National Museums Scotland‘Exceptional’ fossils found on the Isle of Skye could rewrite history of the early mammals that walked with dinosaurs millions of years ago.
A team led by researchers at National Museums Scotland analysed the fossils of an adult and a juvenile Krusatodon kirtlingtonensis, a mouse-sized mammal that lived around 166 million years ago, which were found in Skye.
The discovery marks the first and only juvenile Jurassic mammal skeleton known to science with researchers adding that the adult is the most intact skeleton from this time period in the world.
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.
National Museums ScotlandThe team used X-ray imaging to count growth rings on the animals’ teeth, and found that the adult was about seven years old and the juvenile was between one and two years old – and still in the process of replacing its baby teeth.
This shows for the first time that the earliest mammals didn’t finish replacing their teeth until well into their second year of life, possibly later.
Researchers said the discovery of a juvenile and adult of the same species is “unique” and has allowed for “groundbreaking comparative analysis” into their growth and history.
National Museums ScotlandToday small mammals have significantly shorter lifespans, some living as little as 12 months, and they mature quickly, losing their baby teeth and weaning within months of birth.
The researchers said in a paper published in the journal Nature that the findings indicate that a fundamental shift in the growth patterns and life expectancy of mammals must have taken place during or after the middle Jurassic period (roughly 174 to 161 million years ago).
Dr Elsa Panciroli, lead author and associate researcher of palaeobiology at National Museums Scotland, said: “These fossils are among the most complete mammals from this time period in the world.
National Museums Scotland“They give us unprecedented insights into the lives of the first mammals in the time of dinosaurs.
“Although on the outside Krusatodon looked like a shrew or mouse, on the inside it was quite different; it grew more slowly and lived much longer than small mammals do today.
“As a result, it probably had quite a different physiology and life history as well.
“Skye’s fossils are really putting Scotland firmly on the map when it comes to understanding mammal evolution. This is just the tip of the iceberg in terms of what they can tell us.”
Dr Stig Walsh, senior curator of vertebrate palaeobiology at National Museums Scotland and co-author on the study, said: “Even in the context of the amazing palaeontological finds on Skye in recent years, these fossils are remarkable.
“Mammal fossils of this age are exceptionally rare worldwide, and most are just single teeth found by sieving sediment.
“To find two such rare fossil skeletons of the same species at different growth stages has rewritten our understanding of the lives of the very earliest mammals.
“We’re thrilled they are both now part of Scotland’s National Collection, an important part of the global fossil record, and will be preserved for generations of researchers to come.”
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