The cephalopods of the Kullsberg Limestone Formation, Upper Ordovician, central Sweden and the effects of reef diversification on cephalopod diversity

The cephalopods collected from the mud mounds of the Kullsberg Limestone Formation, late Sandbian–earliest Katian(?), south central Sweden, are highly diverse and comprise 26 identifiable species of 12 families and six orders in a sample of <i>c.</i> 180 specimens. The assemblage is strongly dominated by orthocerids in abundance and diversity. In contrast, the time-equivalent assemblage of the reef limestone of the Vasalemma Formation of Estonia is dominated by actinocerids and less diverse. Only one-third of the species co-occur in these two palaeogeographically relatively close assemblages. The taxonomic composition of the Kullsberg assemblage is, on the order level, more similar to that of the late Katian–early Hirnantian Boda Limestone Formation of south central Sweden, which represents a similar relatively deep depositional environment. The high local differentiation of cephalopod reef faunas exemplifies the importance of the emergent Baltic reef habitats in diversification processes during the early Late Ordovician. Of the described taxa, the following are new: <i>Beloitoceras thorslundi</i> sp. nov., <i>Cameroceras motsognir</i> sp. nov., <i>Clothoceras thornquisti</i> gen. et sp. nov., <i>Danoceras skalbergensis</i> sp. nov., <i>Discoceras amtjaernense</i> sp. nov., <i>D. nilssoni</i> sp. nov., <i>Endoceras naekki</i> sp. nov., <i>Furudaloceras tomtei</i> gen. et sp. nov., <i>Isbergoceras consobrinum</i> gen. et sp. nov., <i>I. niger</i> gen. et sp. nov., <i>Isorthoceras nikwis</i> sp. nov., <i>I. sylphide</i> sp. nov., <i>I. urdr</i> sp. nov., <i>I. verdandi</i> sp. nov., <i>Kullsbergoceras nissei</i> gen. et sp. nov., <i>Ordogeisonoceras uppsalaensis</i> sp. nov. and <i>Valkyrioceras dalecarlia</i> gen et sp. nov. http://zoobank.org/urn:lsid:zoobank.org:pub:F5243F9B-547C-424F-895F-6CCECA8BBF11