Malaconothrus beecroftensis, Colloff, Matthew J. & Cameron, Stephen L., 2013

Colloff, Matthew J. & Cameron, Stephen L., 2013, A phylogenetic analysis and taxonomic revision of the oribatid mite family Malaconothridae (Acari: Oribatida), with new species of Tyrphonothrus and Malaconothrus from Australia, Zootaxa 3681 (4), pp. 301-346 : 318-320

Malaconothrus beecroftensis sp. nov.

(Fig. 11)

Dimensions. Holotype female length 515 μm, breadth 210 μm. Paratype females (n = 5): mean length 492 μm (range 478–504 μm), mean breadth 236 μm (range 221–252 μm). Ratio of prodorsum to total length: 0.3 (holotype).

Female. Prodorsum. Rostrum broad, sub-rectangular, with transverse inter-rostral ridge above acute naso (Fig. 11a). Rostral seta (ro) barbed, thick, re-curved, 31 μm long, shorter than mutual distance on squat tubercle positioned ventral of transverse inter-rostral ridge. Lamellar seta (le) barbed, thick, re-curved, 56 μm, longer than ro and their mutual distance, emerging from flat tubercles just lateral of medial line. Interlamellar seta (in) smooth, narrowly phylliform, short (30 μm), sub-equal in length and shape to adjacent exobothridial seta ex. Pedotectum I well-developed, acute. Prodorsum finely porose; cerotegument of small, regular pits. Well-developed posterior interlamellar ridge merged with lateral curved ridge extending from pedotectum I to inter-rostral ridge.

Notogaster. Dorsosejugal furrow slightly convex; humeral region rounded (Fig. 11a). With 15 pairs of short, curved, thick, barbed setae (Fig. 11c), plus f 1, represented by their alveoli, positioned just anteriomedial of seta h 1. Setae mostly sub-equal in length (26–34 μm), not overlapping; f 2 and h 2 longer (38–41 μm). Notogaster with relatively broad median longitudinal ridges on which are positioned setae c 1, d 1, and e 1, joined with broad posterior M-shaped ridge on which are positioned the alveoli of setae f 1, setae h 1 and h 2. Broad lateral longitudinal ridges present, bearing setae c 2 and d 2, connecting with posterior M-shaped ridge at level of h 1; lateral margin of notogaster consisting of sclerotised ridge extending from seta c 3 to p 1 and bearing these setae plus cp, e 2, f 2 and h 2. Humeral region without diagonal ridges ventrally. Without curved transverse ridge anterior of p 1 and longitudinal ridges lateral of anal and genital plates. Notogastral margins more-or-less parallel, broadest at level of e 2. Ratio of length to breadth 1.43. Caudal margin very slightly indented at level of h 2, otherwise U-shaped. Without short concave ridges between h 3 and p 2 and between p 2 and posterior margin of notogaster. Lyrifissurae ip acute. Notogaster densely porose. Notogastral cerotegument covered with small, regular pits.

Coxisternum. Epimeral setal formula 3-1-3-2 (Fig. 11b). Setae on epimeres I and II short, spiniform, smooth, those on epimeres III and IV barbed; 3b and 3c 35–39 μm long, much longer than others, 4a 28 μm long; 1c in posteriolateral position; 1b in mediolateral position; 3b in mediolateral position; 4b in lateral position on posterior margin of plate. Epimeral plates separated medially except III which is fused anteriorly. Epimeral plates I rounded anteriolaterally, lacking spur. Epimeral plates II acute posteriolaterally, with well-developed spur. Epimeres III and IV of equal width, without paired lateral spines. Apodeme IV strongly concave.

FIGURE 11. Malaconothrus beecroftensis sp. nov., holotype female; a) dorsal; b) ventral; c) seta d 2.

Anogenital Region. With six pairs of barbed, curved, setiform genital setae subequal in length (26–33 μm), g 1-5 closely spaced, g 6 separated: at least twice distance from g 5 as from g 5 to g 4; g 6 directed posteriorly; all setae shorter than width of genital plate (Fig. 11b). Each genital plate 109 μm long, 50 μm broad, with well-developed median carina, broadest anteriorly, becoming narrower and slightly waisted posteriorly. Posterior transverse margin of genital plate acute; posteriolateral margin ridged. Without reticulate or striated cerotegument between adanal plate and ventral margin of notogaster. One pair of anal setae 10 μm long, at least as long as width of anal plate. Each adanal plate 100 μm long, 30 μm broad, with median carina; three pairs of barbed, thick, setiform adanal setae, 32– 40 μm long, longer than width of adanal plate; ad 1 on median carina. Anterior margin of adanal plate acute, without thickened transverse ridge, but not overlapped by posterior margin of genital plate.

Material examined. Holotype female and five paratype females, from moss, Point Perpendicular, Beecroft Peninsula, New South Wales, 36°6'S, 150°48'E, coll. P. Greenslade, 21.iii.1995. Holotype and paratypes deposited in the Australian National Insect Collection, CSIRO Ecosystem Sciences, Canberra.

Etymology. This species is named for its type locality, Beecroft Peninsula.

Remarks. Malaconothrus beecroftensis sp. nov. differs from other members of the genus by the following combination of characters: 1) the barbed, thick rostral setae; 2) the transverse inter-rostral ridge; 3) the very short interlamellar setae, just longer than the exobothridial setae; 4) the well-developed notogastral ridges; 5) the presence of the alveolus of seta f 1; 6) the short, curved, barbed notogastral setae; 7) epimeres I and II with smooth setae, III and IV with barbed setae; 8) with six pairs of barbed genital setae.

Malaconothrus beecroftensis sp. nov. belongs to a group of species with a transverse inter-rostral ridge, short interlamellar setae about the same length or slightly longer than the exobothridial setae, a complete set of medial, lateral and M-shaped notogastral ridges and with five or six pairs of genital setae: M. cordisetus Mahunka, 1993 , M. ensifer Mahunka, 1982 , M. keriensis Hammer, 1966 , M. neoplumosus Balogh & Mahunka, 1969 , M. subrasus Balogh, 1964 , M. stigmatus Yamamoto & Coetzee, 2003 and M. variosetosus Hammer, 1971 . Malaconothrus beecroftensis is morphologically most similar to M. keriensis Hammer, 1966 .