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32 Pāua are ancient rocky shore icons

Mollusca, Gastropoda: Haliotis sp.

Pāua are iconic inhabitants of rocky shores around Aotearoa New Zealand. Known formally as Haliotis, there are three species of pāua living in New Zealand today. And although they have a global fossil record dating back to the Cretaceous, Haliotis is an uncommon discovery in the New Zealand fossil record. Importantly though, the small number of Haliotis fossils that have been found locally reveal that pāua has a long history in Zealandia.

The figure shows two images of the same tiny fossil pāua shell from Cosy Dell. The top image is the external view and the bottom image is the internal view. Both views highlight the row of tiny pores or tremata on the shell's outer margin as well as the iridescent color that has been preserved for 25 million years. The shell is delicate and small, with a scale bar indicating a size of around two centimetres.

External and internal views of a tiny fossil pāua shell from Cosy Dell. Note the row of tiny pores (tremata) and the iridescent colour still preserved after 25 million years. This fragile shell floated out from its protective ‘cave’ inside a larger gastropod when the shell was washed in water. Image credit: Yutong Wu.

The Cosy Dell fossil locality in Southland preserves a rare rocky shore environment from between 25.4 and 24.4 million years ago. Several incomplete specimens of Haliotis have been discovered at Cosy Dell but the one shown here is a perfectly-preserved fragile juvenile, just 3 mm long, which displays the row of tiny pores (tremata) characteristic of pāua and retains traces of iridescent pearly nacre.

Pāua cling to a rock substrate with a strong muscular foot and graze on seaweed. The fossils at Cosy Dell occur with a wide range of intertidal and subtidal animals such as barnacles and algal grazers such as chitons. The pāua and chiton fossils therefore provide indirect evidence for a diverse seaweed flora. This is amazing, as soft and fragile seaweeds are rarely, if ever, preserved in the fossil record.

—Written by Daphne E Lee

Specimen number: OU 44922 Age: 25.4 to 24.4 million years ago (late Oligocene, boundary between the Duntroonian and Waitakian stages)
Locality: Waimumu, Southland Rock Formation: Chatton Formation
Collected by: DE Lee
Citation: Lee D, Lindqvist J, Beu A, Robinson J, Ayress M, Morgans H, Stein J. 2014. Geological setting and diverse fauna of a Late Oligocene rocky shore ecosystem, Cosy Dell, Southland. New Zealand Journal of Geology and Geophysics 57:195–208. doi.org/10.1080/00288306.2014.898666
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