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Abstract
The late Llandovery graptolite fauna of the Retiolites Shales on Kinnekulle Mountain in the province of Västergötland has long been known but never illustrated or studied in detail. New collections of graptolites from an interval at the very top of the exposed succession confirm previous reports of cyrtograptids, which make the shales on Kinnekulle the youngest preserved Palaeozoic rocks in the area. The co-occurrence of Oktavites spiralis and Cyrtograptus lapworthi constrains the strata to the lower lapworthi Biozone of the upper Telychian. The associated graptolite fauna comprises numerous monograptids and Retiolites angustidens as well as Cyrtograptus kinnekullensis n. sp., characterised by its open coiling and the presence of a second-order cladium on the second thecal cladium. This early occurrence of a cyrtograptid species with a second-order cladium on Baltica matches evolutionary patterns observed in Laurentia, suggesting that the ability to grow cladia of both first and higher order evolved approximately, synchronously and at the very beginning of cyrtograptid evolution.
Acknowledgements
Many specimens for this study were collected during undergraduate and graduate courses to Västergötland from 2008 to 2012. We would like to thank all who donated their finds for this study, in particularly Max Telford (London) and Heather Marlow (Heidelberg). Insightful discussion of the 2TRD data plots with Trond Reitan (Uppsala, Oslo) is much appreciated. Stephen Poropat is thanked for linguistic assistance. This study was financially supported by a grant of the Swedish Research Council (VR) to MS. Constructive reviews by David Loydell and Jan Zalasiewicz greatly improved the manuscript.