The Neotrigonia is a Bivalve shell that is found in Australian waters. There are only 3 species in this family and they are the last ones of an ancient bivalve, often called a 'living fossil'. Its all to do with the hinge or dentation - where the shells join together. The shell has a strange primitive mechanism for the hinge. It is called 'trigonid'. It is believed that this family of shells, in ancient times, gave rise to the mussel families.
The Neotrigonia was called the 'brooch' shell because they were used as brooches in the Victorian era - due to their internal nacrous lustre.
It is a beautiful shell and normally found in relatively deep sea, up to 80 metres. However dead shells have been washed ashore on Brighton Beach, Adelaide as a result of the dredging that is occuring offshore.
And I have been collecting them.
Ana Glavinic of Flinders Uni, who is doing her Phd on this shell, says 'Neotrigonia is the sole surviving genus of the Trigoniidae, prominent during the Mesozoic, but only survived by a few species today in the southern ocean, occupying coastal waters of Australia, New Zealand and Papua New Guinea. '
We first met Ana when she was doing her honours degree and we went on an expedition with the Waterhouse Club of the South Australian Museum into the Outback of northern South Australia. Ana was excited by the many shell fossils that she found.
The scientist leading this was Prof. Tim Flannery and we were looking for Cretaceous marine fossils that once inhabited the shallow, cold inland sea of Australia, called the Eromango Sea. We found many shell fossils. Its strange to come across ancient fossil reefs of shells in the middle of a desert. Our team was very happy to find the almost complete fossil of a baby ichthyosaur, like a huge fierce-toothed dolphin. It is now in the South Australian Museum, Origin Gallery.
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