Papiliograptus retimarginatus n. sp., a new retiolitid (Graptolithina) from the predeubeli/deubeli Biozone (upper Homerian, Wenlock, Silurian), the recovery phase after the lundgreni Extinction Event

Papiliograptus retimarginatus n. sp. is reported from the praedeubeli/deubeli Biozone, upper Homerian (Silurian) of the Bartoszyce IG-1 drill core of Poland, Baltica. It is the second species of the genus Papiliograptus Lenz & Kozłowska-Dawidziuk, 2002, belonging to the new retiolitid fauna of the recovery period after the lundgreni Extinction Event. Two characteristic features of the new retiolitid fauna are the development of a geniculum and singular or paired genicular structures. The new form has extremely wide, singular, reticulated genicular processes. It is suggested that these structures may have been an adaptation to prevent the planktonic colony from sinking in the water column.