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Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
An international research team from the Museum für Naturkunde Berlin and from Magdeburg and Paris has for the first time investigated resting traces with the body impressions of early mammalian relatives. The 290-million-year-old trace fossils were discovered over 100 years ago in the Tambach sandstone of the famous Bromacker fossil locality in the UNESCO Geopark of Thuringia and have now been re-examined as part of the ongoing BROMACKER research project. These geologically oldest resting traces of early mammal relatives provide unique insights into reptile-like scales and the social behaviour of our early ancestors. The results have been published in the scientific journal Current Biology.
What came before the fur of mammals? There was and is hardly any direct evidence for this. In the approximately 290-million-year-old Tambach sandstone of the Bromacker locality in the UNESCO Global Geopark Thuringia Inselsberg - Drei Gleichen, however, there are particularly detailed footprints and resting traces that provide unique insights into the structure of the skin surface of our early ancestors. They also allow conclusions to be drawn about the behaviour of the animals, which were newly investigated as part of the BROMACKER project of the Federal Ministry of Research, Technology and Space (formerly BMBF).
‘Palaeontology has repeatedly shown that certain features and characteristics of modern vertebrates, such as skin structure, lifestyle or social behaviour, appeared earlier in the course of evolutionary history than was initially assumed,’ explains Prof. Jörg Fröbisch, the senior author of the study. ‘Our study once again demonstrates the globally unique significance of the Bromacker locality and its enormous potential for future research.’
Scales on the belly, legs and tail
If the mud is very fine-grained and contains water, the feet and other body parts can be seen in great detail. From the layers found within the Tambach sandstone, skin folds on the toes and various types of scales on the upper and lower legs, on the underside of the tail, in the hip area and on the belly can be recognised, which have often been preserved together in the form of a resting traces. The arrangement and shape of the scale marks - sometimes diamond-shaped, sometimes rectangular, sometimes pentagonal to polygonal, sometimes overlapping like roof tiles - is very reminiscent of the horny scales of membranous reptiles.
‘Hanging out’ together
Some of the Tambach trackway slabs - a large number of which are now kept in the Friedenstein Foundation Gotha collection storage - show several traces lying next to each other. Some also show parallel trackways, indicating that animals of the same species probably walked side by side. The authors interpret this as an indication that the track producers - such as Dimetrodon teutonis - basked, rested and cooled down together in shallow pools and puddles in warm and dry climates, similar to today's lizards and mammals. The complex group behaviour of mammals may have later emerged from such encounters.
Publication: Marchetti, L., Logghe, A., Buchwitz, M., and Fröbisch, J. 2025. Early Permian synapsid impressions illuminate the origin of epidermal scales and aggregation behaviour. Current Biology.
More information:
The evolution of the mammals
The evolutionary line of mammals - the so-called synapsids, which include our own early ancestors - is already very old. It is the sister group of today's reptiles and birds, which, together with the synapsids, separated from the stem line over 320 million years ago - long before the typical mammalian characteristics such as hair and mammary glands first appeared. Hardly any fossilised skin remains are known from the late Palaeozoic in connection with fossilised vertebrate skeletons, and certainly not from the early mammalian relatives, many of which, like the sail-backed Dimetrodon, are more reminiscent of lizards.
How do you actually know that the tracks come from mammal relatives?
There are certain characteristics of the footprints that occur together with the resting traces and originate from the same animals. These show a long heel, deep impressions of the base of the toes, narrow short toes and deep impressions of the claws on the tips of the toes and can be assigned to mammal relatives on the basis of these characteristics, which are documented as skeletons from the same site.
As early as 290 million years ago, animals from the mammalian stem lineage had ‘paw-shaped’ hands and feet with upturned fingers and toes, which is reflected in their footprints. In particular, the Dimetrodon teutonis, which is known from a number of finds from the excavation site in the immediate vicinity of the sandstone quarries, matches the tracks in terms of size and foot shape.
Quotes
"We are focussing on fossilised traces, as they occur much more frequently in central Europe than skeletons and complement skeletal evidence in terms of their scientific significance. For example, the skin surfaces of early land vertebrates are known almost exclusively from traces in the sediment," says lead author Dr Lorenzo Marchetti.
"For palaeontologists, this coincidence is surprising insofar as scales and other skin structures of membranous reptiles and mammals have already been studied in detail and they differ in their molecular composition and their developmental biology, for example in the mechanism of keratinisation,’ explains Antoine Logghe from the Paris Natural History Museum. ‘Apparently, however, their common ancestors had a basic inventory of skin structures and formation mechanisms that evolved in adaptation to life on land."
"An important tool for track researchers is to match the tracks to their producers,’ explains Dr Michael Buchwitz from the Museum für Naturkunde Magdeburg. ‘As in criminalistics, when reading fossilised tracks it is important to narrow down the producer as precisely as possible based on shape, proportions and size."
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