A small brachyuran crab, Archaeochiapasa mardoqueoi n. gen., n. sp., is reported from the lower Cenomanian (Upper Cretaceous) of the Sierra Madre Formation at El Chango Lagerstätte, Chiapas State, ...southeastern Mexico. Although it is decorticated and only the counterpart keeps a large part of the cuticle, the single male specimen exhibits an exceptional three-dimensional preservation that allows its description to be based not only on the dorsal carapace, both chelipeds and most walking legs, but also on remarkably conserved ventral structures: mxp3, thoracic sternum, and pleon. Archaeochiapasa mardoqueoi n. gen., n. sp. provides a morphological combination that does not conform to any previously known fossil brachyuran and furthermore to any extant family. The high number of major differential characters suggest that Archaeochiapasa n. gen. must be included in the Eubrachyura Saint Laurent, 1980. A series of apomorphies supports the erection of a new family for which we introduce the new name Archaeochiapasidae n. fam. This fortunate discovery allows us to identify one of the earliest eubrachyurans with unique features, namely a very wide thoracic sternum displaying an unexpected structure for a lower Cenomanian representative, and a depressed, rimmed area (‘flange’) along the carapace postero- and postero-lateral margin. The new family is compared to the other fossil Eubrachyura known from the Early and mid-Cretaceous, which are very scarce and often incomplete, and to the more basal heterotreme Recent clades that are presently recognised on the basis of morphological, larval, spermatozoal and genetic data, e.g. the Dorippoidea MacLeay, 1838, and to the basal families of Majoidea Samouelle, 1819 (Oregoniidae Garth, 1958, Inachoididae Dana, 1851, and Inachidae MacLeay, 1838). A challenging hypothesis based on new interpretations is that the Late Jurassic Lecythocaridae Schweitzer & Feldmann, 2009 (in Glaessneropsoidea Patrulius, 1959), only known by dorsal carapaces and formerly included in the Dromiacea De Haan, 1833, could be related, with still obscure relationships, to the same lineage as the Archaeochiapasidae n. fam. The two families actually show striking similarities, such as the overall morphology of carapace, a depressed area along the carapace posterior margin, and a bifurcate short rostrum. Therefore, we assume that, despite their Jurassic age, Lecythocaridae may well also be Eubrachyura, which brings the first “true crabs” or eubrachyurans (i.e., non-podotreme crabs) back to the Jurassic, contrary to the current opinions of paleontologists. The discovery of Archaeochiapasidae n. fam. raises a crucial question: the development of a very wide thoracic sternum in this old eubrachyuran. Is it the expression of an ancestral dispostion (plesiomorphy) or the result of an already existing evolutionary process of carcinisation (apomorphy)? And what is its phylogenetic significance?
A new family Leptograpsodidae n. fam. is erected to include an unusual genus of grapsoid crabs, LeptograpsodesMontgomery, 1931, represented by a burrowing species from South Australia L. octodentatus ...(H. Milne Edwards, 1837), with setal pouches on the coxae of pereiopods 2 to 4 that are evidence of a high degree of terrestrial adaptation. With nearly 600 extant species, the superfamily Grapsoidea MacLeay, 1838 encompasses a diverse range of morphologies and ecologies. Genetic data question its monophyly, whereas the inter- and intrarelationships of included taxa have not been recently examined through a morphological review using a reliable complex of characters (primarily, proepistome, thoracic sternum, male pleon, male genital region, male gonopore, and penis). The reevalution of the morphological characters of L. octodentatus in order to reappraise its proper taxonomical status has afforded us the opportunity to review most of grapsoids and, in particular, the Gecarcinidae H. Milne Edwards, 1837 (see Appendix), Grapsidae MacLeay, 1838, Varunidae H. Milne Edwards, 1853 (especially Cyclograpsus H. Milne Edwards, 1837), and Xenograpsidae N. K. Ng, Davie, Schubart & Ng, 2007. The discovery that Leptograpsodes shares some characters with Gecarcinidae, especially a stridulatory apparatus similar to that of Discoplax A. Milne-Edwards, 1867, a feature not previously recorded in either genus, has revealed the need to re-examine the taxonomy of Gecarcinidae. This resulted in an unexpected outcome. Discoplax must be restricted to its three troglobitic species: D. longipes A. Milne-Edwards, 1867 (type species), D. gracilipesNg & Guinot, 2001, and D. michalisNg & Shih, 2015. Cardisoma Latreille, 1828 sensu stricto only accommodates C. guanhumi Latreille, in Latreille, Le Peletier, Serville & Guérin, 1828 (type species), C. armatum Herklots, 1861, C. carnifex (Herbst, 1796), and C. crassum Smith, 1870. A new genus, Tuerkayana n. gen. is hereby established to include two species previously assigned to Cardisoma: T. rotundum (Quoy & Gaimard, 1824) n. comb. (type species), T. hirtipes (Dana, 1851) n. comb., plus two others previously regarded as Discoplax: T. celeste (Ng & Davie, 2012) n. comb. and T. magnum (Ng & Shih, 2014) n. comb. Compared to Varunidae, Leptograpsodes bears a superficial resemblance to Cyclograpsus H. Milne Edwards, 1837, a paraphyletic genus that must be restricted to its type species C. punctatus H. Milne Edwards, 1837 and only its closest congeners. The validity of the subfamilial taxon Heliceinae Sakai, Türkay & Yang, 2006 is recognised. The putative sister-group relationship of Leptograpsodes and Xenograpsus supported by molecular analyses of Schubart (2011) and Ip et al. (2015) is not confirmed by morphology, even if the two families share some traits. The synapomorphies of Leptograpsodes justify its separation from all grapsoid lineages as currently conceived. The use of previously overlooked traits, notably related to the thoracic sternum, proves to represent an optimal support for the brachyuran systematics and phylogeny, and presently to redefine the grapsoid taxonomical categories. The complete fusion of thoracic sternites 3 and 4 without any visible suture, even laterally, is proposed as a synapomorphy of Grapsoidea; this character state could be extented to other Thoracotremata in the future. Species of three genera Leptograpsodes, Discoplax and Epigrapsus are reported to exhibit stridulating structures (suborbital pars stridens and plectrum on inner margin of P1 merus). Some nomenclature issues, notably the authorship of the family-group name Gecarcinidae that is here credited to H. Milne Edwards, 1837, are addressed in the Appendix.
All Jurassic brachyuran taxa known to date are based solely upon dorsal carapaces, and only a limited number of Early and mid-Cretaceous crabs retain ventral parts. Therefore, all Jurassic taxa and ...many forms from the first half of the Cretaceous are carapace-based entities. All of them are considered to be “dromiaceans”, podotremes to be precise. The recent discovery of an exceptionally well-preserved male crab from the Upper Cretaceous (lower Cenomanian) of Chiapas (Mexico), Archaeochiapasa mardoqueoiGuinot, Carbot-Chanona & Vega, 2019, at first sight of a podotreme nature, has allowed a detailed description of its thoracic sternum and pleon, which revealed that it was actually a typical eubrachyuran, in need of a new family, Archaeochiapasidae Guinot, Carbot-Chanona & Vega, 2019. This has brought back to life one of my earlier ideas about the possible non-podotreme nature of certain enigmatic Late Jurassic and Cretaceous Brachyura previously placed in various “dromiacean” (i.e., podotreme) families and superfamilies. My investigations have led the me to formulate the present hypothesis that the extinct families Bucculentidae Schweitzer & Feldmann, 2009 (currently assigned to the Homolodromioidea Alcock, 1900), Lecythocaridae Schweitzer & Feldmann, 2009, Glaessneropsidae Schweitzer & Feldmann, 2009, Nodoprosopidae Schweitzer & Feldmann, 2009, and Viaiidae Artal, Van Bakel, Fraaije, Jagt & Klompmaker, 2012 (all four in Glaessneropsoidea Schweitzer & Feldmann, 2009) might, in fact (at least for some of them), be true eubrachyurans (Eubrachyura Saint Laurent, 1980). If correct, these assumptions would date the first “true crabs” as Jurassic, contrary to the currently held view that the earliest Eubrachyura (heterotremes) did not appear until the Cretaceous, and suggest that the evolutionary history of brachyurans started much earlier. This was unpredictable, at least for palaeontologists, but not so in view of a molecular estimate of decapod phylogeny that recovered the Majoidea Samouelle, 1819 as the oldest brachyuran lineage, with a divergence from other brachyurans from, at least, the Middle Triassic. The basal majoid family Oregoniidae Garth, 1958, which comprises only three extant genera, has several characters in common with Archaeochiapasidae; these leave little doubt about their close relationships. Proposals made here are inevitably based on provisional assumptions, until the characteristics of the ventral parts and pereiopods prove or refute them, either entirely or in part. Our science, which is based on the observation of specimens and then on descriptive, explanatory and, above all, predictive concepts, especially where incomplete fossil animals are concerned, should be conceived as a step forward, rather than an achievement, each of these steps being, sooner or later, replaced by a better one, or considered to be such. That is why all species and the composition of the Jurassic and Early Cretaceous genera and families will need to be checked in light of new perspectives. In contrast to the presumed eubrachyurans (see above), the Tanidromitidae Schweitzer & Feldmann, 2008 and the apparently paraphyletic family Longodromitidae Schweitzer & Feldmann, 2009 are podotremes, within the Dynomeniformia Guinot, Tavares & Castro, 2013. The status and composition of the Goniodromitinae Beurlen, 1932 (in the Dromiidae De Haan, 1833), clearly paraphyletic, are briefly revised, while some genera, such as DistefaniaChecchia-Rispoli, 1917, are tentatively assigned to the Sphaerodromiinae Guinot & Tavares, 2003. A table summarises the changes in classification implied by these new proposals and research directions. Some remarks on the new section Callichimaeroida Luque, Feldmann, Vernygora, Schweitzer, Cameron, Kerr, Vega, Duque, Strange, Palmer & Jaramillo, 2019 are provided, as well as on the the putatively callichimaeroid-like family Retrorsichelidae Feldmann, Tshudy & Thomson, 1993.
A new and revised classification of the small family Dorippidae H. Milne Edwards, 1837, which previously comprised two distinct subfamilies (Dorippinae H. Milne Edwards, 1837 and Ethusinae Guinot, ...1977), each of which was subsequently elevated to a familial rank supported by traditional data and genetic phylogenies, is presented on the basis of a morphological analysis involving a large number of characters. The family is in fact highly diverse, at all levels. Several features are described and depicted in detail here for the first time, e.g. the presence of a diversely developed strip along the protrudingly rimmed posterior margin of the carapace; on the dorsally exposed thoracic sternite 8, a process acting as an additional pleonal-retention mechanism in the females of three genera (DorippeWeber, 1795; Philippidorippe Chen, 1986; PhyllodorippeManning & Holthuis, 1981); a callosity at the base of the coxa of the third pereiopod, variously shaped, in two genera (Dorippe and DorippoidesSerène & Romimohtarto, 1969). The generic and specific taxonomy masterfully stabilised by Holthuis & Manning (1991) is undisputed and still valid, except for the composition of the genus Heikeopsis Ng, Guinot & Davie, 2008 that may well contain in northern China a form not entirely consistent with the typical Heikeopsis japonica (von Siebold, 1824) of Japan. A second exception concerns the genus ParadorippeSerène & Romimohtarto, 1969sensu Holthuis & Manning (1991) that may not be monophyletic. The validity of Medorippe crosnieriChen, 1988, questioned by Holthuis & Manning (1990), could not be confirmed here: its distinctive morphological characters from M. lanata (Linnaeus, 1767) suggest that it could be recognised one day. The synthesis of conventional and new characters allows the traditional taxonomic approach to be updated and modernised, more complete and robust diagnoses to be constructed, and groups of genera to be circumscribed. We propose a new subfamily classification whereby the family Dorippidae is recognised as monophyletic but with seven genera assigned to subfamily-level rank, leading to the recognition of seven distinct subfamilies: the Dorippinae H. Milne Edwards, 1837 n. stat. (Dorippe), Dorippoidinae n. subfam. (Dorippoides), Medorippinae n. subfam. (MedorippeManning & Holthuis, 1981), Heikeopsinae n. subfam. (Heikeopsis, NeodorippeSerène & Romimohtarto, 1969, NobilumSerène & Romimohtarto, 1969), Paradorippinae n. subfam. (Paradorippe), Philippidorippinae n. subfam. (Philippidorippe) and Phyllodorippinae n. subfam. (Phyllodorippe). There is a high degree of concordance between several elements of our proposal: 1) the main morphological patterns of the male gonopods lead to the recognition of seven subfamilies; 2) the main morphological patterns of the vulvae correspond to the seven observed gonopod types and lead to the recognition of the same seven subfamilies; 3) the recognition of several subfamilies is supported by the well-defined clades obtained by the molecular analyses; and 4) the female reproductive system, recently documented by histologists in most genera of Dorippidae, which differs from that of all other eubrachyurans studied so far, with an arrangement that undoubtedly represents a new type of organisation, unparalleled in the Brachyura Brünnich, 1772: it further shows unexpected diversity, with a degree of divergence similar to that of the gonopods and vulvae, in accordance with the subfamilies here recognised. A new interpretation of the two main grooves on the dorsal surface of the carapace is widely discussed. The authorship of the family-group name Dorippidae is here ascribed to H. Milne Edwards (1837). The study of Dorippidae is a particular example of how the integration of data from various fields, such as morphological and molecular phylogenetics, larval and post-larval features, behaviour and palaeontology, offers opportunities for reciprocal illumination. The early diversification of the family and its basal position among the Eubrachyura Saint Laurent, 1980 are supported not only by morphological traits but also by other characters, such as spermatozoal ultrastructure, carrying behaviour, forward locomotion and forward burying behaviour, all of which set the family apart from all other Eubrachyura. The substantial morphological variety of female reproductive systems within the Dorippidae, with the discovery in some species of external fertilisation sites, in contrast to the internal fertilisation that is assumed to define all eubrachyurans, challenges several previous ideas on the evolution of sperm storage in Eubrachyura and raises more questions than it answers. According to histologists, the arrangement of the Dorippidae suggests that the family could be sister to a clade including the Heterotremata Guinot, 1977 and the Thoracotremata Guinot, 1977. Two keys to the subfamilies, one based on gonopods and vulvae, the second based on other morphological characters, are provided. The taxonomy, including extant and fossil forms, is accompanied by justifications for the arrangement we propose. The Dorippidae proves to be a special lineage within the Eubrachyura: its diverse and unique features are discussed. The dorippids in legend and myth are the subject of Appendix 1. Fossil Dorippidae and Ethusidae Guinot, 1977 are reviewed, as well as the two extinct dorippoid families (Telamonocarcinidae Larghi, 2004; Tepexicarcinidae Luque, 2015), and also fossil families that were at one time considered to belong to the Dorippoidea, such as Goniochelidae Schweitzer & Feldmann, 2011 (see Appendix 2). Une nouvelle classification subfamiliale de la famille hautement diversifiée des Dorippidae H. Milne Edwards, 1837 (Crustacea, Decapoda, Brachyura, Dorippoidea), fondée sur des données morphologiques, moléculaires et paléontologiques, et plus particulièrement sur le système unique de reproduction chez les femelles. Une classification nouvelle et révisée de la petite famille des Dorippidae H. Milne Edwards, 1837, qui comprenait auparavant deux sous-familles distinctes (Dorippinae H. Milne Edwards, 1837 et Ethusinae Guinot, 1977), chacune ayant été élevée ensuite au rang de famille soutenu par les données traditionnelles et la phylogénie moléculaire, est présentée sur la base d'une analyse morphologique impliquant un grand nombre de caractères. De fait, la famille s'est révélée hautement diversifiée, et ce à tous les niveaux. Plusieurs caractères sont ici décrits et représentés en détail pour la première fois, comme par exemple la présence d'un rebord diversement développé le long du bord postérieur proéminent de la carapace; sur le sternite 8 dorsalement exposé, un prolongement agissant comme un mécanisme additionnel de rétention du pléon chez la femelle de trois genres (DorippeWeber, 1795; Philippidorippe Chen, 1986; PhyllodorippeManning & Holthuis, 1981); une callosité à la base de la coxa du troisième péréiopode, de formes différentes, chez deux genres (Dorippe et DorippoidesSerène & Romimohtarto, 1969). La taxonomie générique et spécifique magistralement stabilisée par Holthuis & Manning (1991) est incontestée et toujours valide, sauf dans le cas de la composition du genre Heikeopsis Ng, Guinot & Davie, 2008, qui pourrait bien contenir dans le nord de la Chine une forme ne correspondant pas entièrement au H. japonica (von Siebold, 1824) typique du Japon. Une deuxième exception concerne le genre ParadorippeSerène & Romimohtarto, 1969sensu Holthuis & Manning (1991) qui pourrait ne pas être monophylétique. Quant à Medorippe crosnieriChen, 1988, dont la validité mise en doute par Holthuis & Manning (1991) n'a pu être vérifiée, ses caractères morphologiques distinctifs de M. lanata (Linnaeus, 1767) laissent à penser qu'elle sera reconnue un jour. La synthèse des caractères conventionnels et nouveaux permet d'actualiser et de moderniser l'approche taxonomique traditionnelle, de construire des diagnoses plus complètes et plus robustes, et de circonscrire des groupes de genres. Nous proposons une nouvelle classification sous-familiale, selon laquelle la famille des Dorippidae est reconnue monophylétique mais avec sept genres assignés à un rang sous-familial, conduisant à la reconnaissance de sept sous-familles distinctes: les Dorippinae H. Milne Edwards, 1837 n. stat. (Dorippe), Dorippoidinae n. sous-fam. (Dorippoides), Medorippinae n. sous-fam. (MedorippeManning & Holthuis, 1981), Heikeopsinae n. sous-fam. (HeikeopsisNg, Guinot & Davie, 2008, NeodorippeSerène & Romimohtarto, 1969, NobilumSerène & Romimohtarto, 1969), Paradorippinae n. sous-fam. (Paradorippe), Philippidorippinae n. sous-fam. (Philippidorippe) et Phyllodorippinae n. sous-fam. (Phyllodorippe). Il y a un haut degré de concordance entre plusieurs éléments de notre proposition: 1) les principaux patrons morphologiques des gonopodes mâles conduisent à la reconnaissance de sept sous-familles; 2) les principaux patrons morphologiques des vulves correspondent aux sept types de gonopodes observés et conduisent à la reconnaissance des mêmes sept sous-familles; 3) la reconnaissance de plusieurs sous-familles est soutenue par les clades bien définis obtenus par les analyses moléculaires; 4) l'appareil reproducteur femelle, récemment documenté par les histologistes chez la plupart des genres de Dorippidae diffère de celui de tous les autres eubrachyoures étudiés jusqu'à présent, avec une disposition qui représente sans aucun doute un nouveau type d'organisation, sans équivalent chez les Brachyura Brünnich, 1772: de plus, il montre une diversité inattendue, avec un degré de divergence similaire à celui des gonopodes et des vulves, en accord avec les sous-familles ici reconnues. Une nouvelle interprétation des deux principaux sillons de la face dorsale de la carapace est largement discutée. La paternité du nom de groupe famille Dorippidae est attribuée à H. Milne Edwards (1837). L'étude des Dorippidae est un exemple particulier de la façon dont l'intégrati
Abstract
The podotreme brachyuran subfamily Cyrtorhinae was established by Guinot (1993) for Cyrtorhina Monod, 1956, an unusual raninid genus from the Atlantic and Western Pacific. Although the ...family-group name has been accepted and used widely, it is not available for nomenclatural purposes. The present note serves to validate the name Cyrtorhininae.
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BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Brachyuran crabs of the family Bythograeidae are endemic to deep-sea hydrothermal vents and represent one of the most successful groups of macroinvertebrates that have colonized this extreme ...environment. Occurring worldwide, the family includes six genera (Allograea, Austinograea, Bythograea, Cyanagraea, Gandalfus, and Segonzacia) and fourteen formally described species. To investigate their evolutionary relationships, we conducted Maximum Likelihood and Bayesian molecular phylogenetic analyses, based on DNA sequences from fragments of three mitochondrial genes (16S rDNA, Cytochrome oxidase I, and Cytochrome b) and three nuclear genes (28S rDNA, the sodium-potassium ATPase a-subunit 'NaK', and Histone H3A). We employed traditional concatenated (i.e., supermatrix) phylogenetic methods, as well as three recently developed Bayesian multilocus methods aimed at inferring species trees from potentially discordant gene trees. We found strong support for two main clades within Bythograeidae: one comprising the members of the genus Bythograea; and the other comprising the remaining genera. Relationships within each of these two clades were partially resolved. We compare our results with an earlier hypothesis on the phylogenetic relationships among bythograeid genera based on morphology. We also discuss the biogeography of the family in the light of our results. Our species tree analyses reveal differences in how each of the three methods weighs conflicting phylogenetic signal from different gene partitions and how limits on the number of outgroup taxa may affect the results.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A new genus and species, Richerius marqueti gen. et sp. nov., of a crab of the family Hymenosomatidae MacLeay, 1838 are described from the inland waters of New Caledonia based on several specimens ...collected in two streams at altitudes of 180 m and 500 m, respectively. Richerius marqueti gen. et sp. nov. was compared to the other freshwater species known in New Caledonia, Odiomaris pilosus (A. Milne-Edwards, 1873), and to species of Amarinus Lucas, 1980, a genus comprising many freshwater species in New Zealand, Australia, Indonesia, the Philippines, and Papua New Guinea, but never recorded in New Caledonia. The barcode fragment of the COI mitochondrial gene was sequenced for seven specimens of R. marqueti gen. et sp. nov., and all sequences were deposited in GenBank. A brief and updated review of the New Caledonian marine and freshwater hymenosmatid fauna is provided.
The patterns of complexity of the male and female sexual openings in Brachyura, which have been the source of uncertainties and conflicting opinions, are documented, together with a study of the ...morphologies of the coxal and sternal gonopores in both sexes, penises, spermathecae, and gonopods. The vulvae, male gonopores and penises are described among selected taxa of Eubrachyura, and their function and evolution examined in the context of a wide variety of mating behaviours. The location of female and male gonopores, the condition of the penis (coxal and sternal openings and modalities of protection), and related configurations of thoracic sternites 7 and 8, which are modified by the intercalation of a wide sternal part (thoracic sternites 7 and 8) during carcinisation, show evidence of deep homology. They represent taxonomic criteria at all ranks of the family-series and may be used to test lineages. Of particular significance are the consequences of the posterior expansion of the thoracic sternum, which influences the condition, shape, and sclerotisation of the penis, and its emergence from coxal (heterotreme) to coxo-sternal, which is actually still coxal (heterotreme), in contrast to a sternal emergence (thoracotreme). The heterotreme-thoracotreme distinction results from two different trajectories of the vas deferens and its ejaculatory duct via the P5 coxa (Heterotremata) or through the thoracic sternum (Thoracotremata). Dissections of males of several families have demonstrated that this major difference not only affects the external surface (perforation of the coxa or the sternum by the ejaculatory duct) but also the internal anatomy. There is no evidence for an ejaculatory duct passing through the articular membrane between the P5 coxa and the thoracic sternum in any Brachyura, even when the sternal male gonopore is very close to the P5 coxa. Trends towards the coxo-sternal condition are exemplified by multistate characters, varying from a shallow depression to a long groove along expanded sternites 7 and 8, and ultimately their complete, extended junction typifying the most derived coxo-sternal condition. The coxo-sternal condition is indicative of a long evolutionary history, as evidenced by the presence of multistate characters (e.g., Dorippidae, Goneplacoidea) or by a single, well-established condition (e.g., Chasmocarcinidae, Ethusidae, Panopeidae Eucratopsinae, Rhizopidae, Scalopidiidae). The penial area proves to be an essential diagnostic feature in Brachyura, with a value comparable to that of the gonopods. Penis protection is ubiquitous in Brachyura irrespective of length, and several modalities of protection prevail, which necessitate different modifications of associated structures. A long penis in a gutter developed from a partial invagination of sternite 8 induces the formation of a new "suture" at the same level as the preceding suture 6/7. Such a "supplementary suture 7/8" exists among unrelated heterotreme families (e.g., Ethusidae, Panopeidae Eucratopsinae, Pseudorhombilidae, Rhizopidae). A fully protected penis, concealed in a groove within a complete invagination of sternite 8 in the form of two contiguous plates, evolved independently (homoplasy) in Palicoidea and Chasmocarcinidae (Goneplacoidea), with sternite 8 present as a single plate in females. In condylar protection, described for the first time and occurring in several heterotreme families, the penis emerges from the extremity of the P5 coxo-sternal condyle or from its anterior border instead of from the coxa itself. A penis precisely lodged in a small excavation on sternite 8, which is lined by a row of stiff setae, is unique to Brachyura, and represents a new synapomorphy of the Homoloidea. Five modalities of penis protection are recognised in Podotremata, eight in Eubrachyura (six in Heterotremata and two in Thoracotremata). Special attention has been paid to Dorippoidea (Dorippidae and Ethusidae), which shows transformation series from coxal to coxo-sternal conditions. The coxo-sternal condition is not an intermediate towards the thoracotreme organisation, and a step in heterotreme evolution is the adoption of the coxo-sternal condition. An extreme carcinisition may also result in the sternal arrangement of male gonopores in the form of a "sternitreme" disposition, as in the case of Hymenosomatoidea, which displays a broad thoracic sternum and true sternal male gonopores (as in thoracotremes) together with several plesiomorphic traits that are assumed to represent an old, deeply-rooted heterotreme clade. A sternitreme condition evolved independently in the most ancestral heterotreme clades (such as Hymenosomatoidea) and in Thoracotremata. The older the lineage of a heterotreme is, the higher the possibility of having evolved carcinisation. Evidence that "derived" traits may be the consequence of a strong carcinisation, rather than being recently acquired, necessitates reconsidering certain character states in Brachyura. Eubrachyurans can only evolve either the heterotreme or the thoracotreme arrangement, the consistency of the inferred ancestral characters states providing a useful criterion for evaluating ancestral trait reconstructions. A widened thoracic sternum together with sternal gonopores may be present in carcinised heterotremes such as hymenosomatoids. The thoracic sternum provides a reliable complex of characters that must be carefully interpreted. The hypothesis of a coxo-sternal disposition in Cryptochiroidea and Pinnotheroidea, generally considered thoracotremes, is rejected, and an alternative interpretation of their status is discussed. A new interpretation of the phylogeny of Cryptochiroidea is outlined, but the origin of Pinnotheroidea remains puzzling. The sella turcica, frequently regarded a synapomorphy of Eubrachyura, is redefined as the structure formed by the endosternal intertagmal phragma that connects the tagma/thorax and the tagma/abdomen to thoracic interosternite 7/8. It is here termed the "brachyuran sella turcica" and is shown to be synapomorphic to all Brachyura. The Eubrachyura synapomorphically shares the fusion of the thoracic interopleurite 7/8 with the brachyuran sella turcica, forming the "eubrachyuran sella turcica". In contrast, some Podotremata (Cyclodorippoidea and Raninoidea) share a connection between the sella turcica and the thoracic interosternite 6/7. Six main patterns of the thoracic sternum in relation to variations in sutures 4/5-7/8 are recognised in Eubrachyura, whereas several subpatterns that include variations in the median line are distinguished. The evolution of the thoracic sternum and axial skeleton is reassessed in Podotremata and Eubrachyura. A posteriormost location of the male gonopore (coxal or sternal) in relation to sternite 8 characterises many brachyurans (Cryptochiroidea, Hymenosomatoidea, Majoidea, Matutidae, Menippidae, Orithyioidea, Parthenopoidea, Ucididae, Grapsoidea--including Percnidae, Plagusiidae, Varunidae), in contrast to a location close to suture 7/8 in other groups. The thoracic sternum/pterygostome junction, which has multistate characters, is shown to be a valuable taxonomic criterion. The shapes of the sterno-abdominal depression and sterno-abdominal cavity provide diagnostic features that are helpful in suprageneric assignments. The monophyly of Brachyura, Eubrachyura, and Thoracotremata is reaffirmed. The monophyly of Brachyura is supported by the interdependence of the two pairs of gonopods and penis. An abdomen permanently flexed and held by the pereopods and/or the homoloid press button (on sternite 4) or typical eubrachyuran press-button (on sternite 5) may be considered a synapomorphy of Brachyura, the absence of this condition considered a loss. The double abdominal-locking system ("double peg") on sternite 5, a device discovered in three families of the extinct Palaeocorystoidea from the Upper Aptian, is similar to the double hook present in living lyreidids, although it is lost in all other raninoid extant members. New evidence shows that the abdominal holding was an early occurrence for a brachyuran crab. The Raninoidea, sister to Palaeocorystoidea, is characterised by gymnopleurity, a condition that results from the lifting of the carapace and thus the exposure of several pleurites. The narrowing of the body and thoracic sternum, almost certainly associated with their burrowing behaviour, is a diagnostic feature of raninoid evolution, in contrast to the widening observed in the remaining Brachyura. The monophyly of Heterotremata is discussed. Although the correct assignment of the coxal male gonopore and sternal female gonopore (vulva) at the base of Decapoda and Eubrachyura, respectively, left no synapomorphies to support the Heterotremata, the group nevertheless should be regarded as the sister group to Thoracotremata. The controversial monophyly of Podotremata is discussed and arguments are presented against the suppression of this taxon. The distinction of Homoloidia from Dromioidia is argued, and a classification of Podotremata, which considers the fossil record whenever possible, is presented. The earliest brachyurans are re-examined, and a new interpretation of the phylogeny of several basal eubrachyuran groups (Dorippoidea, Inachoididae, Palicoidea, Retroplumoidea) is proposed. Stenorhynchus shares a number of characters with the Inachoididae that differentiate them from Inachidae, and also has some distinctive features that warrants its assignment to a separate inachoidid subfamily, Stenorhynchinae, which is resurrected. The concealment strategies among Brachyura are documented and discussed. Podotremes use carrying behaviour, often combined with burying and concealment under substrates, whereas living within a host, burying, and decoration are used by heterotremes, burrowing being essentially a thoracotreme strategy. (ABSTRACT TRUNCATED)
•Our knowledge of brachyuran crabs of Callovian age is extremely poor.•Glaessneropsidae are among the oldest brachyuran crabs known to date.•The orbital structures of glaessneropsid crabs are ...conspicuously complex.•A solid diagnosis for Glaessneropsidae is present, but support for a suprafamilial rank lacks.
A new genus, Meroncarcinus, and two new species, M. boursicoti and Verrucarcinus marsae, are described from Callovian (Middle Jurassic) deposits of Calvados and Maine-et-Loire, France. New material of the type species of the genus Verrucarcinus, V. torosus, is examined, which improves our understanding of the peculiar morphology of this group of crabs. A new genus and species, Vilsercarcinus keuppi, is recognised from Lower-Middle Jurassic strata of Germany-Austria. Charassocarcinus, a Lower-Middle Jurassic crustacean genus of doubtful taxonomic affinity, is revived and here assigned to the Glaessneropsidae. All of this material forms the basis for a re-examination of the Glaessneropsidae, and an enhanced diagnosis is compiled. The morphology of Glaessneropsidae, one of the oldest known brachyuran families, is discussed; its complex orbital structure is remarkable for such an ancient group of crab and raises questions about its relationship with the basal brachyuran group Homolodromioidea. A solid support for a suprafamilial rank for the Glaessneropsidae is lacking.
Two new species of the genus AustinograeaHessler & Martin, 1989 (Bythograeidae Williams, 1980), distinct from A. williamsiHessler & Martin, 1989 and A. alayseaeGuinot, 1990, are here reported from ...hydrothermal vent fields of the southwestern Pacific: A. hourdezi n. sp. and A. jolliveti n. sp., both in the Lau and North Fiji Back-Arc Basins. Austinograea hourdezi n. sp. is characterised by two depressions appearing as dark spots on the palm of both chelipeds in males and differs from the more northern A. williamsi and the Indian A. rodriguezensisTsuchida & Hashimoto, 2002, which show only one spot on the male chelae, near the base of the dactylus. Some individuals exhibiting all morphological characters of A. hourdezi n. sp. bear only one spot on the chelae, near the base of dactylus; the fact that most are left-handed corresponds to the presence of a regenerated cheliped, with handedness reversal after the accidental loss of the major cheliped: these atypical individuals are here treated as A. hourdezi n. sp. The single spot that characterises each chela of A. jolliveti n. sp. is located at the base of the fixed finger in both sexes and shows as a differently pigmented, violaceous “pustule”, being similar to that of Bythograea microps Saint Laurent, 1984 from the East Pacific Rise. Moreover, A. jolliveti n. sp. can be distinguished by the shortest G2 found in Austinograea, especially by its reduced flagellum. A. hourdezi n. sp., represented by numerous specimens, was found to cooccur with A. alayseae in several vent sites of the Lau and North Fiji Back-Arc Basins, and both are probably distributed across a wide geographical range, whereas A. jolliveti n. sp., represented by only a few specimens, was collected from only two vent sites (ABE and Mussel Valley). In the northwestern Pacific, A. williamsi is apparently restricted to the Mariana Trough, where it is the only one member of the family Bythograeidae. The Manus Basin perhaps hosts an additional Austinograea species. In the western Pacific, vent fields are the only hydrothermal systems, except the East Pacific Ridge, that are not linearly distributed; different basins may host different species within the same brachyuran genus (five congeneric species of Austinograea, including A. rodriguezensis from the western Indian Ocean). The morphological distinction between the Austinograea species is supported by molecular analyses, for A. williamsi, A. alayseae, and A. hourdezi n. sp. A key to the five species of Austinograea is provided, in order to be able to potentially identify the crabs photographed in situ in their natural environment.
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