Bennelongia, De Deckker & McKenzie, 1981

Deckker, Patrick De & Martens, Koen, 2013, Extraordinary morphological changes in valve morphology during the ontogeny of several species of the Australian ostracod genus Bennelongia (Crustacea, Ostracoda), European Journal of Taxonomy 36, pp. 1-37 : 7-8

Bennelongia sp. 414 nov. sp.

Figs 11-12

This species is in stark contrast with B. cf. nimala nov. sp.. First of all, it belongs to the lineage of Bennelongia which is most distant to the other taxa examined in this paper.Also, its general appearance is clearly different from any of the other Bennelongia species thus far described ( De Deckker & McKenzie 1981; De Deckker 1981c, 1982; Martens et al. 2012; Shearn et al. 2012): it is triangular in lateral view and the ventrum is flat and broad ( Fig. 11 ); the antero-ventral beak-like feature in adult LV is absent ( Fig. 10 ) and the instars, at first glance, appear smooth on the outer surface of the valves ( Fig. 11 ).

Close examination of the instars’ valve morphology identifies that the ‘domes’ are definitely present in A-4 to A-1 stages, but are again more obvious in the youngest instar stages ( Figs 11-12 ). The dome that was so prominent in B. cf. nimala nov. sp. is a much smaller feature in B. spec. 414 nov. sp.. Instead, the posterior dome is the largest of the two and is also reticulated. We assume that the 2 domes occur in the same position as in B. cf. nimala nov. sp., and are thus homologous, as the depression seen in the former species is also seen behind what we label as the posterior dome ( Fig. 11 , middle right panel in A-4, Fig. 12 middle panels) of B. sp. 414 nov. sp.

In inner view, the inner lamella is surprisingly broad and well calcified in the A-1 instars. In addition, it has an inner list that is prominent along the entire periphery of the inner lamella, a feature that is prevalent in all Bennnelongia A-1 instars examined here (see also below). This feature is in other cypridid ostracods only present in adult specimens.

Finally, juvenile specimens differ from B. cf. nimala nov. sp. juveniles as some cones with outer lips appear to be present ( Figs 11-12 ), but are almost atrophied, and could easily be confused with normal pores with setae.

Figures

Fig. 11. Bennelongia sp. 414 nov. sp. from locality CB35a at Wooramel Station (Halse et al. 2000). For the top two rows, all views are dorsal, except top right image which is a ventral view. The bottom row consists of internal views of the two valves of an A-1 specimen. Note that the domes are only visible in A-2, A-3 and A-4 specimens, with possibly a second set of smaller ones positioned anterior to the larger one. The cones, which are few in number, are also very small and only clearly visible in A-3 and A-4 specimens.

Fig. 12. Bennelongia sp. 414 nov. sp. from locality CB35a at Wooramel Station (Halse et al. 2000). All views are external, except for the right valve displayed at the top right hand corner. As for Figure 11, note that the domes and cones are much more discrete. This is particularly obvious in the bottom image that displays a dorsal view of the carapace of an A-3 juvenile. Note also that the internal view does not show a depression at the location of the dome. The middle right image shows the obvious lateral ridge that defines this new species.

Fig. 10. External views of A-1 carapaces of Bennelongia cf. nimala nov. sp. juveniles from Muggon Lake. The top image shows an A-1 LV, whereas the bottom image shows a RV of an A-1 specimen that has been ‘flipped over’ digitally so as to permit comparison of the type of external ornamentation and respective location. Same comments as for Figure 9 concerning the white lines.