[Crustacea • 2026] Pilumnus guadeloupensis • A New Species of Pilumnus Leach, 1816 (Decapoda: Brachyura) from Guadeloupe, Lesser Antilles

 

Pilumnus guadeloupensis 

Magalhães, Oliveira-Rogeri, Felder & Mantelatto, 2026

DOI: doi.org/10.5252/zoosystema2026v48a16

 Abstract  

Pilumnus Leach, 1861 is a speciose cosmopolitan genus of marine crabs typical from rocky and coral coastal environments and known to occur in tropical and temperate oceans and seas worldwide, including the waters of western Atlantic and Caribbean Sea surrounding the Lesser Antilles, a recognized hotspot of biodiversity in Caribbean. Despite recent sampling efforts, this region remains underexplored, limiting understanding of its marine fauna. To address this gap, several field expeditions have been carried out, including KARUBENTHOS 2012. This expedition extensively collected specimens of various taxonomic groups, expanding documentation of biodiversity in the Lesser Antilles. Among collections, a unique specimen of Pilumnus was recognized and analyzed through morphological and molecular approaches. Genetic analyses of this specimen, a component of molecular phylogenetic studies previously conducted by our team, confirmed its divergence from previously described species. Herein, we performed a thorough morphological examination analyzing most of the taxonomic informative characters used in species descriptions of representatives of Pilumnus. Based on the presently accessed morphological features and previously detected molecular divergence, a new species, Pilumnus guadeloupensis n. sp., is described. This species can be distinguished from others from the genus mainly by the ornamentation and tuberculation patterns of pereopods, number of anterolateral prominences and shape of the carapace. Detailed morphological comparisons with congeners, alongside a comprehensive review of the literature, are provided.

KEYWORDS: Caribbean, KARUBENTHOS 2012, morphology, Pilumnidae, new species, 

Habitus of alcohol-preserved holotype of Pilumnus guadeloupensis n. sp., male (CW = 6.44 mm),  MNHN-IU-2013-16321:
A, dorsal; B, ventral.

 Scale bar: 2 mm.

Holotype of Pilumnus guadeloupensis n. sp., male (CW = 6.44 mm),  MNHN-IU-2013-16321:
A, entire specimen on dorsal view; B, left third maxilliped, external; C, outer surface of major chela; D, left first gonopod, mesial; E, pleon and telson.

 Scale bars (mm): A, 3 mm; B, 0.7 mm; C, 2.5 mm; D, 0.2 mm; E, 1.5 mm.

Alcohol-preserved holotype of Pilumnus guadeloupensis n. sp., male (CW = 6.44 mm),  MNHN-IU-2013-16321:
A, habitus, frontal; B, carapace front, dorsal; C, left anterolateral carapace margin, dorsal; D, left suborbital and pterygostomial carapace regions, ventral; E, left third maxilliped, external; F, left (major) cheliped, dorsal; G, right (minor) chela, external; H, left (major) chela, external; I, right pereopods 4 and 5, meri, carpi, and propodi, dorsal; J, anterior sternites and pereopod coxae, ventral; K, sternopleonal cavity with pleonal lock button; L, left first gonopod, mesial. Not to scale.

Phylum ARTHROPODA Latreille, 1829

Class MALACOSTRACA Latreille, 1802

Order DECAPODA Latreille, 1802

Infraorder BRACHYURA Latreille, 1802

Family PILUMNIDAE Samouelle, 1819

Genus Pilumnus Leach, 1816

Pilumnus guadeloupensis n. sp.

 

Diagnosis. — Carapace anterodorsally with short pubescence; frontal, protogastric, and hepatic regions of dorsal surface with strong tubercules; supraorbital margins strongly toothed; anterolateral margin with four teeth, anteriormost of which formed by outer orbital tooth. Major chela palm with outer surface nearly smooth and glabrous. Ambulatory pereopods with merus dorsal margin mostly smooth, single subdistal denticle on dorsal margin of meri of pereopods 2-4; carpi and propodi with prominent spiniform tubercles.

Etymology. — The specific epithet guadeloupensis refers to Guadeloupe, the type locality of the species, and it is used here as an adjective.

 

Tatiana Magalhães, Lucas Oliveira-Rogeri, Darryl L. Felder and Fernando L. Mantelatto. 2026. A New Species of Pilumnus Leach, 1816 (Decapoda, Brachyura) from Guadeloupe, Lesser Antilles, with morphological comparisons to regional congeners. Zoosystema. 48 (16), 389-399. DOI: doi.org/10.5252/zoosystema2026v48a16 (3 July 2026)

Une nouvelle espèce de Pilumnus Leach, 1816 (Decapoda, Brachyura) de Guadeloupe, Petites Antilles, et comparaisons morphologiques avec les espèces régionales apparentées.

Pilumnus Leach, 1861 est un genre cosmopolite de crabes marins, typique des environnements côtiers rocheux et coralliens. Ces animaux sont présents dans les océans et mers tropicaux et tempérés du monde entier, notamment dans les eaux de l'Atlantique ouest et la mer des Caraïbes, y compris dans les eaux entourant les Petites Antilles, un point chaud de biodiversité en région caraïbe. Malgré de récents efforts d'échantillonnage, cette région reste sous-explorée, ce qui limite la connaissance de sa faune marine. Pour combler cette lacune, plusieurs expéditions de terrain ont été menées, dont KARUBENTHOS 2012. Cette expédition a permis de collecter de nombreux spécimens de divers groupes taxonomiques, enrichissant ainsi nos connaissances sur la biodiversité des Petites Antilles. Parmi les spécimens collectés, un spécimen unique de Pilumnus a été identifié et analysé par des approches morphologiques et moléculaires. Les analyses génétiques de ce spécimen, réalisées dans le cadre d'études de phylogénie moléculaire précédemment menées par notre équipe, ont confirmé sa divergence avec les espèces précédemment décrites. Un examen morphologique approfondi analysant la plupart des caractères taxonomiques informatifs utilisés dans les descriptions des espèces de Pilumnus a été réalisé. Sur la base des caractéristiques morphologiques décrites dans cette étude et des divergences moléculaires précédemment détectées, une nouvelle espèce, Pilumnus guadeloupensis n. sp., est décrite. Cette espèce se distingue des autres espèces du genre principalement par l'ornementation et les tubercules des péréiopodes, le nombre de proéminences antérolatérales et la forme de la carapace. Des comparaisons morphologiques détaillées avec ses congénères, ainsi qu'une revue exhaustive de la littérature, sont fournies.

Caraïbes, KARUBENTHOS 2012, morphologie, Pilumnidae, espèce nouvelle

[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

  facebook.com/ChaoHuang1777/posts/7114897251966610

[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 • 2021] Macromedaeus adelus • A New Species of intertidal xanthid crab of the Genus Macromedaeus Ward, 1942 (Decapoda: Brachyura: Xanthidae) from Singapore

Macromedaeus adelus

Mendoza, 2021

RAFFLES BULLETIN OF ZOOLOGY. 69 

  x.com/Mendoza_JCE

Abstract

 Four species of marine crab (Brachyura) are reported for the first time from Singapore. Three of these have been previously reported from other localities in the Indo-West Pacific region, while one is a new species described herein. The camptandriid crab, Exagorium fidelisi Naruse, Chung & Tangah, 2015, originally described from northeastern Sabah, Malaysia, is reported from the mangroves of northern Singapore. Two xanthid crabs are newly recorded as well: Hepatoporus guinotae (Zarenkov, 1971) and Medaeops edwardsi Guinot, 1967, previously described from the Red Sea and Indian Ocean, respectively. Another xanthid crab, Macromedaeus adelus, new species, is described from the intertidal areas of Singapore. It is most similar to M. distinguendus (De Haan, 1835) and M. voeltzkowi (Lenz, 1905), primarily in having a distinctly areolated and granular carapace and having four teeth on the carapace anterolateral margin. It can, however, be distinguished from congeners by morphological features of the carapace, chelipeds, ambulatory legs, and the male first gonopods. 

Key words. Xanthidae, Camptandriidae, taxonomy, biodiversity, Macromedaeus adelus, Hepatoporus, Exagorium

Live colouration. Macromedaeus adelus, new species (ZRC 2017.0466), West Coast Park, Singapore.
A, paratype, male, 16.0 × 10.3 mm; B, paratype, male, 11.8 × 7.7 mm.

Scale bar: A, B = 5.0 mm.

Macromedaeus adelus, new species

 

Etymology. The specific epithet of the new species is derived from the Greek “adelos”, meaning “unseen, unknown, and obscure”, because the true identity of this crab remained concealed for many decades. Used as a Latin adjective.

Jose Christopher E. Mendoza. 2021. Marine Crabs new to Singapore, with A Description of A New Species of intertidal xanthid crab of the Genus Macromedaeus Ward, 1942 (Crustacea: Decapoda: Brachyura). RAFFLES BULLETIN OF ZOOLOGY. 69: 463–480. [5 November 2021]

  x.com/Mendoza_JCE/status/1456821180103462914

[Crustacea • 2026] Ghatiana dhritiarum • A New Species of freshwater crab in the Genus Ghatiana (Brachyura: Gecarcinucidae) from the central Western Ghats, India

Ghatiana dhritiarum  

Pati, Naik & Gouda, 2026

DOI: doi.org/10.1590/2358-2936e20260586 

Abstract

A new species of freshwater crab, Ghatiana dhritiarum sp. nov., is described from the central Western Ghats of India in the Uttara Kannada District of the Karnataka State. The new species inhabits water-filled holes of tree trunks and laterite boulders in evergreen forests, with an omnivorous diet. Characterized mainly by a proportionately broad carapace, slender eyestalks, and a medially distinctly curved male first gonopod with a relatively long ultimate article, G. dhritiarum sp. nov. also exhibits other unique morphological features and a distinct coloration in life. This new species can be distinguished from its morphologically closest congener, Ghatiana dvivarna Pati, Thackeray, Bajantri and Hegde, 2022, by differences in the distance between the frontal margin and the anterior margin of the epistome, the relative size of the eyes, the shape of the male first gonopod, and the size of the vulvae, as well as live coloration. This discovery raises the total number of known species in Ghatiana Pati and Sharma, 2014, to 14, including seven species from Karnataka, emphasizing the need for continued exploration, especially in the central Western Ghats region.

Keywords: Crustacea; Decapoda; Karnataka; Oriental region; taxonomy; Western Ghats

Ghatiana dhritiarum sp. nov., color in life: A, adult male, holotype (CW 16.4 mm, CL 8.9 mm), ZSI-WRC C.2587; B, adult male, paratype (CW 15.0 mm, CL 8.3 mm), ZSI-WRC C.2589; C, adult male, paratype (CW 14.9 mm, CL 8.5 mm), ZSI-WRC C.2589; D, adult male, paratype (CW 14.5 mm, CL 7.9 mm), ZSI-WRC C.2588; E, subadult male (CW 13.4 mm, CL 7.3 mm), ZSI-WRC C.2591; F, subadult male (CW 9.2 mm, CL 5.3 mm), ZSI-WRC C.2590; G, subadult male (CW 8.9 mm, CL 4.7 mm), ZSI-WRC C.2591; H, adult female, paratype (CW 18.3 mm, CL 9.7 mm), ZSI-WRC C.2588; I, adult female, paratype (CW 18.1 mm, CL 9.9 mm), ZSI-WRC C.2588; J, adult female (CW 17.5 mm, CL 10.0 mm), ZSI-WRC C.2590; K, adult female (CW 15.5 mm, CL 8.4 mm), ZSI-WRC C.2590; L, adult female, paratype (CW 15.3 mm, CL 8.2 mm), ZSI-WRC C.2589; M, adult female (CW 15.3 mm, CL 8.4 mm), ZSI-WRC C.2591; N, subadult female (CW 13.0 mm, CL 6.9 mm), ZSI-WRC C.2591; O, subadult female (CW 9.9 mm, CL 5.4 mm), ZSI-WRC C.2591.
Ghatiana dvivarna Pati, Thackeray, Bajantri and Hegde, 2022, color in life: P-R, not collected.

Ghatiana dhritiarum sp. nov., habitats.
 A, a crab in the tree trunk hole holding the wing of a termite at Hiremane; B, a crab in the hole of a laterite boulder in the open area at Hiremane; C, a crab emerging out of the hole (yellow arrow sign) of a laterite boulder in the well-shaded area at Tarimane. None of these crabs were collected.

Superfamily Gecarcinucoidea Rathbun, 1904

Family Gecarcinucidae Rathbun, 1904

Genus Ghatiana Pati and Sharma, 2014

Type species. Ghatiana aurantiaca Pati and Sharma, 2014,
by original designation; gender of genus feminine.

 

Ghatiana dhritiarum sp. nov.

Diagnosis. Carapace in adult proportionately broad (CW/CL approximately 1.7-1.9), strongly arched (CH/CL approximately 0.7-0.8); lateral margins strongly convex; frontal margin some distance from anterior margin of epistome, exposing antennular fossae (Figs. 1A, B, 2A, B, D, E, 3A, B). Eyes relatively large as compared to orbital space; each eye with relatively slender eyestalk ...

Etymology. The specific epithet "dhritiarum" is formed directly from the personal name "Dhriti" honoring two ladies. First, it recognizes Dr. Dhriti Banerjee, the present Director of the Zoological Survey of India, whose leadership and scholarly work have been instrumental in advancing our understanding of Indian fauna. Secondly, it honors the daughter of one of the authors, G.D. Naik, whose name is also "Druthi" (has the same pronunciation as “Dhriti” in Kannada dialect).

 Sameer Kumar Pati, Gopal Diggya Naik and Sunil Rama Gouda. 2026. Description of A New Species of freshwater crab in the Genus Ghatiana Pati and Sharma, 2014 (Brachyura: Gecarcinucidae) from the central Western Ghats, India. Nauplius. 34; DOI: doi.org/10.1590/2358-29 

[Crustacea • 2025] Tayninhon nuibaden • A New Genus and New Species of Freshwater Crab (Decapoda: Brachyura: Potamidae) from Ba Den Mountain, Southeast Vietnam

 

Tayninhon nuibaden

 Dang, Tien & Tu, 2025

  

DOI: doi.org/10.11646/zootaxa.5693.2.10  

 Researchgate.net/publication/395540785

Abstract

Recent surveys in Ba Den Mountain, Southeast Vietnam, found one new genus and species of the potamid, Tayninhon nuibaden gen. nov., sp. nov. The new genus is characterised by its medium adult carapace size, relatively flat, rugose and striae on the carapace dorsal surface, low epigastric, postorbital cristae and epibranchial tooth; the anterolateral margin is serrated; relatively wide thoracic sternum with smooth surface; sternopleonal cavity reaching to the imaginary line connecting anterior edges of cheliped coxae; relatively narrow telson; the male first gonopod is sinuous with relatively broad subterminal segment, and the terminal segment hook-shaped with a fold at the basal part, distal part curved inwards, tip sharp; and the male second gonopod is relatively short. The present study brings the total number of freshwater crab species belonging to Potamidae in Vietnam to 61.

Crustacea, Potamoidea, freshwater crab, taxonomy, new genus, new species, biodiversity, conservation

 

Tayninhon nuibaden gen. nov., sp. nov.

PHAN DOAN DANG, TRAN VAN TIEN and DO VAN TU. 2025. Tayninhon nuibaden, A New Genus and New Species of Freshwater Crab (Crustacea: Decapoda: Brachyura: Potamidae) from Ba Den Mountain, Southeast Vietnam.  Zootaxa. 5693(2); 291-300. DOI: doi.org/10.11646/zootaxa.5693.2.10 [2025-09-17]

 Researchgate.net/publication/395540785_Tayninhon_nuibaden_a_new_genus_and_new_species_of_freshwater_crab_Potamidae_from_Ba_Den_Mountain_Southeast_Vietnam

https://www.vietnam.vn/en/di-tim-loai-cua-nuoc-nuoc-ngot-tayninhon-nuibaden

[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 • 2024] Tiwaripotamon keeae • A New miniature Species of Freshwater Crab (Decapoda: Potamidae) from the China-Vietnam Border in Napo, Guangxi

Tiwaripotamon keeae 

 Huang, Shih & Ahyong, 2024

DOI: doi.org/10.11646/zootaxa.5476.1.16 

 facebook.com: Chao Huang

Abstract

A new miniature species of freshwater crab from the genus Tiwaripotamon Bott, 1970 (Potamidae), is described from a montane karst area in southern Napo, at the China-Vietnam border. It is the twelfth known species of the genus, and is also the smallest known, with the largest adult specimen observed barely exceeding 20 mm in carapace width. Apart from the small size, features of the eyes, carapace and ambulatory legs further set Tiwaripotamon keeae sp. nov. apart from its congeners. Pairwise genetic distances of the mitochondrial cytochrome oxidase subunit I (COI) gene also support it as a distinct species.

Crustacea, COI, karst, limestone, Potamiscinae, systematics

Tiwaripotamon keeae sp. nov. 

Chao Huang, Hsi-Te Shih, Shane T. Ahyong. 2024. Tiwaripotamon keeae sp. nov. (Crustacea: Decapoda: Potamidae), A New miniature Species of Freshwater Crab from the China-Vietnam Border in Napo, Guangxi.  Zootaxa. 5476(1); 166-176. DOI: doi.org/10.11646/zootaxa.5476.1.16 

 facebook.com/ChaoHuang1777/posts/7429380953851570

[Entomology • 2024] Capitamon gen. n., C. capitatum, C. mizoramense, ... • Identity of the Freshwater Crab Indochinamon beieri (Pretzmann, 1966), with the Description of A New Genus and Four New Species (Decapoda: Brachyura: Potamidae) from northeastern India

 

Capitamon n. gen.

 Pati, Mitra & Ng, 2024

  sciencepress.MNHN.fr/en/periodiques/zoosystema/46/23 

 x.com/Publi_MNHN

The precise identity of the potamid freshwater crab, Indochinamon beieri (Pretzmann, 1966), is ascertained, diagnosed and illustrated after examining the type material from Myanmar. The diagnosis/description of the species and subsequent accounts were based on a wrongly identified and illustrated specimen, probably from Nagaland in northeastern India, which caused substantial confusion among carcinologists, who referred to different taxa as I. beieri. Two such taxa from northeastern India are referred to herein as new species of a new genus, Capitamon n. gen., i.e., C. mizoramense n. gen., n. sp. from Mizoram and C. clarki n. gen., n. sp. probably from Nagaland. Capitamon n. gen. also includes two new species, i.e., C. capitatum n. gen., n. sp. (type species) from Arunachal Pradesh and Nagaland, and C. meitei n. gen., n. sp. from Manipur. Indochinamon manipurense (Alcock, 1909) is also assigned to Capitamon n. gen. as it possesses the characteristics of the new genus. Capitamon n. gen. is thus known by five nominal species from northeastern India, while I. beieri is restricted to its type locality in Myanmar, with the previous Indian records revealed to be erroneous. With the exclusion of I. manipurense, Indochinamon Yeo & Ng, 2007, now contains 42 species. An identification key to the species of Capitamon n. gen. is provided.

Keywords: Crustacea, Potamiscinae, Capitamon, Myanmar, identification key, new combination, new species, new genus.

 Capitamon n. gen., 

C. capitatum n. gen., n. sp. (type species) 

 Indochinamon manipurense (Alcock, 1909) is also assigned to Capitamon n. gen. 

Etymology. All the known congeners of the new genus have an ultimate article of the male first gonopod that resembles a bird's head. The genus name is therefore derived from caput, Latin for head, in arbitrary combination with the genus name Potamon. The gender of the generic name is neuter.

Distribution. Capitamon n.gen.is currently known from northeastern India, with its nominal species recorded from Arunachal Pradesh, Manipur, Mizoram and Nagaland states (Fig.1).

C. capitatum n. gen., n. sp. (type species) from Arunachal Pradesh and Nagaland, 

 C. mizoramense n. gen., n. sp. from Mizoram 

C. clarki n. gen., n. sp. probably from Nagaland. 

C. meitei n. gen., n. sp. from Manipur.

Sameer K. PATI, Santanu MITRA and Peter K. L. NG. 2024. Identity of the Freshwater Crab Indochinamon beieri (Pretzmann, 1966), with the Description of A New Genus and Four New Species from northeastern India (Decapoda, Brachyura, Potamidae). Zoosystema. 46(23); 589-615. 

 sciencepress.MNHN.fr/en/periodiques/zoosystema/46/23

  x.com/Publi_MNHN/status/1841516944169521576