Macrochiridothea setifer Menzies, 1962

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 : 62-63

Macrochiridothea setifer Menzies, 1962

Macrochiridothea setifer Menzies, 1962: 101 –102, fig. 34. — Moreira, 1973: figs 9–10. — Epelde-Aguirre & Lopez, 1975: 161. — Jaramillo, 1977: 79. — Jaramillo, 1982: 184 –185, fig. 7. — Carvacho, 1997: 45 –48, 52, figs 1–20. Macrochiridothea sp. — Carvacho & Saavedra, 1994.

Material. Holotype: Isla de Guafo, near Punta Weather, Chile, 25 m, 43°37'S, 74°49'W, SMNH Type-3103 (male, 4.2 mm, examined by GCBP).

Other material: Playa Totoralillo, Coquimbo, Chile, NMV J58383 , J58384 (> 100 specimens, 4–6 mm, examined by GCBP); Mehuín and Muicolpué, Chile, IZUA (17 specimens, 4.5–10 mm, Jaramillo, 1982); unspecified localities, Chile ( Carvacho, 1997).

Diagnosis. Total body length of male 7.8 mm; female 10.1 mm. Dorsal surface smooth; pleotelson with a weak median keel along whole length. Lateral lobes on head acute. Coxa 6 reaching posteriorly well beyond pleonite 3. Antenna 1 peduncle, article 2 without anterodistal prolongation. Antenna 2 peduncle, article 4, 2.5 times as long as greatest width; article 5, 4 times as long as greatest width. Pereopods 2 and 3 dactyli minute, hook-like. Pereopod 5 ischium without a prominent hook on upper margin. Pleopod 2, appendix masculina straight, apex laterally denticulate.

Distribution. Coquimbo to Isla de Guafo, Chile (30°S–44°S); sandy beaches to 25 m depth.

Remarks. Menzies (1962) illustrated only the dorsal view, end of antenna 1 and apex of the pleotelson of the holotype. His diagnosis was short and not informative; he reported that the pereopods were similar to those of M. stebbingi . The holotype was examined by one of us (GCBP) and found to be a male (not female as stated by Menzies – his figure shows a typical male pereonite 1) and to lack the “pair of flattened elevations at margin of maxillipedal somite groove” reported and illustrated by Menzies. Jaramillo’s (1982) illustrations of a 10.1 mm female and others by Carvacho (1997) of a 7.8 mm male do not figure these elevations. Numerous specimens from Playa Totoralillo, Chile, examined by GCBP lack any ornamentation. It appears Menzies misinterpreted the shape of the head-pereonite suture.

Jaramillo (1977, 1982) reported M. setifer over a wide geographic range throughout Chile based in part on the beach surveys of Epelde-Aguirre & Lopez (1975).