Brachiopods and trilobites from the Ordovician Lower Hovin Group (Arenig/Llanvirn), Hølonda area, Trondheim Region, Norway: new and revised taxa and paleogeographic interpretation

Abstract

Thirteen brachiopod and 13 trilobite taxa in 15 collections from the Hølonda Limestone and Nyplassen Formation of the Lower Hovin Group confirm the late Arenig-early Llanvirn age of these rocks. New monotypic and apparently endemic brachiopods are: the taffiid Chloupskia scabrella n.gen., n. sp.; the leptelline Bockelia angusticostata n.gen. n.sp.; and the syntrophosid Rhabdostrophia striatisculpta n. gen., n, sp. The new leptelline genus, Vehnia (type species, Chonetoidea triangularis Reed) also occurs in northwestern Ireland. The trilobites Blosyropsis cf. B. billingsi Whittington and Ectenontus sp.indet. are newly recorded from these rocks; specific affinities of two trilobites, Illaenus sp. cf. auriculatus Ross, and Calyptaulax cf. C. incepta Whittington are established. Similarity with North American assemblages is supported by co-occurrence of 8 brachipod taxa here and in Nevada and western Newfoundland, and 12 of trilobite taxa from these areas and from Spitsbergen. The superposition of the Lower Hovin Group above volcanic rocks correlated with the Løkken Group indicates their insular origin. The fossils and the rocks that contain them show that this island or island complex lay offshore from the Laurentian craton, at a low latitude in a tropical to subtropical climatic realm.