Fabaeformiscandona dolabella, Smith & Janz, 2008

Smith, Robin J. & Janz, Horst, 2008, Recent species of the Family Candonidae (Ostracoda, Crustacea) from the ancient Lake Biwa, Central Japan, Journal of Natural History 42 (45 - 46), pp. 2865-2922 : 2887-2890

publication ID	https://doi.org/ 10.1080/00222930802361030
persistent identifier	https://treatment.plazi.org/id/6530807D-EC3D-FFBC-AFF0-FDFFFC05FAB8
treatment provided by	Carolina
scientific name	Fabaeformiscandona dolabella
status	sp. nov.

Treatment

Fabaeformiscandona dolabella sp. nov.

( Figures 8 View Figure 8 G–I, 13 and 14)

Fabaeformiscandona siberica: Okubo, 2004 (misidentification)

Type locality

Lake Biwa – north basin, locality 70 (35 ° 08926.70N; 136 ° 00927.50E), depth 7.6 m, substrate muddy with some organic detritus.

Type material

Holotype LBM 1430003309 View Materials , male, appendages mounted on a glass slide, valves stored in a micropalaeontological cavity slide . Allotype LBM 1430003311 View Materials , female, appendages mounted on a glass slide, valves stored in a micropalaeontological cavity slide . Paratype LBM 1430003310 View Materials , female, appendages mounted on a glass slide, valves stored in a micropalaeontological cavity slide . Paratype LBM 1430003307 View Materials , male, whole carapace stored in a micropalaeontological cavity slide . Paratype LBM 1430003308 View Materials , female, whole carapace stored in a micropalaeontological cavity slide .

Derivation of name

From the Latin dolabella meaning axe or hatchet, referring to the shape of the a lobe of the hemipenis ( Figure 14D View Figure 14 ).

Diagnosis

Male carapace with smoothly curved dorsal margin, apex of posterior margin below mid-height, maximum height posterior of mid-length. Female carapace with distinctive, large overlap at apex of posterior margin. Male L5 palps sinuous and thickened, asymmetrical with right one thicker than left. UR straight in males, curved in females. Lobe a of Hp axe-head-shaped, m process small and sub-equally thick throughout length. Female without FRO projection.

Description

Male carapace length 894–900 Mm, height 425–433 Mm H/L50.48, female length 886– 905 Mm, height 400–414 Mm, H/L50.45–0.46. Carapace elongate with maximum height at posterior third of length. Dorsal margin smoothly curved, ventral margin slightly concave. Apex of posterior margin below mid-height. Anterior margin equally curved. Female with more tightly curved posterior margin than male. Dorsal view of female with maximum width at mid-length, left valve strongly overlapping right valve at posterior margin. Posteroventral margin of female right valve with shallow indentation. In whole female carapaces, right valve overlaps left valve at apex of posterior margin. Males without significant overlap in this region. Female left valve with small anterodorsal flap, and ill-defined, very shallow posterodorsal flap. Calcified inner lamella narrow posteriorly, wide anteriorly.

An1 eight-segmented, first two of which are fused to produce one large article, with two dorsal setae and two ventral–subapical setae. Third segment with one dorsal–apical seta. Fourth segment with one apical seta. Fifth and sixth segments each with two dorsal–apical setae and one shorter ventral–apical seta. Seventh segment with one long and three shorter setae. Final segment with three setae of differing lengths and one aesthetasc.

An2 with long and slender Y aesthetasc. Male t2 and t3 setae with triangular ends, Gm just over half the length of GM, z2 reduced claw. Female G2 about half the length of G1, Gm just over half the length of GM.

Md with 3+1+beta setae on second palp segment.

L 5 male palps both sinuous, thinning distally, but asymmetrical in shape, with one wider and more inflated than other.

L6 with relatively long d1 seta. Setae e, f and g all approximately equal in length to next segment respectively.

L7 five-segmented. Seta dp relatively short, shorter than first segment. Seta g long, and seta h1 medium length, about half the length of h2. Both h2 and h3 setae long, sub-equal in length.

UR with long Sp seta. Claw Ga slightly longer and broader than Gp. Female caudal ramus distinctly curved, whereas male’s much less curved.

Hp a lobe with three projections, innermost one wide, distalmost one subpointed, and one on outer edge broadly rounded and striated, giving the appearance of axe head. Lobe h large and truncated distally. Process m slender, small and of subequal thickness along length.

FRO broadly rounded with no posterior projection.

Remarks

This species comes close to Fabaeformiscandona siberica (G. W. Müller, 1912) , found in the Arctic New Siberian Islands, in general carapace shape in lateral view and the morphology of the caudal ramus. However, female specimens from Lake Biwa have a very distinctive indentation on the posterior ventral margin of the left valve. This is clearly missing in Bronshtein’s drawings of F. siberica ( Bronshtein 1988) , as is the distinctive large overlap of the valves at the posterior in the females. Additionally, F. siberica is reported to have a well-developed FRO projection ( Bronshtein 1988); this is missing in the Lake Biwa specimens, which have no FRO projection. This species is also similar to Fabaeformiscandona caudata (Kaufmann, 1900) , but lacks the denticulated posterodorsal lobes of both valves and a FRO projection, both of which are present in F. caudata . Furthermore, the Md palp has 4+1+beta setae on the second segment in F. caudata , whereas F. dolabella sp. nov. has 3+1+beta setae, indicating that they belong to separate groups. The male appendages of both F. siberica and F. caudata are unknown. Localities 70 and 88 in Figure 1 View Figure 1 .