No more dry skin – a dead Geiseltal frog started to decay underwater. Credit: A. Pieri (University of Pisa)
Paleontologists discovered that the exceptional preservation of 45-million-year-old frog fossils can be attributed to the mineralization of their skin, offering new insights into their adaptation to land.
A hundred-year-old mystery of how some fossil frogs preserve their fleshy parts has been solved by paleontologists at University College Cork (UCC), Ireland. They discovered that it’s all down to their skin.
Paleontologists Daniel Falk and Prof. Maria McNamara, together with scientists from Ireland, Germany, and the UK, studied 45-million-year-old fossil frogs from the Geiseltal site in central Germany. Remarkably, the fossils show full body outlines of the soft tissues. The team discovered that the excellent condition of the fossil frogs is due to preservation of ancient skin remnants.
Advanced Analytical Techniques
The team studied the fossils with high-precision techniques including scanning electron microscopy, synchrotron-X-ray analyses, and infrared spectroscopy. These techniques were not available when the fossils were first discovered in the early twentieth century.
“The quality of preservation of the fossil frog skin is amazing – even subcellular structures, such as collagen fibers, are preserved.” said study lead, PhD researcher Daniel Falk. “The skin of the frogs is replicated in the mineral calcium phosphate, which helped it survive for millions of years.”
The replication process of the frog skin at a glance. Credit: D. Falk, see Falk et al. 2024.
Insights Into Fossil Frogs’ Habitat
“The preservation of the skin is so good that we can even work out the habitat of the fossil frogs,” said Daniel. “The preserved skin shows adaptations to prevent drying out, which suggests that these fossil frogs actually spent most of their time on land.”
“Fossil soft tissues often reveal hidden information about the biology of animals,” said senior author Prof. Maria McNamara. “We discovered that the fossil frog skin is preserved in the same way as fossil frogs from other sites in Europe.
Daniel Falk examines the fossil skin samples of a Geiseltal frog with an electron microscope. Credit: Daniel Falk
Reevaluating Historical Fossils
“This discovery is very exciting because it overturns scientific opinion that has lasted for almost one hundred years. What’s more, the repeated pattern of fossil preservation tells us that frogs evolved special adaptations to life on dry land over 45 million years ago.”
The research highlights the usefulness of historic fossil collections and the need to re-evaluate historic specimens using modern techniques.
The study is published today in the journal Scientific Reports.
Reference: “Fossilized anuran soft tissues reveal a new taphonomic model for the Eocene Geiseltal Konservat-Lagerstätte, Germany” 23 April 2024, Scientific Reports.
DOI: 10.1038/s41598-024-55822-y
The study is part of a research cooperation between UCC, the Martin-Luther-University Halle-Wittenberg (Germany), the Natural History Museum Bamberg (Germany), and the University of Oxford (UK) with funding from the Irish Research Council, the European Research Council, and the International Association of Sedimentologists.
