Geosesarma riani, Ng & Wowor & Daisy, 2024

Geosesarma riani , new species

( Figs. 1A–D View Fig , 2 View Fig , 4A–C View Fig , 5A–I View Fig )

Material examined. Holotype: male (12.8 × 11.8 mm) ( MZB Cru 5717), Pulo Majeti hamlet, Purwaharja village , Purwaharja District, Kota Banjar, ca. 2.6 km northeast of Banjar Patroman (Pataruman), West Java, Indonesia, coll. Achmad Sofyan, transferred from Achmad Rian Dietra, June 2022 . Paratypes: 4 males (11.1 × 10.7 mm, 10.9 × 10.5 mm, 10.3 × 10.1 mm, 9.4 × 8.7 mm) ( MZB Cru 5718) , 5 males (11.7 × 11.5 mm, 11.7 × 11.2 mm, 11.5 × 10.7 mm, 11.2 × 9.9 mm, 11.1 × 10.4 mm) ( ZRC 2023.0320 View Materials ), same data as holotype ; 1 male (15.3 × 13.8 mm), 12 females (11.5 × 10.6 mm – 13.4 × 12.1 mm), 14 ovigerous females (11.5 × 10.5 mm – 12.6 × 12.0 mm) ( MZB Cru 5719) , 2 females (13.9 × 12.0 mm, 12.0 × 10.7 mm), 1 ovigerous female (11.2 × 10.2 mm) ( ZRC 2023.0561 View Materials ), same locality as holotype, early July 2023 .

Diagnosis. Carapace squarish, wider than long, lateral margins almost parallel ( Fig. 2A, B View Fig ); dorsal surface with distinct regions, anterior regions with numerous small rounded granules ( Fig. 2A, B View Fig ); front deflexed, frontal lobes very broad with almost truncate margins, separated by broad median concavity; postfrontal cristae sharp ( Fig. 2A–C View Fig ); external orbital tooth acutely triangular, directed obliquely outwards, tip slightly extending beyond anterior part of lateral carapace margin, first epibranchial tooth triangular, low, visible, separated from margin by low, wide concavity, second epibranchial tooth small but visible ( Fig. 2B View Fig ). Ischium of third maxilliped subtrapezoidal, merus ovate, wide; exopod relatively slender, with long flagellum that extends beyond merus width ( Fig. 5A View Fig ). Outer surface of palm of adult male chelae granulate; inner surface distinctly granulated but without distinct transverse comb-like ridge; dorsal margin of dactylus with 5 or 6 evenly spaced tubercle, each with chitinous tip ( Fig. 2D–F View Fig ). Ambulatory legs with relatively more slender meri (fourth leg length-to-width ratio ca. 3.2), with sharp subdistal spine on dorsal margin; ventral margins of propodus and dactylus of adult first ambulatory leg with scattered stiff setae ( Fig. 2A, G View Fig ). Male pleon, wide, triangular; somite 6 wide; telson subtriangular with rounded tip, slightly shorter than broad (length-to-width ratio ca. 0.9); somite 6 with convex lateral margins ( Figs. 4A View Fig , 5B View Fig ). G1 relatively slender; subdistal part of outer margin of stem before chitinous distal part rounded, outer margin of junction between stem and chitinous distal part concave, short; chitinous distal part bent about 45º along longitudinal axis, elongate, tapering, distalmost part flared in lateral view, subspatuliform in mesial view ( Fig. 5C–H View Fig ). Vulva on anterior part of somite 6, with raised vulvar cover, directed mesially ( Fig. 4C View Fig ). Preserved egg size 1.6 × 1.3 – 1.5 × 1.5 mm in diameter.

Notes on habitat. This species inhabits wet areas in a forest, ground which is covered with stones and rocks, at about 60 m asl.

Colour. Carapace grey to greyish-blue, with posterolateral regions dark brown, H-shaped grooves dark brown; frontal surfaces of cephalothorax orange to dull red; eyes iridescent yellow; chelipeds orange; ambulatory legs pale orange to orangish-red, with numerous small dark spots ( Fig. 1A–D View Fig ).

Etymology. The species is named after Achmad Rian Dietra or Rian, who has great interest in all ornamental Indonesian crustaceans especially Geosesarma spp. , and has helped us obtain material for this study.