Scapheremaeus truncatus, Colloff, Matthew J., 2010

Colloff, Matthew J., 2010, The hyperdiverse oribatid mite genus Scapheremaeus (Acari: Oribatida: Cymbaeremaeidae) in Australia, with descriptions of new species and consideration of biogeographical affinities, Zootaxa 2475, pp. 1-38 : 24-26

Scapheremaeus truncatus sp. nov.

( Fig. 12 )

Dimensions. Holotype female: length 434, breadth 258.

Prodorsum. With pattern of irregular ridges laterally and irregular plaques anteriorly ( Fig. 12 a). Rostrum broad, truncate. Rostral seta (ro) smooth, curved ventrolaterally, ca. 25 long. Lateral carinae absent. Lamellar seta short (7), covered with club-shaped cerotegument, on translamellar ridge. Costulae straight, converging apically, extending posteriorly as far as bothridia, together with strongly-developed interbothridial ridge and interlamellar ridge forming a rhomboid structure. Inter-costular region with polygonal plaques. Interlamellar seta absent. Sensillus with large, tuberculate, club-shaped, darkly-pigmented head, ca. 25 long, 22 broad, emerging on short stalk from bothridium (diameter 16) positioned just less than its own diameter from dorsosejugal suture. Region posterior of interbothridial ridge with irregular plaques.

Notogaster. Length 339. Circumdorsal scissure entire, oval ( Fig. 12 a) with humeral extensions absent. Lenticulus wedge-shaped, ovoid (32 long, 19 broad) with discrete margins. Without depressions or tubercles lateral of lenticulus, but series of lateral ridges. Humeral process in the form of a small triangle when viewed dorsally. Dorsal circumnotogastral plate plicate. Centrodorsal plate 254 long, 174 broad, oval, broadest at level midway between setae lm and lp, with well-developed posterior centrodorsal ridge and posteriolateral concavities. Centrodorsal microsculpture consisting of irregular transverse ridges and foveolae. With nine pairs of notogastral setae; those of c, l and h series bacilliform, short (ca. 7-12), smooth, covered in dark, clubshaped cerotegument, positioned on well-developed cylindrical tubercles; two pairs of setae on centrodorsal plate, five pairs on dorsal circumnotogastral plate. With two pairs of setae in p series, bacilliform, with clubshaped cerotegument, positioned on ventral circumnotogastral plate. Opening of gla not visible. With five pairs of lyrifissures visible dorsally. Posterior margin of dorsal circumnotogastral plate rounded, smooth.

Ventral region. Epimeral setae setiform, thin, subequal in length, formula 3-1-2-2 ( Fig. 12 b). Microsculpture of ventral plate with elongate striae medially and convoluted striae laterally. Genital plates slightly broader than long, striate, with six pairs of genital setae positioned close to, but not on, medial edges; g 1 positioned lateral of g 2-6; seta g 1-2 24 long, longer than other genital setae. Anal setae setiform, 13, positioned on posterior half of anal plates, almost their length from median edge. With three pairs of minute, subequal, spiniform adanal setae, positioned at least their length from margin of anal plates. Circumgastric scissure with two V-shaped invaginations medial of setae p 1.

Lateral aspect. Mid-line of rostrum vertical ( Fig. 12 c). Hysterosoma dorsoventrally flattened. Exobothridial seta absent. Humeral process consisting of a short, broad, triangular ridge. Centrodorsal ridge extending from just posterior of lenticulus to level with p 2, then sloping abruptly to caudal region. Body markedly flattened dorsoventrally.

Legs. Heterotridactylous.

Material Examined. Holotype female, soil and moss, burnt area, Eucalyptus forest, Mount Buffalo National Park, 36°42’39”S, 146°50’06”, 621 m. Coll. J. Błoszyk & S. Konwerski, 16.vii.2007 (MTB-032).

Etymology. The specific name truncatus refers to the truncated, strongly transverse rostrum.

Remarks. Scapheremaeus truncatus sp. nov. can be separated from other members of the genus by the following combination of characters: 1) the truncate rostrum; 2) the paired V-shaped notches in the circumgastric scissure post-anally; 3) the striate median cuticle of the ventral plate and convoluted lateral striae; 4) the indented notogastral margin posterior to the humeral region; 5) the tuberculate bothridium; the trapezoid pattern formed by the costulae, translamellar ridge and interbothridial ridge.

Scapheremaeus truncatus sp. nov. is a member of the Petrosus species-group. It is morphologically most similar to S. minjambuta sp. nov., especially in the pattern of centrodorsal microsculpture of irregular transverse ridges and foveolae. It differs in having discrete costulae and an interbothridial ridge and the sensillus with a tuberculate head.

Figures

FIGURE 12. Scapheremaeus truncatus sp. nov. a) dorsal; b) ventral; c) lateral.