Living with dinosaurs: Jurassic mammals grew slowly, enjoyed long life

Analysts recently revealed that mammals living alongside dinosaurs likely developed slowly, but they had a larger lifespan than they do today. The researchers shared this opinion while studying fossils that have been found on the Isle of Skye.

They arrived at these conclusions after analyzing the fossils of an adult and a juvenile Krusatodon kirtlingtonensis . It’s a mouse-sized mammal that lived approximately 166 million years ago.

X-ray analysis reveals lifespan and growth details of ancient mammals

The analysts used X-ray technology to scan the specimens and then examined growth rings in the species’ teeth. They determined that the juvenile mammal died between seven months and two years old, while the adult died at the age of seven.

Dr. Elsa Panciroli, the lead author of the research from National Museums Scotland, spoke about the research and addressed why mammals have become so successful.

“Mammals have the biggest range of body sizes. They’re living in the most habitats. They have the widest range of ecologies. And so everybody’s asking, Why? Of course, to understand that, we have to understand where their unique biology comes from. So this is a piece of that puzzle,” she told The Guardian .

According to the team, the fossils offer a lot of insights into the anatomy of the creature and shed light on the speed at which it grew and matured.

Panciroli added that most of the earliest mammals resembled mice, and they had lived for a very long time.

Fossil analysis reveals insights into the growth and weaning of ancient mammals

The research team also discussed the body masses of the adult and juvenile and conducted an analysis of their teeth. Their study suggests that the juvenile was likely gaining its adult teeth and may have been weaning when it died.

This implies, according to the researchers, that these mammals weaned at a much younger age. This suggests that despite their slow growth, they weaned at a similar age to larger mammals, such as the brush-tailed possum or Barbary macaque.

“We know that all mammals today have this rapid juvenile growth, determinate growth, and that’s probably part of why they’re so successful, but so we need to find out how that happened. And then, of course, once we know how we might be able to start addressing why,” Panciroli said.

Senior curator of vertebrate paleobiology at National Museums Scotland and co-author on the study Dr Stig Walsh said that these fossils are remarkable, particularly in light of the findings on Skye in recent years.

“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,” said Walsh.

“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,” he concluded.