Adelograptus tenellus (Linnarsson 1871): its astogenetic development and its stratigraphical and palaeogeographical distribution

The graptolite fauna of the Tremadoc graptolite zone of Clonograptus tenellus from the type locality at Nygård, Hunneberg, west-central Sweden, has been reinvestigated. Differences between the genera Adelograptus and Clonograptus are shown. Clonograptus tenellus is transferred to Adelograptus as A. tenellus with Clonograptus hians and Clonograptus sarmentosus treated as intraspecifical forms of younger (var. hians) or gerontomorphic (var. sarmentosus) growth stages. A. hunnebergensis as a laterally preserved younger form (compatible with var. hians) becomes a synonym of the older name A. tenellus. It may be concluded that the post-mortem orientation and mode of rhabdosome burial has a great influence on the taxonomic identification of graptolites. A short account on the palaeogeographic distribution and stratigraphic correlation follows.