Macrochiridothea stebbingi Ohlin, 1901

Poore, Gary C. B., 2009, A new species of Chaetiliidae (Crustacea: Isopoda: Valvifera) from the Río de la Plata estuary, Argentina-Uruguay, and reconsideration of Macrochiridothea and Chiriscus, Zootaxa 2119, pp. 51-65 : 63

Macrochiridothea stebbingi Ohlin, 1901

Macrochiridothea stebbingi Ohlin, 1901: 289 –291, pl.12, fig. 9. — Carvacho, 1997: 52 (list). Probably not Macrochiridothea stebbingi . — Sheppard, 1957: 170 –172, fig. 12.

Probably not Macrochiridothea stebbingi . — Menzies, 1962: 98–101, fig. 33.

Probably not Macrochiridothea stebbingi . — Moreira, 1972: fig. 1A. — Moreira, 1973: fig. 1. (= M. multituberculata ).

Material. Holotype: Between Isla Nueva and Isla Navarino, 55°15'S, 66°25'W, Chile, 54 m [30 fm], SMNH (female, 7 mm).

Diagnosis. Total body length of female 7 mm. Dorsal surface generally tuberculate (5 longitudinal rows: median from head to pleotelson, 2 sublaterals and laterals from pereonite 1 converging on pereonite 6); pleotelson with a single strong median keel. Lateral lobes on head rounded. Coxa 6 just overlapping pleonite 2. Antenna 1 peduncle, article 2 without anterodistal prolongation. Antenna 2 peduncle, article 4, 1.1 times as long as greatest width; article 5, 3 times as long as greatest width. Pereopods 2 and 3 dactyli subchelate, closing on truncate palm. Pereopod 5 ischium without a prominent hook on upper margin.

Distribution. Tierra del Fuego, Chile-Argentina, 55°15'S, 66°25'W; 54 m depth; other localities doubtful.

Remarks. Macrochiridothea stebbingi is a problematic species. Ohlin’s (1901) holotype from western Tierra de Fuego is a female with prominent tubercles, especially evident in his illustration of the lateral view. He illustrated many limbs. Sheppard (1957) commented on additional material collected east of southern Argentina at 118–309 m depth. Her illustrations of antennae and pereopod 2 show narrower limbs than in Ohlin’s figure 9. Menzies’ (1962) figure 33a of a specimen collected at Seno Reloncaví, Chile, at 20–25 m depth, considerably north of the type locality, differs from Ohlin’s in tuberculation and apparent head shape. Notably, Menzies’ figure shows fewer tubercles on pereonites 5 and 6. His figure of pereopod 2 does not resemble Sheppard’s. The identity of Sheppard’s and Menzies’ specimens remains uncertain.

Moreira’s (1972, 1973) figures of a male from Rio Grande do Sul, Brazil, even further from the type locality, show a head with more prominent acute lateral lobes and more tubercles than in other illustrations (see M. multituberculata ).

If the subspecies from the Falkland Islands were treated as a distinct species and subsequent records are not of this species, the geographical range of M. stebbingi would not be as extensive as summarised by Moreira (1973) and Carvacho (1997).