Toward the end of the Cretaceous, flowering plants (angiosperms) transformed ground habitats, making them more diverse. While it was known that tree-dwelling mammals faced challenges after the impact of the asteroid, it wasn’t clear if mammals adapted by becoming more ground-based. Earlier research primarily analyzed complete skeletons to study how ancient mammals moved.
A recent University of Bristol study reveals that many mammals were transitioning to a ground-based lifestyle before the asteroid’s impact. By analyzing small bone fragments—an approach never used to study whole communities—the researchers examined fossils from museums in New York, California, and Calgary. Their findings show that a significant shift toward ground-dwelling occurred several million years before the mass extinction that ended the age of dinosaurs.
Researchers examined small fossilized limb bone fragments from marsupial and placental mammals in Western North America. These end-of-limb bones, which carry clues about movement patterns, showed evidence of adaptation to ground-based living. By comparing these bone structures with those of modern mammals, scientists identified behavioral shifts toward terrestrial lifestyles.
Lead author Professor Christine Janis from the University of Bristol’s School of Earth Sciences said, “The vegetational habitat was more important for the course of Cretaceous mammalian evolution than any influence from dinosaurs.”
The study focused on bone articular fragments from therian mammals, including marsupials and placentals. These fragments provided valuable insights into locomotion. However, the methods were not applied to more primitive mammals like multituberculates, which were prevalent at the time, as their bones differed significantly from those of therians.
Professor Janis said: “We’ve known for a long time that mammalian long bone articular surfaces can carry good information about their mode of locomotion, but I think this is the first study to use such small bone elements to study change within a community, rather than just individual species.”
This research concludes by shedding light on how prehistoric mammals adapted to environmental shifts. It reveals significant changes in behavior and habitat preferences millions of years before the asteroid impact that transformed Earth’s ecosystems.
Journal Reference:
- C.M. Janis, A. Martín-Serra, J.M. Theodor and C.S. Scott. Down to Earth: therian mammals became more terrestrial towards the end of the Cretaceous. Palaeontology. DOI: 10.1111/pala.70004
Source: Tech Explorist
