Tyrphonothrus gnammaensis sp. nov.

(Fig. 3)

Trimalaconothrus sp.: Bayly, 1997, p. 169.

Dimensions. Holotype length 601 μm, breadth 308 μm; paratypes (n = 4) mean length 630 μm (range 616–646 μm); mean breadth 328 μm (range 318–333 μm). Ratio of prodorsum to total length: 0.3 (holotype).

Female. Prodorsum. Rostrum acute, smooth, porose (Fig. 3 a). Rostral seta (ro) smooth, curved, setiform, 44 μm long, longer than mutual distance, on lateral tubercle on incomplete inter-rostral ridge. Lamellar seta (le) smooth, setiform, 88 μm, longer than mutual distance, on apex of incurved, S-shaped lateral carina. Interlamellar seta (in) smooth, setiform, extremely long (193 μm), longer than mutual distance. Exobothridial seta ex 1 smooth, 45 μm, 5 × shorter than in. Seta ex 2 represented by alveolus. Prodorsum finely porose, with poorly-developed posterior transverse ridge and lateral curved ridge extending from pedotectum I to posterior of base of le.

Notogaster. Dorsosejugal suture slightly convex (Fig. 3 a). Humeral region with acute process consisting of longitudinal ridge, angled medially at apex and bearing seta c 3. With 15 pairs of smooth, setiform setae. Setae e 2, h 2-3 and p 2 much longer than others. Seta c 1 52 μm, shorter than distance to d 1; c 2 46 μm, shorter than distance to cp; c 3 55 μm, longer than distance to cp; cp 49 μm, shorter than distance to d 2; d 1 31 μm, shorter than mutual distance; d 2 62 μm, subequal in length to distance to e 2; e 1 44 μm, shorter than mutual distance; e 2 100 μm, subequal in length to distance to f 2; f 2 59 μm shorter than distance to h 2; h 1 96 μm, longer than distance to p 1; h 2 133 μm, longer than distance to p 1; h 3 105 μm, markedly shorter than h 2; p 1 57 μm, shorter than mutual distance; p 1 positioned dorsally; p 3 46 μm long, extending as far as base of p 2 (111 μm long). With relatively narrow median longitudinal ridges joined with narrow posterior M-shaped ridge. Lateral longitudinal striate ridges present, but lateral margins not heavily sclerotised. With curved transverse ridge anterior of p 1 and longitudinal ridges lateral of anal and genital plates. Margins slightly convex, more-or-less parallel, broadest between f 2 and e 2. Ratio of length to breadth 1.37. Caudal margin very slightly indented between p 1 and h 2, otherwise U-shaped. With short concave ridges between h 3 and p 2 and between p 2 and posterior margin of notogaster. Lyrifissurae ip transverse. Notogaster densely porose; cerotegument granular.

Coxisternum. Epimeral setal formula 3-1-3-2 (Fig. 3 b). Epimeral setae smooth, setiform; 1b and 1c 34–41 μm long, much longer than others (16–26 μm); 1c in mediolateral position; 3b in posteriolateral position; 4b in median position on posterior margin of plate. Epimeral plates I partly fused medially, rounded anteriolaterally. Epimeral plates II acute posteriolaterally, separated medially. Epimeral plates III separated medially; epimeral plates IV Partly fused posteriomedially. Epimere I widest; IV wider than III. Apodeme IV straight, transverse. Epimeres III and IV without lateral spines.

Anogenital Region. With five pairs of smooth, setiform genital setae (Fig. 3 b), g 1-3 subequal in length (18–23 μm), closely spaced, g 4 46 μm, g 5 35 μm; with twice the distance between insertions of g 3 and g 4 and g 4 and g 5 as between bases of g 1-3; g 5 directed posteriorly; all setae shorter than width of genital plate. Each genital plate 145 μm long, 52 μm broad, without well-developed median carina, broadest anteriorly, becoming narrower and slightly waisted posteriorly. Posterior margin of genital plate transverse. Without reticulate or striated cerotegument between adanal plate and ventral margin of notogaster. One pair of anal setae 18 μm long, at least as long as width of anal plate. Each adanal plate 143 μm long, 40 μm broad; three pairs of smooth, setiform adanal setae, 32–38 μm long, longer than width of adanal plate; ad 1 not on median carina. Anterior margin of adanal plate acute, overlapped by posterior margin of genital plate, without thickened transverse ridge.

Material examined. Holotype and four paratype females, 2–4 cm-deep temporary rock pools on granite outcrop, Cable Beach, Torndirrup National Park, Western Australia, 35°07´S 117°54´E, coll. I.A.E. Bayly, 27.vii.1990. Types deposited in the Western Australian Museum, Perth.

Etymology. This species is derived from the Nyungar Aboriginal word gnamma, meaning rock pool, the microhabitat in which it was found.

Remarks. Tyrphonothrus gnammaensis sp. nov. differs from other members of the genus by the following combination of characters: 1) the acute rostrum; 2) the rostral setae emerging from short tubercles; 3) with setae in five times longer than ex 1; 4) with all body setae smooth; 5) the convex notogastral margins. With the caudal region of the notogaster broadest; 6) the longitudinal striate ridges on the margins of the notogaster. 7) with five pairs of genital setae, with g1–4 clustered and g 5 separated from the rest.

Tyrphonothrus gnammaensis sp. nov. is one of a small group of species with five pairs of genital setae, including T. australis (Hammer, 1958), T. binodulus (Yamamoto & Coetzee, 2004), T. fijiensis (Yamamoto, Aoki, Wang & Hu, 1993), T. mongolicus (Bayartogtokh, 2010), T. gringai sp. nov., T. maritimus sp. nov. and T. taylori sp. nov. All of these have at least some of the body setae barbed except T. australis, which has the interlamellar setae extending only as far as the bases of the lamellar setae and T. mongolicus, which has incomplete centrodorsal ridges. Tyrphonothrus gnammaensis sp. nov. is superficially similar to T. novaezealandiae (Hammer, 1966), though the number of genital setae of this species was not described.

Tyrphonothrus gnammaensis sp. nov. was found by Bayly (1997) in saline water in shallow rock pools where it co-occurred with Scapheremaeus baylyi Colloff, 2010 . Details of the site were given by Bayly (1982).