Surprising Discovery in the Jura: Krusatodon Findings Shed New Light on Aging Processes

Scientists have discovered an unexpected aging pattern in a largely intact juvenile mammalian skeleton from the paleontological era. Normally, small mammals live fast and die young: rodents and shrews mature quickly, mate within a few months, and often exit the stage of life within one to two years. Some large rats survive only six months. However, miniature mammals did not always live such short lives. Recently, researchers analyzed two fossil skeletons of about mouse size that lived among dinosaurs during the Jurassic period. Their findings, published in the journal *Nature*, indicate that these creatures lived much longer and grew slower than their similarly sized descendants. The two specimens were discovered decades apart on the Isle of Skye in Scotland. 166 million years ago, this rugged island was home to marshy lagoons surrounded by dense forests. Sauropod dinosaurs trudged through the mud, while pterosaurs soared above. A variety of Mesozoic mammal relatives scurried underfoot. An ancestor of these mammals was Krusatodon kirtlingtonensis, previously known only from fossilized teeth. The newly described specimens provide a more complete picture of Krusatodon, which resembled a tiny opossum and weighed less than a hockey puck. The larger of the Krusatodon specimens was discovered in the 1970s, while the smaller was found in 2016 by Elsa Panciroli, a paleontologist at the National Museums Scotland and lead author of the new study, and her team. It remains the only relatively complete skeleton of a juvenile Jurassic mammal known to science. Dr. Panciroli expressed delight in discovering, "that the two were an adult and a juvenile of the same species.