Ozestheria minor ( Spencer & Hall, 1896 ), 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 : 95-101

Ozestheria minor ( Spencer & Hall, 1896) comb. nov.

Figs 30–31

Estheria packardi var. minor Spencer & Hall, 1896: 238 , fig. 21.

Caenestheriella packardi var. minor – Daday 1914: 121–122.

Cyzicus packardi var. minor – Brtek 1997: 48.

Ozestheria packardi (in part) – Richter & Timms 2005: 347. — Rogers 2020: 24.

Ozestheria sp. B – Schwentner et al. 2015a: figs 2, 6.; 2020: figs 1–2. — Hethke et al. 2023: fig. 10.

Diagnosis

Ozestheria minor comb. 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, lirae become longer, more pronounced and less anastomosing with progressing growth bands; male rostrum with straight (rarely slightly undulating) anterior margin, apex acute angle (~45–60°), sometimes weakly rounded, ventral margin concave, pointing apex slightly downwards; female rostrum with straight anterior margin, apex rectangular and drawn out into small acute tip, ventral margin weakly concave; 10–16 (male) or 12–16 (female) antenna I lobes reaching to antenna II flagellomeres VI–X (male) or I–V (female); 11–15 (male) or 11–15 (female) antenna II flagellomeres; 19–23 complete thorax segments; 17–28 telsonic spines, spines on anterior third of telson thin and conical, following spines increasing in size, becoming longer, drawn out, aciculate and more closely spaced, all spines comparatively large; 4–10 furcal setae.

Differential diagnosis

Ozestheria minor comb. 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. typica comb. nov., O. fuersichi sp. nov., O. jonnae sp. nov., O. marthae sp. nov., O. selmae sp. nov., O. radiata sp. nov., O. bourkensis 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 minor 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 in 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 male and female rostrum (in particular anterior margin and apex). The apex of the male rostrum of O. beleriandensis is pointed and never rounded (in O. minor slightly rounded) and in the female the apex is finer pointed. The male rostrum of O. selmae has a dorsal concave notch (not in all individuals) and a weakly convex anterior margin. Ozestheria bourkensis and O. typica have a more strongly concave line between the condyle and ocular tubercle, and the female antenna I and II have fewer lobes and flagellomeres. Ozestheria radiata has a more rounded rostral apex in the male and the female rostrum terminates in a finer point.

Type material

Syntypes

AUSTRALIA – Northern Territory or South Australia • 2 ♂♂, 9 ♀♀; Charlotte Waters Central Australia; Horn Expedition leg.; MV J54045 .

Other material examined

AUSTRALIA – New South Wales • 2 ♂♂, 1 ♀; excavated area W of Yarrabundai ; 33°07′28.5″ S, 147°32′09.8″ E; 23 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91513 to P.91515 • 2 ♂♂, 1 ♀; Bloodwood Station, Gidgee Lake ; 29°33′10.4″ S, 144°50′12.7″ E; 19 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P. 91487, P.91489, P.91490 • 1 ♀; Barnato Station , lake next to homestead, 80 km W of Cobar; 31°36′52.4″ S, 144°52′12.6″ E; 29 Mar. 2010; M. Schwentner and B.V. Timms leg.; raised from sediment; AM P. 91486 . – South Australia • 2 ♂♂, 1 ♀; dugout 55 km E of Marla ; 27°18′21.3″ S, 134°07′15.9″ E; 11 Mar. 2011; M. Schwentner and B.V. Timms leg.; AM P.91495, AM P.91496, P.91498 • 1 ♀; dugout 55 km E of Marla ; 27°18′21.3″ S, 134°07′15.9″ E; 11 Mar. 2011; M. Schwentner and B.V. Timms leg.; NHMW-ZOO-CR-28490 . – Queensland • 1 ♂; dead shrub near old borrow pit, 113 km S of Mount Isa ; 21°34′21.0″ S, 139°11′58.4″ E; 4 Mar. 2011; M. Schwentner and B.V. Timms leg.; AM P.91500 • 4 ♂♂, 3 ♀♀; Sumana Station , small pool (H2); 22°18′29.6″ S, 145°21′56.7″ E; 2 Apr. 2009; M. Schwentner and B.V. Timms leg.; AM P.80862, P.91477 to P.91482 • 4 ♂♂, 1 ♀; N of Wyandra ; 27°11′03.2″ S, 145°59′41.2″ E; 17 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91493, P.91494, P.91506 to P.91508 • 3 ♂♂, 2 ♀♀; old borrow pit 8 km E of Boulia ; 22°55′44.6″ S, 139°58′23.7″ E; 4 Mar. 2011; M. Schwentner and B.V. Timms leg.; AM P.91501 to P.91505 .

Additional material (not examined)

AUSTRALIA – New South Wales • 1♀; Bloodwood Station, Vosper Pool ; 29°32′03.9″ S, 144°50′37.7″E; 30 Mar. 2009; M. Schwentner and B.V. Timms leg.; AM P.91476 • 2 juvs; Bloodwood Station, Gidgee Lake ; 29°33′10.4″ S, 144°50′12.7″ E; 19 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91487, P.91488 • 1 ♂; Muella Station, Muella Vegetated Pool 3; 29°30′12.0″ S, 144°55′37.4″ E; 31 Mar. 2009; M. Schwentner and B.V. Timms leg.; AM P.91552 • 1 juv.; big black box swamp; 29°10′19.4″ S, 145°22′41.3″ E; 21 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91526 • 1 juv.; Barnato Lake ; 31°36′45.2″ S, 144°59′20.0″ E; 22 Jan. 2010; M. Schwentner and B.V. Timms leg.; raised from sediment; AM P.91491 . – South Australia • 1 juv.; borrow pit 90 km S of border; 26°49′22.0″ S, 133°19′44.7″ E; 10 Mar. 2011; M. Schwentner and B.V. Timms leg.; AM P.91499 . – Queensland • 1 ♂; Sumana Station , small pool (H2); 22°18′29.6″ S, 145°21′56.7″ E; 2 Apr. 2009; M. Schwentner and B.V. Timms leg.; AM P.80862 • 5 juvs; Sumana Station , small pool (H8); 22°18′29.5″ S, 145°23′00.3″ E; 3 Apr. 2009; M. Schwentner and B.V. Timms leg.; raised from sediment; AM P.89648 to P.89650, P.91474, P.91475 • 6 juvs; SW Bay of Galilee ; 22°25′47.9″ S, 145°42′07.6″ E; 3 Apr. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91483 to P.91485, P.91516 to P.91518 • 3 juvs; Thunda Lake ; 25°25′46.0″ S, 143°08′13.8″ E; 8 Apr. 2009; M. Schwentner and B.V. Timms leg.; raised from sediment; AM P.91519 to P.91521 • 5 juvs; roadside claypan; 29°31′42.5″ S, 146°12′20.5″ E; 21 Jan. 2010; M. Schwentner and B.V. Timms leg.; AM P.91509 to P.91511, P.91524, P.91525 • 1 juv.; old dugout close to Lake Dunn ; 22°36′12.9″ S, 145°40′26.6″ E; 14 Feb. 2010; M. Schwentner, C. Sieves and B.V. Timms leg.; AM P.91523 .

Type locality

Spencer & Hall (1896: 237) did not specify a type locality but generally stated where they collected O. packardi and its newly described varieties as “Common in water-holes along the Finke and its tributaries, also in the Macumba and Stevenson Rivers”. The label of the syntype collection states “Charlotte Waters Central Australia ”.

Description

Males

CARAPACE ( Fig. 30a–c, e, g). Length 3.4–6.1 mm (ST: 3.3–3.6 mm; mean: 4.7 mm), height 2.0– 3.9 mm (ST: 2.2–2.5 mm; mean: 2.9 mm). Coloration yellow-orange to red-orange or reddish-brown, outer margin lighter, whitish (syntypes lighter colored, but this is probably an artifact of the long storage). 18– 63 (ST: 30–38, mean: 34) growth lines, 11–29 (ST: 11–14, mean: 20) widely spaced (rarely secondary growth phase with up to 23 additional widely spaced growth lines) and 2–28 (ST: 16–27, mean: 13) crowded.

CARAPACE SHAPE. Dorsal margin straight, distinct or rounded dorso-posterior corner. Posterior margin broadly rounded, suboval, equicurvate to infracurvate (b/H 0.49–0.56, ST: 0.55, mean: 0.53) with greatest extension below midline. Ventral margin nearly straight, only slightly curved. Umbo position anterior to submedian (Cr/L 0.24–0.33, ST: 0.33, mean: 0.28).

CARAPACE ORNAMENTATION ( Fig. 30f, h–i). Larval valve and growth bands in dorsal parts of carapace punctate or granular. In successive growth bands, poorly defined, irregular lirae forming ventrally. Within median growth bands, lirae dorsally lirae anastomosing and sometimes reticulating, ventrally subparallel, punctae between and along lirae. Further ventrally on carapace (including crowded growth bands), lirae more defined and subparallel; growth bands dorsally nodulous; the interspace between lirae with intermittent, nodular liral structures (visible mainly under SEM); liral structures in crowded growth bands appearing like radial ribs across multiple growth bands (not in all individuals). Under SEM additional small punctae visible across all growth bands. Concentric ridges slightly raised. Setae filiform, preferentially preserved on ventral part of carapace. Setal pores in single row along all growth lines, forming serrate lower margins of concentric ridges in mid-carapace growth bands (visible under SEM).

HEAD ( Fig. 31a–b, d). Condyle long, distally acute; occipital notch narrow. Condyle with or without weakly developed anterobasal hump. Margin between condyle and ocular tubercle straight to slightly concave or slightly convex. Ocular tubercle weakly developed, forming obtuse, nearly straight angle with rostrum. Anterior margin of rostrum straight, rarely slightly undulating. Ventral margin of rostrum with anterior notch; concave along midline, pointing apex slightly downwards; apex with acute angle (~45–60°), sometimes weakly rounded. Naupliar eye subtriangular, rarely oval. Antenna I long with 10–16 lobes (ST: 16; mean: 13), reaching to antenna II flagellomeres VI–X (ST: VIII–X; mean: VIII). Antenna II with 11–15 flagellomeres (ST: 12; mean: 13).

THORAX. 20–22 (ST: 22; mean: 21) segments, 19–22 (ST: 22; mean: 21) thoracopod-bearing and none to one (ST: none) posterior limbless segment not reaching dorsal margin. Last ~14 thoracopod-bearing segments with spine and/or setae bearing dorsal extensions. Setae/spines of dorsal extensions increasing in number posteriorly over successive segments (until ~7 th last segment). Spines short and stout, in posterior segments central spines stouter but shorter than in preceding segments.

THORACOPOD III (only P.91495; Fig. 31f). 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, overreaching epipod. Epipod long, cylindric.

TELSON ( Fig. 31g, i). 18–28 spines (ST: 20; mean: 23). First (anterior) spine enlarged. Spines on anterior third of telson short, thin, conical; following spines increasing in size, becoming longer, drawn out, aciculate and more closely spaced. Dorsal margin anteriorly straight (rarely convex), posterior ⅔ slightly concavely curved. Right terminal claw more strongly curved than left claw in most individuals, rarely both equally curved.

FURCA ( Fig. 31g, i). Proximally with dorsomedial longitudinal row of 4–10 (ST: 4; mean: 8) setae, row ending distally in a single conical spine. Distal part ⅔–¾ of furcal length, with numerous small denticles.

Females

Overall appearance as in males. Carapace ( Fig. 30d) length 3.3–6.2 mm (ST: 3.3–3.7 mm; mean: 4.3 mm), height 2.2–4.1 mm (ST: 2.1–2.5 mm; mean: 2.8 mm); 17–46 (ST: 28–46, mean: 29) growth lines, 12–30 (ST: 12–19, mean: 19) widely spaced and 0–23 (ST: 13–27, mean: 10) crowded; Cr/L 0.26–0.32 (mean: 0.28) and b/H 0.48–0.57 (mean: 0.53). Anterior margin of rostrum straight; apex rectangular, drawn out into small acute tip; ventral margin only weakly concave (straighter than in males); overall rostrum shape trapezoidal ( Fig. 31c, e). Antenna I with 12–16 (ST: 15–16, mean: 14) lobes, lobes smaller than in males and distally often fused (then number of lobes could not be counted); reaching to antenna II flagellomeres I–V (ST: IV–V, mean: III). Antenna II with 11–15 flagellomeres (ST: 11–12, mean: 13). 20–23 (ST: 21–23, mean: 21) segments, 20–23 (ST: 21–23, mean: 21) thoracopod-bearing and none to one posterior limbless segment not reaching dorsal margin. Telson with 17–26 (ST: 17–21, mean: 21) dorsal spines ( Fig. 31h); left and right terminal claws equally curved. Furca with 4–8 setae (mean: 6).

Distribution ( Fig. 31j)

Widely distributed in the arid regions of central and northern New South Wales, large parts of arid Queensland (e.g., catchments of northern and central Murray-Darling Basin, central and northern Cooper Creek catchment) as well as in central Australia. It is one of the few species which occurs in the northern Cooper Creek catchment and areas further to the west or south. This species lives in a variety of habitats ranging from turbid claypans to various clear pools and lakes and even hyposaline lakes (e.g., Gidgee Lake). Noteworthy is the frequent occurrence in various artificial habitats (dugouts, borrow pits).

Remarks

Ozestheria minor comb. nov. was originally described as one of three varieties of O. packardi by Spencer & Hall (1896). Previous workers (e.g., Richter & Timms 2005; Rogers 2020) have synonymized these varieties with O. packardi . However, the large cryptic species diversity, which was revealed by molecular genetic analyses within O. packardi ( Schwentner et al. 2015a) , strongly suggested that O. minor and the other varieties represent valid species. A comparison between the syntypes and the genetically delimited species strongly suggests that O. minor corresponds to Ozestheria sp. B of Schwentner et al. (2015a). Most importantly, the shape as well as the ornamentation (also at the highmagnification SEM-level) of the carapaces is highly similar, including the fine punctae between lirae. Also, the telsonic spines (majority of spines elongate and aciculate) as well as the shape of the female rostrum (apex drawn out, but tip not as minutely pointed as in several other species such as O. typica comb. nov. or O. bourkensis sp. nov.) correspond well to the description of O. minor by Spencer & Hall (1896). The carapace coloration of the syntypes appears lighter than in other specimens (light yellowishbrownish). This may be due to the long storage in ethanol, as Spencer & Hall (1896: 237) described the coloration as “chestnut-brown with a broad, light band around the margin”, which agrees well with the other specimens.

In the geometric morphometric analyses of the carapace shape ( Fig. 6), O. minor comb. nov. partly overlaps with O. jiangi sp. nov., O. jonnae sp. nov., O. selmae sp. nov., O. typica comb.nov., O. bourkensis , O. cancellata comb. nov., O. rincewindi sp. nov., O. weeksi sp. nov., O. glabra sp. nov., and O. echidna sp. nov. Due to the overall similarities with other species in carapace shape, the classification of the mean shape of the syntypes of O. minor (Supp. file 2_4.4) suggested several species, including O. sp. B (sensu Schwentner et al. 2015a; probability 13.7%, typicality 0.52). Highest probabilities were observed for O. cancellata and O. jonnae (42.9% and 19.0%) and the highest typicalities scores for O. frederikeae sp. nov. (0.72), O. jonnae (0.60) and O. cancellata 0.58).

The type specimens were not specifically marked as types of O. minor . However, the historic labels accompanying the specimens explicitly identified them as “ Estheria packardi var. minor ” and stated the locality and expedition as “Charlotte Waters Horn Exp.”, which makes it very likely that these are the type specimens collected and described by Spencer & Hall from the Horn Expedition.