Macrochiridothea multituberculata Nordenstam, 1933

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 : 61

Macrochiridothea multituberculata Nordenstam, 1933

Macrochiridothea stebbingi . — Stebbing, 1914: 354. — Moreira, 1972: 395 –399, fig. 1C. — Moreira, 1973: 13 –15, fig. 1 (only).

Macrochiridothea stebbingi var. multituberculata Nordenstam, 1933: 110 –112, pl. 1 fig. 7, fig 26. — Sheppard, 1957: 170 –172. — Menzies, 1962: 101.

Material. Holotype: Rocks at Port William, Falkland ( Malvinas) Islands, 51°40'S, 57°47'W, SMNH (ovigerous female, 13 mm).

Diagnosis. Total body length of female 13 mm. Dorsal surface tuberculate (pereonite 1 with pair of lateral longitudinal rows of 3 tubercles and transverse row of 9 tubercles; pereonites 1–4 with 5 longitudinal rows of tubercles: median, 2 sublaterals and 2 laterals, plus smaller intermediate tubercles between them; pereonite 5 with 7 tubercles; pereonite 7 with 3 tubercles; pleonite 1 with 3 tubercles); pleotelson with a single strong median keel. Lateral lobes on head rounded. Pereopods 2 and 3 dactyli subchelate, closing on truncate palm. Pereopod 5 ischium without a prominent hook on upper margin.

Distribution. Falkland ( Malvinas) Islands (51°40'S, 57°47'W), Rio Grande do Sul, Brazil (34°S); 65 m.

Remarks. Stebbing (1914) reported on two females of M. stebbingi collected from the Falkland Islands in 1898. Both are about twice as long as the female holotype of the nominal species. Nordenstam’s (1933) subspecies was based on another ovigerous female of similar length and judging on his detailed description of the sculpture and photograph a separate species is justified. Menzies (1962) agreed. Two features clearly distinguish the species: M. multituberculata has wide acute lateral lobes on the head (more rounded in M. stebbingi ) and a double lateral tubercle anteriorly on the pleotelson (not evident in M. stebbingi ). Moreira’s (1972; 1973) figures of an adult male from off Arroio Chuí, Rio Grande do Sul, Brazil, that he attributed to M. stebbingi has more but much smaller tubercles than M. stebbingi . It lacks eyes and has acute head lobes. The pattern of tubercles, notably the lateral longitudinal rows of three tubercles on pereonite 1 and the pattern of median tubercle plus double lateral tubercles on the pleotelson, match the description of M. stebbingi multituberculata .