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New Research Reveals Early Terrestrial Habits of Prehistoric Mammals

A groundbreaking study conducted by the University of Bristol has unveiled that numerous mammals had begun adapting to a terrestrial lifestyle several million years prior to the cataclysmic event that led to the extinction of the dinosaurs.

The research, which appears in the journal Palaeontology, sheds light on how these ancient mammals were transitioning toward life on the ground before the asteroid struck Earth.

Through meticulous examination of small fossilized bone fragments, particularly the ends of limb bones from both marsupial and placental mammals found in Western North America—the only region with a well-preserved terrestrial fossil record from this era—the researchers identified signs of adaptation to ground-dwelling habits. The analysis of these limb bone ends was crucial, as they hold distinct indicators of locomotion patterns that can be contrasted with modern mammal behaviors.

Professor Christine Janis, the lead author from the University of Bristol’s School of Earth Sciences, noted the significance of previous knowledge regarding plant life changes near the close of the Cretaceous period. She stated, “While it was understood that flowering plants, or angiosperms, were creating diverse habitats on land, the difficulties faced by tree-dwelling mammals after the asteroid impact are documented. However, the question of whether mammals were becoming more terrestrial in response to these habitat changes remained unanswered.”

Unlike prior studies that focused on complete skeletons to assess ancient mammalian mobility, this investigation is among the first to employ small bone fragments to investigate evolutionary shifts across entire mammalian communities. The researchers utilized statistical information derived from museum collections located in New York, California, and Calgary to analyze these intricate fossils.

Professor Janis emphasized the importance of vegetation in influencing mammalian evolution during the Cretaceous, asserting, “The vegetational habitat played a more critical role in the course of mammalian evolution than any effects from dinosaurs.”

The team gathered their findings from the bone articular fragments of therian mammals, which encompass marsupials and placentals, while noting that their methods were not suitable for more primitive mammals, such as multiberculates, due to differences in bone structure.