Borneosa brachyphallus ( Ng, 2015 )

Ng, Peter K L & Grinang, Jongkar, 2022, Establishment of A New Bornean Genus of Gecarcinucidae (Crustacea: Brachyura), with Descriptions of Five New Species., Zoological studies 61 (13), pp. 1-35 : 8-11

publication ID	https://doi.org/ 10.6620/ZS.2022.61-13
DOI	https://doi.org/10.5281/zenodo.8055964
persistent identifier	https://treatment.plazi.org/id/CF2E433D-3C35-FFA8-FCDA-FEE3361AFE99
treatment provided by	Valdenar
scientific name	Borneosa brachyphallus ( Ng, 2015 )
status

Treatment

Borneosa brachyphallus ( Ng, 2015) View in CoL

( Figs. 6 View Fig , 7 View Fig , 19C View Fig , 22Q–T View Fig )

Sundathelphusa brachyphallus Ng, 2015: 494 View in CoL , figs. 1, 2, 7A–E.

Material examined: Holotype: male (27.1 ×

22.0 mm) ( MZB Cru 4396), Liang Hintan, Hulu Sungei Barito, 0°27'33"N 115°01'1.0"E, 222–250 m asl, Kalimantan Tengah, Indonesia, coll. C. Rahmadi, 16 June 2004. Paratype: 1 male (29.3 × 23.4 mm, chelipeds missing) ( ZRC 2015.0460), same data as holotype. Others: 1 male (26.1 × 21.8 mm), 2 females (39.8 × 31.2 mm, 35.2 × 27.6 mm) ( ZRC 2021.0840), Liang Hintan, Tumbang Topus, Sumber Barito, Kalimantan Tengah, Indonesia, coll. C. Rahmadi, 14 June 2004.

Diagnosis: Adult carapace transversely subquadrate, width to length ratio 1.23–1.25 ( Figs. 6A, B View Fig , 7I View Fig ); striae on lateral parts of carapace distinct ( Figs. 6B View Fig , 7I View Fig ); branchial regions gently convex in frontal view ( Fig. 6C, E View Fig ); dorsal margin of frontal median triangle contiguous with lateral margins ( Fig. 6C–E View Fig ); exorbital tooth with outer margin almost entire ( Figs. 6B View Fig , 7I View Fig ); epibranchial tooth very low to absent, if visible, separated from rest of margin by shallow low cleft, anterolateral margin may appear entire ( Figs. 6B View Fig , 7I View Fig ); median lobe of posterior margin of epistome acutely triangular ( Fig. 6C–E View Fig ); ischium of third maxilliped subquadrate ( Fig. 7A View Fig ); fingers of adult male cheliped closing along entire cutting margins ( Fig. 7D View Fig ); P3 and P4 dactyli subequal in length ( Fig. 7F, G View Fig ); male pleonal somite 6 subquadrate, slightly longer than broad ( Fig. 7C View Fig ); male sternopleonal cavity not prominently anterior, distance between tip of cavity and suture of thoracic sternites 2 and 3 longer than length of thoracic sternite 2 ( Fig. 7B View Fig ); adult Gl subterminal segment relatively stout; terminal segment subconical, distal half gently curved outwards, tapering gradually to subtruncate tip, 0.35 times length of subterminal segment, distal opening relatively smaller, subovate ( Fig. 20Q–S View Fig ); vulvae almost round ( Fig. 23C View Fig ).

Colour: Not known.

Remarks: Of the various characters Ng (2015) used to distinguish this species from B. tenebrosa and B. aspera , perhaps the most obvious is that the carapace of B. brachyphallus is much smoother, with the striae near the lateral regions relatively lower and more rounded ( Figs. 6A, B, E View Fig , 7I View Fig ). The short G1 terminal segment is a character now also shared with B. bario sp. nov., B. sarawakensis sp. nov. and B. serrata sp. nov., although the subterminal segment of B. brachyphallus is still proportionately the shortest and stoutest among congeners ( Fig. 20Q–S View Fig ).

Biology: Borneosa brachyphallus was collected from inside shallow streams in a horizontal cave in central Kalimantan, in the Barito Basin ( Rahmadi and Suhardjono 2004), but it is clearly not a cavernicolous species as it has no the troglobitic adaptations (cf. Holthuis 1986; Guinot 1988 1994).