Echinothambematidae

Diagnosis: Menzies (1962) “Paraselloidea with fused or free head, eyes lacking. Mandibles normal, molar process well developed and expanded a truncated apex. Antennae shorter than body, about twice the length of cephalon. All peraeopods simple, 2-7 simple walking legs; dactyl with two terminal claws. Uropoda terminal with peduncle. Last one or two peraeonal somites fused with pleon. First three articles of maxillipedal palp expanded, as wide as endite. Coxal plates lacking. First peduncular article of first antenna much expanded. Anus contained within the branchial chamber.”

Key to genera and species in Echinothambematidae

1 Lateral margins of most pereonites extended in irregular cone-shape with 1 or 2 apical spine setae; head and pereonite 1 not fused……… Echinothambema ........................................................................... 2

- Lateral margins of pereonites irregularly rounded without extensions; head and pereonite 1 fused……… Vemathambema ... 3

2 Antennula article 1 with distal projection extending beyond article 2; pereonites 1–7 lateral projection with 1 apical seta, pereonite 2 with 1 additional posterodistal seta; pleotelson lateral margins with seta on fused first pleonite, otherwise smooth.................................................................................. E. ophiuroides

- Antennula article 1 cylindrical without projection; pereonites 1 and 4–7 with one terminal seta on lateral projections, pereonites 2 and 3 with two terminal setae; pleotelson lateral margins with 3 stout setae.............................. E. aculeata

3 Antennula article 1 extended into upward curved sickle-shaped spine............................ V. falciclava sp. nov.

- Antennula article 1 cylindrical........................................................................... 4

4 Pereonites 2–4 middle dorsum vaulted across the segment overreaching other parts of the margin, distally rounded; opercular field covering approximately 80 (♀) and 90 (♂) % of entire ventral pleotelson area.................... V. argentinensis *

- Pereonites 2–4 not transversely vaulted or laterally expanded, individual margins slightly different, 2 with small anterior point, 3 rounded, 4 angular in middle; opercular field covering approximately 65 (♀) and 75 (♂) % of entire ventral pleotelson area........................................................................................ V. elongata

* Assuming that the head is fused with pereonite 1 (see Discussion).