Scandarma finni ( Alcock, 1900 ) Naruse & Ng, 2020

Naruse, Tohru & Ng, Peter K. L., 2020, Revision of the sesarmid crab genera Labuanium Serène and Soh, 1970, Scandarma Schubart, Liu and Cuesta, 2003 and Namlacium Serène and Soh, 1970 (Crustacea: Decapoda: Brachyura: Sesarmidae), with descriptions of four new genera and two new species, Journal of Natural History (J. Nat. Hist.) 54 (7 - 8), pp. 445-532 : 492-493

Scandarma finni ( Alcock, 1900) , comb. nov.

( Figure 25 )

Sesarma finni Alcock, 1900, p. 424 [type locality: Andamans]; Alcock and McArdle 1903, pl. 66, fig. 1.

Sesarma (Sesarma) finni: Tesch 1917, p. 154 .

Labuanium finni: Serène and Soh 1970, p. 402 ; Ng et al. 2008a, p. 221.

Material examined

Holotype. ZSI, female, 11.0 × 11.0 mm, Andamans (photographs examined).

Diagnosis

Carapace subsquarish, external orbital angle blunt, lateral margins slightly divergent posteriorly, with 2 rudimentary epibranchial teeth; 2 pairs of postfrontal lobes present, lateral lobes slightly exceeding mesial lobes anteriorly; anterior margins of all lobes relatively close to but never reaching frontal margin in dorsal view. The male chela, male pleon and G1 are unknown.

Distribution

The only confirmed locality is the Andamans [type locality].

Remarks

Sesarma (Sesarma) finni was described based on a juvenile female specimen (11 × 11 mm) from the Andamans ( Figure 25 ; photographs of the holotype kindly provided by Santanu Mitra, ZSI). Alcock and McArdle (1903, pl. 66, fig. 1) subsequently published a drawing of Se. (Se.) finni without locality but citing Alcock (1900) in the legend of the figure. Since Alcock and McArdle’s (1903) drawing appears similar to Se. gracilipes , records of Se. gracilipes from the eastern Indian Ocean are probably best referred to Sc. finni . Records of ‘ Sesarma gracilipes ’ from the eastern Indian Ocean include Nicobars ( Heller 1865), Atjeh ( De Man 1895) and Nias ( Tesch 1917), and they neither described in detail nor figured the specimens. Crosnier (1965, p. 59) synonymised Se. finni under Se. gracilipes , but it was treated as a valid species in Ng et al. (2008a).

The generic position of Sc. finni is uncertain, as taxonomically diagnostic large male characters, such as major chela, pleon and G1, are not available. Our comparison of the photograph of the holotype of Sc. finni ( Figure 25 ) with similar-sized specimens of morphologically similar species ( Sc. lintou , Sc. gracilipes , Sc. papua and Sc. malagasy ; Figures 17 , 26 ) indicated that they can be distinguished from each other by different combination of carapace characters ( Table 4 ). Scandarma finni is at least different from other Scandarma species and here tentatively placed in Scandarma as a valid species for now.

Pretzmann (1984, p. 142, pl. 2, figs 6–8) recorded ‘ Labuanium finni ’ from the South Andaman Islands. But it clearly differs from Sc. finni s.s. and is here referred to Andamanium thelxinoe ( De Man, 1908) , comb. nov. (see below).

Figures

Figure 17. Dorsal view of carapace of small individuals of Scandarma species. a, Sc. lintou, RUMF-ZC -2024, female, 12.9 × 13.6 mm; b, Sc. gracilipes, RUMF-ZC-5014, female,11.2 × 12.0 mm; c, Sc. papua, NHM 1922.11.9.2–5, female, 11.3 × 12.8 mm.

Figure 25. Scandarma finni (Alcock, 1900). Holotype, ZSI, female, 11.0 × 11.0 mm (Andamans). Photographed by Santanu Mitra, ZSI. a, carapace, dorsal view; b, cephalothorax and chelae, anterior view; c, thoracic sternum and pleon, ventral view.

Figure 26. Scandarma malagasy sp. nov. Holotype, MNHN-B11025, male, 17.0 × 18.4 mm (Madagascar). a, cephalothorax, dorsal view; b, cephalothorax, ventral view; c, left chela, outer view; d, left chela, upper view.