Humerotegaeus concentricus, Colloff, 2023

Colloff, Matthew J., 2023, The oribatid mite superfamily Eutegaeoidea (Acari, Oribatida), with descriptions of new taxa from Australia and New Caledonia and a re-assessment of genera and families, Zootaxa 5365 (1), pp. 1-93 : 41-42

Humerotegaeus concentricus sp. nov.

( Fig. 19 )

Dimensions. Holotype female: length 699 μm, breadth 488 μm. Paratype females (n = 9): mean length 734 μm (range 717–763 μm), mean breadth 511 μm (range 480–530 μm); paratype males (n = 4): mean length 678 μm (range 667–688 μm), mean breadth 469 μm (range 444–493 μm). Ratio of prodorsum to total length: 0.4 (holotype).

Description of adult. Prodorsum: rostrum rounded; rostral setae (ro) curved, with sparse spinose ornamentation basally, visible in dorsal aspect, emerging from lateral margins of rostrum. Lamellae broad, extending well beyond lateral margin of prodorsum, separated medially, parallel, lateral margins curved, convex. Translamella absent. Lamellar setae (le) with sparse spinose ornamentation, strongly curved medially, extending beyond apices of rostral setae, emerging from shallow cup-shaped incisions, flanked by long medial tooth and shorter lateral tooth; lamellar cusps extending well beyond rostrum ( Fig. 19a ). Interlamellar setae (in) very short. Bothridia long, strongly curved, projecting beyond median margins of humeral processes, openings angled anterolaterally, posterior margin convex, with V-shaped anterior condyle of enantiophysis H. Bothridial setae long, bacilliform, smooth, pointed.

Notogaster: ratio of length to breadth: 0.87; notogaster rounded, convex. Humeral processes well-developed, with distinctive rugose microsculpture and lacking dorsal keel; pointed apically, extending anteriorly to point level with middle of lamella ( Fig. 19a ). Base of humeral process with humeral plate (hp) indicated by obtuse anterior suture and acute posterior suture giving plate wedge-shaped appearance. With nine pairs of notogastral setae, l, h and p series present, all marginally positioned, thin, setiform, smooth, short (30-45 μm); l series about same length as h series ( Fig. 19a ).

Ventral aspect: subcapitulum acute apically; mentum as long as broad; subcapitular setae short, smooth, setae m same length as a and h ( Fig. 19b ). Tutorium narrow, without teeth. Epimeral plates I sub-rectangular, partially separated in midline; plates II fused in midline, lacking medial margins, rectangular and shorter than plates I, plates III and IV separated in midline and very narrow; epimeral setation 3-1-3-3; setae sub-equal in length. Epimeral plates III with pair of small tubercles. Pedotectum I (pd I) well-developed, rectangular, with reticulate microsculpture laterally; pd II well developed, trapezoid; discidium short, curved, pointed. Ventral plate broader than long. Genital and anal plates separated by distance just less than length of genital plates; with perigenital carina and enantiophysis E4 present; genital plates 82 µm long, with six pairs of setae sub-equal in length, g 4 displaced laterally, g 1 not longer than others; lyrifissure iad in para-anal position, some distance from margin of anal plate, more than length of iad. Anal plates lozenge-shaped, 120 µm long; setae of the ad series short, no longer than anal setae. Pre-anal organ (po) T-shaped.

Type designation, material examined and locality data. Holotype female, ANIC accession no. 53-1051; paratypes: eight females, three males, ANIC accession no. 53-1052, ANIC 669 , moss and leaf litter, Nothofagus cunninghamii and Atherosperma moschatum rainforest, Mount Field, Mount Field National Park, Tasmania, 42°41'S, 146°43'E, 160–240 m., coll. J. Lawrence and T. Weir , 9.ii.1980 . Paratype: male, ANIC accession no. 53-1053, ANIC 297 , moss and litter, Nothofagus cunninghami rainforest, Cumberland Creek Valley, near Picnic Area [Cumberland Memorial Scenic Reserve], Yarra Ranges National Park , Victoria. 37°34’S 145°52’E, 920 m., coll. R. W. Taylor and R. J. Bartell , 4.xi.1970 . Paratype: female, ANIC accession no. 53-1054, ANIC 592 , leaf litter and decaying log, Cement Creek, 5 km west of Warburton, Victoria, 37°3’3S 145°42’E, coll. J. Lawrence and T. Weir , 18.i.1977 .

Etymology. The specific name refers to the pair of circular structures at the base of the humeral process, with the cuticular ornamentation forming concentric ridges and furrows.

Diagnosis. Humerotegaeus concentricus differs from H. carinatus by the following combination of characters: (1) the long, curved lamellar setae with spinose ornamentation; (2) the free lamellar cusps with a large medial spine; (3) the minute interlamellar setae; (4) the wedge-shaped humeral plate at the base of the humeral process, marked by anterior and posterior sutures; (4) the markedly shorter notogastral setae; (5) the pair of circular structures positioned ventrally at the base of each humeral process; (6) the morphology of the epimeres; (7) the short, pointed discidium and (8) the genital and anal plates are separated by distance just less than the length of the genital plate.

Figures

FIGURE 19. Humerotegaeus concentricus gen. et sp. nov., adult (a) dorsal aspect; (b) ventral aspect. Scale bar = 200 μm.