Idanthyrsus

Opercular lobes completely divided into two free lobes, operculum longer than wide. Operculum with distal end slope present (distal end oblique to longitudinal margin); opercular papillae digitiform, twice longer than wide. Form of tentacular filaments compound (branching). Oral plates absent. Palps shorter or similar in length to operculum. Medial organ (cirrus) at dorsal junction of lobes present. Number of outer paleae 11–59; arrangement of outer paleae in semicircles. Angle of blades and axis of shafts straight; blade of outer paleae flat. Outer paleae denticles on lateral margins present, arrangement alternate or opposite; similar in length along paleae, or increasing in length distally, or larger at mid paleae. Distal margins of outer paleae denticulated. Outer paleae medial plume present; with denticles. Tip of outer paleae symetrical. Middle paleae absent. Number of inner paleae 8–26 pairs; inner paleae giving the appearance of 1 row. Arrangement of inner paleae in line covering inner margin of lobes, angle of blades and axis of shafts straight; blade of inner paleae cylindrical, like spines. Inner paleae with internal fusiform outline present, or absent. Medial organ present; eye spots on sides of medial ridge or medial organ present; ridge present. Nuchal spines or hooks present; number of nuchal spines or hooks 1–3 pairs; tip shape of spines bent, hooklike. Limbation on hooks absent or present, on the concave side of hooks. Neuropodia on segment 1 with 1 pair(s) of cirri. Neurochaetae on segment 1 absent. Number of lateral lobes on segment 2: 2–4 pair(s). Number of parathoracic segments 1. Thoracic branchiae present. Parathoracic neurochaetae with lanceolate and capillary forms. Branchiae in posterior abdominal segments present, or absent. Abdominal uncini with 2 rows of teeth. Dorsal papillae absent.

Description generated from: Hutchings, P.A., Capa, M., & Peart, R. 2012. Revision of the Australian Sabellariidae (Polycheata) and description of eight new species. Zootaxa, 3306: 1-60.

Additional references:
Kinberg, J. G. H. 1866. Annulata nova. Öfversigt af Königlich Vetenskapsakademiens förhandlingar, Stockholm, 23(4): 97-103.
Schmarda, Ludwig K. 1861. Neue wirbellose Thiere beobachtet und gesammelt auf einer Reise un die Erdr 1853 bis 1857. Erster Band (zweite halfte) Turbellarian, Rotatorien un Anneliden. 1-164. Wilhelm Engelmann. Leipzig.
Kirtley, D.W. 1994. A review and taxonomic revision of the family Sabellariidae Johnston, 1865 (Annelida; Polychaeta). Sabecon Press Science Series 1: 1-223 [84]

Australia, Chile, Madagascar, Mozambique, South Africa, New Zealand (North Island), Philippines, Sri Lanka; distribution within Australia: Bass Strait, New South Wales, Northern Territory, Queensland, South Australia, Victoria, Western Australia.

Insufficient data.