[Crustacea • 2026] Lemurophusa empusa & Balssiathelphusa inopinata • Revision of the Southeast Asian freshwater crab Genus Balssiathelphusa Bott, 1969 (Decapoda: Brachyura: Gecarcinucidae)

Lemurophusa empusa

Ng & Guinot, 2026

DOI: doi.org/10.5252/zoosystema2026v48a18 

 Abstract 

The systematics of the gecarcinucid genus Balssiathelphusa Bott, 1969 is revised. Balssiathelphusa has an atypical distribution pattern for a freshwater crab genus, with the four known species recorded from Sumatra, Borneo and Natuna Islands in the South China Sea. The type species, Para-Perithelphusa sucki Balss, 1937 [sic, see infra], is redescribed and figured, and the genus is redefined to include B. sucki, B. cursor Ng, 1986, from East Kalimantan in Indonesian Borneo, and a new species, B. inopinata n. sp., also from East Kalimantan. The type locality of B. sucki was reported as southeastern Sumatra, but the available evidence suggests the holotype was actually collected from South Kalimantan in Borneo. Balssiathelphusa natunaensis Bott, 1970, from Natuna Island, is transferred to a new monotypic genus, Natunusa n. gen., while B. phasma Ng & Guinot, 2014, collected from a cave in East Kalimantan, is referred to a separate genus, Lemurophusa n. gen. A new species, L. empusa n. gen., n. sp., is also described from another karst system in East Kalimantan, whereas a juvenile female from a nearby cave in East Kalimantan is treated as Lemurophusa sp. Particular attention was paid to the thoracic sternum and its sutures, to the median bridges between the sternites, as well to the median line, characters often overlooked but that are particularly useful in this group of small gecarcinucid crabs.

KEYWORDS: Borneo, Sumatra, Natuna Islands, Kalimantan, Gecarcinucoidea, freshwater crab, cave crab, new genera, new species 

 

Superfamily Gecarcinucoidea Rathbun, 1904

Family Gecarcinucidae Rathbun, 1904

Genus Balssiathelphusa Bott, 1969

Balssiathelphusa Bott, 1969: 364; 1970: 98. — Ng 1986a: 207.

Included species. — Balssiathelphusa sucki (Balss, 1937), B. cursor Ng, 1986; B. inopinata n. sp.

Balssiathelphusa inopinata n. sp.

Etymology. — The name is derived from the Latin “inopinatus” for “unexpected” as it had been previously believed that Nobili's (1903) record was Balssiathelphusa cursor and not a new species.

Natunusa natunaensis (Bott, 1970) n. comb., ♂ 12.9 × 11.3 mm (ZRC 2021.0831), Natuna Island:
A, overall dorsal habitus; B, dorsal view of carapace; C, frontal view of cephalothorax; D, frontal median triangle, antennules, antennae and epistome; E, buccal cavity, anterior thoracic sternum, telson and pleonal somites 5 and 6; F, posterior thoracic sternum and pleonal somites 1-4; G, sternopleonal cavity.

Genus Natunusa n. gen.

 

Type species. — Balssiathelphusa natunaensis Bott, 1970, 

by original designation and monotypy.

Diagnosis. — Carapace quadrate, just wider than long; carapace not high, height to width ratio 0.4; epigastric cristae rugose, low but visible, not cristate; postorbital cristae low, rugose, discernible, not cristate; frontal margin divided into two low lobes; frontal median triangle distinct, with dorsal crista straight; external orbital tooth with outer margin 3.0-4.0 times length of inner margin; epibranchial tooth small, low, separated from margin by small notch; rest of anterolateral margins gently convex; posterolateral ...

Etymology. — The name is derived from the name of the type locality, Natuna Island, in arbitrary combination with -phusa, a common suffix for gecarcinucid genera. The gender of the name is feminine.

Included species. — Natunusa natunaensis (Bott, 1970) n. comb.

Lemurophusa empusa n. gen., n. sp.:
 A, C, holotype, ♀ 24.2 × 18.5 mm (MZB Cru), Kalimantan;
B, D, paratype ♀ 22.2 × 17.2 mm (MZB Cru), Kalimantan.
A, B, overall dorsal habitus; C, D, dorsal view of carapace.

Genus Lemurophusa n. gen. 

Type species. — Balssiathelphusa phasma Ng & Guinot, 2014, 

by present designation.

Included species. — Lemurophusa phasma (Ng & Guinot, 2014) n. comb.; Lemurophusa empusa n. sp.

Diagnosis. — Carapace transversely ovate, wider than long, carapace not high, height to width ratio 0.4; epigastric cristae low, rugose but visible; postorbital cristae low, rugose, just discernible, not cristate; frontal margin divided into two low lobes; frontal median triangle distinct, with dorsal crista medially bent, fused with lateral cristae; external orbital tooth distinct, with outer margin about twice length of inner margin; epibranchial tooth small, low, separated from margin by notch; rest of anterolateral margins ...

Etymology. — The name is derived from the Latin word “lēmurēs” for “spirits of the dead”; in arbitrary combination with -phusa, a common suffix for gecarcinucid genera. This alludes to the cave habitat of the species. The gender of the name is feminine.

Lemurophusa empusa n. sp.

Etymology. — The species is named after Empusa, a demigoddess of Greek mythology. The name is used as a noun in apposition.

Peter K. L. Ng and Danièle Guinot. 2026. Revision of the Southeast Asian freshwater crab Genus Balssiathelphusa Bott, 1969 (Crustacea, Decapoda, Brachyura, Gecarcinucidae). Zoosystema. 48 (18); 557-587. DOI: doi.org/10.5252/zoosystema2026v48a18 (13 July 2026)

Révision du genre de crabes d'eau douce d'Asie du Sud-Est Balssiathelphusa Bott, 1969 (Crustacea, Decapoda, Brachyura, Gecarcinucidae).

Bornéo, Sumatra, îles Natuna, Kalimantan, Gecarcinucoidea, crabe d'eau douce, crabe cavernicole, genres nouveaux, espèces nouvelles

[Crustacea • 2026] Geosesarma penrissen • A New Species of Vampire Crab of the Genus Geosesarma De Man, 1892 (Brachyura: Sesarmidae) from A montane forest in southwestern Sarawak, Malaysian Borneo

 

Geosesarma penrissen

Grinang, P. Y. C. Ng & P. K. L. Ng, 2026 

 

The Raffles Bulletin of Zoology. 74; 

Abstract 

 A new species of semiterrestrial crab, Geosesarma penrissen, new species, is described herein from Mount Penrissen in southwestern Sarawak, Malaysia. It represents the third species of Geosesarma known from the montane forests of Borneo, the other two being G. larsi Ng & Grinang, 2018 from Mount Ampungan in Serian, Sarawak, and G. aurantium Ng, 1995 from Mount Silam in Sabah. Diagnostic characters distinguishing G. penrissen, new species, from its congeners are provided, together with ecological notes on its highland habitat. 

Key words. freshwater crab, semiterrestrial, taxonomy, lowland forest, comparative morphology

Geosesarma penrissen, new species, live colouration.
A–C, holotype male (10.6 × 10.2 mm) (ZRC 2024.0567); D, paratype male (10.7 × 10.5 mm) (ZRC 2024.0171); E, adult male, on shrub, Batu Panggah trail, photographed 2311 hrs; 6 July 2023 (not collected); F, subadult, on shrub, Batu Panggah trail, photographed 2118 hrs, 6 July 2023 (not collected).

All specimens from Sarawak. E, F, photographed by Chien Lee.

 Geosesarma penrissen, new species

Diagnosis. Carapace almost square, width-to-length ratio 1.01–1.07, lateral margins gently sinuous, subparallel (Figs. 1A, D, 2A–D, 5A, C, F, 6A, D); dorsal surface with welldefined regions, anterior regions covered with small, rounded or flattened, squamate granules (Figs. 1A, C, E, F, 2A–D, 5A, C, E, 6A, D); front deflexed, with 2 broad subtruncate lobes, separated by shallow median concavity; postfrontal, protogastric lobe prominent, sharp-edged (Figs. 1A, C, D, 2A–D, 3A, 6C, F); external orbital tooth acutely triangular, outer margins curving anteriorly, tooth directed obliquely and laterally, clearly extending beyond lateral margin of carapace (Figs. 2A–D, 5A, C, E, 6A, D). Merus of third maxilliped ...

JONGKAR GRINANG, PAUL Y. C. NG and PETER K. L. NG. 2026. A New Species of Vampire Crab of the Genus Geosesarma De Man, 1892 (Crustacea: Brachyura: Sesarmidae) from A montane forest in southwestern Sarawak, Malaysian Borneo. The Raffles Bulletin of Zoology. 74; 457–464.

[Crustacea • 2025] Umalia modesta • A New Species of Frog Crab Genus Umalia Guinot, 1993 (Brachyura: Raninidae) from the South China Sea, with A Key to Species in the Genus

 

Umalia modesta

Ng, 2025

DOI: doi.org/10.18353/crustacea.54.0_53

Abstract 

A new species of raninid frog crab, Umalia modesta n. sp., is described from the northern part of the South China Sea, near Tungsha Islands. The species is morphologically most similar to U. chinensis (Chen & Sun, 2002) (from southern China) and U. tenuiocellus (Davie & Short, 1989) (from Australia) but can easily be distinguished from them by its carapace form, well developed cornea, and structures of the rostrum, thoracic sternum, third maxilliped and ambulatory legs.  

Key words: Tungsha Islands, Taiwan, Raninoidea, new species, comparative taxonomy, genus key

Umalia modesta n. sp., holotype female (11.0×14.0 mm) (ZRC 2024.0500), South China Sea.
A, overall dorsal view; B, frontal half of carapace (dorsal view); C, frontal view of cephalothorax; D, left anterolateral view of cephalothorax; E, third maxillipeds.

Umalia modesta n. sp., male, station CP4115,
southwest of Tungsha Island, South China Sea [specimen not examined]

[Photograph: T.-Y. Chan].

Superfamily Raninoidea De Haan, 1839 

Family Raninidae De Haan, 1839 

Subfamily Notopodinae Serène & Umali, 1972 

Umalia Guinot, 1993

Umalia modesta, new species 

Diagnosis: Carapace shape trapezoidal, anterior part much wider than posterior part, lateral margins almost straight, subparallel; carapace width more than 0.7 total length; fronto-orbital distance less than half width of carapace; anterior ...

Etymology: From the Latin “modesta” for unassuming, alluding to the simple characters of the species

Peter K. L. Ng. 2025. On A New Species of Frog Crab, Umalia modesta n. sp. (Brachyura: Raninidae) from the South China Sea, with A Key to Species in the Genus. Crustacean Research. 54; 53-61. DOI: doi.org/10.18353/crustacea.54.0_53 [September 27, 2025]

[Crustacea • 2024] Geothelphusa amakusa & G. mutsu • The Identity of the Japanese Freshwater Crab, Geothelphusa dehaani (White, 1847) (Decapoda: Brachyura: Potamidae), with Descriptions of Two New Species from Japan

Geothelphusa mutsu

   Geothelphusa amakusa 

  

Naruse & Ng, 2024

DOI: 10.18353/crustacea.53.0_53 

Abstract 

This study designates a lectotype for and redescribes Thelphusa dehaani White, 1847, a Japanese primary freshwater crab species belonging to the potamid genus Geothelphusa Stimpson, 1858. Geothelphusa dehaani was described based on material exported to the Netherlands by von Siebold. Although the provenance of all his specimens is uncertain (they may be from several locations), our morphological comparison of the lectotype with fresh specimens led us to ascertain that it was almost certainly collected from Nagasaki, where von Siebold stayed. Two new Geothelphusa species are also described from Amakusa Islands and Aomori Prefecture.

Keywords: Taxonomy, primary freshwater crab, Potamoidea, von Siebold

Coloration of Geothelphusa amakusa n. sp. 
A, holotype, RUMF-ZC-8152, male, 30.3×22.5 mm; B, RUMF-ZC-8153, female, 28.8×22.7 mm;
C, D, 20161020; E, 20161020; F, ZRC 2017.0975, male, 18.9×14.8 mm.

Geothelphusa amakusa n. sp. 

Etymology The species is named after the type locality, Amakusa Island. The name is used as a noun in apposition.

Coloration of Geothelphusa mutsu n. sp.
 A, male, ZRC 2018.0716, 19.3×15.1 mm; B, female, ZRC 2018.0716, 24.1× 18.4 mm; C, D, male, ZRC 2018.0716, 20.4 × 15.3 mm.

Geothelphusa mutsu n. sp.

Etymology The species is named after “Mutsunokuni”, a previous estate name of the type locality (Aomori Prefecture) and also a historical province name for a larger area of northern Honshu Island. The name is used as a noun in apposition.

Tohru Naruse and Peter K. L. Ng. 2024. The Identity of the Japanese Freshwater Crab, Geothelphusa dehaani (White, 1847) (Decapoda: Brachyura: Potamidae), with Descriptions of Two New Species from Japan. Crustacean Research. 53; 53-71. DOI: doi.org/10.18353/crustacea.53.0_53

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[Crustacea • 2026] Frodromia elegans, F. granulosa, ... • Revision of Frodromia McLay, 1993 (Brachyura: Dromiidae) and the Status of Frodromiinae Števčić, 2005

A, Frodromia atypica (Sakai, 1936),; B, F. reticulata (Sakai, 1974);
C, F. elegans, new species, holotype male, Taiwan; D, F. granulosa, new species, holotype male, Vanuatu;
 E, F, F. iners, new species, holotype male, Philippines. 

Ng, 2026 

RAFFLES BULLETIN OF ZOOLOGY. 74: 

Photographs: C, T.-Y. Chan; D, J.C.E. Mendoza; E, F, P.K.L. Ng.

Abstract

 The taxonomy of the West Pacific dromiid genus, Frodromia McLay, 1993, is revised using a suite of characters pertaining to the carapace form and armature, proportions of the ambulatory dactylus, and structures of the pereopods, thoracic sternum, male pleon, and gonopods. The identity of the poorly known type species, F. atypica (Sakai, 1936), is clarified and the species is rediagnosed and illustrated based on the single non-type dried specimen available. Frodromia reticulata (Sakai, 1974) is also rediagnosed on the basis of a series of Japanese specimens. The material identified as F. atypica by McLay (1993) from New Caledonia and the Indonesian Moluccas is here shown to belong to two new species, F. granulosa and F. caileani, respectively; with F. granulosa also reported from Vanuatu. Two other new species, F. elegans and F. iners, are described from the South China Sea and the Philippines, respectively. As a result, Frodromia is hereby classified in the subfamily Frodromiinae Števčić, 2005, which was originally established as a tribe in Sphaerodromiinae Guinot & Tavares, 2003, and which is here redefined and rediagnosed.

Key words. sponge crab, Dromioidea, systematics, subfamily definition, new species, key to taxa, Indo-West Pacific

Colour in life. A, Frodromia atypica (Sakai, 1936), after Sakai (1936: pl. 2 fig. 1); B, F. reticulata (Sakai, 1974), after Sakai (1976: pl. 5 fig. 1);
C, F. elegans, new species, holotype male (6.6 × 7.5 mm) (ZRC 2024.0144), Taiwan; D, F. granulosa, new species, holotype male (6.5 × 7.1 mm) (ZRC 2024.0517), Vanuatu;
E, F, F. iners, new species, holotype male (6.3 × 7.0 mm) (ZRC 2024.0518), Philippines [partly covered with sand particles and debris].

Photographs: C, T.-Y. Chan; D, J.C.E. Mendoza; E, F, P.K.L. Ng.

Frodromia granulosa 

F. caileani 

F. elegans 

 F. iners

PETER K. L. NG. 2026. Revision of Frodromia McLay, 1993 (Crustacea: Brachyura: Dromiidae) and the Status of Frodromiinae Števčić, 2005. RAFFLES BULLETIN OF ZOOLOGY. 74: 332–358. DOI: 10.26107/RBZ-2026-0023  [4 May 2026]

[Crustacea • 2026] Merapohra karsticola • On A New Genus and Species of Karst-dwelling Freshwater Crab (Brachyura: Potamidae) from Peninsular Malaysia

 

Merapohra karsticola  

Tan, Ooi & Ng, 2026

 

DOI: doi.org/10.3897/zookeys.1277.181453  

Abstract

Recent explorations of caves in Pahang, central Peninsular Malaysia yielded specimens of an unusual long-legged terrestrial, cave-dwelling crab. Morphological examinations of the specimens collected, in comparison with known species from the region suggests that they belong to a new genus and species, which are described herein. Merapohra karsticola gen. nov. et sp. nov., is differentiated from other potamids by characters of the carapace epigastric and postorbital cristae, ambulatory legs, male thoracic sternum, male pleon, and diagnostic structure of the male first gonopod. The discovery of this new genus and species of cave-dwelling crab highlights the importance and high diversity of karst systems in Peninsular Malaysia, which are imperilled in light of ongoing quarrying and mining activities.

Key words: Cave, karst, limestone, Potamiscinae, taxonomy

Merapohra karsticola gen. nov. et sp. nov., in life.
A. Holotype, male (37.2 × 26.7 mm) (ZRC 2024.0327);
B. Paratype, female (30.0 × 21.4 mm) (ZRC 2024.0328).

(Photo credit: Mr. Ang Yu Pin for the paratype).

Merapohra karsticola gen. nov. et sp. nov.

 Zhi Wan Tan, Qie Ooi, Peter K. L. Ng. 2026. On A New Genus and Species of Karst-dwelling Freshwater Crab (Crustacea, Brachyura, Potamidae) from Peninsular Malaysia. ZooKeys. 1277: 113-136.  DOI: doi.org/10.3897/zookeys.1277.181453 [9 Apr 2026]

[Crustacea • 2026] Geosesarma wongi • A distinctive New Species of semiterrestrial crab (Brachyura: Sesarmidae) from Tapah Hills in Perak, Peninsular Malaysia; with Notes on G. peraccae (Nobili, 1903) and G. cataracta Ng, 1986

Geosesarma wongi

Ng. 2026

 

DOI: doi.org/10.3897/zookeys.1266.172575

Photograph: Francis Seow-Choen.

Abstract

A new species of semiterrestrial freshwater crab is described from Tapah Hills in Peninsular Malaysia. Geosesarma wongi sp. nov. is the 13th member of the genus reported from the country and is most similar to G. peraccae (Nobili, 1903) and G. cataracta Ng, 1986, but easily separated by its distinct carapace features and structures of the adult male chela and male first gonopod. The types of G. peraccae are figured for the first time. Geosesarma cataracta is also figured in detail, and the type series is shown to be mixed.

Key words: Comparative taxonomy, freshwater crab, Malay Peninsula, new taxon, sesarmid crab, Southeast Asia, taxonomy

Geosesarma wongi sp. nov., holotype male (12.7 × 11.3 mm) (ZRC 2025.0023), Perak. Colour in life.

Photograph: Francis Seow-Choen.

Geosesarma wongi sp. nov., holotype male (12.7 × 11.3 mm) (ZRC 2025.0023), Perak.
A. Dorsal habitus; B. Dorsal view of carapace; C. Frontal view of cephalothorax; D. Ventral surface of cephalothorax.

 Geosesarma wongi sp. nov.

 

Diagnosis. Carapace rectangular, wider than long, width to length ratio 1.11–1.14, lateral margins almost straight, gently divergent towards posterior carapace margin (Fig. 2A, B); dorsal surfaces with well-defined regions, anterior half with prominent low, rounded tubercles and granules; postfrontal lobes distinct, median lobes with transverse row of relatively dense short setae, setae sparser on lateral lobes; epibranchial region raised; protogastric region gently convex; urogastric region raised, with gastrocardiac groove deep (Fig. 2A, B); frontal margin distinctly deflexed, frontal lobes broad, with gently convex margins in dorsal view, separated by wide shallow median concavity; postfrontal cristae sharp, distinct (Fig. 2A–C); external orbital angle triangular, directed anteriorly, not extending beyond lateral carapace margin, outer lateral margin gently convex; separated from first epibranchial tooth by V-shaped cleft; first epibranchial tooth distinct, wide, second epibranchial tooth just visible as low lobe (Fig. 2A, B); merus of third maxilliped subovate; exopod slender, flagellum elongate, longer than width of merus (Fig. 5A); outer surfaces of palm of chela covered with ...

Peter K. L. Ng. 2026. Geosesarma wongi sp. nov., A distinctive New Species of semiterrestrial crab from Tapah Hills in Perak, Peninsular Malaysia; with Notes on G. peraccae (Nobili, 1903) and G. cataracta Ng, 1986 (Crustacea, Brachyura, Sesarmidae). ZooKeys. 1266: 281-298. DOI: doi.org/10.3897/zookeys.1266.172575

[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 ) 

[Crustacea • 2025] Geosesarma bunian • On A New Species of Vampire Crab from the Geosesarma foxi species-group (Brachyura: Sesarmidae) in northern Peninsular Malaysia

Geosesarma bunian

 Ng, Khadijah-Ahmad & Ahmad, 2025

RAFFLES BULLETIN OF ZOOLOGY . 73;

Abstract

 Geosesarma bunian, new species, is described from Gunung Jerai in the northern Malaysian state of Kedah. Collected from over 1,100 m above sea level, the species is a member of the G. foxi (Kemp, 1918) species group, and is the fifth species known. Morphologically, G. bunian is closest to G. faustum Ng, 2017 from Penang, but the species can be distinguished by characters of the male first gonopod, male chelae and live coloration. 

Key words. taxonomy, Kedah, Peninsular Malaysia, Gunung Jerai, comparative morphology, Southeast Asia

Geosesarma bunian, new species. Colour in life.
 A, C, holotype male (10.1 × 10.1 mm) (ZRC 2024.0558), Kedah;
B, D, paratype female (10.1 × 9.9 mm) (ZRC 2024.0559), Kedah.

Geosesarma bunian, new species.
 Holotype male (10.1 × 10.1 mm) (ZRC 2024.0558), Kedah.
 A, frontal view of cephalothorax; B, dorsal view of right cheliped; C, outer view of left chela; D, dorsal view of left chela; E, buccal cavity, anterior thoracic sternum and pleon; F, male pleonal somites 3–6 and telson (setae denuded).

Family Sesarmidae Dana, 1851 

Genus Geosesarma De Man, 1892 

Type species. Sesarma (Geosesarma) nodulifera De Man, 1892, 

subsequent designation by Serène & Soh (1970). 

Geosesarma bunian, new species

Diagnosis. Carapace quadrate, as wide as long, adult width to length ratio ca. 1.0, lateral margins parallel (Figs. 2, 4A, B); dorsal surface with regions just visible, anterior regions with small, low rounded granules on gastric regions (Figs. 2C, D, 4A, B); front distinctly deflexed, 2 frontal lobes broad with almost straight margins in dorsal view; postfrontal, postorbital cristae sharp, distinct (Figs. 2C, D, 3A, 4A, B); external orbital tooth (= first lateral tooth) triangular, directed obliquely laterally, outer margin gently convex to almost straight, tip extending just beyond lateral margin; second lateral tooth low, distinct, separated from rest of margin by cleft (Figs. 2C, D, 4A, B). Merus of third maxilliped subovate, shorter than ischium; exopod slender ...

Etymology. The name is derived from a Malay term used to describe the “hidden people” of the forest or Orang Bunian. They are often described as beautifully dressed forest denizens. The name, bunian, here used as a Latin noun in apposition, alludes to the beautiful colours of the new species as well as it escaping scientific attention until now. 

Peter K. L. NG, S. KHADIJAH-AHMAD and Amirrudin B. AHMAD. 2025. On A New Species of Vampire Crab from the Geosesarma foxi species-group (Crustacea: Brachyura: Sesarmidae) in northern Peninsular Malaysia. RAFFLES BULLETIN OF ZOOLOGY . 73; 162–168.

[Crustacea • 2025] Bathynomus vaderi • A New Species of supergiant Bathynomus A. Milne-Edwards, 1879 (Isopoda: Cirolanidae) from Vietnam, with Notes on the Taxonomy of Bathynomus jamesi

Bathynomus vaderi

 Ng, Sidabalok & Nguyen, 2025 

 

DOI: doi.org/10.3897/zookeys.1223.139335 

Abstract

A new supergiant species of Bathynomus A. Milne-Edwards, 1879 from Vietnam is described. Bathynomus vaderi sp. nov. is characterised by its wide, rectangular clypeal region with parallel lateral margins, concave distal margin, and narrowly acute apex; the distally narrowing and posteriorly curved coxa of pereopod 7; and the presence of 11 upwardly curved pleotelson spines. The new Bathynomus is the fourth species with upwardly curved pleotelson spines and the second supergiant in the South China Sea. The taxonomy of B. jamesi Kou, Chen & Li, 2017 from the South China Sea is also discussed based on a large series of specimens. Previously reported differences in body form and pleotelson spines, which suggest that there may be two forms or species, are regarded as intraspecific variation for the time being. The contemporary culinary trend and fishing of Bathynomus in Vietnam, which have contributed to this discovery, are also discussed.

Key words: Deep sea, fisheries, morphology, new taxon, taxonomy, seafood

Bathynomus vaderi sp. nov., paratype ♂ (258 mm) (ZVNU 110001), Vietnam, colour in life
A dorsal view B body, ventral view C cephalon, anterior view.

A–D Bathynomus vaderi sp. nov., holotype ♂ (266 mm) (ZRC 2022.0621), Vietnam
E–H B. jamesi Kou, Chen & Li, 2017, ♂ (320 mm) (MNHN IS.2290), Philippines
A, E clypeal region B, F pereon lateral view C, G pleotelson, dorsal view D, H pleotelson, lateral view.

Abbreviations: c6 = coxa of pereopod 6; c7 = coxa of pereopod 7.

Bathynomus vaderi sp. nov. 

Diagnosis: Clypeal region with lateral margin parallel, distal margin concave, apex narrowly acute, transversely rectangular (Figs 4C, 5C, 6C, 9A). Coxa of pereopod 7 narrows distally, curved posteriorly (Figs 5D, 6D, E, 9B). Distinct row of setae present between pleotelson spines; 11 upwardly curved pleotelson spines; pleotelson 0.6 as long as wide (Figs 5A, 9D); pleotelson vaulted laterally (Figs 6E, 9C). Appendix masculina slightly shorter than or reaching to end of endopod of pleopod 2 (Fig. 10A).

Etymology: The species named after the most famous Sith Lord in the Star Wars movie series, Darth Vader, whose helmet resembles the head of the new Bathynomus species.

 Peter K. L. Ng, Conni M. Sidabalok and Thanh Son Nguyen. 2025. A New Species of supergiant Bathynomus A. Milne-Edwards, 1879 (Crustacea, Isopoda, Cirolanidae) from Vietnam, with Notes on the Taxonomy of Bathynomus jamesi Kou, Chen & Li, 2017. ZooKeys. 1223: 289-310. DOI: doi.org/10.3897/zookeys.1223.139335 

[Crustacea • 2023] Stoliczia setoiyenica • A New Species of Freshwater Crab (Decapoda: Brachyura: Potamidae) from southern Thailand

 Stoliczia setoiyenica

 Tan, Lheknim & Ng, 2023

 

DOI: 10.11646/zootaxa.5360.4.4 

twitter.com/ZhiWanTan

 

Abstract

A new species of freshwater crab is described from southern Thailand, near the border with Peninsular Malaysia. Species of Stoliczia are characterised by their relatively flat carapace, a third maxilliped exopod that possesses no or a very short flagellum, and a conical male gonopod terminal segment that lacks or only has a very low dorsal fold. Stoliczia setoiyenica, new species, most closely resembles S. perlensis and S. kedahensis from northern Peninsula Malaysia but can be easily distinguished from congeners by differences in carapace and male gonopod morphology. Comparisons to the two known Thai Stoliczia species, S. panhai and S. ekavibhathai, are also provided for completeness.

Crustacea, Satun Province, Isthmus of Kra, Potamoidea, taxonomy

Stoliczia setoiyenica, new species

 Zhi Wan Tan, Vachira Lheknim, and Peter K. L. Ng. 2023. Stoliczia setoiyenica, A New Species of Freshwater Crab from southern Thailand (Crustacea: Decapoda: Brachyura: Potamidae).  Zootaxa. 5360(4); 531-544. DOI: 10.11646/zootaxa.5360.4.4

 twitter.com/ZhiWanTan/status/1786297840156995868

[Crustacea • 2024] Demanietta moror • A New Species of Freshwater Crab (Brachyura: Potamidae) from A Karst Formation in southern Thailand

Demanietta moror

 Tan, Lheknim & Ng, 2024

 brill.com/view/journals/cr/97/3-4/article-p307_11.xml

 twitter.com/ZhiWanTan

Abstract

A new species of potamid crab belonging to the genus Demanietta Bott, 1966 is described from a creek draining out of a karst formation associated with the Phuket Mountain Range in southern Thailand. Demanietta moror new species, belongs to a group of Demanietta species that has a relatively inflated and smooth carapace, and a male first gonopod that is weakly bent, appearing more vertically projected. It can be immediately distinguished from all congeners by its carapace, gonopod morphology and unique colour pattern in life.

Keywords: Surat Thani Province; Isthmus of Kra; taxonomy; Potamoidea

Demanietta moror new species

 Zhi Wan Tan, Vachira Lheknim, and Peter K. L. Ng. 2024. A New Species of Freshwater Crab, Demanietta moror, from A Karst Formation in southern Thailand (Brachyura, Potamidae).  Crustaceana. 97(3-4); 307–319. DOI: 10.1163/15685403-bja10362

 brill.com/view/journals/cr/97/3-4/article-p307_11.xml

 twitter.com/ZhiWanTan/status/1786297840156995868

Résumé: Une nouvelle espèce de crabe Potamidae appartenant au genre Demanietta Bott, 1966, est décrite d’un ruisseau s’écoulant d’une formation karstique associée à la chaîne de montagnes de Phuket, dans le sud de la Thaïlande. Demanietta moror n. sp., appartient à un groupe d’espèces du genre Demanietta qui possède une carapace lisse et relativement bombée, et un premier gonopode mâle faiblement recourbé, apparaissant projeté plus verticalement. Elle se distingue immédiatement de tous ses congénères par sa carapace, la morphologie du gonopode et une couleur unique à l’état vivant.

[Crustacea • 2024] Sundathelphusa roberti • A New Species of Freshwater Crab (Brachyura: Gecarcinucidae) from Highlands in Batangas, Luzon, Philippines

Sundathelphusa roberti

Ng & Mendoza, 2024

brill.com/view/journals/cr/97/3-4/article-p221_5.xml 

 twitter.com/Mendoza_JCE

 

Abstract

A new species of freshwater crab belonging to a group of species morphologically similar to Sundathelphusa philippina (Von Martens, 1868) is described from highlands in the province of Batangas, southern Luzon, Philippines. Sundathelphusa roberti new species, however, differs from members of this group by the position and strength of the epigastric and postorbital cristae, form of the posterior epistomal margin, shape of the third maxillipeds, and structure of the male first gonopod. The new taxon is the 35th species of Sundathelphusa known from the Philippines.

Keywords: Gecarcinucoidea; comparative taxonomy; description; montane species; Southeast Asia;

 

Sundathelphusa roberti new species

 Peter K. L. Ng and Jose C. E. Mendoza. 2024. A New Species of Freshwater Crab, Sundathelphusa roberti (Brachyura, Gecarcinucidae) from Highlands in Batangas, Luzon, Philippines.  Crustaceana. 97(3-4); 221–233. DOI: 10.1163/15685403-bja10364

 brill.com/view/journals/cr/97/3-4/article-p221_5.xml

  twitter.com/Mendoza_JCE/status/1786930224413991232/

[Crustacea • 2024] Lepidothelphusa menneri (Brachyura: Gecarcinucidae) • First Record of the Genus from Kalimantan, Indonesia

Lepidothelphusa menneri 

Ng & Wowor. 2024 

DOI: 10.11646/zootaxa.5397.2.3

 

Abstract

The gecarcinucid freshwater crab genus, Lepidothelphusa Colosi, 1920, is known only from Sarawak in northern Borneo, with six recognised species i.e. Lepidothelphusa cognettii (Nobili, 1903); L. flavochela Grinang & Ng, 2015; L. limau Grinang & Ng, 2015; L. loi Grinang & Ng, 2015; L. padawan Grinang & Ng, 2015; and L. sangon Grinang & Ng, 2015. The genus is now reported from Indonesian Borneo for the first time, from specimens recently collected from Gunung Kelam in Sintang Regency, Kalimantan Barat Province. Lepidothelphusa menneri n. sp. has a very distinctive tri-coloured pattern in life, unique among congeners. It can also easily be separated from congeners by carapace, epistome, male pleonal and male first gonopod characters.

Crustacea, taxonomy, Gecarcincoidea, new taxon, freshwater crab, western Borneo, Southeast Asia.

Peter K. L. Ng and Daisy Wowor. 2024. Lepidothelphusa menneri n. sp. (Crustacea: Brachyura: Gecarcinucidae), First Record of the Genus from Kalimantan, Indonesia. Zootaxa. 5397(2); 218-224. DOI: 10.11646/zootaxa.5397.2.3

 Researchgate.net/publication/377151155_Lepidothelphusa_menneri_n_sp__first_record_of_the_genus_from_Kalimantan_Indonesia

[Crustacea • 2023] Limnopilos miromekong • A New Species of Furry Crown Crab, Limnopilos Chuang & Ng, 1991 (Brachyura: Hymenosomatidae) from Tonle Sap, Cambodia

Limnopilos miromekong

Ng & Chhuoy, 2023

DOI: 10.1163/15685403-bja10313 

 Researchgate.net/publication/374199389 

  facebook.com/MekongWonders

Abstract

A new species of the wholly freshwater hymenosomatid crab genus Limnopilos Chuang & Ng, 1991, is described from Tonle Sap River in the lower Mekong drainage, Cambodia. This is the fourth species known, and the second one from Indochina. The type species, of Limnopilos, L. naiyanetri Chuang & Ng, 1991, was from the Chao Phraya drainage to the west in central Thailand. The new species is characterized by the presence of a rostrum, relatively shorter ambulatory legs and a different structure of the male first gonopod. Limnopilos sumatranus Naruse & Ng, 2007, is also recorded from southern Peninsular Malaysia for the first time.

Keywords: Taxonomy; new species; Hymenosomatoidea; freshwater crab; Mekong River; Indochina;

 Peter K. L. Ng and Samol Chhuoy. 2023. A New Species of Furry Crown Crab, Limnopilos Chuang & Ng, 1991 (Brachyura, Hymenosomatidae) from Tonle Sap, Cambodia.  Crustaceana. 96(9): 885–895. DOI: 10.1163/15685403-bja10313

  Researchgate.net/publication/374199389_A_new_species_of_Limnopilos_from_Tonle_Sap_Cambodia

.facebook.com/MekongWonders/posts/614626534193184/

 

Résumé: Une nouvelle espèce du genre de crabe Hymenosomatidae, Limnopilos Chuang & Ng, 1991, entièrement d’eau douce, est décrit du fleuve Tonlé Sap dans le bassin versant du Mékong inférieur, au Cambodge. C’est la quatrième espèce connue, et la seconde d’Asie du Sud-Est. L’espèce-type du genre Limnopilos, L. naiyanetri Chuang & Ng, 1991, était connue du bassin versant du Chao Phraya à l’ouest dans le centre de la Thaïlande. La nouvelle espèce est caractérisée par la présence d’un rostre, de pattes ambulatoires relativement plus courtes et une structure différente du premier gonopode mâle. Limnopilos sumatranus Naruse & Ng, 2007, est aussi signalé pour la première fois dans le sud de la Malaisie péninsulaire.