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Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
New research conducted by palaeontologists from the Museum für Naturkunde Berlin (MfN) and Humboldt-Universität zu Berlin reveals a burst in jaw variety in the earliest amniotes – which includes the ancestors of all reptiles, birds and mammals. The international team lead by former MfN doctoral student Dr. Jasper Ponstein analyzed over 200 fossilized jaws from periods, when tetrapods first adapted to life on land. Amniotes evolved a huge diversity of jaw shapes, while amphibians remain limited to simple jaw shapes. This versatility allowed amniotes to exploit new food sources and establish their ecological success. The results are published in the open-access scientific journal PeerJ.
One of the most extraordinary events in the history of life is the water-to-land transition, from fish to land-dwelling tetrapods (four-limbed vertebrates). The forerunners of all terrestrial vertebrates emerged about 370 million years ago, during the Devonian period. Living on land provided new challenges that required substantial modifications to these animals’ body plan; for example, they needed limbs sturdy enough to carry their own weight when out of water. An often-overlooked challenge is the shift from feeding underwater to feeding on land. “Many fishes use suction feeding - sucking in food by rapidly opening their jaws - but that doesn’t work well on land. On land, tetrapods need to grab food with their jaws instead”, says Dr. Ponstein, former Museum für Naturkunde doctoral student and lead author of the study.
During the following Carboniferous and Permian periods (360 – 250 million years ago), tetrapods explored the various new untapped resources the land provided. Some, for example, started to feed on the many resident insects. Others, eventually, became the first known plant-eaters. “It really is an exciting time window to study how animals adapt to new dietary niches”, Dr. Ponstein added.
Modern tetrapods include amphibians and amniotes (reptiles, birds, mammals and their kin). Amniotes boast incredible ecological diversity today, ranging from top predators like lions and eagles, to plant-eaters such as tortoises and hares, and everything in between. On the other hand, amphibians, like frogs and salamanders, are almost exclusively opportunistic insect-eaters. How did this skewed ecological diversity between amphibians and amniotes come about? Could it be traced back to their first steps on land?
To study how long-extinct tetrapods fed, researchers commonly examine the lower jaw – representing the only bony structure which primary function is food capture and processing. Jaw shape, as well as muscle insertion sites, inform how the animal would operate the jaw and thus provide unique insights in the critical biological function of feeding.
An international Museum für Naturkunde-lead team, in collaboration with colleagues from the Staatliches Museum in Stuttgart and the Museum of Natural Sciences in Raleigh, North Carolina, USA, compiled the largest dataset of tetrapod jaws from the Carboniferous and Permian to date, encompassing over 200 species. The team made two remarkable discoveries, which are now published in the open-access scientific journal PeerJ.
First, perhaps surprisingly, jaw shape did not change much following the water-to-land transition. For much of the Carboniferous period, land-living tetrapods retained long and slender jaws, suitable to catch fish and potentially insects.
Secondly, this stasis changed when amniotes evolved. Amniote jaws have been vastly more diverse than amphibian jaws since the start of the Permian period, 300 million years ago. Specifically, amniote have more robust jaws than amphibians, and have a greater variation in muscle insertion sites, granting the ability to chew tough food such as plant matter. “The ability to evolve a greater versatility in jaw shapes would have allowed amniotes to adapt to newfound diets that amphibians could not, leading to the fascinating diversity of reptiles, birds and mammals seen today”, Dr. Ponstein concludes.
Publication: Ponstein J, MacDougall MJ, Schaeffer J, Kammerer CF, Fröbisch J. 2025. Mandibular form and function is more disparate in amniotes than in non-amniote tetrapods from the late Palaeozoic. PeerJ 13:e20243 DOI 10.7717/peerj.20243
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