Analysis of two unique Jurassic fossil discoveries from the Isle of Skye (Scotland) have shown that mammals in the time of the dinosaurs grew more slowly and lived longer than mammals today. Synchrotron studies of the fossils at the ESRF contributed to the research. The findings are published in Nature.
An international team of researchers led by National Museums Scotland discovered two Krusatodon kirtlingtonensis fossils, one adult and one juvenile, both in Skye. These mouse-sized mammals lived around 166 million years ago. The specimens represent the only juvenile Jurassic mammal skeleton known to science, while the adult is one of the most intact mammal skeletons from this time period in the world.
The fact that both specimens, the juvenile and the adult, belong to the same species of early mammals is unique and has allowed groundbreaking comparative analysis into their growth and life history. This was possible thanks to X-ray computed tomography carried out in several laboratories, including cutting-edge facilities, notably the ESRF’s ID19 beamline.
The ages of the specimens at death were determined using X-ray imaging to count the growth rings in their teeth. The adult was found to be around 7 years old and the juvenile between 1 – 2 years, and still in the process of replacing its baby teeth.
Shift in mammal growing patterns
Today, small mammals have significantly shorter lifespans, some living as little as 12 months, and maturing quickly, losing their baby teeth and weaning within months of birth. The Krusatodon fossils reveal for the first time that the earliest mammals didn’t finish replacing their teeth until well into their second year of life, possibly later. This tells us that a fundamental shift in the growth patterns and life expectancy of mammals must have taken place during or after the Middle Jurassic.
The specimens were discovered decades apart, with the adult being one of the earliest Jurassic finds on Skye in the 1970s, while the juvenile was discovered in 2016.
Read more on ESRF website