Ozestheria bourkensis, Schwentner & Hethke, 2025

Schwentner, Martin & Hethke, Manja, 2025, Revision of the Australian Ozestheria Schwentner & Richter, 2015 (Crustacea: Branchiopoda: Spinicaudata) fauna, with the descriptions of 27 new species, European Journal of Taxonomy 992, pp. 1-172 : 32-35

Ozestheria bourkensis sp. nov.

urn:lsid:zoobank.org:act:C29BB36B-13F0-4068-8659-A76389D2BFB9

Fig. 11

Ozestheria sp. R – Schwentner et al. 2015a: figs 2, 6; 2020: figs 1–2.

Diagnosis

Ozestheria bourkensis sp. nov. is characterized by a long condyle and a narrow occipital notch; carapace ornamentation dorsally on carapace punctate, in following growth bands anastomosing lirae forming ventrally within growth band, lirae become longer and more pronounced with progressing growth bands (continue to be strongly anastomosing); male rostrum with weakly convex anterior margin, apex broadly rounded with angle close to 90°, ventral margin straight, with or without notch close to apex; female rostrum anterior margin undulating, apex drawn out to a fine pointed tip, ventral margin straight; 13 (male) or 8 (female) antenna I lobes reaching to antenna II flagellomeres VIII (male) or IV (female); 10 (female) antenna II flagellomeres; 20–21 complete thorax segments; 17–24 large telsonic spines, anterior spines conical, posterior spines larger, thinner, aciculate and increasing in size; 6 furcal setae.

Differential diagnosis

Ozestheria bourkensis sp. nov. can be differentiated from many other species of Ozestheria by the narrow occipital notch and long condyle in combination with the carapace ornamentation (dominated by punctate ornamentation dorsally on carapace, transitioning to distinct, subparallel lirae during ontogeny), except from O. cancellata comb. nov., O. minor comb. nov., O. typica comb. nov., O. fuersichi sp. nov., O. jonnae sp. nov., O. marthae sp. nov., O. selmae sp. nov., O. radiata sp. nov., O. rincewindi sp. nov., O. barcaldinensis sp. nov., O. ngamurru sp. nov., O. beleriandensis sp. nov., O. quinlanae sp. nov., O. glabra sp. nov., O. pilbarensis sp. nov. and O. weeksi sp. nov., and differentiating these species can be difficult. Ozestheria bourkensis differs from O. cancellata , O. fuersichi , O. jonnae , O. marthae , O. rincewindi , O. barcaldinensis , O. ngamurru , O. quinlanae , O. glabra , O. pilbarensis and O. weeksi by having at least the posterior half of the telsonic spines long, elongate and aciculate (in the other species fewer telsonic spines are long and aciculate and more spines shorter and conical) and by the shape of the female rostrum (undulating and apex drawn out into a minutely pointed tip). In O. selmae , O. radiata , O. beleriandensis , and O. minor lirae are more defined in growth bands of later ontogenetic stages (less anastomosing than in O. bourkensis ). Ozestheria minor yields a straighter line between condyle and ocular tubercle and females have more lobes and flagellomeres on antennae I and II. In O. selmae and O. minor the apex of the female rostrum is not as minutely pointed. Ozestheria typica usually has more telsonic spines and the angle between the ocular tubercle and rostrum is obtuse in males (vs rectangular). In male O. beleriandensis the angle between the ocular tubercle and rostrum is obtuse (vs rectangular) and the anterior margin of the rostrum straight or slightly undulating, but convex in O. bourkensis .

Etymology

The species is named after Bourke, a town in northern New South Wales as both known localities of O. bourkensis sp. nov. are ~ 50–80 km N of Bourke.

Type material

Holotype

AUSTRALIA – New South Wales • ♂; temporary pool next to highway past Bourke (~ 170 km to Hungerford); 29°51′22″ S, 145°38′49″ E; 18 Jan. 2010; M. Schwentner and B.V. Timms leg.; GenBank no: KJ705362 ( COI); AM P.82538.

Paratypes

AUSTRALIA – New South Wales • 2 ♀♀; same data as for holotype; GenBank nos: KJ705361, KJ705994 ( COI); AM P.82537, P.91767 .

Other material examined

AUSTRALIA – New South Wales • 1 ♂ roadside claypan; 29°31′42.5″ S, 146°12′20.5″ E; 21 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91768 .

Type locality

Australia, New South Wales, temporary pool next to highway past Bourke (~ 170 km to Hungerford), 29°51′22″ S, 145°38′49″ E.

Description

Males

CARAPACE ( Fig. 11a, c–d). Length 3.9 mm, height 2.4 mm. Coloration lightly yellowish-brown, slightly darker at umbo, lateral margin whitish. 18– 25 (HT: 25) growth lines,15–16 (HT: 15) evenly spaced, and 2–10 (HT: 10) crowded.

CARAPACE SHAPE. Dorsal margin straight, posterior corner present, but not distinct. Posterior margin broadly rounded, sub-oval, equicurvate (b/H 0.47–0.51, HT: 0.51). Ventral margin nearly straight. Umbo position submedian (Cr/L 0.27–0.31, HT: 0.31).

CARAPACE ORNAMENTATION ( Fig. 11e–g). Larval valve granular to punctate. In dorsal part of carapace growth bands densely punctate. In following growth bands, the interspaces between punctae raised, forming shallow, indistinct, highly anastomosing and reticulating lirae; lirae appear first only ventrally within growth bands and extend in length in consecutive growth bands, continuing to be dorsally anastomosing in anterior and ventral part of carapace resulting in a nodular or pitted appearance. Crowded growth bands with well defined, parallel short lirae forming deep pits. Concentric ridges slightly raised and smooth in dorsal and mid-carapace, with nodules in moniliform row on concentric ridges of crowded growth bands. No setae visible, with setal pores in single row along all growth lines (visible under SEM).

HEAD ( Fig. 11h). Condyle long, distally acute; occipital notch narrow. Condyle with anterobasal hump. Margin between condyle and ocular tubercle concave. Ocular tubercle well developed, forming obtuse angle with rostrum (close to 90°). Anterior margin of rostrum widely convex, ventral margin straight, with or without notch close to apex (HT: without), apex broadly rounded, angle close to 90°. Naupliar eye triangular. Antenna I with 13 lobes, reaching to antenna II flagellomere VIII. Antenna II damaged.

THORAX. 20 thoracopod-bearing segments, no limbless segment. Last fourteen thoracopod-bearing segments with dorsal extensions bearing spines. Dorsal extensions increasing in size posteriorly over successive segments. Spines thin and elongate, central spines stronger and broader in posterior segments.

THORACOPOD III (only P.82538). Endite I short and curved dorsally. Endites II–V broad, decreasing in size. Endite V palp two-segmented, basal segment longer than endopod. Exopod ventral extension subequal to slightly larger in extension to endopod, dorsal extension wide, narrowing distally, overreaching epipod. Epipod long, cylindric.

TELSON ( Fig. 11j–k). 22–24 spines (HT: 22). First (anterior) spine enlarged. Spines on anterior third or half of telson shorter and conical, unequal in size, spines on posterior half slightly larger, thinner, drawn out. Anterior third to half of dorsal margin nearly straight to slightly convex, posteriorly slightly concavely curved. Right terminal claw more strongly curved than left.

FURCA ( Fig. 11j–k). Proximally with dorsomedial longitudinal row of 6 setae, row ending distally in a single conical spine. Distal part ⅔ of furca length, with numerous small denticles.

Females

Overall appearance as in males. Carapace ( Fig. 11b) length 3.4–3.9 mm, height 2.1–2.4; 23–26 growth lines, of these 14–16 widely spaced and 7–12 crowded; Cr/L 0.26–0.29 and b/H 0.53–0.55. Hump at base of condyle absent; margin between condyle and ocular tubercle straight; ocular tubercle weakly developed with nearly straight line to rostrum ( Fig. 11i). Antenna II 10 flagellomeres. Rostrum dorsally protruding, anterior margin undulating; apex drawn out to a fine pointed tip; ventral margin straight. 21 segments, all of these thoracopod-bearing and none limb-less, not reaching dorsal margin. Telson with 17 dorsal spines (furca was damaged and not assessed).

Distribution ( Fig. 11m)

Currently known only from two localities in northern New South Wales.

Remarks

Because only few specimens were available, the morphological variability of the species is not well characterized. The carapace shape of Ozestheria bourkensis sp. nov. ( Fig. 6) is distinct from those of most other species and overlaps partly with those of O. jiangi sp. nov., O. minor comb. nov., O. selmae sp. nov., O. radiata sp. nov., and O. typica comb. nov.