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Family  Psammobiidae

Sunset clams

The Psammobiidae is a medium-sized family of about 100 species (Huber, 2010) distributed worldwide in mainly tropical regions. It is well represented in the Indo-West Pacific Ocean, including northern Australia. In NSW there are seven species recorded; four of these are endemic to Australia with a southern Australian distribution, while the other three have a tropical Indo-West Pacific distribution and only extend southwards into northern NSW.

Psammobiids are burrowing bivalves, living in sand or mud in a range of situations. In NSW, one species is restricted to river estuaries, several prefer sand flats in sheltered waters, while one species shows a preference for regions of strong water flow.  At least two species live very shallowly, restricted to the intertidal zone or a few centimetres below.

Anatomically, psammobiids are very similar to tellinids. They have a pair of long siphons posteriorly which are extended to the surface to draw in the sediment and to expel waste. They are deposit feeders, drawing in a stream of water laden with food particles among other debris, and ejecting a stream of rejected particles in the outward water flow.

Family Reference

The family in Australia was revised by Willan (1993)

 Willan, R.C. 1993. Taxonomic Revision of the family Psammobiidae (Bivalvia: Tellinoidea) in the Australian and New Zealand region. Records of the Australian Museum Supplement 18.

Coverage

All the species of the family recorded from NSW are covered here.

Identification Notes

Shell form

Shells in this family are moderately large, elongate and fairly fragile. The family is closely related to the Tellinidae, but there is no posterior flexure of the shell as in Tellinidae.

Hinge and Ligament

The hinge has one or two cardinal teeth in each valve, but lateral teeth are absent in this family.  The ligament is external, attached to nymphs which project above the dorsal margin, behind the umbo. Fig. 1 shows an internal view of a conjoined pair of Gari livida, with detail of the hinge plate; the ligament in the middle and the cardinal teeth – two in the right valve and one in the left valve.

Shell Interior

The shell interior shows scars of the anterior and posterior adductor muscles, and a very large pallial sinus, extending to or past the shell midline. The shell margin is smooth.

Acknowledgement

This work relies heavily of the treatment of the family by Dr Richard Willan, as given in the Family Reference above. In some cases, particularly the habitat and distribution of species, Dr Willan’s work is quoted directly; such quotations are not referenced individually but are recognised here. I express my thanks to Dr Willan for allowing use of his work and his substantial assistance with the text.

Fig. 1 Internal view if Gari livida showing hinge and cardinal teeth (C.074201)