Dumetoniscus Taiti & Checcucci, 2009

Taiti, Stefano & Checcucci, Ilaria, 2009, New species and records of terrestrial Isopoda (Crustacea, Oniscidea) from Socotra Island, Yemen, ZooKeys 31 (3), pp. 73-103 : 85-87

Genus Dumetoniscus Taiti & Checcucci , gen. n.

urn:lsid:zoobank.org:act:6215D3F2-93DE-4086-A955-C49EC486387A Type-species: Dumetoniscus graniticus sp. n.

Diagnosis. Animals unable to roll up into a ball, runner type. Back with shallow tubercles and small T-shaped scale-setae; no glandular fields at lateral margins of pereional segments; one series of noduli laterales per side, nuduli on pereionites 4 and 7 clearly more distant from the lateral margins of the segments. Cephalon with frontal lobes well developed, lateral lobes obliquely directed downwards; suprantennal and frontal lines present. Posterior margin of pereionite 1 straight. Pleon slightly narrower than pereion; pleonites 3–5 with well developed posterior points. Telson triangular, reaching distal margin of uropodal protopod. Antennule of three articles with a tuft of aesthetascs at apex. Antenna with flagellum of two articles, the first longer than the second. Mandible with molar penicil dichotomized, 1+1 free penicils on the right mandible and 2+1 on the left. Maxillule with outer branch equipped with 4+6 (5 cleft) teeth; inner branch with 2 penicils and a posterior point. Maxilliped with endite bearing 3 large triangular spines at apex and no penicil. Pereiopods with flagelliform dactylar and ungual seta on dactylus; distal margins of merus and carpus with a row of short scales. All pleopodal exopods with no respiratory struc- tures. Uropodal protopod with a triangular incision on lateral margin; endopod inserted proximally to exopod.

Etymology. Latin Dumetum = bush + Oniscus . Gender masculine. The name refers to the habitat where the type species was collected.

Remarks. According to the “World catalog of terrestrial isopods” by Schmalfuss (2003), the family Bathytropidae currently includes seven genera: Bathytropa Budde- Lund, 1885, Australoniscus Vandel, 1973a , Neotroponiscus Arcangeli, 1936 , Papuasoniscus Vandel, 1973b , Laninoniscus Reca, 1973 , Monitus Lewis, 1998 , and Cubanoscia Vandel, 1981 . Cubanoscia is unavailable since it was described on three species without selection of the type-species (see Schmidt and Leistikow 2004: 26). Australoniscus is a junior synonym of Nagurus Holthuis, 1949 (see remarks in Schmidt and Leistikow 2004: 13), but the species “ Australoniscus ” springetti Vandel, 1973c from Western Australia is certainly not in Nagurus . A re-examination of the type- or topotypic specimens is necessary for a correct generic abscription.

The family includes all the genera of Crinocheta which are unable to conglobation, have T- or Y-shaped dorsal scale-setae, a two-jointed antennal flagellum (except Monitus with three flagellar articles), and no visible respiratory structures on the pleopods (except Bathytropa wahrmani Strouhal, 1968 which has Trachelipus - type uncoverd pleopodal lungs). As pointed out by Schmidt (2003) the monophyly of the family is questionable and in need of an accurate revision. Schmidt (2003) redefined the family only on the basis of one species in the type-genus Bathytropa , without taking into consideration all the other genera included until now.

The specimens from Adho Dimelho in the Hagghier Mts (see below) that we examined do not fit in any of the genera included in the family and are described in the new genus Dumetoniscus . It is distinguishable from Bathytropa in the position of the noduli laterales, cephalon with medial frontal lobe triangular instead of quadrangular, presence of suprantennal line, pereion and pleon epimera less developed; from Neoptroponiscus in the medial frontal lobe less developed, triangular instead of quadrangular, the presence of a suprantennal line, the less developed pleon epimera and the triangular telson with straight sides; from Monitus in the two-jointed antennal flagellum, the less developed frontal lobes on cephalon and epimera of pereion and pleon, and the triangular telson; from Papuasoniscus in the presence of a suprantennal line, different disposition of the noduli laterales and the triangular telson. The new genus shows closest similarity with Laninoniscus from which it differs in the tuberculated instead of smooth dorsum, the more developed frontal lobes, and the presence of a distinct frontal line.