Billcypris davisae gen. et sp. nov.

urn:lsid:zoobank.org:act: 3904885C-9677-4739-8B10-5E83D36EB09A

Figs 12–13

Diagnosis

Valves highly arched, greatest height situated almost in middle. RV with anterior inwardly displaced selvage, more so in female than in male; marginal tubercles absent or very small and few. LV with postero-dorsal extension in male (less developed in females), also visible in carapace in right-lateral view. Lpp with elongated first and second segment, first segment with parallel margins, second segment without long distal flagellum. Hp with very large, sub-rectangular lobe ls and pointed lobe ms, the latter only ventrally developed.

Etymology

This species is named in honour of Prof. Jenny Davis (Charles Darwin University, Darwin, Australia), in recognition of her significant contributions to Australian limnology, especially of wetlands.

Measurements

See Table 1.

Type locality

Lake Cowan, Western Australia. Approximate coordinates: 31°42′04″ S, 121°54′14″ E. All type specimens collected by Shane Chaplin, 8 Apr. 1999 (voucher sample no. OSTR064B).

Material examined

Holotype AUSTRALIA • ♂; Western Australia, Lake Cowan; 31°42′04″ S, 121°54′14″ E; 8 Apr. 1999; Shane Chaplin leg.; voucher sample no. OSTR064B; with soft parts dissected in glycerine on a sealed slide and with valves stored dry in a micropalaeontological slide; WAM 67217.

Allotype AUSTRALIA • ♀; same collection data as for holotype; dissected and stored as the holotype; WAM 67218.

Paratypes AUSTRALIA • 1 ♂; same collection data as for holotype; dissected and stored as the holotype; RBINS INV 138038 • 2 male and 2 female carapaces; same collection data as for holotype; used for SEM and stored dry in a micropalaeontological slide; WAM 67219 to 67222 .

Other material

AUSTRALIA • 1 ♂; Western Australia, Lake Lefroy; 31°17′35″ S, 121°41′16″ E [approximate coordinates]; 8 Apr. 1999; Shane Chaplin leg.; dissected and stored as the holotype; WAM 67224 • 6 ♂♂, 7 ♀♀; same collection data as for preceding; in 70% EtOH as bulk vouchers; WAM 67225 .

Description

Male

RV (Fig. 12B–C, K). Arched, greatest height situated in, or just behind, middle; anterior margin rounded, dorsal margin straight and posteriorly sloping over a short distance, posterior margin relatively straight in dorsal section and broadly rounded ventrally, ventral margin almost straight. With both anterior and posteroventral sub-marginal selvage, posterior one somewhat more inwardly displaced than anterior one. Anterior and posteroventral margins with some remnants of marginal tubercles. Calcified inner lamellae narrow, more so posteriorly.

LV (Fig. 12A, J). With a shape generally comparable to that of RV, slightly larger; anterior calcified inner lamella slightly wider than in RV, anteriorly with blunt inner list running parallel to most of valve margin, posteriorly without inner list. Posterodorsal extension of valve present.

CARAPACE. In dorsal view (Fig. 12F) without anterior rostrum; greatest width situated behind middle. In lateral view (Fig. 12H) with posterodorsal extension on LV prominent.

PREHENSILE PALPS ON T1. Asymmetrical, chaetotaxy of endopodite as typical for family (not shown). Rpp (Fig. 13B, F) with second segment relatively narrow and curved, distal margin either straight (Fig. 13B) or rounded (Fig. 13F) (possibly depending on position of limb on slide); first segment broad. Lpp (Fig. 13C, E) with nearly rectangular first segment. Second segment sickle- shaped and narrow, of variable length, and without distal flagellum-like expansion.

ZENKER ORGAN. As typical of family, i.e., ca 3–5 × as long as wide and with numerous spinous whorls.

HEMIPENIS (Fig. 13A, D). With lobe ls large and sub-rectangular, with blunt point extending ventrally beyond edge of hemipenis; ms triangular and bluntly pointed.

CAUDAL RAMUS (Fig. 13H). Curved and proximally hardly expanded; its attachment (Fig. 13G) uniramous (note: the bifurcation on the left side on Fig. 13G is actually the proximal part of the CR itself).

Female

VALVES (Fig. 12 D–E). With shape similar to those of male, but with posteroventral extension on LV much smaller and even absent in some specimens. Valve margin anatomy as in male, except for selvage in RV being more inwardly displaced, both anteriorly and posteriorly.

CARAPACE. In dorsal view (Fig. 12L) as in male. In lateral view (Fig. 12G, I) with posteroventral lump of LV still visible in some specimens, absent in others.

A1, Md, Mx1, T2, T3 and attachment of CR as in male.

A2 (not shown). With distal chaetotaxy showing sexual dimorphism as typical of family.

T1 (not shown). With palp not segmented, relatively short and broad.

Differential diagnosis

This species can at once be distinguished from all others in the subfamily Cyprinotinae by the very large lobe ls and the pointed lobe ms on the hemipenis. The posterodorsal extension on the LV, especially in the male, is also characteristic, but similar features have been seen in other, as yet undescribed, species of West Australian Heterocypris .

Ecology and distribution

Billcypris davisae gen. et sp. nov. appears to be a halophilic species, collected from Lakes Cowan and Lefroy near Norseman, Western Australia. Both are shallow hypersaline playas that are typically dry but may be shallowly inundated for a few months in wet years. Both lakes are surrounded by smaller playas that are inundated by smaller rainfall events and tend to be less saline. No information on salinities at the time of collecting is available.