Tuesday, October 31, 2017

[Crustacea • 2017] Salangathelphusa peractio • A New Species of Lowland Freshwater Crab (Brachyura, Gecarcinucidae) from Pulau Langkawi, Peninsular Malaysia


Salangathelphusa peractio  Ng, 2017


Abstract
A new species of lowland freshwater crab of the family Gecarcinucidae, Salangathelphusa peractio, is described from Langkawi, an island off the northwestern coast of peninsular Malaysia. Salangathelphusa peractio sp. n. can be separated from S. brevicarinata (Hilgendorf, 1882) in having a proportionately broader external orbital tooth, a distinctly concave posterolateral margin, and the terminal segment of the male first gonopod is not distinctly bent laterally outwards; and from S. anophrys (Kemp, 1923) by its more quadrate carapace and the terminal segment of the male first gonopod possessing a relatively longer and less curved distal part. This is sixth wholly freshwater brachyuran species known from the island.

Keywords: Gecarcinucidae, Langkawi Island, Malaysia, new species, Salangathelphusa, taxonomy


Figure 5. Salangathelphusa peractio sp. n., colour in life.
 A–D male (22.4 × 17.7 mm) (ZRC 2017.210) E male (21.9 × 17.3 mm) (ZRC 2017.210), Langkawi. 

Systematics
Family Gecarcinucidae Rathbun, 1904
Genus Salangathelphusa Bott, 1968

Type species: Parathelphusa salangensis Ortmann, 1893, by original designation.

Salangathelphusa peractio sp. n.

Diagnosis: Carapace subquadrate, broader than long (Fig. 1); external orbital tooth broadly triangular, outer margin twice length of inner margin (Fig. 1); all ambulatory legs relatively short, merus not elongate (Fig. 1A); male pleonal somite 6 subquadrate, lateral margins gently sinuous, distal margin slightly shorter than proximal margin (Fig. 2C); posterolateral margin concave (Fig. 1); G1 with stout subterminal segment, terminal segment with tip directed upwards towards buccal cavity (Fig. 3A–E).

Etymology: The species name is derived from the Latin word “peractio” which means “ending of a story”. It alludes to the discovery of the present freshwater species, arguably the last one the author will describe from Langkawi, ending his 30-year history with the island. Gender feminine.


 Peter K. L. Ng. 2017. Salangathelphusa peractio, A New Species of Lowland Freshwater Crab from Pulau Langkawi, Peninsular Malaysia (Crustacea, Brachyura, Gecarcinucidae). ZooKeys. 711; 53-65.  DOI: 10.3897/zookeys.711.20621

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