Morphometrics and palaeoecology of the coral Agetolites from the Xiazhen Formation (Upper Ordovician), Zhuzhai, South China

Abstract

Sun, N., Elias, R.J., Choh, S.-J., Lee, D.-C., Wang, X.-L. & Lee, D.-J., February 2016. Morphometrics and palaeoecology of the coral Agetolites from the Xiazhen Formation (Upper Ordovician), Zhuzhai, South China. Alcheringa 40, xxx-xxx. ISSN 0311-5518.Agetolites is a peculiar cerioid coral possessing traits of both tabulates and rugosans. The presence of numerous mural pores has been considered by some workers to indicate a relation to tabulates, although an affinity to rugosans has also been proposed based mainly on well-developed septa that alternate in length. Agetolites is by far the most common colonial coral in the Upper Ordovician Xiazhen Formation at Zhuzhai, in the JCY (Jiangshan-Changshan-Yushan) triangle region of South China. It occurs in various lithofacies representing a wide range of depositional environments. Five species are recognized and verified by cluster analysis, discriminant analysis, descriptive statistics and bivariate plots: A. yushanensis Lin, 1960, A. raritabulatus Lin, 1960, A. waicunensis (Lin & Chow, 1977), A. oculiporoides Lin, 1960 (including A. huangi Lin, 1960 as a junior synonym) and A. maxima (Lin & Chow, 1977). Agetolitids from the JCY triangle described previously under the generic name Agetolitella are herein transferred to Agetolites. In the Xiazhen Formation at Zhuzhai, A. waicunensis and A. maxima are restricted to the lower part of the formation, whereas A. yushanensis occurs in the upper part. Agetolites raritabulatus and A. oculiporoides have greater stratigraphic ranges in the lower and upper parts of the formation. The size and shape of Agetolites coralla at Zhuzhai are considered primarily to be intrinsic characteristics of the species but in some cases also seem to be related to lithofacies; large and domical coralla are dominant in calcareous mudstone facies, whereas small coralla with various forms are commonly found in reef or reef-related facies. In the latter facies, spatial competition is indicated by common occurrences of both Agetolites encrusting stromatoporoids and stromatoporoids encrusting Agetolites.