Eocyzicus breviantennus, Tippelt & Schwentner, 2018

Tippelt, Lisa & Schwentner, Martin, 2018, Taxonomic assessment of Australian Eocyzicus species (Crustacea: Branchiopoda: Spinicaudata), Zootaxa 4410 (3), pp. 401-452 : 424-427

Eocyzicus breviantennus sp. nov.

( Figs. 11 and 12 )

Eocyzicus lineage S Schwentner et al., 2014, 2015b

Etymology. The name is derived from Latin words "brevus" and "antennus" meaning short antenna and is based on the small number of antennary segments, which is characteristic for this species.

Type locality. South Australia, Lake Eyre basin, Finke River, a large claypan 40 km north of Marla, 26°59´48.9´´S, 133°24´55.2´´E.

Type material. Holotype. Male (AM P.89453, GenBank KC583818 ).

Allotype. Female. (AM P.89449, GenBank KC583814 ).

Paratypes. 2 males (AM P.89451, GenBank KC583816 ; AM P.89452, GenBank KC583817 ), 1 female (AM P.89450, GenBank KC583815 ), collected by M. Schwentner, S. Richter and B. V. Timms, 10-III-2011.

Further material examined: no material from other localities available

Description. Holotype male ( Fig. 11 a, c and d ). Carapace. 2.3 mm high, 3.4 mm long, height/length ratio 0.68; height without "crowded" growth lines 2.1 mm; length without "crowded" growth lines" 3.1 mm; shape oval; dorso-posterior corner nearly absent; 18 growth lines, of these 14 "non-crowded" and four "crowded"; umbo small, hemispheric, growth lines absent ( Fig. 11a ).

Head. Condyle rounded, section between condyle and external eye contour straight; eye bulge absent, compound eye round; straight angle between head and rostrum; anterior margin of rostrum convex, transition between anterior and ventral margin rounded ( Fig. 11c ). Antennule with 22 lobules, closely arranged; longer than antenna. Antenna with ten antennary segments, middle antennary segment anteriorly with four spines.

Thorax. 19 thorax segments, of these 17 "complete" and two "incomplete" ( Fig. 11d ); dorsal spines beginning at 7th thorax segment, eleven thorax segments with dorsal spines; one dorsal spine at each thorax segment, first dorsal spine smaller than following one, last dorsal spine smaller than preceding one, last "complete" thorax segment with dorsal spine ( Fig. 11d ).

Telson. 14 telsonic spines, of these three enlarged, telsonic spines end after base of apex; telson symmetric; telsonic filaments situated between third and fourth telsonic spine. Furca with two setae, as long as proximal part of furca; small spine before row of spinules absent, spinules long ( Fig. 11d ).

Allotype female ( Fig. 11b, e and f ). Carapace. 3.2 mm high, 4.8 mm long, height/length ratio 0.67; height without "crowded" growth lines 2.8 mm, length without "crowded" growth lines 4.1 mm; dorso-posterior corner clearly present; umbo with growth lines ( Fig. 11b ).

Head. Compound eye oval; anterior margin of rostrum straight ( Fig. 11e ). Antennule with 17 lobules; reaches to 7th antennary segment. Antenna with eleven antennary segments.

Thorax. 19 thorax segments, of these 18 "complete" and one "incomplete" ( Fig. 11f ); dorsal spines beginning at 8th thorax segment; first dorsal spine same size as following one, last dorsal spine same size as preceding one.

Telson. One enlarged telsonic spine, telsonic spines end at base of apex. Furca with five setae, longer than proximal part of furca ( Fig. 11f ); small spine before row of spinules present.

Ovigerous flagella situated at 9th and 10th thorax segment.

Variability. Males. Carapace. 2.3–2.6 mm high, 3.4–4.0 mm long, height/length ratio 0.65–0.68, height without "crowded" growth lines 2.1–2.6 mm, length without "crowded" growth lines 3.1–4.0 mm; dorso-posterior corner clearly present or nearly absent; 15–18 growth lines, of these 13–15 "non-crowded" and up to four "crowded".

Head. Section between condyle and external eye contour straight or convex; obtuse to straight angle between head and rostrum, anterior margin of rostrum straight or convex ( Fig. 12a ). Antennule with 17–23 lobules, closely or widely arranged; reaches to 8th–10th antennary segment ( Fig. 12b ). Antenna with middle antennary segment anteriorly with two or four spines ( Fig. 12e ).

Thorax. 19–21 thorax segments, of these 17–19 "complete" and one or two "incomplete" ( Fig. 12f ); dorsal spines beginning at 6th or 7th thorax segment, 11–13 thorax segments with dorsal spines; last "complete" thorax segment with or without dorsal spine ( Fig. 12f ).

Telson. 14–16 telsonic spines, of these up to three enlarged; telsonic spines end at or after base of apex; telsonic filaments situated between third and fourth telsonic spine. Furca with two to eight setae, as long as or longer than proximal part of furca ( Fig. 12f ).

Variability. Females. Carapace. 3.1–3.2 mm high, 4.7–4.8 mm long, height/length ratio 0.66–0.67; length without "crowded" growth lines 4.1–4.2 mm; 18 growth lines, of these 1 4–15 "non-crowded"; and three or four "crowded"; umbo with or without growth lines.

Head. Antennule with 17–20 lobules.

Thorax. Dorsal spines beginning at 7th or 8th thorax segment, eleven or twelve thorax segments with dorsal spines; last "complete" thorax segment with or without dorsal spine.

Telson. 14–16 telsonic spines, of these up to three enlarged, telsonic filaments situated between the third and fifth telsonic spine. Setae on furca shorter than or longer than proximal part of furca.

Differential diagnosis. see remarks for E. richteri sp. nov.

Distribution and ecology. Eocyzicus breviantennus sp. nov. was found in a single fresh and turbid habitat and occurred sympatrically with E. argillaquus .

Figures

FIGURE 11. Eocyzicus breviantennus sp. nov. a, carapace of male holotype (AM P.89453). b, carapace of female allotype (AM P.89449). c, head of male holotype. d, telson of male holotype.e, head of female allotype. f, telson of female allotype. ce = compound eye, co = condylus, ds = dorsal spine, fu = furca, gl = growth lines, is = „incomplete" thorax segments, md = mandible, ro = rostrum, sp = spinules, tf = telsonicfilaments, ts = telsonic spines, um = umbo.

FIGURE 12. Eocyzicus breviantennus sp. nov. male paratype (AM P.89451). a, rostrum (left antenna removed). b, antennule. c, first right clasper, arrow indicates the scales at the tip of the movable finger. d, detail of the tip of the movable finger of first right clasper. e, fourth and fifth segment of the right antenna. f, telson, arrow indicates "incomplete" thorax segment. A1 = antennules, ds = dorsal spine, fu = furca, lp = large palpus, mf = movable finger, ro = rostrum, sc = scales, sp = spinules, tf = telsonic filaments, ts = telsonic spines.