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Journal of Paleontology

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THE MIDDLE CAMBRIAN EODISCOID TRILOBITE DAWSONIA OELANDICA (WESTERGÅRD, 1936)

¹ GeoBiosphere Science Centre, Department of Geology, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden, <Niklas.Axheimer@geol.lu.se>

The first 20% of the full text of this article appears below.

	INTRODUCTION

 
THE EODISCINA comprises small, isopygous trilobites with either two or three thoracic segments. Small eyes may be present, but several genera and species lack visual organs. Eodiscoids are characteristic elements of many Cambrian faunas and are important for correlations of upper Lower Cambrian and lower Middle Cambrian strata (e.g., Robison et al., 1977; Ahlberg and Bergström, 1993; Geyer and Shergold, 2000; Fletcher, 2003).

Only five eodiscoid species are known from the Middle Cambrian of Sweden; Eodiscus scanicus (Linnarsson, 1883), E. borealis Westergård, 1946, E. punctatus (Salter, 1864), Dawsonia oelandica (Westergård, 1936), and Opsidiscus bilobatus (Westergård, 1946). The last-mentioned species is from the upper Middle Cambrian Lejopyge laevigata Zone (sensu Westergård, 1946) in Sweden, and is one of the latest known occurrences of an eodiscoid hitherto known (Rasetti, 1952).

The purpose of this paper is to refine and augment the concept of the Middle Cambrian eodiscoid trilobite D. oelandica. Insufficient work has been published on the species and the most recent thorough descriptions of the genus date back to the nineteenth and early to middle twentieth century (e.g., Matthew, 1896; Westergård, 1936, 1946; Rasetti, 1952). The specimens in this study were collected on the island of Öland, southeastern Sweden, and briefly discussed by Westergård (1936, 1946), supplemented with new, well-preserved material from the province of Jämtland, central Sweden.

	LOCALITIES AND GEOLOGIC SETTING

 
The material discussed in this paper was collected from three localities in Sweden (Fig. 1). Five cephala (Fig. 2.1–2.12) and two pygidia (Fig. 3.1–3.6) were collected by T. Weidner from a block of dark gray limestone found at a road section near the small community of Mon (Fig. 1.1, 1.2), located . . . [Full Text of this Article]