Platychirarma buettikoferi
Creators: name: Schubart, Christoph D.
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Sesarmidae
Platychirarma
Platychirarma buettikoferi

description: Platychirarma buettikoferi (De Man, 1883)
(Figs. 13H–J, 14H, 17, 18F, 21H–L, 43J)
Sesarma büttikoferi De Man, 1883: 163; De Man, 1891: 50; Thallwitz, 1892: 37; Aurivillius, 1889: 11, pl. 3 figs. 1–4; Fransen et al., 1997: 128.
Sesarma (Parasesarma) büttikoferi – Rathbun, 1900: 280.
Sesarma buettikoferi – Johnston, 1906: 861.
Sesarma buttikoferi – Büttikofer, 1890: 464, 487; Rossignol, 1957: 91, text-fig. 6, pl. 2: fig. 5.
Sesarma (Holometopus) buttikoferi – Dartevelle, 1950: 48.
Sesarma (Holometopus) buettikoferi – Tesch, 1917: 140; Rathbun, 1921: 449, pl. 47 figs. 5–9; Monod, 1956: 447, figs. 606, 607; Rossignol, 1962: 121. Sesarma (Holometopus) buttikoferi – Rossignol, 1957: 91, 122 [key].
Sesarma (Chiromantes) buettikoferi – Manning & Holthuis, 1981: 243.
“ Chiromantes ” buettikoferi – Ng et al., 2008a: 220.
Material examined. Lectotype (here designated): male (14.1 × 11.6 mm) (RMNH D 148), Liberia, coll. J. Büttikofer & J.A. Sala, January 1881. Paralectotypes: 1 male (10.0 × 8.7 mm), 1 female (9.1 × 7.9 mm) (SMF-ZMG 636), Fisherman Lake, Liberia, coll. Büttikofer, 1881. LIBERIA – 1 male (RMNH D 147), Grand Cape Mountain, coll. Büttikofer, 1882; 2 males (10.1 × 8.1 mm, 9.4 × 7.6 mm), 1 female (10.4 × 8.7 mm) (MNHN B16229), Junk River, coll. Stamplli, 1886. CAMEROON – 1 male (10.7 × 8.8 mm) (SMF 25980), West Nimbe (Limbe or Victoria), Mile 6, north of Nimbe, between pieces of basalt, coll. C.H. Otto, 7 January 1984; 2 males (12.6 × 10.4 mm, 11.9 × 9.4 mm), 1 ovigerous female (11.3 × 9.1 mm) (ZRC 2015.0298), Mouang Ko, mangrove area recently destroyed, coll. P.A. Mvogo-Ndongo, 22 July 2015.
Diagnosis. Carapace distinctly wider than long, trapezoidal; frontal margin gently bilobed; lateral margins of carapace converging to posterior carapace margin; cheliped merus with inner margin serrated with distal angle expanded into projection; adult male chela more slender, outer surface distinctly flattened, with lateral part of chela prominently expanded laterally, elbow-like; male thoracic sternites 2–4 relatively wider in adults, suture between sternites 3 and 4 distinct; male sternopleonal cavity reaching three-quarters length of sternite 4 to just before anterior margin of sternite 2; male thoracic sternite 5 smooth, without depression on anterior part; male pleon relatively wider, telson more rounded; G1 relatively slender, long, chitinous part long.
Colour. The colour in life was described by Rossignol (1957: 91): carapace reddish-brown with patches of lighter colour; chelae violet-purple, pollex reddish-orange; ventral surfaces greyish (translated from the French).
Remarks. In naming this species, De Man (1883: 163, 164) did not indicate how many specimens he had. All he stated was that he described one male measuring 13.5 by 11.0 mm from Fisherman’s Lake in Liberia collected by Büttikofer in January 1881. He did not state if this was the holotype or if he had other specimens. In RMNH is a male specimen which corresponds very closely to the measurements and data specified by De Man and was regarded as the holotype of Sesarma buettikoferi De Man, 1883, by Fransen et al. (1997: 128). Article 72.4.1.1 of the code (ICZN, 1999), however, notes that “for a nominal species or subspecies established before 2000, any evidence, published or unpublished, may be taken into account to determine what specimens constitute the type series”. In this case, SMF also has two specimens (labelled as types) collected by Büttikofer from the same type locality with the same date. As such, they were almost certainly also examined by De Man (1883), but being smaller, were probably just not listed in his description. We here regard all three specimens as syntypes and designate the male specimen from Leiden (RMNH D 148) as the lectotype of Sesarma buettikoferi De Man, 1883.
The flattened outer face of the adult male chela of P. buettikoferi is very distinctive and is even apparent on smaller specimens (Figs. 13J, 17). In larger males, it is more prominent, with the ventral margin blade-like and the outer margin of the chela prominently expanded laterally, forming a distinct “elbow” (Figs. 13J, 17). This is less developed in smaller males (Figs. 13H, 17B). The form of this chela closely resembles that of two species now included in the new genus Contusarma, viz. C. bocourti and C. cheirogonum from Southeast Asia (Fig. 28), but in these species, the outer surface of the chela is prominently granulated and the lateral edge is never expanded to form an elbow-like structure.
Biology. Rathbun (1921: 449–451) describes the biology of this species at length, noting that it prefers the brackish areas of the supralittoral back mangroves. Rathbun (1921: 450) also observed that the flattened chelae of P. buettikoferi is used for display to attract females. The species appears to be common among the leaf axils of plants in the mangroves (Stefano Cannicci, pers. comm.).
Distribution. Liberia to Angola (Monod, 1956; Manning & Holthuis, 1981).
description: Published as part of Schubart, Christoph D. & Ng, Peter K. L., 2020, Revision of the intertidal and semiterrestrial crab genera Chiromantes Gistel, 1848, and Pseudosesarma Serène & Soh, 1970 (Crustacea: Brachyura: Sesarmidae), using morphology and molecular phylogenetics, with the establishment of nine new genera and two new species, pp. 891-994 in Raffles Bulletin of Zoology 68 on pages 938-939, DOI: 10.26107/RBZ-2020-0097, http://zenodo.org/record/5351295