Mastigoceras Handschin 1924

GenusMastigocerasHandschin, 1924 Type species. Mastigoceras camponoti Handschin, 1924. Diagnosis. Fusiform small hyaline ciliate scales, without ribs, present at least in dorso-anterior Th. III – Abd. III, present or absent on dorsal head, Th. II, and Abd. IV; antennae, legs, ventral tube, tenaculum and furca scaleless. Body also densely covered by secondary ciliate mic; dorsal macrochaetotaxy reduced. Antennae very long, 2–4 × the body length; antennae with five segments, Ant. I subdivided, Ant. II stiff or weakly annulated, Ant. III – IV longer than other segments, annulated and whip-like; Ant. IV apical bulb absent. Eyes 8 + 8, PAO present. Tergal sensilla and microsensilla formulae of Th. II – Abd. V as 1, 1 | 0, 3, 3, +, 9 and 1, 0 | 1, 0, 1, 0, 0, respectively. Th. II anterior (a) series, including the collar, with up to 17 mac. Abd. IV less than 1.5 × the length of Abd. III in the midline. Abd. VI of males short and rounded; of females long and conical. Trochanteral organ variably developed. Tenaculum without chaetae. Manubrium dorsally with one or two bothriotrichum-like chaetae; dens crenulate, without spines; mucro bidentate with the basal spine (adapted and updated from Handschin 1924; Cassagnau 1963; Mari-Mutt 1978; Cassagnau and Oliveira 1992). Remarks. Our updated diagnosis adds the tergal sensilla and microsensilla formulae to Mastigoceras, details on the distribution of body scales, and outlines the presence of the PAO. This last feature was overlooked in the original description of M. camponoti (Handschin 1924), along with its subsequent redescriptions (Cassagnau 1963; Mari-Mutt 1978; Cassagnau and Oliveira 1992). However, we could confirm the presence of this structure in a specimen of M. camponoti from the type locality (Mariana municipality, south of Minas Gerais state, Brazil), as well as in Mastigoceras handschini sp. nov. In Mari-Mutt (1978: 46, fig. 8), there is a SEM picture of the right eyepatch of M. camponoti showing the PAO as a small cuticle fold in front of A eye lens. The overall morphology of Mastigoceras species resembles other Entomobryoidea in several aspects. These shared features include the presence of a trochanteral organ and post-ocular bothriotricha, dorsal body covered with abundant secondary ciliate mic, alongside some larger ciliate mes and blunt mac, Abd. II – IV bothriotricha formula 2, 3, 2, and dens crenulate with a bidentate mucro holding the basal spine (Soto-Adames et al. 2008). Even so, the disposition of Abd. IV bothriotricha in Mastigoceras is quite unusual, being posteriorly displaced (see Figs 4 E, 6 F; Cassagnau and Oliveira 1992: 30, fig. 2 b). This condition does not relate with other Orchesellidae or Entomobryoidea (Szeptycki 1979; Zhang et al. 2019; Nunes et al. 2020) and makes it difficult to understand the homology of the lateral chaetae on the same tergite.