Bat consumption by holostean fishes in the Eocene Lake Messel: insights into the trophic adaptability of extinct gars and bowfins.

Direct evidence of trophic interactions between extinct species is rarely available in the fossil record. Here, we describe fish-mammal associations from the middle Eocene of Messel (Germany), consisting of three specimens of holosteans (one Atractosteus messelensis (Lepisosteidae) and two Cyclurus kehreri (Amiidae)) each preserved with a bat specimen (Palaeochiropteryx tupaiodon) lying in close contact with its jaws. This suggests that these fishes probably died after failed swallowing attempts, with the bat wing membrane entangled in their jaws resulting in a fatal handicap. Based on data from modern gars and bowfins, A. messelensis and C. kehreri may have opportunistically attacked drowning and dying individuals or scavenged on floating/sinking carcasses. This hypothesis is also supported by the unusually high number of bat specimens preserved in the deposits of the Eocene Lake Messel, suggesting that this group of small mammals may have represented a substantial food source for generalist feeders. This is the earliest case of chiropterophagy and the first known evidence of bat consumption by lepisosteid and amiid fishes, emphasizing the high trophic variability and adaptability of these groups throughout their evolutionary histories. The newly described associations provide important information for reconstructing the Eocene Lake Messel palaeoecosystem and its trophic web.