The Pliensbachian at the Peniche Global Stratotype Section and Point (GSSP, Portugal) – a section full of remarkably preserved worms

Abstract The limestone and marlstone succession of the Pliensbachian Vale das Fontes and Lemede formations at the Global Boundary Stratotype Section and Point (GSSP) at Peniche (Portugal) received much attention in numerous studies. It contains abundant pyritic and limonitic aggregates, which are herein described and interpreted as remarkably preserved soft-bodied organisms (worms) for the first time. The slender to compact bodies with a cylindrical or dorsoventrally flattened cross-section are several centimetres long and have a diametre/width of 0.5–8 mm. They occur on bedding planes or are partly preserved within their burrows. Although their taphonomic history did not favour the preservation of many details, key features such as body shape, size and composition, as well as occasionally preserved segmentation and body appendages, allow a rough assignment to the phyla Nemertea, Annelida and Nematoda. Favourable circumstances such as intermittent dysoxic to anoxic bottom conditions, microbial activity and sudden burial have probably contributed to a reduced decay of the soft bodies. Comparison with similar successions globally shows that such a preservation of worms is not a unique process but occurs in several thick, fine-grained units throughout the Phanerozoic. Such inadequately preserved soft-bodied animals are still often overlooked but have the potential to add to our knowledge of the distribution and evolution of major clades of non-skeletal organisms.