Cheirurina (Trilobita) from the Upper Ordovician of Västergötland and other regions of Sweden

Abstract

Upper Ordovician (Ashgill) Cheírurina (Trilobita) from Västergötland, Sweden, are described on the basis of a new collection from Skultorp, as well as old collections housed in Swedish museums. Some Ashgill trilobites from other regions of Sweden and Poland are discussed for comparison. Where available, the relevant originals of Linnarsson (1869), Holm (1898), Olin (1906), Törnquist (1905) and Warburg (1925) are refigured. Eighteen species belonging to ten genera (one not determined) are described or discussed. Two new species, Pseudosphaerexochus parallelus and Pseudosphaerexochus? dubius are described. Sphaerocoryphe thomsoni Reed, 1906 from the Ashgill of Girvan, Scotland, is regarded as a junior subjective synonym of S. dentata Angelin, 1854 from the Ashgill of Västergötland. The Swedish Cybeloides loveni (Linnarsson, 1869) differs from the Scottish Cybeloides girvanensis (Reed, 1906) only on a subspecific level. In addition to nineteen species previously known to be common to the lower-middle Ashgill of Poland and Västergötland, three more species occur in both regions: Pseudosphaerexochus wolkae Kielan, 1960, Pseudosphaerexochus? dubius n. sp., and Pseudosphaerexochus parallelus n. sp. Dindymene plasi Kielan, 1960? is recorded from the upper Lower Ordovician of Sweden.

Key Words:

• Trilobita
• Cheirurina
• Ordovician
• Ashgill
• Jonstorp Formation
• Ulunda Mudstone
• Västergötland
• Sweden