Ozestheria carnegiensis, 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 : 41-44

Ozestheria carnegiensis sp. nov.

urn:lsid:zoobank.org:act:16235DFE-FAC3-4158-B253-6F1FF8B4D8B9

Fig. 14

Diagnosis

Ozestheria carnegiensis sp. nov. is characterized by an elongate, but strongly rounded condyle with a narrow occipital notch (which is wider than in most species with a long condyle); carapace ornamentation dominated by punctae, in later growth bands nodular and very inconspicuous lirae (best seen under SEM) forming between dominant punctae, concentric ridges weakly developed and punctate; male rostrum with strongly convex (sometimes undulating) anterior margin, apex rounded with nearly rectangular angle, ventral margin weakly concave; 11–15 (male) antenna I lobes reaching to antenna II flagellomeres VIII–X (male); 12–14 (male) antenna II flagellomeres; 19–20 complete thorax segments; 11–20 telsonic spines, widely and irregularly spaced, varying in length with several larger spines interspersed, anteriorly broad, conical and posteriorly thinner and elongated, increasing in size posteriorly, most spines rather large; 7–8 furcal setae.

Differential diagnosis

Ozestheria carnegiensis sp. nov. can be differentiated from all other species of Ozestheria by the length of the condyle (which is somewhat intermediate between the typically short or long condyle) and the carapace ornamentation, which is dominated by punctae with a very inconspicuous transition to a liraedominated ornamentation on growth bands of the secondary growth phase. Other species with such a punctae-dominated carapace ornamentation are O. timmsi sp. nov. and O. frederikeae sp. nov., which both have longer condyles and a larger number of complete thorax segments (≥21 vs 19–20), antenna II flagellomeres (≥ 14 vs ≤ 14) and telsonic spines (17–31 vs 11–20), and distinct carapace shapes with more convexly curved ventral margins. Ozestheria gemina sp. nov. has a similar condyle length but differs in carapace ornamentation (well-developed lirae, fewer and less dominant punctae), rostrum shape and telson spination (spines smaller, usually only 2–3 larger interspersed). Moreover, Ozestheria carnegiensis sp. nov. appears to be the only species with a short, nodular epipod in most thoracopods.

Etymology

The species is named after Lake Carnegie, the only locality where the species has been recorded so far.

Type material

Holotype

AUSTRALIA – Western Australia • ♂; Lake Carnegie (Windidda 2); 26°15′52.7″ S, 122°16′29.23″ E; 4 Jun. 2020; D.J. Cale leg.; GenBank no: PQ427040 ( COI); WAM C78003 .

Paratypes

AUSTRALIA – Western Australia • 3 ♂♂; same data as for holotype; WAM C80213 , WAM C80214 , WAM C80215 • 1 ♂; same data as for holotype; NHMW-ZOO-CR-28497 .

Type locality

Western Australia, Lake Carnegie (Windidda 2), 26°15′52.7″ S, 122°16′29.23″ E.

Description

Males

CARAPACE ( Fig. 14a–d). Length 5.7–6.4 mm (HT: 6.1 mm), height 3.5–4.0 mm (HT: 3.8 mm). Coloration light brownish, crowded growth bands lighter. ~70 (in most individuals the carapace was covered in thick layer of dirt and algae, preventing detailed study of carapace features) growth lines, ~16 widely spaced and ~55 crowded.

CARAPACE SHAPE. Dorsal margin straight, distinct dorso-posterior corner. Posterior margin broadly rounded, suboval, equicurvate to infracurvate (b/H 0.54–0.61, HT: 0.61). Ventral margin widely rounded. Umbo position submedian (Cr/L 0.31–0.35, HT: 0.33).

CARAPACE ORNAMENTATION (due to very thick layer of dirt and fungi, difficult to study; Fig. 14e–g). Larval valve probably punctate. In the dorsal and median part of the carapace, growth bands punctate; in later growth bands very short, inconspicuous nodular lirae appearing between punctae (best visible under SEM), lirae not reaching across full growth band width. Crowded growth bands and growth bands of the secondary growth phase with short, inconspicuous, subparallel lirae. Concentric ridges shallow, punctate, with smooth dorsal and smooth to serrate ventral margins. No obvious setae preserved (setal pores in single row along all growth lines under SEM).

HEAD ( Fig. 14h). Condyle long, distally rounded; occipital notch narrow (but wider than in most species with a long condyle). Condyle lacking anterobasal hump. Margin between condyle and ocular tubercle concave. Ocular tubercle well developed, forming obtuse angle (~100–110°) with rostrum. Anterior margin of rostrum strongly convex, sometimes undulating. Apex rounded with nearly rectangular angle. Ventral margin of rostrum with slight notch anteriorly and weakly concave mid-length. Naupliar eye large and subtriangular. Antenna I long with 11–15 lobes (HT: 11), reaching to antenna II flagellomeres VIII–X (HT: X). Antenna II with 12–14 flagellomeres (HT: 14).

THORAX. 21–22 (HT: 21) segments, 19–20 (HT: 20) thoracopod-bearing and none to two (HT: one) posterior limbless segments not reaching dorsal margin. Most segments with dorsal extensions bearing several short spines, especially on last segments spines very short and inconspicuous.

THORACOPOD III (only WAM C78003; Fig. 14j). 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 in extension to endopod, dorsal extension wide, narrowing distally, greatly overreaching epipod. Epipod very short, rounded, nodular.

TELSON ( Fig. 14i). 11–20 spines (HT: 20). First (anterior) spine enlarged. Spines on anterior ⅔ of telson broad, conical; following spines becoming longer and slightly thinner. Spines vary in size, overall large-sized, several particularly large spines interspersed. Dorsal margin anterior ⅔ straight to slightly concave, then concave. Right terminal claw more strongly curved than left.

FURCA ( Fig. 14i). Proximally with dorsomedial longitudinal row of 7–8 (HT: 7) setae, row ending distally in a single conical spine. Distal part ½ of furcal length, with numerous small denticles.

Female

Unknown.

Distribution

Ozestheria carnegiensis sp. nov. is known from a single locality in central Western Australia.

Remarks

Currently, only males are known. In most individuals the carapace was covered by a thick layer of dirt and algae, preventing detailed study of carapace features. The extremely short epipod observed at the third thoracopod of the holotype appears like a damage or growth defect; however, also most other thoracopods of this and all other specimens have similarly short epipods. In some specimens these are slightly longer (about twice the length seen in the holotype), but still much smaller than in all other species. The claspers and a few more posterior thoracopods have the long and elongated epipods observed in all other species.

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