Brachiopod and molluscan faunas of Everett's Quarry, Kakanui

Robinson, Jeffrey H.

The bioclastic limestone exposed in the small, long disused quarry known as Everett's Quarry, near Kakanui, North Otago, contains probably the most diverse invertebrate fossil of Cenozoic age in New Zealand. The assemblage in the Everett's Quarry limestone (EQl) appears to be a biocoenosis (life assemblage) which accumulated on the upper flanks or top of a volcanic seamount. A single 235 gram sample extracted from an uncemented, friable upper layer yielded ea. 300 different species of brachiopods, molluscs, bryozoans, foraminifera, ostracods, corals, echinoderms, serpulids, barnacles etc from the sediment fraction greater than 2 phi (0.25 mm). Thus the EQl provides an exceptional window into Late Eocene biodiversity in a mid latitude, shallow southern hemisphere biota. This study demonstrates that the species diversity in the EQl in the Late Eocene is at least as great as that of the skeletal carbonate sediments presently accumulating in the Three Kings region (Keane, 1986). This thesis discusses the morphology, systematics and paleoecology of thirteen species of brachiopod and twelve species of bivalve mollusc from Everett' s Quarry. One Recent species of inarticulate brachiopod is redescribed and three new species of inarticulate brachiopod, one Recent and two of Late Eocene age are described. A study is made of brachiopod pedicle traces in carbonate shells from Everett' s Quarry and other Recent and fossil localities. New illustrations of 53 species of benthic foraminifera, 23 species of ostracod and 80 species of bryozoan from Everett' s Quarry are presented together with a list of all known taxa from the EQI. Fossil Novocrania huttoni from Everett's Quarry and two older localities is described for the first time. Recent Valdiviathyris quenstedi is redescribed and figured in detail; the unique internal processes are considered to be the site of attachment for the brachial protractor muscles. A new fossil species Valdiviathyris campbelli of Late Eocene age is described. Two new species of spinose Novocrania are described; living N. spinina and fossil N. spinosa of Late Eocene age. Aetheia gualteri and Tegulorhynchia sublaevis are described briefly. Liothyrella concentrica is described and ratios of shell dimensions of L. concentrica and other fossil and Recent Liothyrella species in New Zealand are compared. L. circularis and L. kakanuiensis are .placed in synonymy. Terebratulina suessi is described and a lengthfrequency analysis is carried out an of assemblage of 874 specimens from a single sample of Everetts Quarry limestone. The analysis suggests that the 874 specimens represent a life assemblage, that T. suessi has a steady growth rate during its adult lifetime and that increasing levels of competition for space among brachiopods results in an increasing mortality rate. A new fossil species, Argyrotheca oamarutica, is described from Everett' s Quarry and a number of other localities. M age !la carinata is briefly described. Terebratella oamarutica is reassigned to the genus Aneboconcha and a possible close taxonomic relationship with Magella carinata is suggested. Neobouchardia minima is briefly described. Stethothyris uttleyi is described; the pedicle muscle scars are analysed and a free-living mode of life is proposed for this species. The three main pedicle types of brachiopods, and characteristic footprints made by each type of pedicle are discussed. Some subfamiles of brachiopod have distinctive footprints. The ichnogenus and ichnospecies of Bromley & Surlyk (1973) are rediagnosed and two new ichnogenera are proposed. New terms 'colonist' and 'host' are proposed for an attached brachiopod and its calcareous shelled animal substrate respectively. Colonisthost relationships within a single brachiopod species; between two brachiopod species; and between brachiopod and mollusc species are traced back to the latest Eocene and Miocene. Bivalve molluscs Pteria sp.; Semipallium sp.; Serripecten n. sp. A and new species Serripecten n. sp. B; Mesopeplum sp.; two probable new species of Cyclochlamys, A and B; Dimya sp.; Anomia sp., Pododesmus sp.; Limatula trulla; Limea sp. and Pycnodonte (Notostrea) subdentata are briefly described and their Recent and fossil occurrences in New Zealand are discussed. A gastropod operculum, probably of the family Colloniinae, and a cephalopod Aturia sp. are described briefly. The bivalve mollusc fauna are largely attached forms suggesting an environment with significant current activity. An assemblage of 524 upper valves of Pycnodonte (Notostrea) subdentata was measured and the resulting mortality rate suggests they are a life assemblage. Three different types of predatory drill hole which are found in the bivalve mollusca and other taxa at Everett's Quarry are described and possible predators discussed.

xiii. 292 p. ill. 30 cm.

2004Robinson