BRYOZOAN STUDIES 2019 Bryozoan Skeletal Index (BSI): a measure of the degree of calcification in stenolaemate bryozoans Patrick N. Wyse Jackson1*, Marcus M. Key, Jr.2 and Catherine M. Reid3 1 Department of Geology, Trinity College, Dublin 2, Ireland [*corresponding author: e-mail:
[email protected]] 2 Department of Earth Sciences, Dickinson College, Carlisle, Pennsylvania 17013-2896, USA [e-mail:
[email protected]] 3 School of Earth and Environment, University of Canterbury, Private Bag 4800, Christchurch, New Zealand [e-mail:
[email protected]] ABSTRACT minimal. In this study the differences observed in The Upper Ordovician of the Cincinnati Arch region BSI between trepostome and cystoporate species in of the United States has yielded a highly diverse the Cincinnatian is significant, and ramose colonies bryozoan fauna, and which provides an excellent show a higher BSI than encrusting zoaria in the data source for use in this study that proposes same fauna. a novel measure of the degree of skeletal material in Palaeozoic stenolaemate bryozoans. This study is based on 16 trepostome species and one cystoporate INTRODUCTION species described from the Dillsboro Formation Bryozoans of the Class Stenolaemata are characterised (Maysvillian to early Richmondian, Cincinnatian) of by having autozooecial chambers that are broadly Indiana and in 20 species (15 trepostomes and five tubular in nature. They were significant members of cystoporates) from the Lexington Limestone and the Palaeozoic faunas appearing in the Ordovician Clays Ferry