XANTHOIDEA MacLeay, 1838

Wicksten, Mary K., 2012, Decapod Crustacea of the Californian and Oregonian Zoogeographic Provinces 3371, Zootaxa 3371, pp. 1-307 : 237-238

SUPERFAMILY XANTHOIDEA MacLeay, 1838

Xanthoid crabs demonstrate enormous species diversity in tropical and subtropical regions. Until recently, all of them were considered to belong to only one family, the Xanthidae . Guinot (1971, 1978) and Ng (1998) divided the old family Xanthidae into new families and subfamilies. The work largely was based on morphology of the male gonopods, used in this work to separate the Panopeidae from the Xanthidae in the new sense. Pilumnus spinohirsutus (Lockington, 1877) now is placed in the superfamily Pilumnoidea , family Pilumnidae . See Ng (1998) for illustrations of the gonopods, a key to the families and a more recent systematic treatment of xanthoid crabs worldwide.

The tremendous diversity in size, body shape, habitat, commensal associations, and pereopod morphology has created confusion in trying to assemble the xanthoids into natural assemblages. There has been no recent comprehensive systematic work on the xanthoid crabs of the eastern Pacific. The keys to species presented here are artificial. Following Ng (1998), Malacoplax californiensis (Lockington, 1877) ; formerly considered to belong the family Goneplacidae , now is included in the Panopeidae . The key to the species of Lophopanopeus is modified from that of Menzies (1948). Subspecies are treated in the sections on the species.

Xanthoids commonly are called mud, pebble or rubble crabs, appropriate for the many species that hide among shells, under rocks, in kelp holdfasts or among worm tubes. They are most diverse and abundant from Point Conception southward, but Lophopanopeu s bellus (Stimpson, 1862) ranges as far north as Alaska.

Like species of the family Cancridae , with which they can be confused, xanthoids can be common in intertidal areas, especially in southern California. Among xanthoids, the antennules fold obliquely or transversely, not lengthwise. The flagellum of the antenna is smooth, not setose. The anterolateral teeth of the carapace often are fewer in number or are more blunt than those of cancrids. The chelipeds may differ greatly in size. The fingers may bear a large crushing tooth. Only Cycloxanthops novemdentatus (Lockington, 1877) grows to the size of an edible cancrid in this area. Xanthoids rarely inhabit sandy shores or sandy areas of the continental shelf, and do not have flattened appendages, as do some common cancrids.

Schmitt (1921: 248) reported the crab Heteractaea lunata (Milne-Edwards & Lucas, 1847) (family Xanthidae ) as occurring in San Diego, California. Garth (1957) noted that this is primarily a species of the tropical eastern Pacific, and is associated with corals of the genus Pocillopora . These corals do not live in California. There are no new records of this species in California. See Hendrickx (1995c) for the recorded geographic range of this crab in the eastern tropical Pacific. The original locality record may have been in error.

Stimpson (1871) described Micropanope latimanus briefly and without illustrations. Rathbun (1930) mentioned that the type was not extant, nor was the material mentioned by Lockington (1877a). The species is included here in the family Xanthidae , to which other species of Micropanope have been assigned. This crab may not be correctly assigned to genus. There have been no reports of this crab in California since Rathbun (1930) quoted even earlier reports.

Martin &Velarde (1997:105) reported yet another xanthoid-like crab, Pilumnoides rotundus Garth, 1940 off San Diego at 695 m. Other records of this crab come mostly from the Gulf of California with a single record from Cedros I., western Baja California. Garth (1940: pl. 23) gave a description and illustration. Originally placed in the family Xanthidae , this crab now is considered to belong to a separate family, the Pilumnoididae , in the superfamily Pseudozioidea ( Ng et al. 2008: 179) .