A sample of Cyclocardia bivalves from the Otekaike Limestone, Hakataramea Valley, south island.
Although in the Otago Geology department we mainly focus on fossil marine vertebrates from the South Island, some occasional work is done on marine invertebrates. One of Ewan's undergraduate students was interested in doing a morphometric analysis of bivalves, and Ewan suggested she work on the small cockle-like bivalve Cyclocardia. Cyclocardia is not abundant within the late Oligocene Otekaike Limestone, but it is distinctive and easily identified in the field.
Some of these have naticid gastropod borings, probably from Magnatica.
On one of our last field days in Hakataramea Valley in the austral fall, we took a break from excavating a large mysticete to collect some Cyclocardia specimens for the student project. Over about a 20 minute period, the four of us (Ewan, lab tech Sophie, fellow student Yoshi Tanaka, and myself) picked up about 120 specimens or so. Some have margins that are too chipped.
It must be nice to have large sample sizes...