Acta Palaeontologica Polonica

Phosphatised olenid trilobites and associated fauna from the Upper Cambrian of Västergötland, Sweden

Per Ahlberg, Hubert Szaniawski, Euan N.K. Clarkson, and Stefan Bengtson

Acta Palaeontologica Polonica 50 (3), 2005: 429-440

Secondarily phosphatised olenid trilobites from organic-rich limestones (orsten) in the Furongian (Upper Cambrian) of Västergötland, south-central Sweden, are described and illustrated. All trilobites originate from the Peltura scarabaeoides Zone and were collected on the western slope of Kinnekulle. Only the dorsal exoskeletons have become secondarily phosphatised, and the ventral appendages are not preserved. Yet the material is otherwise remarkably well preserved and reveals the morphology of the olenid trilobites in greater detail than hitherto known. Species belonging to the genera Ctenopyge, Sphaerophthalmus, Parabolina, and Peltura are identified, and several juvenile specimens are present in the material. The material is disarticulated and fragmentary, and it has only been possible to identify a few specimens to species level. In addition to chaetognaths and conodonts, the trilobites are associated with pelmatozoan columnals, a possible camaroid, and fossils of uncertain affinities. These fossils, along with a probable conulariid fragment from the Peltura minor Zone, are also described and discussed. The presence of a benthic fauna of pelmatozoans, and possible conulariids and camaroids, indicates that at least parts of the Peltura zones were deposited during dysoxic rather than anoxic periods. Moreover, the sea floor must have been firm enough to allow colonisation by sessile organisms.

Key words: Olenidae, Trilobita, Problematica, phosphatisation, Cambrian, Alum Shales, Västergötland, Sweden.

Per Ahlberg [], GeoBiosphere Science Centre, Department of Geology, Sölvegatan 12, SE−223 62 Lund, Sweden; Hubert Szaniawski [], Instytut Paleobiologii, Polska Akademia Nauk, ul. Twarda 51/55, PL−00−818 Warsaw, Poland; Euan N.K. Clarkson [], Grant Institute of Earth Sciences, School of Geosciences, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, UK; Stefan Bengtson [], Department of Palaeozoology, Swedish Museum of Natural History, Box 50007, SE−104 05 Stockholm, Sweden.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (for details please see, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.