Colerolumnus, Ng, Peter K. L., 2010

Ng, Peter K. L., 2010, On the Planopilumnidae Serène, 1984 (Crustacea: Brachyura: Pseudozioidea), with diagnoses of two new pilumnoid genera for species previously assigned to Planopilumnus Balss, 1933, Zootaxa 2392, pp. 33-61 : 55-57

Colerolumnus new genus

Type species. Planopilumnus fuscus Balss, 1933 , by present designation and monotypy.

Diagnosis. Carapace broader than long ( Figs. 13 C, 14D, 17A); dense, short wool-like pubescence which does not form distinct patterns, smooth underneath or only with scattered granules ( Figs. 13 C, 14D); dorsal carapace regions convex, not demarcated by deep grooves ( Figs. 13 C, 14D, 17A); epigastric, mesogastric, postorbital cristae not discernible, although areas with scattered granules ( Figs. 13 C, 14D, 17A); posterolateral, posterior carapace, sub-branchial regions with scattered granules or ridges but never forming discrete channels ( Figs. 13 C, 14D, 17A). Frontal margin with 2 subtruncate lobes separated by fissure; no lateral lobule discernible, margin contiguous with supraorbital margin ( Figs. 13 C, 14D, 17A); supraorbital margin gently concave with single fissure ( Fig. 17 A). Suborbital margin prominently dilated to form shelflike crest ( Fig. 17 B). Anteroexternal angle of third maxilliped distinct but not prominently auricuiliform ( Fig. 17 C). External orbital tooth triangular, anterolateral margin with 3 teeth, first 2 large, triangular, lobiform, third tooth very small, directed laterally ( Figs. 13 C, 14D, 17A). Chelipeds distinctly unequal ( Figs. 13 C, 17E, F); almost entire outer surfaces of palms of both chelae covered with numerous granules, wool-like setae, tips of larger granules visible ( Fig. 17 E, F). Ambulatory legs smooth, without distinct granules, crests or ridges; surfaces completely obscured by numerous long, short setae ( Figs. 13 C, 17G). Anterior thoracic sternum relatively wide, surfaces with scattered granules; surface of anterior thoracic sternum smooth or with scattered small granules ( Fig. 17 D, 18A); sternites 1, 2 completely fused without trace of suture; s2/3 complete; s3/4 almost complete but medially very shallow, almost undiscernible; s4/5, s5/6, medially interrupted; s6/7, s7/8 complete; longitudinal median groove present from sternites 6-8; male press button distinct, positioned on anterior part of sternite 5. Male abdomen triangular; outer surfaces almost smooth; all abdominal somites, telson mobile ( Fig. 18 A). G1 very slender, sinuous, distal part tapering to sharp or rounded tip ( Fig. 18 B–E). G2 about one fifth or less length of G1 ( Fig. 18 F).

Etymology. The name is derived from the Greek "koleros" for short-wooled; in arbitrary combination with the genus Pilumnus . The gender of the genus is masculine.

Remarks. The carapace of Colerolumnus fuscus new combination is superficially similar to that of Planopilumnus spongiosus and Rathbunaria orientalis in its general shape, relatively flat dorsal surface and form of the anterolateral margin, and it was probably these reasons why Balss (1933) originally referred Planopilumnus fuscus to this genus. The pubescence on C. fuscu s, however, is quite different, being much longer and softer than that in P. spongiosus and R. orientalis . Most significantly, the structures of the G1 and G2 are typically pilumnid. The G1 is slender and sinuous (stout and almost straight in Planopilumnus and Rathbunaria ), and the G2 is short, sigmoidal and less than a quarter the length of the G1 (about half the length of the G 1 in Planopilumnus and Rathbunaria ). Compared to Ve ll u mnu s new genus, Colerolumnus can easily be distinguished by its setae been uniformly distributed on the carapace ( Figs. 13 C, 14D) rather than in clear tracts ( Fig. 13A ), the dorsal surface of the carapace is almost smooth, without ridges ( Figs. 13 C, 14D, 17A) (with prominent ridges or granule rows in Vellumnus ; Fig. 15 A), the anterolateral teeth with two large teeth and one small one ( Figs. 13 C, 14D, 17A) (with three subequal teeth in Vellumnus ; Figs. 14A , 15 A), the presence of the shelf-like suborbital margin ( Fig. 17 B) (normal non-cristate or expanded margin in Vellumnus ; Fig. 13B ) and the relatively broader male anterior thoracic sternum ( Fig. 17 D) (proportionately narrower in Vellumnus ; Fig. 14B ). Compared to the rest of the Pilumnidae (sensu Ng et al. 2008), there is no species which has the carapace form and the prominent suborbital margin (shelf-like) observed in C. fuscus .

Figures

FIGURE 15. Vellumnus labyrinthicus (Miers, 1884). A, B, paralectotype male (9.0 × 8.0 mm) (NHM 1882: 93); C – G, 1 male (9.0 × 8.0 mm) (ZRC 1983.10.14.1). A, overall view (carapace partly denuded); B, outer view of left chela; C, left G 1 (ventral view); D, distal part of left G 1 (ventral view); E, distal part of left G 1 (dorsal view); F, left G 2; G, distal part of left G 2. Scales: C, F = 0.5 mm; D, E, G = 0.07 mm.

FIGURE 17. Colerolumnus fuscus (Balss, 1933), lectotype male (7.3 × 5.4 mm) (ZMB 23359). A, dorsal view of right side of carapace (denuded); B, frontal view showing orbits, epistome, antennule and antenna (denuded); C, right third maxilliped (denuded); D, right side of anterior thoracic sternum (denuded); E, outer view of left major chela; F, outer view of right minor chela; G, left fourth ambulatory leg (denuded). Scales: 1.0 mm.

FIGURE 18. Colerolumnus fuscus (Balss, 1933), lectotype male (7.3 × 5.4 mm) (ZMB 23359). A, abdomen (denuded); B, left G 1 (ventral view); C, left G 1 (dorsal view); D, distal part of left G 1 (ventral view); E, distal part of left G 1 (dorsal view); F, left G 2; G, distal part of left G 2. Scales: A = 1.0 mm; B – F = 0.5 mm; D, E, G = 0.25 mm.

FIGURE 13. A, B, Vellumnus labyrinthicus (Miers, 1884), paralectotype female (15.8 × 13.0 mm) (NHM 1882.165 b); C, Colerolumnus fuscus (Balss, 1933), lectotype male (7.3 × 5.4 mm) (ZMB 23359. A, C, dorsal overall views; B, frontal view of carapace.

FIGURE 14. A – C, Vellumnus labyrinthicus (Miers, 1884), male (13.5 × 10.8 mm) (ZRC 1999.397); D, Colerolumnus fuscus (Balss, 1933), lectotype male (7.3 × 5.4 mm) (ZMB 23359). A, D, right side of denuded dorsal surfaces of carapaces; B, anterior thoracic sternum (denuded); left third maxilliped (denuded).