Macrochiridothea 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 : 54

Macrochiridothea Ohlin, 1901

Macrochiridothea Ohlin, 1901: 286 . — Stebbing, 1914: 353 -354. — Nordenstam, 1933: 105. — Sheppard, 1957: 168 –173. — Menzies, 1962: 98. — Hurley & Murray, 1968: 244. — Moreira, 1973: 12 (key). — Jones & Fenwick, 1978: 619. — Poore, 1984: 71 –72 (part). — Harrison-Nelson & Bowman, 1990: 127 (list of species). — Carvacho, 1997: 46 –47 (key).

Type species. Macrochiridothea michaelseni Ohlin, 1901 , subsequent designation by Menzies, 1962: 98.

Diagnosis. Body smooth, or ornamented with tubercles, spines or ridges. Head with lateral incisions. Eyes present or absent. Pereonites with dorsal coxal plates visible dorsally on 5–7 only. Pereonite 7 tergite about 6 times as wide as long. Pleonites 1–3 free. Coxa 7 significantly smaller than coxa 6. Antenna 1 peduncle article 2 with or without anterodistal prolongation; article 3, 0.4–0.7 times as long as article 2. Antenna 2 peduncle, article 4 quadrate or linear, without a posterodistal lobe overlapping article 5; article 4, 1–3 times as long as greatest width; article 5, 2–8 times as long as greatest width. Mandibles without molar; incisor with 4 acute teeth on left, 5 uneven teeth on right; lacinia mobilis with concave, denticulate margin on left, about as broad as incisor and with 4 blunt teeth on right; spine row of denticulate spines. Maxillipedal palp of 4 articles, articles 4 and 5 free. Pereopod 1 with grossly widened propodus, about as wide as long, much wider than propodus of pereopods 2 and 3. Pereopods 2 and 3 basis anterior margin with setae along most of length, or with setae only on proximal half ( lilianae only); carpus posterodistal corner angular, not dominating propodus, or grossly produced as a lobe (about half as long as and dominating propodus), bearing long distal setae ( marcusi only); dactyli subchelate, half as long as propodus, or subchelate (closing on truncate palm), or a minute terminal hook. Pereopod 4 dactylus short, cylindrical, with a minute terminal seta, or vestigial, dome-like, with a minute terminal seta, or present as a short seta only. Pereopod 5 dactylus short, cylindrical, with a long terminal seta. Pereopod 6, 1.3 times as long as pereopod 5. Pereopod 7 dactylus short, cylindrical, with long terminal seta. Pleopod 2, appendix masculina straight, apex laterally denticulate (with 20 saw-like teeth) or strongly curved, laterally with minute setae. Uropod endopod half length of exopod. Oostegites 1 broad, overlapping, longer than broad; oostegites 2–4 almost circular, overlapping; oostegites 5 linguiform, reaching midline.

Remarks. Macrochiridothea is differentiated from Chiriscus by the quadrate or linear article 4 of the antenna 2 peduncle that lacks a posterodistal lobe, the presence of dactyli on pereopods 2 and 3, and the short pereonite 7.