The lignite mine of Hambach, near Cologne (Germany), is a well-known fossil site that has yielded numerous fossil remains of vertebrates that lived in a marshy and riverine environment. The site includes two distinct levels: one from the middle Miocene (around 15 million years ago) and another from the late Pliocene (around 3 million years ago). This separation of approximately 12 million years corresponds to two very different climatic contexts, which are reflected in the faunal composition.

A recently published article in Paleontologia Electronica, led by Andrea Villa, a 'Beatriu de Pinós' researcher at the Institut Català de Paleontologia Miquel Crusafont (ICP), describes the presence of 12 different taxa of amphibians, including caudates (tail-bearing amphibians like newts and salamanders), and anurans (tailless ones like frogs and toads) during the middle Miocene and 9 taxa during the late Pliocene. It highlights the presence of Euronecturus grogu, a peculiar urodele from the proteid family that was described in late 2021 and has only been identified in the Miocene level of this site.

"The amphibian species we've discovered in the Miocene strata acord with what was previously known of this period in Europe. However, what has been truly surprising are the taxa we've identified in the more recent stage, the Pliocene," Villa explains. In several cases, the individuals found represents the last evidence of their taxa in Europe. While the diversity of amphibians doesn't change significantly, what we observe during this period is the disappearance of reptiles. "Their absence is likely due to a decrease in temperatures, a factor to which reptiles are highly sensitive," Villa explains. The findings for this group acord with observations from other sites in northern Europe.

The unexpected amphibian diversity in the Pliocene at Hambach suggests a consistently humid climate in this area throughout much of the Neogene, possibly creating a refuge zone that persisted until the late Pliocene (and potentially into the early Pleistocene). While it was known that during the Neogene many amphibian species sought refuge in Mediterranean peninsulas (Iberia, Italy, and the Balkans), there was no record of them doing so in northern European areas like present-day Germany.

It seams that this refuge zone could have extended throughout the entire area of the Rhine-Meuse delta system, which was previously located closer to Hambach and maintained similar levels of humidity.

Main image: Vertebrae and humerus of a cryptobranchid or giant salamander from the Miocene of Hambach (extracted from Villa et al., https://doi.org/10.26879/1323).

Original article:  

• Villa, A., Macaluso, L., & Mörs, T. (2024). Miocene and Pliocene amphibians from Hambach (Germany): new evidence for a late Neogene refuge in northwestern Europe. Palaeontologia Electronica, 27, a3. https://doi.org/10.26879/1323