Early Llandovery monograptids from Bornholm and the southern Urals: taxonomy and evolution

Abstract

The most complete Lower Llandovery succession of mudrocks yielding graptolites within the ascensus, acuminatus and vesiculosus Biozones was studied in the Billegrav-1 core, South Bornholm. Special attention is given to the taxonomy and stratigraphical ranges of monograptids found in the vesiculosus Biozone in the core and nearby exposures in Øle Å. Monograptids of the ascensus-acuminatus and vesiculosus Biozones were also discovered in condensed carbonaceous shale sequences of the Sakmara Formation in the southern Urals. Monograptids from Bornholm and the southern Urals are described, and referred to 5 genera and 17 species (4 new and 4 in open nomenclature). The new genus Huttagraptus (type species H< praestrachani) is erected. Based on the present taxonomical studies the main morphological trends, phylogenetical relationships and diversity dynamics of the earliest monograptids are discussed.