Identity of the tree-spider crab, Parasesarma leptosoma (Hilgendorf, 1869 (Decapoda: Brachyura: Sesarmidae), with descriptions of seven new species from the Western Pacific

The identity of the tree-spider crab, Parasesarma leptosoma (Hilgendorf, 1869) (family Sesarmidae), which is believed to be widely distributed in the Indo-West Pacific, is reassessed and shown to be a species-complex with nine species, seven of which are here described as new. Parasesarma leptosoma sensu stricto is now restricted to South and East Africa; and P. limbense (Rathbun, 1914) from Sulawesi, which had been regarded as a junior synonym, is here recognized as a valid species. The following species are described as new: P. gecko n. sp. from Vanuatu, Fiji, Guam and Japan; P. macaco n. sp. from Taiwan and the Philippines; P. kui n. sp. from Taiwan; P. parvulum n. sp. from the Philippines; P. gracilipes n. sp. from Indonesian Papua; P. purpureum n. sp. from Malaysia; and P. tarantula n. sp. from Sulawesi, Indonesia. The nine species of the Parasesarma leptosoma species-complex can be separated by the different shapes of their carapaces, the form of the dactylar tubercles on the male chelipeds, proportions of their ambulatory legs and the structure of the male first gonopod.

A new sesarmid crab of the genus Karstarma (Crustacea: Decapoda: Brachyura) associated with limestone formations in East Java, Indonesia

A new stygobitic sesarmid crab species is described from underground freshwater cave streams in the southern Malang karst range on the south coast of East Java Province, Indonesia. Karstarma malang n. sp. is morphologically most similar to K. jacobsoni (Ihle, 1912) from an underground river cave system in the southern coast of the Special Region of Yogyakarta Province in central Java, but differs in having a relatively larger cornea, less swollen ocular peduncle which lacks a ridge along the median part, proportionately shorter ambulatory legs and a more slender male first gonopod. This paper increases the number of the species of Karstarma Davie Ng, 2007, to 16; the new species being the eighth of the genus from Indonesia. It is also the third species which has a distinctly reduced cornea.

A new species of deep-water spider crab of the genus Paramaya De Haan, 1837 from the Bay of Bengal, India (Crustacea, Brachyura, Majidae)

The identity of the majid species of Paramaya De Haan, 1837, in the Indian Ocean is clarified with the collection of fresh specimens from the Bay of Bengal. Previously identified as P.spinigera (De Haan, 1837) which is known only from Japan, Taiwan, and Korea, the material from eastern India is here referred to a new species, P.mullisp. n. The new species can easily be distinguished from all congeners by its relatively shorter pseudorostral and carapace spines, more swollen branchial regions, distinctly granulated male thoracic sternum, and the G1 is not prominently curved with the dorsal projection on the sub distal part short and the tip rounded.

A new species of the genus Raphidopus Stimpson, 1858 (Crustacea: Decapoda: Anomura: Porcellanidae) from Peninsular Malaysia, with additional records of R. johnsoni Ng Nakasone, 1994 from Southeast Asia, and a key to species in the genus

A new species of the porcellanid genus Raphidopus Stimpson, 1858, is described on the basis of specimens from Penang and Kuala Selangor, Peninsular Malaysia. Raphidopus brevipes n. sp. is distinguished from its allied congeners, R. indicus Henderson, 1893 and R. johnsoni Ng Nakasone, 1994, by the proportionally narrower carapace and stouter ambulatory legs, as well as the different dentition on the cutting edge of the dactylus of the larger cheliped. Raphidopus johnsoni, previously known only by the holotype from Singapore, is now also recorded from Phuket (Thailand) and Java (Indonesia). Raphidopus indicus and R. johnsoni are rediagnosed on the basis of the respective type material and other specimens. A key to species of the genus Raphidopus is provided.

Redescription of Arcotheres placunae (Hornell Southwell, 1909) (Crustacea: Decapoda: Brachyura: Pinnotheridae) from India and Pakistan

The identity of Arcotheres placunae (Hornell Southwell, 1909) (Pinnotheridae), a pea crab associated with the window pane shell, Placuna placenta, has been confused as the types are lost and the original figures are inaccurate and do not match the description given of the species. In the present study, fresh specimens of the species were collected from the type locality (Gulf of Kachchh, Gujarat, India), and the species is here redescribed and refigured, and its affinities with similar species is discussed. To stabilize the taxonomy of A. placunae, a neotype is chosen from amongst the fresh material.

New records of species of the Polyonyx sinensis group (Crustacea: Decapoda: Anomura: Porcellanidae) from Japan, the Philippines, Singapore, and Malaysia, with descriptions of two new species

Five species of the genus Polyonyx Stimpson, 1858 are reported from southern Japan, the Philippines, Singapore, and Peninsular Malaysia. All of them belong to the P. sinensis group, which is morphologically defined by having the dactyli of the ambulatory legs each with the dorsal claw being much smaller than the ventral claw. Two species are described as new to science, one each from Peninsular Malaysia and the Ryukyu Islands in Japan, and their affinities are discussed. Polyonyx boucheti Osawa, 2007, P. heok Osawa Ng, 2016, and P. thai Werding, 2001, are also newly reported from southern Japan, the Philippines, and Singapore. A key to the Indo-West Pacific species of the P. sinensis group is provided.

The freshwater crabs of Danum Valley Conservation Area in Sabah, East Malaysia, with a description of a new species of Thelphusula Bott, 1969 (Crustacea, Brachyura, Gecarcinucidae, Potamidae, Sesarmidae)

Seven species of freshwater crabs from three families are recorded from and around the Danum Valley Conservation Area in Sabah, Malaysian Borneo: Thelphusulacapillodigitussp. n., Thelphusuladicerophilus Ng & Stuebing, 1990, Arachnothelphusaterrapes Ng, 1991, Terrathelphusasecula Ng & Tan, 2015, Parathelphusavalida Ng & Goh, 1987 (new record) (Gecarcinucidae); Isolapotamoningeri Ng & Tan, 1998 (Potamidae); and Geosesarmadanumense Ng, 2002 (Sesarmidae). The new species of Thelphusula Bott, 1979, can be distinguished from all congeners by a unique combination of morphological features, most notably the presence of dense patches of short setae on the fingers of the adult male chelipeds, as well as the structure of the male first gonopod. Arachnothelphusaterrapes is confirmed to be a phytotelm species. A key to all species in the conservation area is provided.

A new species of trogloplacine crab of the genus Australocarcinus Davie, 1988 from a freshwater stream in Mahé, Seychelles (Crustacea, Brachyura, Chasmocarcinidae)

A new species of freshwater chasmocarcinid crab, Australocarcinusinsperatussp. n., is described from the Seychelles Islands in the Indian Ocean. This is the first record of the genus and the subfamily Trogloplacinae Guinot, 1986, from the Indian Ocean, with all other members previously recorded from Australia, New Britain, New Caledonia, and Palau in the Pacific Ocean. The disjunct distribution of Australocarcinus is unexpected considering all trogoplacines are believed to practice direct development, lacking free-swimming larval stages. The new species is morphologically most similar to A.riparius Davie, 1988, from Queensland, Australia, but can be distinguished from its three congeners on the basis of the structures of its carapace, ambulatory legs and male first gonopod.

Tubuca alcocki, a new pseudocryptic species of fiddler crab from the Indian Ocean, sister to the southeastern African T. urvillei (H. Milne Edwards, 1852) (Crustacea, Decapoda, Brachyura, Ocypodidae)

A new pseudocryptic species of fiddler crab, Tubuca alcockisp. n., is described from the northern Indian Ocean. The new species was previously identified with T. urvillei (H. Milne Edwards, 1852), but can be distinguished by the structures of the anterolateral angle of the carapace and male first gonopod. The molecular data of the mitochondrial cytochrome oxidase subunit I gene shows that both are sister taxa and the divergence time is estimated at 2.2 million years ago, around the beginning of the Pleistocene. While the new species is widely distributed in the northern part of Indian Ocean, occurring from the Red Sea to India and the Andaman Sea; T. urvillei sensu stricto has a more restricted range, and is known only from southeastern Africa.

Redescription of Parilia alcocki Wood-Mason, in Wood-Mason Alcock, 1891 (Decapoda, Brachyura, Leucosiidae) from southeast India

Parilia alcocki Wood-Mason, in Wood-Mason Alcock, 1891, the type species of Parilia Wood-Mason, in Wood-Mason Alcock, 1891, described from the Bay of Bengal, is one of the largest known leucosioid crabs, reaching carapace widths of over 50 mm. It is, however, not well known and its male gonopods have never been figured. A series of specimens of this species obtained from a fishing port in Tamil Nadu, India, allows for a comprehensive re-description and illustrations of the species. Its distinguishing characters from congeners are discussed.

Further polyphyly of pinnotheroid crabs: the molecular phylogenetic position of the polychaete-associated Aphanodactylidae

Pea crabs of the superfamily Pinnotheroidea De Haan, 1833 are known for their obligate commensal relationships with other marine invertebrates. The concomitant specialisations and adaptations of pinnotheroids have resulted in superficially similar body forms that include a high degree of structural reduction. This has confounded interpretation of their phylogenetic position in the Brachyura and interrelationships within Pinnotheroidea, though all were nevertheless believed to be united by a monophyletic origin of obligate commensalism. The family Aphanodactylidae Ahyong & Ng, 2009 was proposed for a group of genera associated with tube-dwelling polychaetes formerly classified in Pinnotheridae, and provisionally retained in the Pinnotheroidea. We investigated the phylogenetic position of Aphanodactylidae using molecular data from three markers (mitochondrial 12S and 16S rRNAs, and nuclear histone H3) covering five of the 12 described aphanodactylid species and a total of 15 thoracotreme families. We found Aphanodactylidae to be monophyletic, but widely distant from Pinnotheridae and instead most closely related to Macrophthalmidae (Ocypodoidea) and Varunidae (Grapsoidea). Therefore, the family Aphanodactylidae is corroborated, but its placement in Pinnotheroidea is rejected. Instead, the phylogenetic position of Aphanodactylidae, as clearly distant from other pinnotheroids, demonstrates that obligate commensalism has evolved independently multiple times within Thoracotremata.

A new species of freshwater crab of the genus <i>Oziotelphusa</i> Müller, 1887 (Crustacea: Decapoda: Brachyura: Gecarcinucidae) from Tamil Nadu, southern India

A new species of gecarcinucid freshwater crab of the genus Oziotelphusa Müller, 1887, is described from stationary or slow-flowing bodies of water in Keeriparai near Nagercoil, in the state of Tamil Nadu in southern India. Oziotelphusa ravi, new species, is distinguished from its congeners by several distinct characters: the median tooth of the posterior margin of epistome forms a distinct bilobed tip in frontal view, the male pleonal somite 6 is narrowly trapezoidal and slightly wider than long with the lateral margins concave, the terminal segment of the male first gonopod is distinctly bent laterally (along the longitudinal axis) at an angle of about 45°, and the proximal part of the outer margin of the subterminal segment of the male first gonopod has a prominent deep concavity.

A new large oregoniid spider crab of the genus Pleistacantha Miers, 1879, from the Bay of Bengal, India (Crustacea, Brachyura, Majoidea)

A new species of deep-water oregoniid spider crab of the genus Pleistacantha Miers, 1879, is described from the Indian Ocean. The species is distinct in possessing a prominently inflated carapace in which the median parts of the branchial regions almost meet. It can also be distinguished from its closest congeners, P.moseleyi (Miers, 1885), P.pungens (Wood-Mason, in Wood-Mason & Alcock, 1891), and P.ori Ahyong & Ng, 2007, in its more elongate and less spinose chelipeds and ambulatory legs, shorter third maxilliped, trapezoidal male pleon and a male first gonopod which is relatively stout with a short subdistal dorsal papilla.

Notes on two crabs (Crustacea, Brachyura, Dynomenidae and Iphiculidae) collected from red coral beds in northern Taiwan, including a new species of Pariphiculus Alcock, 1896

Two brachyuran species of the families Dynonemidae and Iphiculidae are reported from red coral beds in northern Taiwan. The dynonemid Acanthodromiamargarita (Alcock, 1899) has hitherto been reported from the Andaman Sea, Japan, and Philippines and the species is here recorded for the first time from Taiwan. A new species of iphiculid, Pariphiculusstellatussp. n., is also described. The new Pariphiculus, which also occurs in the Philippines, is superficially similar to P.agariciferus Ihle, 1918, a species known from Indonesia, Japan, Philippines, South China Sea, Taiwan, and Vanuatu, but can be distinguished by distinct carapace, pleonal and male first gonopod features.

Salangathelphusa peractio, a new species of lowland freshwater crab from Pulau Langkawi, Peninsular Malaysia (Crustacea, Brachyura, Gecarcinucidae)

A new species of lowland freshwater crab of the family Gecarcinucidae, Salangathelphusaperactio, is described from Langkawi, an island off the northwestern coast of peninsular Malaysia. Salangathelphusaperactiosp. n. can be separated from S.brevicarinata (Hilgendorf, 1882) in having a proportionately broader external orbital tooth, a distinctly concave posterolateral margin, and the terminal segment of the male first gonopod is not distinctly bent laterally outwards; and from S.anophrys (Kemp, 1923) by its more quadrate carapace and the terminal segment of the male first gonopod possessing a relatively longer and less curved distal part. This is sixth wholly freshwater brachyuran species known from the island.

On the taxonomy of two poorly known species of <i>Geosesarma</i> De Man, 1892 (Crustacea: Brachyura: Sesarmidae) from the Philippines

The identities of two poorly-known species of semiterrestrial crabs of the genus Geosesarma De Man, 1892, from the Philippines, are clarified. The types of Sesarma (Sesarma) vicentense Rathbun, 1914 (from Luzon), and Sesarma (Geosesarma) rathbunae Serène, 1968 (from Panay), are examined and both species are rediagnosed with detailed figures. Comparisons with allied congeners are also provided.

A new genus and new species of Potamidea (Crustacea: Decapoda: Brachyura: Potamoidae), the first stygomorphic cave crab known from China and East Asia

A new genus and species of freshwater crab, Diyutamon cereum n. gen., n. sp., is described from a cave in Guizhou, China. This is the first record of a true stygomorphic crab from China and East Asia, possessing pale body coloration, strongly reduced eyes, and long ambulatory legs. While superficially similar to Chinapotamon Dai & Naiyanetr, 1994, and Tiwaripotamon Bott, 1970, the new genus possesses a diagnostic combination of carapace, ambulatory leg, thoracic sternal, and male abdominal characters that easily distinguishes it from other genera. Molecular data derived from the mitochondrial 16S rDNA supports the establishment of the new genus.

The systematics of land crabs of the genus Gecarcoidea and recognition of a pseudocryptic species, G. humei, from the eastern Indian Ocean (Crustacea : Decapoda : Gecarcinidae)

The gecarcinid genus Gecarcoidea H. Milne Edwards, 1837 is currently represented by two species from the Indo-West Pacific – the widely distributed purple land crab, G. lalandii H. Milne Edwards, 1837, and the red crab endemic to Christmas Island, G. natalis (Pocock, 1889). One species, G. humei (Wood-Mason, 1874), described from the Nicobar Islands, has had a confused taxonomic history, but was treated as a junior synonym of G. lalandii by Türkay (1974) in his revision of the family. In this study, using molecular as well as morphological characters, we show that G. humei is a valid species. Gecarcoidea lalandii and G. humei have distinct non-overlapping distributions throughout much of their range, with G. lalandii occurring in most of South-east Asia and the West Pacific, while G. humei is known only from the eastern Indian Ocean. On Christmas Island, in the eastern Indian Ocean, however, all three species are present. As a result, Christmas Island is the only locality where all extant species of Gecarcoidea are found. The three species can also be separated by differences in live colours and patterns, as well as proportions of the carapace, male abdomen, ambulatory legs and third maxillipeds, and details of the orbits and male first gonopods.

A new species of long-legged terrestrial <i>Terrapotamon</i> Ng, 1986 (Crustacea: Brachyura: Potamidae) from limestone formations in Satun, southern Thailand

A new species of terrestrial potamid crab, Terrapotamon longitarsus, is described from limestone hills in Satun Province in southern Thailand. It is easily distinguished from other Terrapotamon species by its conspicuously long ambulatory legs (all congeners have proportionately short legs), relatively smooth dorsal surface of carapace, transversely narrow male thoracic sternites 1-4, and a characteristically structured male first gonopod.

A new species of pea crab of the genus Serenotheres Ahyong & Ng, 2005 (Crustacea, Brachyura, Pinnotheridae) from the date mussel Leiosolenus Carpenter, 1857 (Mollusca, Bivalvia, Mytilidae, Lithophaginae) from the Solomon Islands

The pea crab genus Serenotheres Ahyong & Ng, 2005 (Pinnotheridae) is currently only represented by one species, Serenotheresbesutensis (Serène, 1967). A new species is now assigned to this genus, described from a date mussel Leiosolenusobesus Carpenter, 1857 (Mollusca: Bivalvia: Mytilidae: Lithophaginae) collected in the Solomon Islands. Serenotheresjanussp. n. differs from Serenotheresbesutensis in possessing a conspicuously broader carapace, with the lateral margins of the dorsal lamellum distinctly produced and the posterolateral part deeply concave, the dorsal lamellum being highest at the median cleft, the rostrum is relatively more prominent, the surfaces of the anterolateral margin and hepatic region are less prominently pitted and eroded, the ischiomerus of the third maxilliped is relatively more rectangular, and the P2 merus is proportionately longer.

Revision of the spider crab genus Sargassocarcinus Ward, 1936 (Crustacea: Brachyura: Epialtidae)

The Western Pacific epialtid genus Sargassocarcinus Ward, 1936, is revised. The genus had been regarded as monotypic but is here shown to contain three species: S. sublimis (Rathbun, 1916), S. cristatus (Balss, 1924), and S. foliatus Ward, 1936 (type species). The many unusual characters possessed by Sargassocarcinus are figured and discussed; and diagnostic features of the three species are clarified. The taxonomy of the three species and aspects of their ecology are discussed. Sargassocarcinus species are found free-living on coral rubble habitats and not associated with macrophytic algae.

The taxonomy of Speodromia platyarthrodes (Stebbing, 1905) (Crustacea: Brachyura), an unusual dromiid crab endemic to South Africa

The poorly known dromiid crab Speodromia platyarthrodes (Stebbing, 1905), endemic to South Africa, is redescribed and figured. Speodromia is unique among dromiids in possessing a large cavity on the anterior part of the sub-branchial region, which is believed to be associated with respiration. The systematics of the genus is discussed and is confirmed to be a member of Dromiinae De Haan, 1833, s. str.