Neotrigonia margaritacea (Lamarck, 1804), Common Brooch Shell

General Description

Shell has 22 ridges with scales that radiate from the hinge to the shell edge. Colour brown, inside shell white and shiny. Shell up to 5 cm long.

Biology

Brooch Shells are considered living fossils. They belong in a group that is abundant around the world as fossils, but there are only a few living species, all found in Australia. They live buried in a few centimetres of coarse sand in areas with moderate currents. The strong ornamentation of their shells may help them remain buried in place even when there are strong currents. Brooch Shells have two sexes, but until recently little was known about how the species reproduced. Work published in 2012 shows that spawning probably occurs as a continuous trickle through summer rather than in single large events.

Distribution

South-eastern Australia.

Habitat

Sand areas with moderate currents, from depths of 10 m to greater than 70 m.