Paratherochaeta n. gen.

TYPE SPECIES. — Therochaeta antoni Kirkegaard, 1996.

GENDER. — Feminine.

DISTRIBUTION. — Species of the genus thrive in tropical and subtropical regions, living in sediments from shallow waters (11 m) to deep waters (3330 m).

DIAGNOSIS. — Body anteriorly swollen or tapered, often constricted between chaetigers 2 and 3. Chaetiger 1 short, chaetiger 2 long, with a transverse constriction on its posterior margin, chaetiger 3 elongated, dorsally elevated, with a narrow transverse band of long papillae. Anterior margin of chaetiger 1 with a dorsal lobe. Cephalic cage made by chaetigers 1-2. Tunic generally covered with sediment grains. Chaetigers 5-7 with multiarticulated neurospines, rarely capillaries; posterior neurochaetae anchylosed hooks or aristate, tapered multiarticulate capillaries. Eight or more cirriform branchiae, sessile on a low branchial plate.

KEY TO SPECIES OF PARATHEROCHAETA N. GEN.

1. Sediment particles fine, often forming sediment tubercles throughout five chaetigers. 2

— Sediment particles large, often forming sediment tubercles throughout at least ten chaetigers ............................................................................................................................ 6

2. Anterior shield ventrally continuous ............................................................................3

— Anterior shield ventrally discontinuous; first neurohooks from chaetiger 5 ..................... ........................................................................................................... P. orensanzi n. sp.

3. Median neurochaetae aristate capillaries ....... P. scutigeroides (Augener, 1918) n. comb., restricted

— Median neurochaetae falcate neurohooks ................................................................... 4

4. Body of a single color, not markedly bicolor ............................................................... 5

— Body markedly bicolor, anteriorly whitish, posteriorly dirty orange or pale brownish; first neurohooks from chaetiger 7 .................................................................. P. ehlersi n. sp.

5. Median and posterior neurohooks falcate, robust; notochaetae of middle or posterior regions with longest median articles 5-6 times longer than wide ...... P. coronata (Ehlers, 1908) n. comb., restricted

— Median and posterior neurohooks almost straight, thin; notochaetae of middle or posterior regions with longest median articles three times longer than wide P. antoni (Kirkegaard, 1996) n. comb.

6. Median neurochaetae aristate capillaries ............................................. P. augeneri n. sp.

— Median neurochaetae falcate neurohooks ................................................................... 7

7. Neurochaetae markedly sigmoid ............................. P. scutigera (Ehlers, 1887) n. comb.

— Neurochaetae feebly falcate, almost straight P. africana (Rullier, 1965) n. comb., n. stat.

ETYMOLOGY.— Paratherochaeta n. gen. is derived from a combination of the name of its stem genus, Therochaeta, with the Greek prefix para (beside, near, by), to indicate its close resemblance to it.

REMARKS

Paratherochaeta n. gen. is closely allied to Therochaeta as indicated in a phylogenetic analysis using morphological features (Salazar-Vallejo et al. 2008). Both genera include species with a longer second chaetiger and at least the first three chaetigers may have a cover of cemented sediment grains. Their main difference is that in Paratherochaeta n. gen. there are no pseudocompound chaetae present, but falcate hooks or capillary chaetae.