Crotonia sterigma, Colloff, Matthew J., 2010

Colloff, Matthew J., 2010, The Gondwanan relict oribatid genus Crotonia (Acari: Oribatida: Crotoniidae) from rainforests in Queensland and Northern New South Wales: new species show a mixed pattern of short-range and long-range endemism, Zootaxa 2649, pp. 1-51 : 4-6

Crotonia sterigma sp. nov.

( Figs. 1 , 18 a, 21)

Dimensions: holotype female length 1280, breadth 384. Paratype female length 1165, breadth 336. Ratio of length of prodorsum to total body length: 0.3 (holotype).

Description of female. Prodorsum: ratio of length to breadth 1.21. Rostrum well-developed, with prominent naso, lateral edges slightly concave; rostral seta 51, straight, spiniform, smooth ( Fig. 1 a). Lamellar seta 332, recurved, smooth, flagelliform. Lamellar apophyses 130, straight, parallel, slightly shorter than their mutual distance; extending anteriorly beyond apices of rostral setae. Interlamellar apophysis twice as long as broad; interlamellar seta 373, flagelliform, smooth, extending beyond apex of curve of lamellar setae. Prodorsal ridges very short, directed medially, extending anteriorly less than a third of distance between bases of interlamellar and lamellar apophyses. Diameter of bothridium 45; anteriolateral auriculate ridge a blunt spine with invaginated ridge apically ( Fig. 18 a); hexagonal reticulations of operculum sparingly ornamented with well-developed ridges and with point of origin near lateral margin. Inter-bothridial ridge a very faint shallow curve without a median invagination. Median field of muscle sigilla present. Prodorsal microsculpture smooth, porose.

Notogaster: ratio of length of notogaster to breadth of notogastral shield 3.96; notogastral shield broadest at bases of seta c 3 ( Fig. 1 a); ratio of width of shield to entire notogastral width 0.51; lateral margins of notogastral shield lozenge-shaped, inflated. Dorsosejugal suture discrete, simple; region posterior of apophyses of seta c 3 strongly concave, waisted; lyrifissure ia located in concavity posteriolateral of apophysis of seta c 3. With 14 pairs of smooth notogastral setae. Pre-notogastral shield separated from notogastral shield by broad (47) transverse hyaline strip; bearing long (74), stout, apophysis of seta c 3 and compound apophyses of setae c 1 and c 2, subequal in length to those of c 3, consisting of basal cylinder with bifurcating apices; subapophysis of seta c 1 shorter and thinner (24 long and broad) than those of c 2 (30 long, 20 broad). Setae of c series long, stout, flagelliform; c1 405, c2 540, c3 336, cp 435. Notogastral shield smooth, narrow, sides parallel, tapering to U-shape anterior of caudal apophyses; with pair of faint median ridges extending from just anterior of seta d 2 to just posterior of seta f 2. Lateral hyaline strip (suprapleural scissure) well-developed, with well-developed (34 long, 14 broad) cylindrical apophyses of seta cp and short tubercle of seta e 2 and f 2 on medial margin. Seta d 2 short (27), setiform, mutual distance sub-equal (112) to that between setae c 1-2; setae e 2 and f 2 short, setiform, subequal in length (81). Opisthosomal gland opening gla positioned medial of seta f 2. Caudal apophyses on narrow, elongated stalk projecting posteriorly from caudal margin. Caudal apophyses bilobed, those of h 2 diverging apically, 142 long, with those of f 1 (47) projecting at right angles to main stalk, some distance anterior of those of h 1; apophysis of h 1 (51) projecting dorsally from base of apophysis of seta h 2. Flagelliform setae f 1 and h 1 94 and 142. Seta h 2 195, setiform, recurved. Seta h 3 not visible dorsally.

Ve n t e r: epimeral microsculpture smooth, porose ( Fig. 1 b); epimeral setae smooth, spiniform, some with cerotegument, formula 3-1-3-3; subequal (ca. 35–52); seta 3c on well-developed tubercle. With lcs broad, curved, forming a broadly obtuse angle (ca. 140°) with pcs. Anteriolateral margin of adanal plate with a narrow, shallow indentation. Genital plates sub-circular; posterior margin transverse; posteriolateral margins straight, diverging. Perigenital region smooth. Each genital plate 228 long, 143 broad with eight setiform setae, subequal in length (35); two pairs of aggenital setae, subequal in length to genital setae. Anal plate 66 broad, 298 long with three short (31) setiform setae on posterior half of plate; three pairs of spiniform adanal setae, ad 2-3 slightly shorter and thinner than spiniform stout ad 1 (54). Ventral margin of notogaster surrounding anal plates V-shaped. Seta p 1 curved, short (20) on short tubercles, their mutual distance slightly more than twice their length. Apophysis of seta h 3 located directly below those of p 1, slightly longer; seta h 3 curved, 97.

Lateral view: Caudal margin almost perpendicular to notogastral shield, curving ventrally ( Fig. 1 c); dorsal and ventral surfaces parallel, distance between them ca. 365. Apophysis of seta f 1 and h 1 pointing posteriodorsally, those of h 2 horizontal; those of h 3 positioned anterioventral of f 1, pointing laterally. Caudal cluster at same level as notogastral shield. Apophysis of seta p 1 on caudal margin midway between underside of caudal stalk and ventral surface; p 2 immediately anterioventral of p 1; p 3 twice distance from p 2 as that between p 1 and p 2. Pleuraspis smooth, porose.

Material examined. Holotype female, QM S26070 , stick brushing, rainforest, Nob Creek, Byfield, Queensland, 22°52'S 150°37'E, 200 m., coll. G.B. Monteith, 27.iv.1979. Paratype female, QM S26063 , under logs and rocks, rainforest, Mount Brisbane, Queensland, 27°05'S 152°32'E, 450 m., coll. R.J. Raven, 6.x.1979. Holotype and paratype deposited in the Queensland Museum, Brisbane.

Etymology. The specific name sterigma is Greek, meaning a support or forked prop; referring to the shape of the caudal apophyseal cluster.

Remarks. Crotonia sterigma differs from all other Crotonia spp. by the following combination of characters: 1) the caudal setae are on apophyses extending from the caudal stalk - none are on the notogastral shield; 2) the presence of compound, bifurcate apophyses bearing setae c 1 and c 2 on a single basal stalk; 3) the apophyses of setae f 1 are some distance anterior of those of setae h 1, not adjacent to them; 4) the narrow notogastral shield with parallel margins; 5) setae f 1 extending laterally and dorsally from caudal stalk, separated from apophyses of setae h 1; 6) setae cp are flagelliform and very long; 7) the extremely long, flagelliform setae c 1 and c 2.

Crotonia sterigma is morphologically most similar to C. borbora Luxton, 1987 . Both species have an elongated, narrow prodorsum and notogastral shield, a well-developed caudal stalk from which emerge the paired, adjacent, elongate apophyses of setae h 2. In lateral view, both species are slightly dorsoventrally flattened and the dorsal and ventral surfaces are parallel. They also share the flagelliform setae c 1 and c 2 originating on compound, bifurcating apophyses; a defining characteristic of the Borbora species-group (cf. remarks section on C. borbora below). Crotonia sterigma has faint median ridges on the notogastral shield and elongate flagelliform setae cp, whereas in C. borbora setae cp are short and setiform. Also, the pleuraspis and lateral margins of the notogastral shield of C. sterigma are smooth, not sparingly tuberculate, the caudal apophyseal cluster in lateral view does not project above the level of the notogastral shield, the prodorsum is smooth and porose, lacking the plaques of C. borbora , and the anteriolateral bothridial ridge is in the form of a blunt spine rather than a flat ridge.

Figures

FIGURE 1. Crotonia sterigma sp. nov. holotype female a) dorsal; b) ventral; lcs = lateroventral circumgastric scissure; pcs = perianal circumgastric scissure; c) posteriolateral.

FIGURE 18. Details of bothridia of a) Crotonia sterigma sp. nov.; b) Crotonia borbora Luxton, 1987; c) Crotonia brisbanensis sp. nov.; d) Crotonia maculata sp. nov.; e) Crotonia capistrata Luxton, 1987; f) Crotonia ardala Luxton, 1987; g) Crotonia monteithi sp. nov.; h) Crotonia daviesae sp. nov.; i) Crotonia weiri sp. nov.; j) Crotonia yeatesi sp. nov.; k) Crotonia cameroni sp. nov.; l) Crotonia eungella sp. nov. m) Crotonia queenslandiae sp. nov.; n) Crotonia seemani sp. nov.; o) Crotonia raveni sp. nov.