Family PORCELLANIDAE Haworth, 1825

<em>Lissoporcellana quadrilobata </em>[from Miers 1884: pl. 30 fig. D]

Lissoporcellana quadrilobata [from Miers 1884: pl. 30 fig. D]

<em>Petrolisthes haswelli</em> [from Miers 1884: pl. 29 fig. A]

Petrolisthes haswelli [from Miers 1884: pl. 29 fig. A]

<em>Polyonyx obesulus</em> [from Miers 1884: pl. 29 fig. D]

Polyonyx obesulus [from Miers 1884: pl. 29 fig. D]

<em>Pachyeles sculptus</em> [from Grant & McCulloch 1906: pl. 2 fig. 2]

Pachyeles sculptus [from Grant & McCulloch 1906: pl. 2 fig. 2]

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Family PORCELLANIDAE Haworth, 1825

Porcellanidae Haworth, A.H. 1825. A new binary arrangement of the macrurus Crustacea. Philosophical Magazine and Journal 65: 183-184 [184].

Introduction

Porcellanids are commonly known as 'Porcellain Crabs'. Unlike other anomurans they have the abdomen flattened and tucked under the body in a manner similar to true crabs; this crab-like impression is further enhanced by robust claws held out in front of the body. However, unlike true crabs, porcellanids have retained a well-developed tailfan.

Porcellanids occur in a wide variety of habitats across the continental shelf, but are most abundant in sheltered intertidal and shallow subtidal zones of reefs, rocky shores, and estuarine mangroves. Many have flattened bodies which allow them to live in narrow spaces on the undersides of rocks and dead coral; if the rocks are turned up the crabs are very quick to scurry out of sight. Others tend to be thicker-bodied, and are common members of epifaunal fouling communities. Commensal or ectosymbiont relationships are common in this family, with species frequently living in association with sponges, and on a variety of cnidarians such as Pennatulacea (sea pens), hard and soft corals, gorgonians and alcyonarians. The beautiful Neopetrolisthes maculatus lives commensally amongst the tentacles of giant anemones such as Stichodactyla, Entacmaea and Heteractis species. Another native Australian species, Polyonyx transversus (Haswell, 1882), is notable for living commensally inside the parchment tube of a large polychaete worm (Chaetopterus) and inside the shell cavity of bivalve molluscs (Aspergillum). Porcellanids are typically suspension feeders, catching food on long feathered setae as their elongate third maxillipeds are pulled through the water.

The Australian fauna is relatively diverse and includes 51species in 14 genera. Even so, there has been relatively little taxonomic study, and the fauna is significantly more diverse than these figures indicate. The majority of work on this family has been undertaken by Haig (1964, 1965, 1966, 1973, 1974, 1978, 1979, 1981, 1987, 1988), Ball & Haig (1972) and Haig & Ball (1988)—all important papers for identifying the Australian fauna.

Diagnosis

Body crab-like. Rostrum obsolete. Supraocular spines present, or absent. Carapace smooth or with faint striae or tubercles. Tailfan well developed, folded under preceding pleomeres. Maxilliped 1 exopod flagellum well developed. Maxilliped 3 operculiform; ischium and merus broad, expanded mesially. Maxilliped 3 without crista dentata; without epipod. Cheliped flattened.