Description of trace fossils in bones and teeth (dentin). The u-shaped burrows occurred in horn cores, bones and in teeth from sediments of the Later Tertiary (Middle Miocene": Badenian and Sarmatian; Late Miocene: Pannonian) from Lower Austria (Vienna Basin and “Molasse”-zone). The trace fossils are original U-tubes with “Spreite”. It is suggested that the producers are aquatic nymphs from may-flies (Ephemeroptera: Polymitarcidae: Asthenopodinae). The recent nymphs of Asthenopodinae are living in submerse woods in a fluviatic or lacustric biotop. The new type of the trace fossil is described as Asthenopodichnium ossibiontum n. sp.