A reappraisal of the late Quaternary fossil vertebrates of Pyramid Valley Swamp, North Canterbury, New Zealand

Abstract

The late Quaternary fossil vertebrate fauna from deposits at Pyramid Valley, North Canterbury, New Zealand is reassessed. The faunal composition as contained in previous lists is updated, and minimum numbers of individuals represented are given. Measures of faunal diversity are presented and compared with values for present New Zealand systems and other fossil sites. The revised faunal list includes a tuatara, one gecko, at least 46 species of bird, and one species of bat. The avifauna was dominated by moas and waterfowl. The fossil record was biased towards large taxa because of the taphonomic properties of the site. Deposition was slow: individuals were added a few per year and not as a result of catastrophes. Bird diversity, by various measures, was high for a New Zealand site. Diversity indices and rarefraction curves suggest that a site, or group of comparable smaller sites, must contain more than 300 individuals before adequate estimates of the species richness of the sampled fauna are possible. Ten diurnal vertebrate guilds are recognised, several of which are now extinct; all guilds have lost at least 50% of their former constituent species. Sample sizes of two moa taxa were sufficient to allow preliminary analysis of age and sex ratios: in Dinornis giganteus the sex ratio was skewed strongly in favour of the putative female individuals; in Emeus crassus the ratio was nearly equal. Consequences of the differences are discussed. Evidence is presented that Gallirallus minor, reported from fossil deposits, was based on individuals of Gallirallus australis at the lower end of the size range. Evidence of predation of adult moas by Haast's eagle is recorded, and the predator‐prey ratio for a system based on birds is given. The chronology, environment, and components of the fauna are discussed.