Family XANTHIDAE MacLeay, 1838

<em>Xanthias lamarcki</em> [from A. Milne Edwards 1873]

Xanthias lamarcki [from A. Milne Edwards 1873]

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Family XANTHIDAE MacLeay, 1838

Compiler and date details

May 2012 - Peter Davie, Queensland Museum, Brisbane

Antrocarcininae Ng, P.K.L. & Chia, D.G.B. 1994. The genus Glyptocarcinus Takeda, 1973, with descriptions of a new subfamily, two new genera and two new species from New Caledonia (Crustacea: Decapoda: Brachyura: Xanthidae). Raffles Bulletin of Zoology 42(3): 701-730 [702].
Type genus:
Antrocarcinus Ng & Chia, 1994.

Taxonomic Decision for Synonymy

Introduction

The Xanthidae is the most diverse of the crab families in Australian waters. Xanthids are found in a variety of habitats from the intertidal to moderately deep water, but they are most abundant in shallow water, coastal reef environments. Because many species have the fingers of the claw darkly pigmented, they are often called `black-fingered crabs'. Xanthids range in feeding type from algal scrapers that have the fingers of the claw ending in broad cusps, to aggressive predators with sharply pointed claws; a few even live in symbiotic relationships with corals and other cnidarians. Some have been reported to be highly toxic, and their consumption has caused deaths in other parts of the Indo-west Pacific region. The toxicity is unpredictable, and a range of different toxins is implicated; thus it appears that the crabs are incorporating them from their food. Such toxins have also been reported in a range of small reef crabs belonging to several other families (for review of Australian species, see Llewellyn & Davie 1987).

In the past their great diversity and lack of a general taxonomic treatment made identification of xanthids extremely difficult. This problem was alleviated considerably with the milestone publication by Serène (1984) on the Xanthoidea of the western Indian Ocean. This work provided the first comprehensive keys to the Indo-west Pacific subfamilies, genera and species. However, a number of other important works have dealt with the Australian fauna, including those of Hess (1865), Grant & McCulloch (1906), Rathbun (1911), Hale (1927), Montgomery (1931), Ward (1933a, 1933b, 1934, 1936), Balss (1935), McNeill (1968), Serène (1972), Guinot (1976), Davie (1989), Ng (1993) and Davie & Turner (1994).

The taxonomic arrangement of Xanthidae has changed greatly over about the last 30 years. The present classification follows that of Ng et al. (2008).

Diagnosis

Carapace hexagonal, transversely hexagonal to transversely oval, sometimes subcircular; dorsal regions (areolation) generally, but not always, well defined; surface usually ridged or granular. Frontal margin more or less bilobed. Anterolateral margins generally with two to six teeth, spines, or lobes, sometimes weakly differentiated. Epistome with ridges that define efferent branchial canals absent or confined to the posterior part of the buccal cavity, not continuing on to meet the anterior buccal frame. Chelipeds with fingers pointed or spoon-tipped. Walking legs with or without a dactylo-propodal articulation formed by a rounded prolongation of propodal lateral margin sliding against and beneath a projecting button situated proximally on lateral margin of dactylus. Thoracic sternum relatively narrow. Male abdomen consisting of five movable segments with segments 3–5 fused (sutures may sometimes be more or less evident). Male genital openings coxal; female openings sternal. Male first gonopod slender, curved or sinuous, relatively simple apically, lacking complex lobes or folds; typically with long setae distally or subdistally; second gonopod short, less than 0.25 times length of first.