Metatiron Rabindranath, 1972

(Fig. 1; Fig. 43 a, b)

Metatiron Rabindranath, 1972, p. 84, fig. 1.

Type species. Pseudotiron brevidactylus Pillai, 1957 .—Original designation.

Component taxa. Metatiron bonaeriensis Alonso de Pina, 1998; M. brevidactylus (Pillai, 1957); M. triocellatus (Goeke, 1982); M. tropakis (J.L. Barnard, 1972) .

New diagnosis. Tironid Synopiidae without mandible palp. Cephalon in lateral view forming an even curve (occasionally slightly angular in males) terminating in a downward pointing short, acute rostrum. Interantennal head lobes triangular pointed or bluntly rounded. Maxilla 1 outer plate apex broad with two rows of pointed, generally denticulate spine-setae (Fig. 43b). Coxal plates 1 and 2 of subsimilar length and shape, plate 3 the largest, expanded in middle, posterior margin tapering from middle to blunt apex, plate 4 the shortest, anterior and distal margins broadly rounded, posterior margins straight to shallow concave comma-shape, plates 5 and 6 posterolobate, together, wider than plates 1–4; coxal plate 7 short, much wider than deep. Gnathopod 1 basis nearly straight (Fig. 43a), carpus nearly as long as basis. Pereopods 3–7 merus, carpus and propodus short, with stubby dactylus/unguis. Urosomites 1 and 2, or all 3, with posterior dorsal spine. Uropod 3 outer ramus of single article.

Distribution. Travancore SW India, Eastern America (Virginia to Florida), Caribbean Sea (Venezuela), Golf of Mexico, SW Atlantic (Brazil to Argentina), Eastern Pacific (California to Peru).

Key to species of Metatiron

1. Telson with small simple dorsal setae on each lobe........................................................... 2

- Telson with strong robust setae in row on each lobe.......................................................... 3

2. Pereopod 7 basis round, broader than long; uropod 3 peduncle about half as long as outer ramus, outer ramus with 7 robust setae dorsally...................................................................... M. brevidactylus (Pillai, 1957)

- Pereopod 7 basis broadly rounded, as broad as long; uropod 3 peduncle about 9/10 length of outer ramus, outer ramus with 4 (5) robust setae dorsally......................................................... M. triocellatus (Goeke, 1982)

3. Gnathopod 1 basis with row of long plumose setae on anterior margin; uropod 3 peduncle about half as long as outer ramus, outer ramus with about 8 dorsal robust setae; telson lobes with dorsal row of 7 8 small robust setae........................................................................................... M. bonaerensis Alonso de Pina, 1998

- Gnathopod 1 basis with simple setae of varying length on anterior margin; uropod 3 peduncle about 2/3 length of outer ramus, outer ramus with about 15 robust dorsal setae; telson lobes with dorsal row of about 8 long robust setae............................................................................................ M. tropakis (J.L. Barnard, 1972)