Micropalaeosoma balticus (formerly Palaeosoma balticus) was reported as an extinct, fossil turbellarian flatworm known from Baltic amber of Kaliningrad, Russia, that lived approximately 40 million years ago. It measured approximately 1.5 mm in length. It was considered the oldest and most complete free-living flatworm body fossil. However, much older flatworm fossils have been reported Knaust, D. (2010). Remarkably preserved benthic organisms and their traces from a Middle Triassic (Muschelkalk) mud flat. Lethaia, 43(3), 344-356.De Baets, K., Dentzien-Dias, P., Harrison, G. W. M., Littlewood, D. T. J., & Parry, L. A. (2021). Fossil constraints on the timescale of parasitic helminth evolution. In The evolution and fossil record of parasitism: identification and macroevolution of parasites (pp. 231-271). Cham: Springer International Publishing. and it has been re-interpreted as a pseudo-inclusion (largely consisting of air bubbles).Szadziewski, R., Szwedo, J., & Sontag, E. (2018). Fauna lasu bursztynowego/Fauna of the amber forest. Bursztyn Bałtycki—Skarb Zatoki Gdańskiej/Baltic Amber—Treasure of the Bay of Gdańsk, 216-217.
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