Orbiniids are burrowing deposit feeders that do not make permanent tubes. They
are common in tidal flats and sometimes attain dense populations in sediments that are of mixed sands and muds. Their bodies are distinctive with a well-developed, smooth, firm flattened thoracic region and a long, tapering, fragile and ragged-appearing abdominal region bearing branchiae and parapodial lobes. The prostomium is smooth without any sensory appendages or palps.
Diversity
The most important modern review of orbiniid systematics is by Hartman (1957),
who redefined all the genera. She was also the first to create the 2 subfamilies;
Orbiniinae and Protoariciinae. None of the later works (Day, Mackie and Solis-Weiss & Fauchald) substantially alters the system established by Hartman (1957).
Fauchald (1977) recognises 15 genera and 124 species in the world. The interactive key contains the 17 genera now recognised in the world, and describes
21 species from the 6 genera found in Australian waters (as well as 2 species
found in New Zealand).
The interactive key documents the southeastern Australian Orbiniidae fauna at species level, based on material from subtidal sediments in inshore bays
(Port Phillip, Western Port, and Jervis Bays) and the continental shelf of
eastern Bass Strait. Also included are a number of species collected from
intertidal mud flats in Port Hedland, northwestern Western Australia.
