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Family  Thyasiridae

Thyasirids

The Thyasiridae is a little known family of mostly small, deep water bivalves with greatest diversity and abundance in temperate and cold waters of both northern and southern hemispheres. The number of described species is perhaps 100-150, but due to their small size and deep water habitat there are probably many undescribed species. In shell morphology thyasirids are similar to lucinids, but they differ anatomically in the structure of the gills.

There are only five species recorded from NSW, all of which occur subtidally, from 66-1463 m depth. They are all small, the largest having a maximum size of 12 mm, while the smallest is typically only 3 mm. Two of the species are known from only the type specimens and a few other lots, although the other species are moderately common.

Thyasirids are suspension feeders and some host symbiotic bacteria on the gills, as do the lucinids.

Family Reference

The Australian species were catalogued by Lamprell & Healy (1998).

Coverage

All the NSW species are detailed here.

Identification Notes

Three of the thyasirid species are readily identified by the presence of a strong posterior fold in the shell. The other two species have unusual specific characters which allow them to be easily identified.