3 April 2024

11:45 – 12:30

Amphi 2

Jean-Sébastien Steyer

Jean-Sébastien Steyer has a PhD in paleontology, is a researcher at the CNRS and is attached to the Muséum national d’Histoire naturelle in Paris. He is one of the few specialists studying life on Earth before the dinosaurs. He has also been working on the reconstruction of extinct species for almost twenty years. The author of numerous scientific articles, this enthusiastic popularizer regularly publishes works that are rapidly becoming benchmarks, such as La Terre avant les dinosaures (2009), Exquise planète (2014), and Demain, les animaux du futur (2015). Between paleontological expeditions to the four corners of the globe, he is also a science columnist for the magazines Pour la science and Espèces.

How did dinosaurs manage their energy?

Dinosaurs are fascinating. Small, giant, herbivorous, carnivorous, quadrupedal or bipedal, with horns or with crests, they disappeared 66 million years ago (birds excluded) although they occupied most of the terrestrial ecological niches. They shared the particularity to move on land with their limbs below the body, like mammals, not laterally like other reptiles – paleontologists speak about evolutionnary innovation. Since the first discoveries, questions arise: were they warm-blooded like mammals or cold-blooded like reptiles? To answer, paleontologists observe the inner structure of fossil bones (bone paleohistology): the bone tissue type (fibrolamellar, lamellar-zonal etc.) and the growth zones bring information on animal physiology. Yesterday, paleontologists cut bones to observe thin-sections under microscope. Today, they scan them (X-ray microtomography) to penetrate the inner bony structure. Formerly considered as clumsy and cold-blooded, the dinosaurs are seen today as dynamic reptiles, whose thermoregulation is as sophisticated as diversified: a beautiful energy in the Jurassic!