An unusual invertebrate trace fossil from the Thuringian Rotliegend

Recently, a trace fossil of unusual morphology was found in the Cabarz quarry in the Thuringian Forest near Bad Tabarz (Thuringia, central Germany). The specimen was collected at the base of Floor 2B of the quarry exposing rocks of the Lower Goldlauter Formation (Lower Rotliegend, early Permian). The trace fossil is preserved as epi-/hyporeliefs on two siltstone slabs representing part and counterpart. The siltstone surface is of greyish-red colour and shows rain drop marks. The deposit is interpreted as floodplain facies. The trace fossil is discussed to be composed of a central crawling track of the invertebrate body and, along with it, impressions of walking legs on both sides. In the concave epirelief, the crawling track exhibits a string-of-pearls-like structure. Compared to literature, morphological similar impressions of walking legs and the pearl-like central track were known from Diplichnites and Imponoglyphus, respectively. Both ichnogenera have been reported from the study area before. Combining these characteristics in a single trace corresponds morphologically to Glaciichnium, which is currently interpreted to represent locomotion traces of isopods or caddisfly larvae. Glaciichnium-like traces are hitherto unknown from the Thuringian Rotliegend. The inferred locomotion, combining pulsating crawling (Imponoglyphus) and walking (Diplichnites), suggests a behaviour that has not yet been described from any other invertebrate trace fossil from the Thuringian Rotliegend and therefore seems to be rare in the study area.