Lepidothelphusa menneri n. sp. (Crustacea: Brachyura: Gecarcinucidae), first record of the genus from Kalimantan, Indonesia.

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.

Diversification of freshwater crabs on the sky islands in the Hengduan Mountains Region, China.

The numerous naturally-fragmented sky islands (SIs) in the Hengduan Mountains Region (HMR) of southwestern China constitute discontinuous landscapes where montane habitats are isolated by dry-hot valleys which have fostered exceptional species diversification and endemicity. However, studies documenting the crucial role of SI on the speciation dynamics of native freshwater organisms are scarce. Here we used a novel set of comprehensive genetic markers (24 nuclear DNA sequences and complete mitogenomes), morphological characters, and biogeographical information to reveal the evolutionary history and speciation mechanisms of a group of small-bodied montane potamids in the genus Tenuipotamon. Our results provide a robustly supported phylogeny, and suggest that the vicariance events of these montane crabs correlate well with the emergence of SIs due to the uplift of the HMR during the Late Oligocene. Furthermore, ancestrally, mountain ridges provided corridors for the dispersal of these montane crabs that led to the colonization of moist montane-specific habitats, aided by past climatic conditions that were the crucial determinants of their evolutionary history. The present results illustrated that the mechanisms isolating SIs are reinforced by the harsh-dry isolating climatic features of dry-hot valleys separating SIs and continue to affect local diversification. This offers insights into the causes of the high biodiversity and endemism shown by the freshwater crabs of the HMR-SIs in southwestern China.

Two centuries of biodiversity discovery and loss in Singapore.

There is an urgent need for reliable data on the impacts of deforestation on tropical biodiversity. The city-state of Singapore has one of the most detailed biodiversity records in the tropics, dating back to the turn of the 19th century. In 1819, Singapore was almost entirely covered in primary forest, but this has since been largely cleared. We compiled more than 200 y of records for 10 major taxonomic groups in Singapore (>50,000 individual records; >3,000 species), and we estimated extinction rates using recently developed and novel statistical models that account for "dark extinctions," i.e., extinctions of undiscovered species. The estimated overall extinction rate was 37% (95% CI [31 to 42%]). Extrapolating our Singapore observations to a future business-as-usual deforestation scenario for Southeast Asia suggests that 18% (95% CI [16 to 22%]) of species will be lost regionally by 2100. Our extinction estimates for Singapore and Southeast Asia are a factor of two lower than previous estimates that also attempted to account for dark extinctions. However, we caution that particular groups such as large mammals, forest-dependent birds, orchids, and butterflies are disproportionately vulnerable.

Convergent adaptation of true crabs (Decapoda: Brachyura) to a gradient of terrestrial environments.

For much of terrestrial biodiversity, the evolutionary pathways of adaptation from marine ancestors are poorly understood, and have usually been viewed as a binary trait. True crabs, the decapod crustacean infraorder Brachyura, comprise over 7,600 species representing a striking diversity of morphology and ecology, including repeated adaptation to non-marine habitats. Here, we reconstruct the evolutionary history of Brachyura using new and published sequences of 10 genes for 344 tips spanning 88 of 109 brachyuran families. Using 36 newly vetted fossil calibrations, we infer that brachyurans most likely diverged in the Triassic, with family-level splits in the late Cretaceous and early Paleogene. By contrast, the root age is underestimated with automated sampling of 328 fossil occurrences explicitly incorporated into the tree prior, suggesting such models are a poor fit under heterogeneous fossil preservation. We apply recently defined trait-by-environment associations to classify a gradient of transitions from marine to terrestrial lifestyles. We estimate that crabs left the marine environment at least seven and up to 17 times convergently, and returned to the sea from non-marine environments at least twice. Although the most highly terrestrial- and many freshwater-adapted crabs are concentrated in Thoracotremata, Bayesian threshold models of ancestral state reconstruction fail to identify shifts to higher terrestrial grades due to the degree of underlying change required. Lineages throughout our tree inhabit intertidal and marginal marine environments, corroborating the inference that the early stages of terrestrial adaptation have a lower threshold to evolve. Our framework and extensive new fossil and natural history datasets will enable future comparisons of non-marine adaptation at the morphological and molecular level. Crabs provide an important window into the early processes of adaptation to novel environments, and different degrees of evolutionary constraint that might help predict these pathways.

Shift in symbiotic lifestyle as the major process shaping the evolution of pea crabs (Decapoda: Brachyura: Pinnotheroidea).

The pea crabs, superfamily Pinnotheroidea, are exceptional among brachyuran crabs in their diverse symbiotic associations involving both inquilinism and protective symbiosis. While this group presents a rare opportunity for evolutionary comparative study of host switching and morphological evolution in marine macroinvertebrates, previous phylogenetic studies have been focused on systematics. Here, we reconstructed the most extensive phylogeny of Pinnotheroidea based on two mitochondrial and six nuclear markers, with the aim of elucidating the host switching pathways and the correlation between symbiotic lifestyles and selected morphological adaptations. Ancestral state reconstruction of host association revealed a monophyletic origin of symbiosis in the form of inquilinism. Subsequent shifts in microhabitat preference for burrows or worm tubes, and the move to protective symbiosis, primarily in the switch to mollusc endosymbiosis, contributed to radiation in Pinnotheridae. Further parallel colonisations of echinoderms and tunicates occurred but did not lead to extensive diversification, except in the Clypeasterophilus + Dissodactylus lineage, which experienced a unique switch to echinoderm ectosymbiosis. The evolution of the third maxillipeds, carapace shape and ambulatory pereiopods suggests a rather strong coupling with the symbiotic lifestyle (whether inquilinism or protective symbiosis). Phenotypic diversity of these characters was higher among species engaged in protective symbiosis, with convergence in form (or function) among those sharing the same host affiliation. Species having different host affiliations or symbiotic lifestyles might also exhibit convergence in the form of the three morphological traits, suggesting a common adaptive value of the specialisations. Pinnotherid crabs overall exhibited a lower trait diversity than the also symbiotic palaemonid shrimps with comparable species diversity. This may plausibly be attributed to differences in potential for morphological modification to serve additional functions among the traits analysed in the two groups, the less frequent host switching and the less diverse host affiliations, and thus a less complicated evolutionary history in pinnotherids.

Revision of the Genus Lacunipotamon Dai, Song, He, Cao, Xu & Zhong, 1975 (Crustacea: Decapoda: Brachyura: Potamidae), with Descriptions of Eight New Species from Vietnam.

The taxonomy of the potamid genus Lacunipotamon Dai, Song, He, Cao, Xu & Zhong, 1975, is revised. Three species are known from southern China: L. albusorbitum Dai, Song, He, Cao, Xu & Zhong, 1975 (type species); L. yuanshi Huang, Shih & Ahyong, 2020; and L. cymatile Huang, Shih & Ahyong, 2020. Eight new species are here described from northern Vietnam: L. globus, L. panda, L. contrastum, L. sublividum, L. mimicum, L. thuanchau, L. pectum and L. purpureum. This is the first record of the genus in Vietnam, with all the new species obtained from karst formations. The species are differentiated by the characters of carapace shape, anterolateral armature, posterior margin of the epistome, male sternopleonal cavity, chelipeds, ambulatory legs, male thoracic sternum, male pleon, and structures of the male first gonopods and vulvae.

On the identities of the sesarmid crabs, Sesarma villosum A. Milne-Edwards, 1869, and Clistocoeloma suvaense Edmondson, 1951, with the description of a new species from the West Pacific (Decapoda, Brachyura, Thoracotremata).

The identities of two sesarmid crabs, Clistocoeloma villosum (A. Milne-Edwards, 1869), and C. suvaense Edmondson, 1951, both currently in Clistocoeloma A. Milne-Edwards, 1873, are poorly known and the types have not been studied in detail since their description. Clistocoeloma villosum, supposedly widespread, has been recorded from Madagascar and East Africa to Singapore, Japan, Korea, and Samoa. Clistocoeloma suvaense is only known for certain from one male collected from its type locality, Fiji. The taxonomy of C. villosum, and C. suvaense is clarified on the basis of the type specimens from Samoa and Fiji, respectively. A new species, which has long been confused with C. villosum, is described from Southeast Asia and Western Pacific.

New and rare deep-sea majoid crabs (Crustacea: Brachyura) from Papua New Guinea.

Additional spider crab (superfamily Majoidea) material from four major French-led expeditions to the Papua New Guinea region were examined in this study. One new genus and four new species from the families Inachidae and Oregoniidae are described. Dorhynchus profundus n. sp. is close to D. rostratus (Sakai, 1932) but can easily be separated by the shape of the ambulatory dactylus and the proportionately lower protogastric spines. Achaeus pholcus n. sp. is unusual in that it occurs in deeper waters (beyond 500 m), and can be separated from A. lacertosus Stimpson, 1857, A. villosus Rathbun, 1916, and A. brevidactylus Sakai, 1938, by its distinctive carapace shape, structure of the frontal margin, regions of the carapace, antennular fossa, ambulatory dactylus, male pleon, and proportions of the chela. Parapleisticantha aie n. sp. is closest to P. japonica Yokoya, 1933, but differs in its proportionately longer carapace, more elongated basal antennal article, longer third maxilliped ischium and the relatively less curved male first gonopod with the distal part differently structured. A new genus (Orbicantha n. gen.) with one new species (Orbicantha sacrebleu n. gen., n. sp.) is also described; it is allied to Pleistacantha Miers, 1879, Parapleisticantha Yokoya 1933, and Pleisticanthoides Yokoya, 1933, but is distinctive in its subcircular carapace, shorter regions, short pseudorostral spines, possession of spines on the gastric, cardiac and branchial regions, some of which have rounded tips, a short ocular peduncle, a very short third antennal article, a quadrate epistome, and the more reduced P4 and P5. New records from the family Epialtidae are also reported: Griffinia gilloloensis (Rathbun, 1916), Hyastenus borradailei (Rathbun, 1907), and Oxypleurodon luzonicum (Rathbun, 1916). The taxonomy of Grypachaeus tenuicollis Takeda, 1978 (Oregoniidae) and Griffinia lappacea (Rathbun, 1918) (Epialtidae) is also discussed.

On the identity of Pronotonyx laevis (Miers, 1884) (Crustacea: Brachyura: Pilumnidae).

The poorly known brachyuran crab, Pronotonyx laevis Ward, 1936, from northern Australia, is redescribed based on type and other material. We document adults of both sexes and confirm the taxonomic placement of the Pronotonyx in the Pilumnidae. Pronotonyx is most similar to the Australian Pseudocryptocoeloma parvum Ward, 1936, differing in features of the carapace and pereopods.

Two new species of semiaquatic freshwater crabs of the genera Tortomon and Aiyunamon from karst forests in northern Vietnam (Crustacea: Brachyura: Potamidae).

Two new genera of freshwater crabs (Potamidae) are recorded from northern Vietnam, Tortomon Huang, Wang & Shih, 2020, and Aiyunamon Pan, Ng & Sun, 2022. These genera had previously only been reported from southern China and eastern Myanmar. Each genus is represented by a new species. Tortomon distinctum n. sp. is markedly different from its two Chinese congeners in its proportionately wider carapace, more elongate third maxilliped, the carpus of the cheliped being armed only with a low tubercle, possessing relatively more slender and longer ambulatory legs, a gently curved male first gonopod and a more elongate male second gonopod. Aiyunamon vietnamicum n. sp. is distinct from its five congeners in its proportionately less convex dorsal surface of the carapace, relatively lower epigastric cristae, lower rugosities of the postorbital cristae, wider median lobe of the posterior margin of the epistome, relatively narrower male pleon, and a male first gonopod that has the terminal segment more distinctly curved with a wider concavity on the outer margin of the subterminal segment.

Two new species of hairy crabs (Pilumnidae) and the first record of Crinitocinus alcocki (Borradaile, 1900) (Acidopsidae) (Crustacea: Brachyura) from Taiwan.

Two new species of pilumnid crabs, Heteropilumnus planus n. sp. and Pseudolitochira taiwang n. sp., are described from reefs in Taiwan. Heteropilumnus planus n. sp. is most similar to H. hirsutior (Lanchester, 1900) from Singapore and Japan, but can easily be distinguished by its distinctly flatter carapace, different anterolateral carapace armature, longer ambulatory legs, and male first gonopod structure. Pseudolitochira taiwang n. sp. is most similar to P. crinita Ng & Clark, 2022, from Papua New Guinea but can easily be separated by its carapace physiognomy, armature of the anterolateral carapace margin and proportionately shorter ambulatory legs. Heteropilumnus setosus (A. Milne-Edwards, 1873) is also transferred to Pseudolitochira; and compared with P. taiwang n. sp. The rarely reported acidopsid, Crinitocinus alcocki (Borradaile, 1900) is also recorded from Taiwan for the first time, substantially extending its known range northwards.

Tuerkayana latens, a New Species of Land Crab from French Polynesia, with a Discussion on the Phylogeny of the Genus (Crustacea: Decapoda: Brachyura: Gecarcinidae).

The taxonomy of the gecarcinid land crab Tuerkayana rotundum (Quoy & Gaimard, 1824) is revised. The taxon, the type species of the genus, occurs from the western Indian Ocean to the western Pacific, and varies substantially in colour and various morphological features, but the male first gonopod structure is constant and the extensive genetic data from mitochondrial 16S rDNA, cytochrome c oxidase subunit 1 and control region markers confirms the recognition of one wide-ranging species. Specimens from Tuamotu in French Polynesia and Pitcairn Island, however, differ in having a smoother and slightly more swollen carapace, and significantly, the male first gonopod structure is distinctly different. The genetic data also supports their differentiation. As such, this material is here recognised as a new species, Tuerkayana latens n. sp.

Review of the pilumnid crab genus Lophoplax Tesch, 1918 from the western Pacific, with descriptions of two new species, and the clarification of the identity of Pseudocryptocoeloma parvus Ward, 1936 (Crustacea: Brachyura).

The taxonomy of the pilumnid crab genus Lophoplax Tesch, 1918, is discussed. Lophoplax sculpta Stimpson, 1858) is redescribed and a neotype is selected in the interests of nomenclatural stability. Two new species allied to L. sculpta are described: L. sordida n. sp. from Indonesia, and L. pannosa n. sp. from Vanuatu. Pilumnus vermiculatus A. Milne-Edwards, 1873, is here transferred to Lophoplax. The poorly known Pseudocryptocoeloma parvus Ward, 1936 (type species of Pseudocryptocoeloma Ward, 1936), known only from Australia thus far, is redescribed and figured; and Pseudocryptocoeloma symmetrinudum Edmondson, 1951 (from Samoa and Japan), is transferred to Lophoplax.

Allopatric mosaics in the Indo-West Pacific crab subfamily Chlorodiellinae reveal correlated patterns of sympatry, genetic divergence, and genitalic disparity.

Molecular studies have revealed that many species once thought to be wide-ranging in the Indo-West Pacific contain allopatric mosaics of endemic lineages. These lineages provide compelling evidence that substantial time is needed to evolve isolating mechanisms sufficient to permit successful secondary sympatry, and that divergence is initiated in allopatry. In this context, questions arise regarding the nature, timing, and origin of isolating mechanisms that permit secondary sympatry. We present a phylogeny of the crab subfamily Chlorodiellinae which displays allopatric mosaics within species. These allopatric lineages typically do not have divergent male genitalia, while older sympatric lineages do. We tested the relationship between genetic distance (proxy for time), sympatry, and the divergence of male genitalic morphology. Our results suggest that male genitalic divergence is not involved in the initiation of speciation in chlorodielline crabs, having likely occurred only after isolation began in allopatry. However, morphological evolution of genitalia seemingly does play an important role in completing the process of speciation in these crabs.

Stoliczia setoiyenica, a new species of freshwater crab from southern Thailand (Crustacea: Decapoda: Brachyura: Potamidae).

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.

On the correct lectotype for Marmessoidea unicolor Redtenbacher, 1908 (Insecta: Phasmatodea).

Hennemann, F.H., Conle, O.V. & Brock, P.D. (2023) The types of Phasmatodea (= Phasmida) deposited in the Eidgenssisches Technisches Hochschulzentrum, Zrich, Switzerland (ETHZ). Zootaxa, 5278 (1), 176188. https://doi.org/10.11646/zootaxa.5278.1.10 Hovinga, H. (2010) The Sumatra Railroad: Final destination Pakan Baroe, 19431945. Brill, Leiden, 391 pp. https://doi.org/10.1163/9789004253711 ICZN [International Commission on Zoological Nomenclature] (1999) International Code of Zoological Nomenclature. International Commission of Zoological Nomenclature. 4th Edition. Adopted by the XXI General Assembly of the International Union of Biological Sciences. International Trust for Zoological Nomenclature, in association with the British Museum (Natural History), London, 338 pp. Redtenbacher, J. (1908) Die Insektenfamilie der Phasmiden. III. Phasmidae Anareolatae (Phibalosomini, Acrophyllini, Necrosciini). Wilhelm Engelmann, Leipzig, pp. 341589, pls. 1627. Seow-Choen, F. (2021) A Taxonomic Guide to Stick Insects of Peninsular Malaysia. Vol. 1. Natural History Publications, Borneo, Kota Kinabalu, 944 pp. Weidmann, W. (1936) Der Schweizer als Pionier und Kolonist in Sumatra. In: Der Schweizer Verein Deli-Sumatra (Ed.), Der Schweizer Verein Deli-Sumatra: Zum fnfzigjhrigen Bestehen, 18861936. Buchdruckerei der Neuen Zrcher Zeitung, Zrich, pp. 3348.

On the systematic placement of the fossil crab Lathahypossia aculeata (Busulini, Tessier & Visentin, 1984) (Crustacea: Decapoda: Brachyura).

The systematic placement of the iconic fossil crab, Lathahypossia aculeata (Busulini, Tessier & Visentin, 1984) (formerly in Titanocarcinus A. Milne-Edwards, 1864), from the Eocene of Italy is revised. The examination of two specimens that had the ventral and subcephalic features well preserved has allowed us to better understand the morphology of this species. As a result, Lathahypossia aculeata must be removed from the Hypothalassiidae (Eriphioidea), where it is now placed, and moved to the Xanthidae (Xanthoidea). The present work again highlights the importance of ventral characters in the study of fossil crabs and allows a more accurate systematic classification.

New Genus and Two New Species of Semiterrestrial Crabs (Decapoda: Brachyura: Gecarcinucidae) from the Southern Western Ghats, India.

One new genus and two new species of semiterrestrial freshwater crabs are described from the Southern Western Ghats mountain range in India: Pavizham gavi gen., sp. nov. and Rajathelphusa brunnea sp. nov. The carapace of Pavizham n. gen. is superficially similar to Baratha and Snaha described from the same region, but it can be distinguished from Baratha in having no visible postorbital cristae, complete sutures between male thoracic sternites 2 and 3, the possession of a triangular male pleon and the elongate terminal segment of the male first gonopod; and from Snaha by the presence of a long flagellum on the exopod of the third maxilliped, a complete suture separating male thoracic sternites 2 and 3, and its triangular male pleon. Rajathelphusa brunnea sp. nov. can easily be distinguished from congeners in possessing a distinctly more slender and elongate male first gonopod.

Establishment of A New Bornean Genus of Gecarcinucidae (Crustacea: Brachyura), with Descriptions of Five New Species.

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.

Geosesarma garutense n. sp., a new species of vampire crab (Crustacea, Brachyura, Sesarmidae) from Garut in western Java.

A new species of vampire crab, Geosesarma garutense n. sp. is described from Garut in the eastern part of West Java, Indonesia. The species is unusual among congeners in Java in that the exopod of the third maxilliped does not possess a flagellum, the carapace is broadly rectangular in shape and the G1 relatively is short and stout, with the chitinous distal part spatuliform.