[Crustacea • 2022] Borneosa gen. nov., Borneosa bario, B. kapit, B. serrata, ... • Establishment of A New Bornean Genus of Gecarcinucidae (Brachyura), with Descriptions of Five New Species

Borneosa bario 
B. sarawakensis
B. kapit 

Ng & Grinang, 2022 

DOI: doi.org/10.6620/ZS.2022.61-13 

The freshwater gecarcinucid species from Borneo previously referred to Sundathelphusa Bott, 1969, are transferred to a new genus. Borneosa gen. nov. can be diagnosed by the presence of a distinct frontal median triangle that is shorter than the frontal margin, a relatively longer male thoracic sternum in which the sternopleonal cavity reaches more anteriorly, and a male first gonopod that has the terminal segment prominently covered with long setae. The eight species recognised: B. tenebrosa (Holthuis, 1979), B. aspera (Ng & Stuebing, 1989), B. brachyphallus (Ng, 2015), and five new species, B. niah, B. bario, B. kapit, B. sarawakensis and B. serrata; can be distinguished by characters of the frontal median triangle, epibranchial tooth, anterolateral margin, third maxillipeds, ambulatory legs, male sternum, male pleon and male first gonopod.   

Key words: Freshwater crab, Gecarcinucoidea, New species, New genus, Malaysia, Brunei, Indonesia, Taxonomy, Distribution, Key

A, type locality of Borneosa sarawakensis sp. nov., Sungei Musing, first order stream feeding Batang Ai reservoir, Sri Aman, Sarawak;
B, B. sarawakensis sp. nov., holotype male (35.5 × 28.1 mm) (ZRC 2021.0516), Batang Ai, Sarawak (freshly preserved);
C, B. kapit sp. nov., paratype male (32.3 × 25.6 mm) (ZRC 2021.0520), Sungei Lebau, Pelagus, Kapit, Sarawak (freshly preserved).  

Colour in life. A–C, Borneosa aspera (Ng & Stuebing, 1989), female (44.5 × 33.7 mm (ZRC 2013.746), Temburong, Brunei; D, E, B. aspera (Ng & Stuebing, 1989), female (44.1 × 33.1 mm) (ZRC 2014.845), Temburong, Brunei; F, G, B. aspera (Ng & Stuebing, 1989), male (32.3 × 25.4 mm) (ZRC 2014.845), Temburong, Brunei;
H, B. bario sp. nov., holotype male (29.6 × 23.1 mm) (ZRC 2021.0692), Bario, Sarawak; I, B. bario sp. nov., paratype male (31.1 × 23.9 mm) (UNIMAS.C.00011), Bario, Sarawak; J, B. bario sp. nov., Sungei Lawan, tributary of Sungei Tutoh, Baram basin, Miri, specimen not caught.

Photographs: A, B, Mohd. Abdul Majid; C–F, Low Yee Wen. 

  

Peter K. L. Ng and Jongkar Grinang. 2022. Establishment of A New Bornean Genus of Gecarcinucidae (Crustacea: Brachyura), with Descriptions of Five New Species. Zoological Studies. 61:13. DOI: doi.org/10.6620/ZS.2022.61-13 (05 May 2022 )