Tetreres, CAULLERY, 1913

Capa, María, Hutchings, Pat & Peart, Rachael, 2012, Systematic revision of Sabellariidae (Polychaeta) and their relationships with other polychaetes using morphological and DNA sequence data, Zoological Journal of the Linnean Society 164 (2), pp. 245-284 : 269

TETRERES CAULLERY, 1913

Tetreres Kirtley, 1994: 188 .

Type species: Hermella varians Treadwell, 1901 , designation by Kirtley, 1994. Type locality: Mayagüez Harbour, Puerto Rico.

Diagnosis: The autapomorphy that defines the group is the arrangement of the inner paleae in a short ventral line on each inner margin of the opercular lobes. Nuchal hooks are large and with broadened shafts, also unique among sabellariids.

Description: Operculum longer than wide with lobes partially fused to each other (with deep indentation on ventral margin) and distal disc perpendicular to longitudinal axis, with large conical papillae around its perimeter. Outer paleae arranged in semicircles, straight, with flat blades and smooth margins. Inner paleae few in number, arranged in a single straight row on ventral side of operculum, with straight, flattened blades. One pair of large nuchal spines, with bent tips (hooks); without limbations or enlarged shaft. Palps wrinkled and deeply grooved, longer than operculum. Tentacular filaments arranged in single rows. Buccal flaps absent. Small median organ at the dorsal junction of the lobes of the opercular stalk. Neuropodia of segment 1 with one cirrus on each side of building organ; capillary neurochaetae present. Four long, tapering lateral lobes on segment 2. Thoracic branchiae absent. Four parathoracic segments. Parathoracic notochaetae lanceolate and capillaries alternating, similar in shape but smaller in neuropodia. Abdominal branchiae present, diminishing in size posteriorly.

Remarks: Tetreres shares with Bathysabellaria , Gesaia , and Mariansabellaria the occurrence of a long operculum with perpendicular distal disc, long opercular papillae, and single tentacular filaments without buccal flaps. Tetreres is unique amongst these genera in having an operculum partially fused along its length, the arrangement of the inner paleae on the ventral-inner side of the opercular lobes and the presence of four lateral lobes (at least in the specimens examined). There are ten species within the group reported from mostly deep waters in the Atlantic, Pacific, and Southern Oceans ( Kirtley, 1994).