Scyra bidentata Marin & Golubinskaya & Sharina 2023, comb. nov.
Creators: name: Marin, Ivan N.
name: Golubinskaya, Darya D.
name: Sharina, Svetlana N.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Epialtidae
Scyra
Scyra bidentata

description: Scyra bidentata (A. Milne-Edwards, 1873) comb. nov.
(Figs 2–6)
Libinia bidentata Milne Edwards A., 1873b: 253.
Doclea orientalis Miers, 1879: 28, pl. 2, fig. 1.
Doclea bidentata Ortmann, 1893: 48.
Pisoides bidentatus Sakai, 1938: 290, fig. 39.
Material examined. 10 non-ovigerous ♀♀, 5♁♁, MIMB 42933–42948, and 2 non-ovigerous ♀♀, 2♁♁, ZMMU Ma-6226-6228: Russian Federation, the Sea of Japan, Peter the Great Bay, Amursky Bay, 43°04ʹ37ʹʹN, 131°50ʹ27ʹʹE, on sandy bottom in the sublittoral zone, March 2021.
Diagnosis. CARAPACE (Figs 2–4) about 1.2 times longer than broad, teardrop-shaped, with feebly separated and elevated regions, surface smooth with microscopic, apically flattened setae, thickly covered with tomentum; gastric region with oblique row of dense hooked setae, with 7 tubercles, 3 of which placed in median line; cardiac region with apical tubercle, small tubercle on posterior slope and 1–2 small tubercles on anterior slope; intestinal region somewhat convex, with tubercle; hepatic region with 2 tubercles, one conical, large; branchial region with 9–10 tubercles, 2–3 of which placed near cardiac region, 1 prominent, conical tubercle at junction of anterolateral and posterolateral borders. Pseudorostral spines relatively short, slightly reflexed downwards and deeply divided. Preocular tooth obtuse, postocular lobe markedly pointed and its inner surface slightly cupped. ANTENNA with basal segment bearing terminal tooth and tubercle on outer border near base. PTERYGOSTOMIAL RIDGE (Fig. 4 c, d, g) with 3–4 tubercles behind this series, 1 tubercle above base of cheliped. CHELIPEDS similar in size and form, stouter than ambulatory legs in both sexes, covered with velvet-like tomentum; fingers occluding throughout their whole length (Fig. 5 a). AMBULATORY PEREIOPODS (Fig. 2) decreasing in length posteriorly, surface generally smooth, with microscopic, apically-flattened setae; meri subcylindrical, with rudimentary distal tubercles; propodi subcylindrical; dactyli long, strongly curved and acuminate, without calcareous spines on flexor surface (Fig. 5 b). THORACIC STERNITES (Figs. 4 g, 5 c) smooth, with shallow broad depression on sternites II–IV; sternite II with pair of small depression anteriorly; sternites III–IV faintly ridged medially. STERNO-PLEONAL CAVITY without long setae on anterolateral margins (Fig. 5 c). GONOPORES comma-shaped (Fig. 5 c), nearly circular in lateral 2/3 and elongated in mesial 1/3. PLEON with 6 pleomeres and telson; pleomeres III–VI fixed, with distinct suture. Shaft of GONOPOD I (Fig. 6) straight, trilobate in distal part; dorsal lobe elongate triangular, more than twice longer than ventral lobe, weakly curved inwards; ventral lobe triangular, with subacute tip; mesial lobe as long as ventral lobe, projecting nearly perpendicular to dorsal lobe, strongly curled downwards; hiatus between dorsal, mesial lobes wide; mesial, lateral margins from dorsal to ventral lobe clearly concave medially; lateral margin higher than mesial margin, dilated in median part. GONOPOD II (Fig. 6) shaft stout, slightly narrowed distally, truncated apically; apex with relatively large, triangular, subacute projection.
Size. Carapace of largest ♁ (width × height): 27.1 × 32.8 mm; largest ♀: 22.4 × 26.7 mm.
GenBank (NCBI) accession numbers. COI (OL982506–OL982521), 16S (OM049808–OM049814), 18S (OM049793–OM049807).
Distribution. The species is presently known from the Tatar Strait to the coast of North Korea and the Pacific coasts of the northern Japanese islands, usually inhabiting soft sandy and silty bottoms, from the littoral zone to a depth of 100–150 meters (Yokoya 1928, 1933; Sakai 1938, 1976; Vinogradov 1950; Kim 1973; Levin 1976; Takeda & Miyauchi 1992; Komai et al. 1992; Marin 2013; Spiridonov et al. 2013; Marin & Kornienko 2014).
Taxonomic remarks. The morphology of S. bidentata comb. nov. differs significantly from that of the type species of the genus Pisoides, Pisoides edwardsii, distributed in the southeastern Pacific from southern Peru to the Straits of Magellan (Garth 1958). These species differ both in body size and proportions of all appendages (S. bidentata comb. nov. is much larger with longer legs) and, as well as in the shape of the carapace with almost completely reduced rostral armature (horns) in S. bidentata comb. nov. in comparison with P. edwardsii. Molecular genetic analysis using several mitochondrial and nuclear gene markers convincingly shows its close relationship to the genera Scyra, Pugettia and Taliepus nuttallii (Randall, 1840) (see Fig. 1).
description: Published as part of Marin, Ivan N., Golubinskaya, Darya D. & Sharina, Svetlana N., 2023, Ecology determines appearance: a new taxonomic solution for the soft bottom dwelling spider crab Pisoides bidentatus (A. Milne-Edwards, 1873) from the Sea of Japan, with remarks on Pisoides ortmanni (Balss, 1924) and the northwestern Pacific Pugettia Dana, 1851 (Majoidea: Epialtidae), pp. 221-234 in Zootaxa 5264 (2) on pages 226-228, DOI: 10.11646/zootaxa.5264.2.4, http://zenodo.org/record/7836463