Ozestheria christiani, 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 : 44-46

Ozestheria christiani sp. nov.

urn:lsid:zoobank.org:act:ED04772A-3C1F-4DCA-8725-76752888C3E3

Fig. 15

Ozestheria sp. F – Schwentner et al. 2015a: figs 2, 6.

Ozestheria sarsii – Schwentner et al. 2020: figs 1–2.

Diagnosis

Ozestheria christiani sp. nov. is characterized by a short condyle and wide occipital notch; a rounded ventral carapace margin with well-defined most ventral point; carapace ornamentation with large, well-developed polygonal reticulations, many polygons intermittent and with small projections towards the polygon’s center, each polygon without secondary ornamentation (best seen under SEM); male rostrum with convex anterior margin, apex rounded, ventral margin with anterior hump then strongly concave, pointing apex downwards; 20–23 (male) antenna I lobes reaching to antenna II flagellomeres VI–VII (male); 10–11 (male) antenna II flagellomeres; 22–23 complete thorax segments; 15–18 small spines, anterior spines conical spines, posterior spines elongate and aciculate; 7–12 furcal setae.

Differential diagnosis

Ozestheria christiani sp. nov. can be easily differentiated from most other species of Ozestheria by the shape and ornamentation of the carapace as well as the telson spination. The morphologically most similar species are O. sarsii , O. rufa , O. paralutraria sp. nov. and O. lutraria . These can be easily differentiated by their ornamentation, as the polygonal reticulations of O. christiani are partly intermittent and with small projections towards the polygon’s center.

Etymology

The species is named after Christian Pott, the partner of MH.

Type material

Holotype AUSTRALIA – South Australia • ♂; dugout on Wentworth Road, about 15 km W of Lake Victoria; 33°53′03.4″ S, 140°58′39.1″ E; 13 Mar. 2011; M. Schwentner and B.V. Timms leg.; GenBank no: KJ705663 (COI); AM P.91434 .

Paratypes AUSTRALIA – South Australia • 3 ♂♂; same data as for holotype; GenBank nos: KJ705660 to KJ705662 (COI); AM P.91431 to P.91433 • 1 ♂; same data as for holotype; GenBank no: KJ705664 (COI); NHMW-ZOO-CR-28479 .

Type locality

South Australia, dugout Wentworth Road, about 15 km W of Lake Victoria, 33°53′03.4″S, 140°58′39.1″ E.

Description

Males

CARAPACE ( Fig. 15a–c ). Length 8.9–10.5 mm (HT: 8.9 mm), height 5.0– 6.1 mm (HT: 5.0 mm). Coloration dark brown, with lighter ventral margin and lighter (yellowish) spot on mid-frontal carapace. 21–23 (HT: 22) growth lines, 13–15 (HT: 14) widely spaced and 6–9 (HT: 8) crowded.

CARAPACE SHAPE. Dorsal margin straight, dorso-posterior corner rounded. Posterior margin broadly rounded, suboval, supracurvate to equicurvate (b/H 0.39–0.46, HT: 0.40). Ventral margin strongly curved, with clearly defined point of greatest extension. Umbo position anterior (Cr/L 0.18–0.21, HT: 0.21).

CARAPACE ORNAMENTATION ( Fig. 15d–e ). Larval valves appear smooth (probably artifact due to abrasion). Each growth band with medium to large polygonal reticulations with each polygon usually being a pentagon, hexagon or heptagon. Many polygons not fully closed and with additional lirae projecting into the polygon’s center. No secondary reticulation visible under SEM. Crowded growth bands without apparent ornamentation, but with uneven texture. Concentric ridges raised. No setae visible, under SEM setal pores in single row along posterior growth lines.

HEAD ( Fig. 15f–g ). Condyle short, rounded; occipital notch wide. Condyle lacking anterobasal hump. Margin between condyle and ocular tubercle concave. Ocular tubercle well developed, forming obtuse, close to 90° angle with rostrum. Small tubercle ventrally below eye in most specimens (HT: present). Anterior margin of rostrum convex. Apex strongly rounded with obtuse angle, followed by ventral indentation (lacking in one individual). Ventral margin of rostrum with hump following indentation, then deeply concave with obtuse angle about half-length, pointing apex slightly downwards. Naupliar eye small, triangular. Antenna I long with 20–23 lobes (HT: 22), reaching to antenna II flagellomeres VI–VII (HT: VI). Antenna II with 10–11 flagellomeres (HT: 11).

THORAX. 23–24 (HT: 24) segments, 22–23 (HT: 22) thoracopod-bearing and 1–2 (HT: two) posterior limbless segments not reaching dorsal margin. Dorsal extensions with numerous short spines, decreasing in number posteriorly. In posterior segments central spines stouter.

THORACOPOD III (only P.91434; Fig. 15j ). Endite I short and curved dorsally. Endites II–V broad, decreasing in size. Endite V palp two-segmented, basal segment shorter than endopod. Exopod ventral extension subequal or slightly longer in extension to endopod, dorsal extension wide, narrowing distally, overreaching epipod. Epipod long, cylindric.

TELSON ( Fig. 15h–i ). 15–18 spines (HT: 15). First (anterior) spine enlarged. Spines conical, posteriorly slightly thinner, drawn out and aciculate. Most spines small (compared to telson size), few (usually 1–3) slightly larger spines interspersed in anterior half of telson. Anterior most spines not arranged along dorsal margin but slightly lateral; spacing of spines irregular, usually widely spaced. Anterior half to two-thirds of dorsal margin nearly straight, posteriorly concavely curved. Right terminal claw more strongly curved than left.

FURCA ( Fig. 15h–i ). Proximally with dorsomedial longitudinal row of 7–12 (HT: nine) setae, row ending distally in a single conical spine. Distal part ⅓ of furcal length, with numerous small denticles.

Female

Unknown.

Distribution ( Fig. 15k )

The species is known only from its type locality, an artificial pool in south-eastern South Australia.

Remarks

Currently, only males are known. Schwentner et al. (2020) wrongly identified this species as O. sarsii . A comparison with the respective type material showed that O. christiani sp. nov. is not conspecific with O. sarsii . This was further corroborated by the classification based on carapace shape, where the probability that O. sarsii can be assigned to O. christiani was 0% with a typicality of 0.0. The carapace shape of O. christiani ( Fig. 5 ) is distinct from that of most other species and overlaps partly with those of O. rubra and O. matuwa sp. nov.

Figures

Fig. 15. Ozestheria christiani sp. nov. a. Carapace (male, holotype, P.91434). b. Carapace (male paratype, P.91433), SEM. c. Carapace, dorsal view (right valve only, male, holotype, P.91434). d–e. Carapace ornamentation (positions marked in a and b by rectangles). d. Mid-carapace, (male paratype, P.91433), SEM. e. Mid-carapace (male, holotype, P.91434). f–g. Head (antennae not shown). f. Male, holotype (P.91434). g. Male, paratype (P.91433), SEM. h–i. Telson. h. Male, holotype (P.91434). i. Male, paratype (P.91433), SEM. j. Third left thoracopod (male, holotype, P.91434). k. Distribution map (produced in ArcMap 10.7; see caption Fig. 7 for sources). Scale bars: a–c =1 mm; d–e =0.1 mm; f–j=0.5 mm.

Fig. 5. Morphometrics of short-condyled species. Scores on upper PC1 and PC2 of Fourier shape coefficients of 248 outlines, including 233 new individuals and 15 historic type specimens, four of which are drawings ofOzestheria elliptica (Sars, 1897),O. lutraria (Brady, 1886) andO. berneyi (Gurney, 1927). One of the drawings of O. berneyi corresponds to the studied syntype. The names used by Schwentner et al. (2015a) to identify genetically delimited species (e.g., C, D etc.; extended for the newly identified species, e.g., X1) are provided. New specimens are represented by convex hulls, type specimens by data points. lower. Mean shape of each species, calculated based on up to 73 individuals per species.