30 Long extinct relative of ‘The Chambered Nautilus’

Mollusca, Cephalopoda: Aturia mackayi

In the introduction to the Mollusca section of the eBook we describe cephalopods with many-chambered and coiled shells. We mention two lineages of these cephalopods, the ammonoids and the nautiloids. Nautiloids have simple septa and sutures inside the shell and usually a central siphuncle in contrast to the often very complex septa and sutures and ventral siphuncle of the extinct ammonites. All ammonoids globally died out at the same time as the last of the non-avian dinosaurs, around 66 million years ago. However, the nautiloids survived this mass extinction and a few are still swimming in modern oceans, mostly in seas around the southwest Pacific. The fossil diversity of nautiloids is therefore much larger than the living diversity and includes some truly spectacular discoveries.

A spectacular example of nacreous shell of the nautiloid Aturia mackayi (specimen OU 39928). Image credit: JH Robinson.

The Geology Museum collections display many extinct nautiloids including this nacreous specimen which is a very large, and nearly complete example of the extinct genus Aturia.

This handsome and well-preserved specimen was collected in 1990 by Andrew Grebneff and Ewan Fordyce from a locality of Bortonian (Late Eocene) age near Evans Crossing, Pareora River in South Canterbury. Andrew identified it as Aturia mackayi, a species named by Charles (later Sir Charles) Fleming in 1945.

There are currently three species of Aturia recognised from Aotearoa New Zealand: Aturia mackayi, which ranges in age from the Paleocene to the Eocene; Aturia coxi, which is known from Middle to Late Miocene sites; and Aturia cubaensis, with an overlapping range of Early to Late Miocene.

Living Nautilus are scavengers and live on fish, cast-off moults of lobsters, and crabs, and other decaying material. Scientists have suspended the remains of chickens from research vessels as bait when endeavouring to catch live animals for study. It is assumed that fossil nautiloids such as Aturia were also ocean scavengers.

Nautilus shells are beautiful examples of logarithmic spirals and, as such, are often used in art works and logos. ‘The Chambered Nautilus’ is the name of the school song of Otago Girls’ High School in Ōtepoti Dunedin and the school symbol. A 1.8 metre tall bronze sculpture of two hands holding up a chambered nautilus was specially commissioned for the school’s 150th jubilee celebrations. It seems appropriate that animals that swam in seas around Zealandia for millions of years are celebrated in this way even though seas around New Zealand are too cold for nautiloids to survive in today.

—Written by Daphne E Lee