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| Lemurophusa empusa Ng & Guinot, 2026 |
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.
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.
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


































