Shoulder joint and inner ear of Tachypteron franzeni, an emballonurid bat from the Middle Eocene of Messel

A rare, exceptionally well-preserved fossil bat from the Middle Eocene Messel Pit reveals that Tachypteron franzeni possessed shoulder joint and inner ear structures indistinguishable from modern emballonurid bats. This suggests that bioacoustic specializations and flight adaptations in this lineage were already fully evolved 48 million years ago, predating the diversification of its extant relatives. The study analyzed two specimens, focusing on their shoulder morphology—a key innovation linked to wing biomechanics—and compared them with living and extinct bat lineages. It identified a derived shoulder joint type unique to emballonurids, reinforcing evidence for parallel evolution in chiropteran flight mechanics.

Habersetzer, J., Schlosser-Sturm, E., Storch, G., & Sigé, B. (2012). Shoulder joint and inner ear of Tachypteron franzeni, an emballonurid bat from the Middle Eocene of Messel. Evolutionary History of Bats, 67–104. https://doi.org/10.1017/cbo9781139045599.004