Scleroplax Rathbun, 1893

Campos, Ernesto, 2006, Systematics of the genus Scleroplax Rathbun, 1893 (Crustacea: Brachyura: Pinnotheridae), Zootaxa 1344, pp. 33-41 : 34-37

Scleroplax Rathbun, 1893

Type species. Scleroplax granulata Rathbun, 1893 , by original designation and monotypy. Gender feminine.

Hosts. Crustacea, Decapoda ( Callianassidae and Upogebidae); Echiurida ( Urechidae ). In burrows.

Distribution. Pacific Ocean coast, Canada to northern México.

Diagnosis. Carapace hard, subheptagonal, highly convex dorsally, anterolateral margins not forming angle with posterolateral margins; MXP3 slightly oblique, covers buccal cavity, ischio-merus subtrapezoidal, propodus extending to end of dactylus, both spoon-shaped and larger than carpus. WL1-4 of similar shape, third pair slightly longer, fourth not noticeably reduced.

Taxonomic remarks. The revised diagnosis allows the separation of Scleroplax from all the known genera in the Pinnixa complex. Diagnostic features of Scleroplax include the carapace and MXP3. In contrast to Scleroplax , in Pinnixa sensu stricto, the dactylus always protrudes beyond the distal tip of the shorter propodus. This feature is also observed in the genera Indopinnixa Manning & Morton, 1987 , and Austinixa Heard & Manning, 1997. The shape and insertion point of the articles of MXP 3 in Glassella Campos & Wicksten, 1997 , and Tetrias Rathbun, 1898 , are so different from Scleroplax that misidentification is unlikely (Fig, 2C, E–F). Members of the Pinnixa complex can also be separated from Scleroplax by their relatively flat carapace that is noticeably wider than long, with WL3 clearly longest and the thin WL4 the shortest.

An analysis of Rathbun (1918), Tesch (1918), Shen (1932), Glassell (1938), Garth, (1960), Righi (1967), Fenucci (1975). Manning & Morton (1987), Manning & Felder (1989), Zmarzly (1992), Campos & Wicksten (1997), Heard & Manning (1997), Campos et al. (1998) and Martins & D’Incao (1998) accounts and the study of voucher material listed in Table 1 revealed that the genera Austinixa , Glassella , Indopinnixa , Pinnixa , Scleroplax , and Tetrias should be considered a presumed homogeneous group. All these taxa share at least two inclusive characters, including a distinct carapace that is wider than long and a conspicuous lobe on the outer margin of the basal segment on the exopod of the third maxilliped ( Fig 1 C –D, 2 A–F). These novelties distinguish these genera within the Pinnotheridae and may represent a separate monophyletic assemblage. Alarconia Glassell, 1938 (see Campos & Wicksten 1997) and the South Pacific genus Pinnotherelia Milne Edwards & Lucas, 1843 , should not be considered members of this group despite sharing a carapace that is also wider than long. Both genera lack the exopod lobe of MXP3. The systematics of these genera will be discussed elsewhere.

Figures

FIGURE 1. A – C Scleroplax granulata Rathbun, 1893 (female, cl 4.2 mm, cb 6.0 mm., El Coyote estuary, Abreojos Point, Baja California Sur, México, UABC); D) Pinnixa sp. (female, cb = 6.0 mm, El Verde estuary, Mazatlán, Sinaloa, México, EMU- 842; E) Auxtinixa cristata Rathbun, 1900, (male cb 6.3 mm., St. Lucie, Florida, USA, USNM). A, E) dorsal view; B) WL 1 – 4; C – D) MXP 3. Illustrations not to scale. Dotted lines indicate the setae of the propodus and dactylus. (E from Manning and Felder, 1989).