Family GONEPLACIDAE MacLeay, 1838

<em>Carcinoplax meridionalis</em> [from Rathbun 1923: pl. 18]

Carcinoplax meridionalis [from Rathbun 1923: pl. 18]

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Family GONEPLACIDAE MacLeay, 1838

Compiler and date details

May 2012 - Peter Davie, Queensland Museum, Brisbane

Taxonomic Decision for Synonymy

Alcock, A. 1900. Materials for a Carcinological Fauna of India. No. 6. The Brachyura Catametopa, or Grapsoidea. Journal of the Asiatic Society of Bengal 69(Pt 2 No. 3): 279-456
Guinot, D. 1969. Recherches préliminaires sur les groupements naturels chez les Crustacés Décapodes Brachyoures. VII. Les Goneplacidae (suite et fin). Bulletin du Muséum National d'Histoire Naturelle, Paris [published 1907-1971] 41(3): 688-724 figs 83-146 pls III-V
Manning, R.B. & Holthuis, L.B. 1981. West African Brachyuran Crabs (Crustacea: Decapoda). Smithsonian Contributions to Zoology No. 306: i-xii, 1-379 figs 1-88, 2 appendices

Introduction

Goneplacids are found in a variety of habitats, from estuaries to the deep sea, but seem to be most diverse on softer offshore substrates, from which they are commonly trawled or dredged. They range from small to medium-sized crabs, but are not large enough, or common enough, to have any commercial value in Australia.

The Goneplacidae has been, for a very long time, a convenient repository for an assortment of crabs that do not quite fit other family definitions. Thus it has been, and continues to be, a relatively poorly defined, polyphyletic grouping needing a definitive taxonomic revision. Many goneplacids have a typical xanthoid fascies, while others can be remarkably different. Guinot (1969a, 1969b, 1969c, 1971) has made the most significant contribution to our understanding of the phylogenetic relationships of Goneplacidae. She recognised six separate lineages, although she stopped short of formalising these nomenclaturally. However, her ideas have led to a number of her groupings now being removed formally from the older family concept. These include the Rhizopinae, now considered a subfamily of the Pilumnidae (see Ng 1987); Galene and Halimede also to the Pilumnidae (see Guinot 1971, 1978), with the names Galeninae Alcock, 1898, and the Halimedinae Alcock, 1898, already available to accommodate them. The Panopaeinae is now accorded full family status (see Guinot 1978) and includes the Eucratopsinae, also previously placed in the Goneplacidae.

The Hexapodinae, first treated as a subfamily of the Pinnotheridae, was later transferred to the Goneplacidae by Alcock (1900: 287), and continued to be treated as such until Manning & Holthuis (1981: 166) gave it full family status, though still recognising its goneplacid affinities.

Although groups have been removed from the Goneplacidae, still others have been added. The Trogloplacinae was erected by Guinot (1986) and included in the Goneplacidae. This interesting group is represented in Australia by the freshwater and estuarine Australocarcinus riparius Davie, 1988. The Trogloplacinae is raised in the present work to full family status and the justification for this is given under that family account. The Pilumnoidinae was erected for Pilumnoides by Guinot & Macpherson (1987); and lastly, Ng & Wang (1994: 84) raised the tribe Pseudozioida Alcock, 1898, to subfamily status within the Goneplacidae. Previously, Pseudozius was placed tentatively in the Oziidae [= Eriphiidae]. Similarities between Flindersoplax and Pseudozius are very strong (see Davie 1989; Ng & Wang 1994), and I here provisionally include Flindersoplax in the Pseudoziinae.

Serène (1984), as part of his key to the Xanthoidea, erected the Planopilumninae in the Pilumnidae, for Planopilumnus. However, based on the form of the male first and second gonopods, a feature that is very constant among other pilumnids, Planopilumnus clearly does not belong to the Pilumnidae (see Ng et al. 2001). In the type-species of the genus, Planopilumnus spongiosus (Nobili, 1905) the first gonopod has a spatulate tip, while the second gonopod is straight, and about half the length of the first. Indeed the gonopods are extremely reminiscent of those of Pseudoziinae and Pilumnoidinae. It seems likely that the three groups are closely allied and on further investigation may even warrant establishment of a separate family. Planopilumnus labyrinthicus (Miers, 1884) is, however, a typical pilumnid and a new genus is being described to accommodate it (P.K.L. Ng pers comm.)

Important works for identifying members of the Australian fauna include: Tesch (1918), Campbell (1969), Griffin & Campbell (1969), Sakai (1976), Guinot (1989).

Diagnosis

Carapace hexagonal, transversely rectangular, trapezoidal, or transversely ovate; dorsal surface more or less convex, typically smooth, regions poorly defined; frontal margin usually entire, sometimes bi- to multilobate; anterolateral margins usually armed with 1–4 teeth or lobes, but sometimes entire. Orbits complete, may be moderately or greatly elongate. Interantennular septum typically narrow. Antenna folding obliquely or transversely. Third maxillipeds with carpus articulating at or near antero-internal angle of merus. Ambulatory legs gressorial, not broadly flattened for swimming. Male abdomen with seven free segments or with segments 3–5 fused and immovable. Male first gonopod moderately stout, weakly curved or sinuous; second gonopod short or long, but usually shorter than first. Male genital openings sternal or sterno-coxal, with vas deferens passing along open or closed groove in sternum.