Lyphira acutidens
Creators: name: Rahayu, Dwi Listyo
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Leucosiidae
Lyphira
Lyphira acutidens

description: Lyphira acutidens (Chen, 1987)
(Figs. 3D, 6B, 7D, 9B, 10C, 11C, 13B, C, 14B, 15D, 16C, 17H–L, 21B)
Phylira acutidens Chen, 1987: 201, fig. 1; Chen & Sun 2002: 381, text fig. 170, pl. 15.1; Ng et al. 2008: 93.
Lyphira heterograna.— Galil, 2009: 300 (part). (not Philyra heterograna Ortmann, 1892).
Material examined. 1 male (8.9 × 8.6 mm), 1 female (13.4 × 12.9 mm), ZRC 2002.0504, station 4027, Yellow Sea, coll. Institute of Oceanography, Chinese Academy of Science, 9 December 1958.
Diagnosis. Carapace slightly broader than long, dorsal surface of carapace covered with closely spaced minute granules, hepatic and intestinal regions with larger, more prominent granules (Figs. 3D, 6B). Frontal margin granulated, postfrontal lobe slightly convex (Figs. 11C, 13B, C). Endostomial spine absent (Figs. 13B, C, 14B). Lateral and posterolateral margin of carapace with row of small granules interspersed by several larger granules (Fig. 3D, 6B); posterior carapace margin gently concave with row of larger granule, medially slightly produced (Figs. 3D, 10C). Third maxilliped exopod 2.9 times as long as broad, as broad as basal part of endopod, forming petaliform structure with convex outer margin, endopod with completely fused basis-ischium, as long as merus, with shallow submarginal sulcus near inner margin (Figs. 11C, 17H). Chelipeds subequal; merus, carpus and chela surfaces smooth or covered by closely spaced, small rounded granules (Figs. 3D, 6B); chela stout, fingers longer than length of palm, surface with longitudinal sulcus flanked by row of granules; pollex slightly bent, cutting edge lined with denticles; dactylus 1.2 times as long as palm along upper margin, row of small granules on upper margin, cutting edge with median large tooth lined with denticles, remaining of edge with small denticles (Fig. 15D). P2–P5 slender, short; merus distinctly longer than carpus and propodus; dactylus longer than propodus, lanceolate, terminating in corneous tips (Figs. 3D, 6B); fourth leg shortest with merus 4.1 times as long as broad, margins lined with small granules, more prominent on ventral margin (Fig. 16C). Thoracic sternites transversely narrow, surface finely granulated, larger granules laterally (Fig. 7D). Sternopleonal cavity deep, reaching to proximal distance between fused thoracic sternites 1–3. Pleon narrow, somites 2–6 fused, somite 6 longitudinally subrectangular, surface with one low granule medially, lateral margins gently convex; telson triangular (Figs. 7D, 17I). G1 elongate, slender, same size from proximal to distal area; distal process bilobed, tip rounded (Fig. 17J‒L). Female pleon broad, convex, smooth, somites 2‒6 fused, suture between somites 2 and 3; telson as long as its basal width (Fig. 9B); vulvae positioned closer to median part of sternite 6, each opening prominently crescent-shaped, relatively long, without opercular cover (Fig. 21B).
Colour. Not known.
Remarks. Chen (1987) described Philyra acutidens from a large series of specimens from the East China Sea and Yellow Sea (87 males and 101 females), and she compared it with P. heterograna, noting that it can be distinguished by its slightly smaller adult size (largest carapace length 16.5 mm versus 18.5 mm), slightly longer carapace, the presence of more granules on the carapace, the third maxilliped exopod is slightly narrower, the proportionately shorter fingers of the chela, the cutting margin of the fingers lacking a large tubercle, male pleonal somite 6 with median tooth, and the female telson is longer than broad. She figured a specimen of what she regarded was L. heterograna s. str. (Chen 1987: fig. 2) but did not state where it was from. From her figures, Chen’s (1987: fig. 2) “ Philyra heterograna ” agrees well with L. heterograna s. str. as defined here.
Galil (2009) commented that L. acutidens is a junior synonym of L. heterograna, arguing the differences observed were only due to their subadult nature. This is not the case; the species is not small, with the holotype male measuring 15.0 × 16.0 mm and allotype female 11.9 × 12.0 mm. The present male specimen (ZRC 2002.0504) is relatively small (8.9 × 8.6 mm) and does not appear fully adult; but the slightly larger female (13.4 × 12.9 mm) has the pleon round and domed and is clearly adult. Their characters, however, agree in most aspects with Chen’s (1987) detailed descriptions and figures.
We are of the opinion the two species are distinct. The differences in the adult size observed by Chen (1987) are actually not significant, and carapace proportions alone is not enough to justify recognizing two species. The authors have on hand two non-type topotypic specimens from the Yellow Sea but are part of Chen’s (1987) original series, and they do show the other differences highlighted by her. Most marked are the denser concentration of granules on the dorsal surface. The median tubercle on male pleonal somite 6 of L. acutidens is slightly sharper than those of L. heterograna and is slightly more subdistal in position, just behind the distal margin (Figs. 7D, 17I) whereas in L. heterograna, it is positioned a bit further back (Figs. 7A‒C, 17B). Chen’s (1987) figure of the male pleon is slightly inaccurate, the median tubercle on somite 6 is not distal in position (Chen 1987: fig. 1.3) but is actually subdistal. Also significant is that the vulvae are differently structured, with the opening in L. heterograna is short and weakly crescent-shaped (Fig. 21A) whereas it is slit-like and distinctly more crescent-shaped in L. acutidens (Fig. 21B). As such, we believe it is better to recognize L. acutidens as a distinct species for now.
Type locality. Yellow Sea, North China Sea.
Distribution. Bohai Sea, Yellow Sea and Northern China Sea.
description: Published as part of Rahayu, Dwi Listyo & Ng, Peter K. L., 2024, On the genus Lyphira Galil, 2009 (Crustacea: Brachyura: Leucosiidae), with descriptions of four new species from the West Pacific, pp. 358-392 in Zootaxa 5476 (1) on pages 364-368, DOI: 10.11646/zootaxa.5476.1.29, http://zenodo.org/record/12681921