The earliest leperditicope arthropod: a new genus from the Ordovician of Spitsbergen

Mark Williams,David J Siveter

doi:10.1144/jm.27.2.97

Abstract

Abstract. A new leperditicope from the carbonate-dominated sequence of the Nordporten Member of the Kirtonryggen Formation, Spitsbergen, is the oldest confirmed representative of this group of bivalved arthropods. It occurs at a stratigraphical level low in the Floian Stage of the Early Ordovician, and below rocks bearing graptolites of the Pendeograptus fructicosus Biozone. Its occurrence emphasizes an ‘out of Laurentia’ palaeogeographical origin for leperditicopes, though there are no obvious antecedents in the earlier, Cambrian record of that palaeocontinent.

Highlights

Leperditicopida are large bivalved arthropods typically 5–50 mm in length
Leperditicopes first become common in the Middle Ordovician of North America and Greenland (e.g. Poulsen, 1937; Harris, 1957, 1960; Berdan, 1976, 1984)
A new and early occurrence of an isochilind leperditicope is reported from the Early Ordovician Nordporten Member of the Kirtonryggen Formation, Spitsbergen

Summary

Introduction

Leperditicopida are large bivalved arthropods typically 5–50 mm in length. Conventionally treated as ostracods (e.g. Whatley et al, 1993), their biological affinities are unclear, compounded by a lack of evidence from soft tissue preservation and the absence of post-Devonian representatives of the group (Vannier et al, 2001). Leperditicopes first become common in the Middle Ordovician of North America and Greenland (e.g. Poulsen, 1937; Harris, 1957, 1960; Berdan, 1976, 1984). A new and early occurrence of an isochilind leperditicope is reported from the Early Ordovician Nordporten Member of the Kirtonryggen Formation, Spitsbergen.

Results

Conclusion