Ovilyra Ng 2021, n. gen.
Creators: name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Leucosiidae
Ovilyra

description: Ovilyra n. gen.
Type species. Philyra fuliginosa Targioni-Tozzetti, 1877, by present designation.
Diagnosis. Carapace longitudinally ovate, distinctly longer than wide (length to width ratio 1.17–1.26); dorsal surface smooth, covered with minute to small granules and small depressions (Figs. 1A, B, 2A, B, 3A–C); frontal region not produced anteriorly, with shallow median longitudinal depression; frontal margin granulated, with low median triangular tooth (Figs. 1B, 2B, 5D, E, 7A, D); hepatic facet well defined by rows of granules and cristae, elongate, distal part of lower margin prominently angular, with broad tooth on distal one-third (Figs. 1B, D, 2B, D, 4A); posterolateral margin demarcated from posterior margin by lobiform tooth (Figs. 1A, B, 2A, B, 3A–C, 7A, D); third maxilliped exopod wider than basal part of endopod (Figs. 1C, 2C, 3E, 5A–C); endopod with basis-ischium longer than acutely triangular merus (Figs. 1C, 2C, 3E, 5A–C); cheliped merus subcylindrical, symmetrical along entire length, chela stout, pollex bent at angle of 45–60º along longitudinal axis, cutting edge of pollex with broad, large subproximal tooth lined with denticles, that of dactylus with subproximal concavity lined with denticles (Figs. 1A, 2A, 3A–C); P2–P5 slender, short, merus unarmed (Figs. 1A, F, 2A, F); male thoracic sternite 8 visible when pleon closed, between margins of somites 2 and 3 (Fig. 4B); sternopleonal cavity deep, reaching to mid-distance between fused thoracic sternites 1–3 (Figs. 1E, 2E, 4A); male pleon narrow, with somites 1 and 2 free, somite 1 longitudinally narrow, somite 2 yoke-like, reaching coxae of fourth ambulatory leg (Figs. 1E, 2E, 4B, 5F, G), somites 3–6 fused, forming elongate trapezoidal plate, surface smooth, unarmed (Figs. 3D, 4B, 5F, G), somite 6 longitudinally subrectangular, free, surface unarmed (Figs. 1E, 2E, 3D, 4A, 5F, G), telson triangular, longer than wide (Figs. 1E, 2E, 3D, 4A, 5F, G); G1 elongate, slender, distal quarter sharply bent backwards 120–150º from the longitudinal axis; with curved, tapering subdistal process, outer margin lined with 1 or 2 rows of 5–8 elongate spines, distal projection elongate, curved, hook-shape, reaches to, overlaps or overreaches shaft, opening distal (Fig. 6A–C, E–G, I–K); G2 short, ca. one-third length of straight part of G1, apex subspatuliform (Fig. 6D, H, L); female pleon longitudinally ovate, somites 1 and 2 free, somites 3–6 completely fused to form domed plate (Fig. 7B, E); vulvae large, obliquely ovate, on anterior part of sternite 6, without sternal vulvar cover (Fig. 7C, F).
Etymology. The genus name is derived from the Latin “ovalis” for oval, in arbitrary combination with the suffix of the genus name Philyra. Gender feminine.
Remarks. In Galil’s (2009) revision of Philyra Leach, 1817, the articulation of the first two male pleonal somites is a major generic character, separating Philyra s. str., Afrophila Galil, 2009, Atlantolocia Galil, 2009, and Ryphila Galil, 2009, from other genera. With regards to this character, Philyra fuliginosa Targioni-Tozzetti, 1877 (and its junior synonym, P. olivacea Rathbun, 1909, see below), clearly belongs with the species in this group of genera. Philyra fuliginosa can, however, be immediately distinguished by its carapace being distinctly longer than wide (length to width ratio 1.17–126); the others being all wider than long or at most subequal. The lobiform tooth present at the junction between the posterolateral and posterior carapace margins (Figs. 1B, 2B) is diagnostic for P. fuliginosa, a feature absent in the other genera (Galil 2009: figs. 1A, 4A, 5A, 22A; Galil & Ng 2015: fig. 9A, B). Afrophila and Ryphila have visible hepatic facets (Galil 2009: figs. 4A, 22A; Galil & Ng 2015: fig. 9A, B) but these are short compared to those in P. fuliginosa (Figs. 1B, D, 2B, D), and the ventral margins do not have a distal submedian lobe; Philyra and Atlantolocia have no clear hepatic facets (Galil 2009: figs. 1A, 5A). The cutting edge of the fingers of the chelae are distinctively structured in P. fuliginosa, with a subproximal lobe present on the pollex which fits into a concavity on the opposing cutting edge of the dactylus (Figs. 1A, 2A). Such a structure is present in Philyra (Galil 2009: fig. 1A), but absent or indistinct in the other three genera (Galil 2009: figs. 4A, 5A, 22A; Galil & Ng 2015: fig. 10A). The narrow and slender male pleon of P. fuliginosa (Fig. 5F, G) is very different from the proportionately more triangular structures of Philyra, Afrophila or Ryphila where somite 3 is proportionately wider (Galil 2009: figs. 1B, 4B, 22B), and in Atlantolocia, the pleon is wider and subrectangular in shape (Galil 2009: fig. 5B). The strongly bent distal quarter of the G1 with the presence of a long subdistal process is also a character unique to P. fuliginosa (Fig. 6A, E, I) and is not shared by these genera; all of which have straight or almost straight G1 structures (e.g., Galil 2009: figs. 2A–E, 21). In fact, none of the genera which have been previously associated with Philyra have such a strongly bent G1. As such, we here establish a new genus, Ovilyra, for Philyra fuliginosa.
In describing Philyra alcocki from Lake Chilka in eastern India, Kemp (1915: 214, 215) commented that his species was closest to P. olivacea and to a lesser degree to P. fuliginosa. Although the carapace shape and features are superficially similar, P. alcocki is probably not congeneric with P. fuliginosa as its carapace is only slightly longer than wide, being almost round, the male thoracic sternum is proportionately much wider, male pleonal somites 1–5 are fused (although sutures between somites 1–3 are still visible) with somite 3 very wide, giving the male pleon a distinctly triangular shape (Kemp 1915: 214, fig. 2, pl. 12 fig. 2). In Ovilyra species, the carapace is longitudinally ovate and much longer than wide, the male thoracic sternum proportionately narrow and male pleonal somite 3 is only slightly wider than the other somites, with the male pleon not obviously triangular in shape. “ Philyra ” alcocki will need to be re-examined to ascertain its generic position.
Ovilyra is monotypic for the time being.
description: Published as part of Ng, Peter K. L., 2021, Ovilyra, a new genus of leucosiid crab (Crustacea: Decapoda: Brachyura) from the West Pacific, pp. 369-380 in Zootaxa 4952 (2) on pages 370-371, DOI: 10.11646/zootaxa.4952.2.9, http://zenodo.org/record/4674237