Scotland: Two incredibly rare fossils discovered from Scotland’s Isle of Skye have reshaped human understanding of mammal evolution. Scientists have found that one of the first mammals to roam the Earth, alongside dinosaurs, could live for seven years or more, a sharp contrast to modern small mammals that often live just a year.
The fossils belong to Krusatodon kirtlingtonesis, a primitive shrew-like mammal. Among the rare finds are two exceptionally complete skeletons: a juvenile and an adult. These discoveries are crucial, as only a handful of Krusatodon fossils have ever been found by scientists.
Researchers have employed advanced X-ray imaging to analyse growth patterns in the teeth of these fossils. Dr. Elsa Panciroli, Associate Researcher of Palaeobiology at National Museums Scotland, emphasised that the juvenile was still weaning at around two years of age, a significant finding that sheds light on mammalian evolution.
Modern small mammals typically have much shorter lifespans, maturing quickly and losing their baby teeth within months of birth. In contrast, Krusatodon lived around 166 million years ago during the Jurassic period when Skye was a sub-tropical paradise with warm shallow seas and dense forests. These early mammals were gaining a foothold in the shadow of the dinosaurs, acting as precursors to the diverse mammals we see today.
The juvenile Krusatodon fossil, discovered in 2016, is the only known juvenile Jurassic mammal skeleton, while the adult, found in the 1970s, is one of the most intact mammal skeletons from this period globally.
Dr. Stig Walsh, Senior Curator of Vertebrate Palaeobiology at National Museums Scotland and co-researcher stated that finding two rare fossil skeletons of the same species at different growth stages has rewritten our understanding of early mammal life. The study involved researchers from the American Museum of Natural History, the University of Chicago, European Synchrotron Radiation Facility, and Queen Mary University of London.