Spineremaeus, Colloff, Matthew J., 2011

Colloff, Matthew J., 2011, A new genus of oribatid mite, Spineremaeus gen. nov. and three new species of Scapheremaeus (Acari: Oribatida: Cymbaeremaeidae) from Norfolk Island, South-west Pacific, and their biogeographical affinities, Zootaxa 2828, pp. 19-37 : 21

Spineremaeus gen. nov.

Diagnosis. Cymbaeremaeidae with the following combination of characters: interbothridial ridge entire bearing prominent interlamellar setae emerging from well-developed apophyses with protuberant apical rims. With ten pairs of notogastral setae; lm and lp and lyrifissurae im in central position on notogaster, on lateral margins of an elongate, irregular, sub-rectangular notogastral ridge. Circumdorsal scissure absent. Lenticulus large, bulbous, protuberant; notogaster with centrodorsal region strongly domed and lateral region flat. Type species: Spineremaeus smithi sp. nov.

Remarks. Spineremaeus is closest morphologically to Scapheremaeus Berlese, 1910 . The new genus is established based on the presence of the prominent, broad interlamellar setae emerging from well-developed rimmed apophyses on an entire interbothridial ridge. The well-developed, thick, barbed interlamellar setae represent a synapomorphic character within the Cymbaeremaeidae , shared with Bulleremaeus from New Zealand ( Hammer, 1966). The prominent, rimmed apophyses of the interlamellar setae are considered autapomorphic within the Oribatida . The crenellated, sub-rectangular centrodorsal ridge might conceivably represent the vestige of a circumdorsal scissure, and is an autapomorphy within the Oribatida . Setae lm and lp and lyrifissurae im have migrated from lateral positions, as found in most species of Scapheremaeus , to centrodorsal positions along the margins of the circumdorsal ridge. The interpretation that the centrodorsal setae are lm and lp, rather than dm and dp, is based partly on lyrifissurae im co-located in the centrodorsal position, but also that Scapheremaeus spp. belonging to the Humeratus species-group ( Colloff, 2009), for example Sc. hungarorum Mahunka 1986 (cf. also Mahunka, 2010), show a tendency for setae lm and lp to be positioned towards the centrodorsal region, though not lyrifissurae im. Scapheremaeus emarginatus Hammer, 1966 also has setae lm and lp positioned centrodorsally. Spineremaeus shares the absence of a circumdorsal scissure with two of the non-plicate species-groups of Scapheremaeus , as well as with all other genera within the Cymbaeremaeidae . The members of the Humeratus species-group have the circumdorsal scissure reduced to its anterior portion only, with the posterior portion fused. In the Emarginatus group the circumdorsal scissure is absent altogether ( Colloff, 2009). Members of the Emarginatus group are found in Australia, Java, New Zealand, and a somewhat anomalous member, Sc. morenoi ( Balogh & Mahunka, 1974) is from Cuba ( Colloff, 2010a). Scapheremaeus pinguis sp. nov. described herein from Norfolk Island (cf. below) is also a member of the Emarginatus group.