A new species of Chaetiliidae (Crustacea: Isopoda: Valvifera) from the Río de la Plata estuary, Argentina-Uruguay, and reconsideration of Macrochiridothea and Chiriscus Author Poore, Gary C. B. text Zootaxa 2009 2119 51 65 journal article 10.5281/zenodo.188066 ab6365d5-73f9-4961-b482-3020feb144a3 1175-5326 188066 Macrochiridothea marcusi Moreira, 1972 Macrochiridothea marcusi Moreira, 1972 : 395 –399, fig. 1B. — Moreira, 1973 : 19 –22, 32–39, figs 17–47. — Carvacho, 1997 : 51 (list). Material. Lectotype : SE of Ilha Anchieta, São Paulo, Brazil , 12–21 m , 23°35´S , 45°05´W , MZUSP (male, 5.0 mm, designated as “ holotype ” by Moreira, 1973 ). Paralectotypes : Southern Brazil , 21°15´S – 32°05´S , 8–65 m depth, MZUSP ( 257 specimens ). Diagnosis. Total body length of male 6.6 mm ; female 7 mm . Dorsal surface with transverse rows of small tubercles along posterior margins of head, pereonites and pleonites; pleotelson with median and submedian keels near anterior margin. Lateral lobes on head rounded. Coxa 6 just overlapping pleonite 2. Antenna 1 peduncle, article 2 without anterodistal prolongation. Antenna 2 peduncle, article 4, 3 times as long as greatest width; article 5, 7 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. Southern Brazil , 21°15´S – 32°05´S , 8–65 m depth. Remarks. See the previous species for an explanation of the date of publication and type designation. Moreira (1973) illustrated differences between the setation of pereopod 1 of males (with dense strong setae along the margin of the carpus and propodal palm enveloping the dactylus) and females (mostly short setae and few longer setae). The female is larger and more vaulted, and the tubercles sharper. The pattern of ridges on the pleotelson is diagnostic.