Bennelongia De Deckker & McKenzie, 1981

Martens, Koen, Halse, Stuart & Schön, Isa, 2012, Nine new species of Bennelongia De Deckker & McKenzie, 1981 (Crustacea, Ostracoda) from Western Australia, with the description of a new subfamily, European Journal of Taxonomy 8, pp. 1-56 : 9-11

Genus Bennelongia De Deckker & McKenzie, 1981

Diagnosis (modified after De Deckker & McKenzie 1981)

Adults with asymmetrical valves, especially anteriorly. LV overlapping RV anteriorly, ventrally and posteriorly, sometimes also dorsally.

LV antero-ventrally with a beak-like expansion of the valve margin; anterior calcified inner lamella with two incomplete inner lists, a ventro-proximal one and a dorso-distal one, both extending to about the

middle of the valve and slightly or significantly overlapping each other; ventro-proximal list protruding and forming a sulcus running along the proximal inner list and extending in the lip-like structure.

RV with short antero-ventral inner list, and antero-ventrally either with a small, transparent flange (here termed ‘lapel’) or with valve forming a bulbous expansion; RV set with tubercles along most of the anterior, ventral and posterior valve margin.

Juveniles with completely different valve morphology, with symmetrical valves, without beak-like expansion on LV or lapel on RV and with external surface either pitted or reticulated or set with wartlike tubercles in most lineages in the genus.

A1 and A2 with medium-long natatory setae. Md-palp with alpha-seta long and smooth, beta-seta stout and hirsute in distal half, gamma-seta relatively slender and hirsute in distal half. Mx1-palp with distal segment rectangular. T1 with prehensile palps in males strongly asymmetrical, right palp with broad terminal segment, left palp with sickle shaped distal segment. T2 with seta d1> d1, sometimes twice as long, penultimate segment of endopod (segment 3) divided. T3 a cleaning leg. Caudal ramus and attachment slender. Hemipenis consisting of at least two, asymmetrical penal sheets.

Remarks

The extent of the difference in morphology between juveniles and adults in most lineages of Bennelongia is unusual in non-marine Ostracoda. The difference of the extent of this dimorphism between the lineages, and its relevance, will be discussed elsewhere in a separate paper.

Differential diagnosis

Bennelongia is immediately distinguishable from all other cypridid genera by the peculiar morphology of the anterior parts of the valves, especially of the LV (see above).

Type species

Bennelongia harpago De Deckker & McKenzie, 1981 (Queensland, Australia).

Other species allocated (only area of type locality given)

See Table 2.

Bennelongia australis ( Brady, 1886) : SA

Bennelongia barangaroo De Deckker, 1981 : WA

Bennelongia bidgelongensis sp. nov.: WA, Gascoyne

Bennelongia coondinerensis sp. nov.: WA, Pilbara

Bennelongia cuensis sp. nov.: WA, Yilgarn

Bennelongia cygnus sp. nov.: WA, Swan Valley

Bennelongia frumenta sp. nov.: WA, Wheatbelt

Bennelongia gwelupensis sp. nov.: WA, Perth, southwest coast

* Bennelongia harpago De Deckker & McKenzie, 1981 : QLD

Bennelongia kimberleyensis sp. nov.: WA, Kimberley

Bennelongia lata sp. nov.: WA, Gascoine-Murchinson region

Bennelongia nimala De Deckker, 1981 : NT

Bennelongia pinpi De Deckker, 1981 : QLD

Bennelongia strellyensis sp. nov.: WA, Pilbara

Bennelongia tunta De Deckker, 1982 : QLD

Distribution

The genus is most likely endemic to Australia and New Zealand and can be considered as one of the more typical ostracod groups of the Australasian region. De Deckker (1981a) suggested that Strandesia flavescens Klie, 1932 and Strandesia feuerborni Klie, 1932 , both from Indonesia (Sumatra, Java), might also belong in this genus, but Savatenalinton & Martens (2010) and Martens & Savatenalinton (2011) retained both species in their original genus, Strandesia Stuhlmann, 1888 .

General valve morphology ( Figure 4 )

In order to allow accurate descriptions of species in this genus, it is necessary to unequivocally establish the homology of the different marginal structures in both valves, as these have undergone remarkable evolutionary changes ( Figure 4A ).

In the LV, the valve margin and two inner lists are of importance. The valve margin shows an anteroventral beak-like expansion. The anterior calcified inner lamella carries two inner lists, a proximal ventral and a distal dorsal one. Together, these lists line a sulcus, a depression in the calcified inner lamella which further expands in the beak-like expansion. The proximal inner list can be significantly elevated ( Figure 4B ).

In the RV, an outer list, the valve margin, a selvage and two inner lists form a complex structure. The outer list is invariably modified, completely or partially. In B. cygnus sp. nov., the middle part of the outer list is still a list, the posterior part is modified into a row of tubercles and the anterior part in a row of tubercles and a lapel ( Figure 4C ). In most (all?) species of the B. australis group (see below), the entire outer list is modified into a row of tubercles and the antero-ventral lapel ( Figure 4D ). In the species of the B. pinpi lineage, the entire outer list is modified into a row of tubercles, which stops where in other species the lapel is formed and where in these species the bulbous expansion occurs ( Figure 4E ). What looks to be the anterior valve margin in the RV is actually a selvage, which can be modified in places, with swollen or flange-like parts near the lapel. The actual anterior valve margin is strongly reduced, but can in most species still be detected as a row of small tubercles set with setae ( Figure 4 C-E). The calcified inner lamella also has two incomplete inner lists, here the ventral one is distal and the dorsal one more proximal. Internal to the ventral inner list, the calcified inner lamella forms a shallow sulcus, which matches the deeper one in the LV. The posterior selvage is more easily recognizable as such.

Most Bennelongia species have some form of valve ornamentation, either a pitted surface or set with tubercles and/or with long setae. This is species-dependent (though seemingly with similar patterns within a lineage) and can vary with water-chemistry. But even species with almost smooth valve surfaces (e.g. the B. cygnus lineage, see below) invariably have a field of external tubercles along the anterior margin on the RV (see Figure 4F, G - not to be confused with the marginal row of tubercles in the RV, which is mostly internally visible). This field can be narrower or wider, according to species, but is always present. Its function remains unknown.

Figures

Fig. 4. General morphology of Bennelongia valves. A. B. cygnus sp. nov., ♀, CpV (WAM.C49378). B. B. cuensis sp. nov., ♀, LV dorso-anterior view, tilted, showing elevated inner list (WAM.C49408). C. B. cygnus sp. nov., ♀, RV, antero-ventral view, tilted, showing tear-like lapel and row of tubercles (OC.3311). D. B. lata sp. nov., ♀, RV, antero-ventral view, tilted, showing broad lapel and row of tubercles (specimen lost). E. B. kimberleyensis sp. nov., ♀, RV, antero-ventral view, tilted, showing absence of lapel and expansion of valve (WAM.C49433 allotype). F. B. frumenta sp. nov. ♀, CpRL view (WAM.C49383). G. B. gwelupensis sp. nov. ♀, CpRL view, detail of antero-ventral part (WAM. C49395A). Not to scale.