Idanthyrsus australiensis

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. Number of opercular papillae 11–13. 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 15–16; 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; similar in length along 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 12–13 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. Medial organ present; ridge present. Nuchal spines or hooks present; number of nuchal spines or hooks 3 pairs; tip shape of spines bent, hooklike. Limbation on hooks absent. Neuropodia on segment 1 with 1 pair(s) of cirri. Neurochaetae on segment 1 absent. Number of lateral lobes on segment 2: 3 pair(s). Number of parathoracic segments 1. Thoracic branchiae present. Parathoracic neurochaetae only lanceolate. Branchiae in posterior abdominal segments present. 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:
Haswell, William A. 1883. On some new Australian tubicolous annelids. Proceedings of the Linnean Society of New South Wales, 7: 633-638.

Australia; distribution within Australia: New south Wales, Nortyern Territory, Queensland, South Australia, Victoria, Western Australia.

Marine, inshore (including inshore bays) and marine, shelf.