Tetraxanthus rathbunae Chace 1939

Tetraxanthus rathbunae Chace, 1939

(Fig. 1)

Measurements of larvae: CL, 0.45 ± 0.03 mm; n = 10.

Carapace (Fig. 1a): globose; dorsal spine long, lightly curved backward, without setae; rostral spines shorter than antennal protopod; lateral spines short; anterodorsal and posterodorsal sensory dorsal organs (SDO); 1 pair of posterodorsal, distally simple, setae; sessile eyes.

Antennule (Fig. 1c): not articled, with 2 long and 2 shorter and thinner terminal aesthetascs, 1 simple seta; accessory flagellum absent.

Antenna (Fig. 1d, e): uniramous; long, well-developed multispinulate protopod; endopod spine present; not articled exopod, with 5 unequal terminal simple setae and 1 lateral simple seta on outer side.

Mandible (Fig. 1f): with medial dentate molar process and enlarged lateral incisor process; palp absent.

Maxillule (Fig. 1g): coxal endite with 7 (3 subterminal + 4 terminal) plumodenticulate setae; basial endite with 5 plumodenticulate setae; 2-articled endopod, with 1 plumodenticulate seta on proximal articled and 6 (2 subterminal + 4 terminal) plumodenticulate setae.

Maxilla (Fig. 1h): coxal endite bilobed, with 4 (3 plumose + 1 plumodenticulate) + 4 (2 plumose + 2 plumodenticulate) setae; bilobed basal endite, with 5 + 4 plumodenticulate setae; bilobed endopod, with 3 plumodenticulate + 5 (4 plumodenticulate + 1 sparsely plumose) setae; scaphognathite with 4 marginal plumose setae and 1 stout posterior process.

First maxilliped (Fig. 1i): coxa with 1 simple seta; basis with 10 sparsely plumose setae arranged in 2+2+3+3; 5-articled endopod, with 3 (1 simple seta + 2 sparsely plumose) setae, 2 (1 simple + 1 sparsely plumose) setae, 1 sparsely plumose seta, 2 sparsely plumose setae, and 5 (1 simple + 4 terminal plumodenticulate) setae; 2-articled exopod, with 4 terminal natatory plumose setae.

Second maxilliped (Fig. 1j): coxa without setae; basis with 4 medial sparsely plumose setae arranged in 1+1+1+1; 3-articled endopod, with 1 simple seta, 1 plumodenticulate seta, and 6 (2 long and 1 short sparsely plumose + 2 simple + 1 plumodenticulate) setae; not articled exopod with 4 terminal natatory plumose setae.

Third maxilliped: absent.

Pereiopods: absent.

Pleon (Fig. 1b): with 5 segments; somites 2–5 with pair of posteromedian simple setae; somites 3–5 with posterolateral processes; somites 2–3 with dorsolateral processes; sixth somite merged with telson; pleopods absent.

Telson (Fig. 1k): bifurcated; each furca with 3 lateral spines and 2 simple setae; median shorter than others; inner margins with 3 + 3 stout spinulate setae separated by medial sinus.