The fossil algaChaetocladus gracilisrevisited: new material from the Silurian of Sweden

In 2006, a new species of non-calcified dasycladalean alga,Chaetocladus gracilis, from the upper Silurian of Skane (Scania), southernmost Sweden, was erected. The original description was based on a single incomplete fossil recovered from the abandoned limestone quarry at Bjarsjolagard, a classic geologic locality in Scania. Here we present four additional and, importantly, more complete specimens from this same site and type stratum. This new material largely corroborates the general anatomical features ofC. gracilis, but also adds some intricate details, most notably with regards to the external sheet-like phytoleim and organisation of the laterals. Elemental mapping confirmed an expected carbonaceous composition of the fossils, which are embedded in a calcareous mudstone. These additional fossils show that the originally described specimen was not a singular occurrence at this locality. Based on the state of preservation of our algal fossils, we note that the mudstone facies of the Ludlow Bjarsjolagard Limestone Member of the Klinta Formation (oved-Ramsasa Group), from which allC. gracilishave been recovered, share characteristics with deposits typically referred to as "algal-Lagerstatten".