Reassessment of Miocene putative coprolites from Poland suggests a biogenic origin and probable squamate (reptilian) producers.

Additional ferruginous excrement-shaped masses interpreted as putative coprolites were recovered from Miocene deposits of the Kleszczów Graben, central Poland. Earlier studies favored an abiotic origin, but our reassessment provides evidence supporting a biogenic interpretation. Key indicators include their consistent size and morphology, fine surface striations, and the presence of hair-like inclusions. These features distinguish the relatively homogeneous, elongated, and variably compressed forms from morphotypes previously described in the Turów and Kleszczów areas (southwestern and central Poland, respectively). Comparisons with modern faeces suggest that squamates (lizards and/or snakes) were the most probable producers, consistent with reptilian remains documented from the Miocene deposits of Bełchatów. Alternative vertebrate producers and non-biogenic explanations appear less consistent with the observed characteristics. Our findings highlight the palaeobiological processes involved in the formation of these structures and provide new insights into the faunal composition and ecological dynamics of Miocene ecosystems in central Poland.