Bennelongia cygnus, Martens & Schön, 2012

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 : 13-20

publication ID	https://doi.org/ 10.5852/ejt.2012.8
publication LSID	lsid:zoobank.org:pub:A8804F82-A49A-481E-BB04-2CB4D004EB01
DOI	https://doi.org/10.5281/zenodo.3858826
persistent identifier	https://treatment.plazi.org/id/F402B944-F6D4-4F93-BFE6-D1D184345A6A
taxon LSID	lsid:zoobank.org:act:F402B944-F6D4-4F93-BFE6-D1D184345A6A
treatment provided by	Carolina
scientific name	Bennelongia cygnus
status	sp. nov.

Treatment

Bennelongia cygnus View in CoL sp. nov.

( Figs 5-9 View Fig View Fig View Fig View Fig View Fig )

Bennelongia View in CoL sp. – Davies & Christidis, 1997: 82, fig. 8.3.22.

Etymology

The type locality of this new species is situated in the Swan Valley near Perth. We thus name this species after the (black) swan, Cygnus in Latin.

Diagnosis

Valves triangular in lateral view, weakly pitted, relatively narrow in dorsal view and with rostrum weakly developed. LV with beak weakly developed. RV with lapel long and narrow, ventrally tear-like, almost pointed. Hemipenis with ls extending beyond ms, ls distally rounded and with bluntly pointed apex. ms dorsally with additional lobe-like expansion. Lpp with distal segment sickle-shaped, but relatively short. Rpp with sub-trapezoidal distal segment.

Measurements (all measurements in µm)

Male: RV: L = 1330; H = 933-954. LV: L = 1330-1410; H = 968-969.

Female: RV: L = 1450-1600; H = 1000-1070. LV: L = 1550-1750; H = 1030-1130. Cp: L = 1690-1790; W = 1120-1130; H = 1100.

Type locality

Ellen Brook Nature Reserve, Swan Valley, near Perth (WA); approximate coordinates: 31º 44’ 00”S 116º 01’ 00”E. Material used for the present description was collected on 25 Sep. 1991, 3 Oct. 1997 and 2 Oct. 1998, all by SH.

Type material

Holotype

Male ( WAM.C49370 ), with soft parts dissected in a sealed slide and valves stored dry in a micropalaeontological slide.

Allotype

Female ( WAM.C49371), with soft parts dissected in a sealed slide, and valves stored dry in a micropalaeontological slide.

Paratypes

Five males dissected and stored as the holotype ( WAM.C49372-49375, OC.3310); RV + LV of one female (OC.3311).

Several in toto specimens in EtOH (voucher specimens WAM.C49376).

Other material investigated

Perth Airport unnamed swamp, collected by SH on 12 Sep. 1995, approximate coordinates: 31º 56’ 00”S 115º 58’ 00”E

Goonaping Swamp, collected by Adrian Pinder and Jane McRae on 3 Oct. 1997, approximate coordinates: 32º 27’ 46”S 119º 25’ 1”E. (illustrated specimens from this locality: RV + LV of a female ( WAM.C49377); two female carapaces ( WAM.C49378) all from OST11C).

Christopher Brook, collected by Adrian Pinder and Jane McRae on 28 Oct. 1997, approximate coordinates: 32º 10’ 12”S 116º 47’ 39”E. (illustrated specimens from this locality: RV + LV of a female ( WAM.C49379) from OST11A).

Cobertup Swamp, collected by Andrew Storey and SH on 19 Oct. 1996, approximate coordinates: 34º 27’ 00”S 116º 49’ 00”E.

One Tree Hill, collected by SH and Adrian Pinder on 11 Aug. 1999, approximate coordinates: 29º 35’ 19”S 115º 26’ 31”E.

Differential diagnosis

Bennelongia cygnus sp. nov. defines the B. cygnus lineage by its triangular shape, the simple type of hemipensis and the pointed lapel. It can be distinguished from the other species in this lineage, B. frumenta sp. nov. (see below), by the absence of a cavity in the selvage near the lapel, the presence of a dorsal lobe on the ms of the hemipenes, the short second segment of the Lpp and the broad base of the second segment of the Rpp.

Additional descriptions

Male valves ( Figure 5C, D View Fig ) slightly smaller and more highly arched than female valves ( Figure 5A, B, H View Fig ), otherwise very similar in appearance. Both valves triangular, with greatest height situated in the middle of the valves, dorsal margins equally sloping to both anterior and posterior margins, ventral margin almost straight. Valves weakly pitted and set with few, very short setae.

LV ( Figure 5A, C View Fig ) with posterior calcified lamella narrow, inner list running along valve margin and creating a narrow sulcus; the latter continuing towards the anterior side and widening up in between both inner lists (see diagnosis of genus); antero-ventral beak weakly developed.

RV ( Figure 5B, D, H View Fig ) of similar shape as LV, smaller and slightly less high; posterior and ventral margin set with tubercles, anterior calcified lamella with short inner list; lapel relatively long, rather ventrally situated and tear-shaped at its ventral edge ( Figure 5I, J View Fig ); posterior side with long inner list (reaching almost up to dorsal margin) and with selvage clearly inwardly displaced.

Width of carapace in dorsal ( Figure 5E View Fig ) and ventral ( Figure 5F View Fig ) views more than half the length, greatest width situated in the middle, LV overlapping RV on all sides, especially anteriorly and posteriorly ( Figure 5 View Fig ), anterior rostrum very weakly built, to almost absent.

A1 ( Figure 6E View Fig ) with all segments relatively short and narrow, natatory setae long, chaetotaxy as typical of the family.

A2 ( Figure 6A, C View Fig ) with 5 natatory setae extending beyond tips of end claws, basic chaetotaxy and sexual dimorphism in chaetotaxy of penultimate segment as typical of the family: in female with claws G1-G3 and z1-3 setae; in males with G1 a short claw, G2 a large claw and G3 a seta of intermediate length; z1 and z2 large claws, z3 a long seta.

Md coxa ( Figure 7A View Fig ) relatively slender, without special features. Mandibular palp ( Figure 7 View Fig B-D, G) with chaetotaxy as typical of the family, endclaws and gamma seta unusually slender.

Mx1 ( Figure 7E, F View Fig ) with second palp segment rectangular, c. twice as long as basal width, 3 claws of this segment relatively slender. Third endite with smooth ‘zahnborsten’. Sideways directed bristles on first endite of unequal length.

T1 ( Figure 8 View Fig C-E) with endite bearing 16, mostly hirsute, setae of unequal length. Females with endopod a palp bearing 3 unequal apical setae. Males with endepod developed in asymmetrical prehensile palps. Rpp ( Figures 8D View Fig , 9C View Fig ) with basal segment stout and only slightly longer than the largest width, subapically with two unequal sensory organs; second segment trapezioidal, with blunt dorsal and pointed ventral edge. Lpp ( Figures 8C View Fig , 9D View Fig ) with first segment more slender, almost twice as long as wide, distal segment sickle-shaped but relatively short (L = <half L of first segment).

T2 ( Figure 6B View Fig ) a walking leg with seta d1> d2.

T3 ( Figure 6D View Fig ) a cleaning limb.

CR ( Figure 9E View Fig ) and its attachment ( Figure 9F View Fig ) slender.

Hemipenes ( Figures 8A, B View Fig ; 9A, B View Fig ) almost symmetrical, with ls slender, with rounded dorsal margin and bluntly pointed distal edge; ms consisting of two sub-lobes, one rectangular, the second one elongated and ventrally directed, with rounded edge.

Ecology and distribution

The species appears to be comparatively widespread in freshwater bodies in south-western parts of Western Australia. The species was found in clear or darkly coloured water with conductivity ranging from 80-3120 µS cm-1 and pH 6.8-8.5.

Remarks

One male specimen (WAM.C49375 – Figure 9A, B View Fig ) had aberrant morphology of hemipenes and Rpp. The hemipenes were asymmetrical, with one being typical of the species, the other bearing an additional thumb-like expansion of the ls. The same specimen also had an additional distal thumb-like expansion of the second segment of the Rpp. Rather than considering this a different species, we decided that it is most likely a teratological specimen.