Vellumnus tki Ng & Clark 2023, n. sp.
Creators: name: Ng, Peter K. L.
name: Clark, Paul F.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pilumnidae
Vellumnus
Vellumnus tki

description: Vellumnus tki n. sp.
(Figs. 4–6)
Zoobank: urn:lsid:zoobank.org:pub: 31ABBD35- 9781-4D92-82E7-A3BCF8BB61BF
Material examined. Holotype: male (7.8 × 6.0 mm) (NHM 1932.7.7.22, ex 1893.11.3), Macclesfield Bank, South China Sea, coll. P.W. Bassett-Smith, 1893.
Diagnosis. Carapace relatively quadrate (Figs. 4A, 5A); setae on carapace evenly distributed, without ridges or vermiform patterns (Figs. 4A, 5A); setae on pereiopods covered with dense, short, soft pubescence almost completely obscuring margins and surfaces (Figs. 4A, 5A); epigastric, mesogastric, postorbital cristae low, gastric, subhepatic and branchial regions with on anterior margins (Figs. 5A, 6A); frontal margin convex, lateral lobe distinct, bilobed; supraorbital margin with distinct median fissure (Figs. 5A, 6A); external orbital tooth acutely triangular, anterolateral teeth relatively smaller, triangular, third tooth smallest, margins lined with small granules (Figs. 5A, 6A); anteroexternal angle of merus of third maxilliped angular but not auriculiform, ischium with shallow oblique sulcus (Fig. 6C); outer surface of chelae with numerous round granules, vaguely arranged in longitudinal rows, carpus with numerous round granules, without distinct tooth on inner angle, fingers shorter than palm (Figs. 4A, B, 5B, C); ambulatory legs relatively short, without distinct crests or ridges; surfaces completely obscured by numerous setae(Figs.4A, B, 5D); anterior thoracic sternum with surfaces relatively smooth, sternites 3, 4 fused with shallow groove and lateral sutures demarcating them (Figs. 4B, 6E); tubercle of sterno-pleonal locking mechanism rounded, on submedian part of sternite 5 (Fig. 3F); male pleon relatively narrow; somite subrectangular, somites 1 and 3 subequal in width, telson subtriangular (Figs. 4B, 6F); G1 slender, sinuous, distal part bent laterally with subtruncate tip forming small flap on dorsal part (Fig. 6H–I).
Etymology. This species is named for the High Commissioner of the Republic of Singapore, London, in gratitude for all his support of the natural history digital repatriation project between the Lee Kong Chian Natural History Museum, Singapore, and the Natural History Museum, London. His Excellency Lim Thuan Kuan is known as “TK” to his friends (pronounced “tee-kay”), and is the origin of “ tki ”.
Remarks. The holotype was examined by Heinrich Balss in June 1932 and identified as “? Lophoplax (Pilumnoplax) sculpta ”, but it is not this pilumnid species (see Takeda, 1977b; Maenosono, 2019; Ng and Rahayu, 2023). Instead, it is considered here to be an undescribed Vellumnus species.
In the relatively larger size, (ca. carapace width> 4–5 mm), a more quadrate shaped carapace, distinct carapace areolation, e.g., regions well demarcated, and relatively wider male anterior thoracic sternum, Vellumnus tki n. sp. is most similar to V. minabensis, but differs in that the carapace is more quadrate in shape, e.g., width to length ratio1.30; Figs. 4A, 5A (vs. carapace proportionately wider, e.g., width to length ratio 1.4 in V. minabensis); the frontal lobe is convex; Figs. 5A, 6A (vs. frontal lobe strongly convex in V. minabensis); the regions of carapace have scattered granules only on the anterior margins; Figs. 5A, 6A (vs. regions of carapace covered with numerous granules in V. minabensis); the anterolateral teeth are proportionately smaller; Figs. 5A, 6A (vs. anterolateral teeth large and prominent in V. minabensis); the granules on the carpus and chela are distinctly more dispersed; Fig. 5B, C (vs. granules on the carpus and chela densely packed in V. minabensis); and the ambulatory merus appears to be relatively shorter; Figs.4A, 5D (vs. ambulatory merus relatively longer in V.minabensis; cf. Sakai, 1969: text-fig. 13; Sakai, 1976: text fig. 263, pl. 176, fig. 1). The G1 structures of the two species are similar, with the distal part slightly shorter with the tip more truncate in V.tki n. sp.; Fig. 6G–I (vs. longer and more tapering in V. minabensis; Sakai, 1969: text-fig. 12a) but this difference is not significant at the species level. The arrangement of setae on the carapace of V. tki n. sp. is also different from that of V. minabensis. Sakai (1969) described the setae on the carapace of V. minabensis as arranged in a “vermiform” manner (Sakai, 1969: 266) but his original figure (Sakai, 1969: text-fig. 13) does not illustrate this character. In a later color figure of the species, however, he showed the vermiform setal patten (Sakai, 1976: pl. 176 fig. 1). This carapace setation pattern resembles that of V. labyrinthicus except that in V.minabensis, the carapace is proportionately wider and the anterolateral teeth are relatively weaker and directed obliquely anteriorly (Sakai, 1969: fig. 13; Sakai, 1976: text fig. 263, pl. 176, fig. 1) (vs. carapace more quadrate, with the anterolateral teeth stronger and directed more laterally; cf. Ng, 2010: figs. 13A, 14A, 15A). The setae on the carapace of V. tki n. sp. are evenly distributed (Figs. 4A, 5A) and there are no ridges or vermiform patterns formed.
description: Published as part of Ng, Peter K. L. & Clark, Paul F., 2023, Redescription of Vellumnus penicillatus (Gordon, 1930) from Hong Kong and description of a new species from Macclesfield Bank, South China Sea (Crustacea: Brachyura: Pilumnidae), pp. 1-10 in Nauplius (e 2023014) (e 2023014) 31 on pages 6-9, DOI: 10.1590/2358-2936e2023014, http://zenodo.org/record/10905096