Eocyzicus timmsi Tippelt & Schwentner 2018, sp. nov.

Eocyzicus timmsi sp. nov.

(Figs. 7 and 8)

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

Etymology. The species is named in honor of Prof. Brian V. Timms. Prof. Timms has contributed significantly to our knowledge of the taxonomy and ecology of Australian Branchiopoda, including the first descriptions of Australian Eocyzicus species. Without his help and support this study would not have been possible.

Type locality. Queensland, Cooper Creek, Sumana Station, small pool (H2), 22°18´29.6´´S, 145°21´56.7´´E.

Type material. Holotype. Male (AM P.89531, GenBank KC583896).

Allotype. Female (AM P.89530, GenBank KC583895).

Paratypes. 2 males (AM P.80902, GenBank KC583710; AM P.89529, GenBank KC583894), collected by M. Schwentner and B. V. Timms, 02-IV-2 0 0 9.

Further material examined: Queensland: 2 males (AM P.80901, AM P.89546), 2 females (AM P.89544, P.89545) Small pool (H1), Sumana Station, 22°18´38.8´´S, 145°22´57.0´´E, 02-IV-2009; 1 female (AM P.89535) Small pool (H4), Sumana Station, 22°17´47.1´´S, 145°21´21.3´´E), 02-IV-2009; 2 males (AM P.89539, AM P.89540) Small pool (H5), Sumana Station, 22°17´41.6´´S, 145°21´21.9´´E, 02-IV-2009; 1 female (AM P.89548) Small pool (H8), Sumana Station, 22°18´29.5´´S, 145°23´00.3´´E, 03-IV-2009; 1 female (AM P.89549) Morra Creek (M1), Yarromere Station, 21°28´51.9´´S, 145°49´34.0´´E, 03-IV-2009; 1 male (AM P.89560), 2 females (AM P.89558, AM P.89559) Lake Galilee, 22°25´37.3´´S, 145°42´13.4´´E, 15-II-2010; 3 males (AM P.89554, AM P.89552, AM P.89553), 2 females (AM P.89551, AM P.89555) Artificial pool south of Lake Dunn, 22°39´44.8´´S, 145°44´40.2´´E, 14-II-2010.

Description. Holotype male (Fig. 7a, c and d). Carapace. 4.5 mm high, 7.1 mm long; height/length ratio 0.63; height without "crowded" growth lines 4.3 mm; length without "crowded" growth lines 6.7 mm; shape oval; dorsoposterior corner nearly absent; 28 growth lines, of these 26 "non-crowded" and two "crowded"; umbo large, coneshaped, growth lines present (Fig. 7a).

Head. Condyle rounded, section between condyle and external eye contour straight; eye bulge absent, compound eye oval; straight angle between head and rostrum; anterior margin of rostrum straight, transition between anterior and ventral margin rounded (Fig. 7c). Antennule with 21 lobules, widely arranged; reaches to 12th antennary segment. Antenna with 14 antennary segments, middle antennary segment anteriorly with five spines.

Thorax. 22 thorax segments, of these 20 "complete" and two "incomplete" (Fig. 7d); dorsal spines beginning at 9th thorax segment, twelve 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. 7d).

Telson. Nine telsonic spines, of these one enlarged, telsonic spines end after base of apex; telson symmetric; telsonic filaments situated between third and fourth telsonic spine. Furca with eight setae, longer than proximal part of furca; small spine before row of spinules absent, spinules long (Fig. 7d).

Allotype female (Fig. 7b, e and f). Carapace. 5.4 mm high, 8.1 mm long, height/length ratio 0.67; height without "crowded" growth lines 4.9 mm, length without "crowded" growth lines" 7.1 mm; 24 growth lines, of these 19 "non-crowded" and five "crowded"; umbo hemispheric (Fig. 7b).

Head. Compound eye round; transition between anterior and ventral margin of rostrum angular (Fig. 7e). Antennule with 16 lobules; reaches to 8th antennary segment.

Thorax. 21 thorax segments, of these 19 "complete" and two "incomplete" (Fig. 7f); dorsal spines beginning at 8th thorax segment; last dorsal spine same size as preceding one.

Telson. 16 telsonic spines, of these two enlarged. Furca with 15 setae, shorter than proximal part of furca (Fig. 7f).

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

Variability. Males. Carapace. 3.8–5.2 mm high, 5.9–7.9 mm long, height/length ratio 0.63–0.70; height without "crowded" growth lines 3.5–4.3 mm; length without "crowded" growth lines 5.4–6.7 mm; dorso-posterior corner clearly present or nearly absent; 17–40 growth lines, of these 14–28 "non-crowded" and 1–14 "crowded"; umbo small or large, cone-shaped or hemispheric.

Head. Section between condyle and external eye contour concave or straight; eye bulge absent or present, if present large, compound eye oval or round; acute or obtuse to straight angle between head and rostrum; anterior margin of rostrum straight or convex, transition between anterior and ventral margin rounded or angular (Fig. 8a). Antennule with 15–23 lobules, closely or widely arranged (Fig. 8b); reaches to 9th –13th antennary segment. Antenna with 12–15 antennary segments, middle antennary segment anteriorly with four to seven spines (Fig. 8g).

Thorax. 20–23 thorax segments, of these 18–21 "complete" and one or two "incomplete" (Fig. 8d); dorsal spines beginning at 8th –10th thorax segment, 9–13 thorax segments with dorsal spines; last dorsal spine smaller than or same size as preceding one, last "complete" thorax segment with or without dorsal spine (Fig. 8d).

Telson. 11–15 telsonic spines, of these up to four enlarged, telsonic spines end at or after base of apex; telsonic filaments situated between second and fifth telsonic spine. Furca with five to ten setae (Fig. 8d); small spine before row of spinules present or absent.

Variability. Females. Carapace. 2.3–5.6 mm, 3.6–8.5 mm, height/length ratio 0.64–0.68; height without "crowded" growth lines 2.2–5.0 mm, length without "crowded" growth lines 3.4–7.5 mm; dorso-posterior corner clearly present or nearly absent; 11–38 growth lines, of these 11–32 "non-crowded" and up to 14 "crowded"; umbo small or large, hemispheric, growth lines present or absent.

Head. Section between condyle and external eye contour concave or straight; eye bulge absent or present, if present small, compound eye oval or round; acute or obtuse to straight angle between head and rostrum, transition between anterior and ventral margin of rostrum rounded or angular. Antennule with 12–16 lobules, closely or widely arranged; reaches to 5th –8th antennary segment. Antenna with 10–14 antennary segments, middle antennary segment anteriorly with three to five spines.

Thorax. 20–21 thorax segments, of these 18–19 "complete" and up to two "incomplete"; dorsal spines beginning at 8th –10th thorax segment, nine to twelve thorax segments with dorsal spines; last dorsal spine smaller than or same size as preceding one, last "complete" thorax segment with or without dorsal spine.

Telson. 11–16 telsonic spines, of these up to six enlarged, telsonic spines end before, at or after base of apex; telsonic filaments situated between second and fifth telsonic spine. Furca with 2–15 setae, shorter than, as long as or longer than proximal part of furca; small spine before row of spinules present or absent.

Differential diagnosis. Eocyzicus timmsi sp. nov. has the highest observed number of all and of "noncrowded" growth lines. In general it exhibits a large morphological intraspecific variability that spans the whole range of character states observed in several other species (Tables 1 and 2). It was not distinguished from E. argillaquus in the PCA and CVA (Fig. 2b and d). However, the observed ranges of character states of several morphological characters – e.g., the number of thorax segments with dorsal spines or number of telsonic spines – support their differentiation. Furthermore, E. argillaquus is genetically well differentiated and not the putative sister species to E. timmsi sp. nov. Its putative sister species - E. ubiquus sp. nov. – can be morphologically distinguished by the total number of all growth lines and the number of thorax segments with dorsal spines (Tables 1 and 2, Figs. 2b and d) and both species are clearly genetically differentiated (Schwentner et al., 2014). Because both species are strictly allopatric, reproductive isolation cannot be unambiguously inferred at present as would be required by the Biological Species Concept (Mayr, 1942). Nevertheless, E. timmsi sp. nov. represents a distinct species according to the PSC sensu Wheeler & Platnick (2000) and the ESC (Wiley & Mayden, 2000).

Distribution and ecology. This species is distributed in clear and turbid fresh water bodies and does not occur sympatrically with any other species.