and distribution of Falcomurus.