Fossil Hints That Jurassic Mammals Lived Slow and Died Old
Published: 04:08 PM,Aug 10,2024 | EDITED : 08:08 PM,Aug 10,2024
Fossil Hints That Jurassic Mammals Lived Slow and Died Old
Small mammals often live fast and die young. Rodents and shrews mature quickly, mate within months and usually go belly up in a year or two. Some giant rats kick the bucket in just six months.
But miniature mammals have not always burned out so quickly. Researchers recently analyzed a pair of fossilized skeletons belonging to a mouse-size mammal relative that lived among dinosaurs during the Jurassic period. Their findings, published in the journal Nature, reveal that these critters lived much longer and grew more slowly than their similarly sized descendants.
The two specimens were discovered decades apart on Scotland’s Isle of Skye. This island was home to swampy lagoons fringed by dense forests 166 million years ago. Sauropod dinosaurs stomped across the mud as pterosaurs flew overhead. Scurrying underfoot was a menagerie of Mesozoic mammal relatives.
Krusatodon kirtlingtonensis was among these ancestral mammals. The two newly described specimens provide a picture of Krusatodon, which resembled a pint-size possum and weighed less than a hockey puck.
The larger of the Krusatodon specimens was found in the 1970s. The smaller Krusatodon was discovered in 2016 by Elsa Panciroli, a paleontologist at National Museums Scotland and the lead author of the new study, and her team.
Panciroli said she was delighted “to realize that the two of them were an adult and a juvenile of the same species.”
The team took high-resolution CT scans to compare the two fossil skeletons. To gauge how old each Krusatodon was when it died, the researchers analyzed rings of mineralized dental tissue called cementum. The cementum bands revealed that the adult Krusatodon was about 7 years old when it died — a ripe old age compared with living mammals of similar size. The juvenile, which was roughly half as large as the adult, was somewhere between 7 months and 2 years old. Surprisingly, this Krusatodon was still in the process of replacing its baby teeth when it died.
“We didn’t expect it to be such an old juvenile,” Panciroli said. Based on its size, “you would expect it to replace its teeth within weeks or months, not two years.” — JACK TAMISIEA/NYT
But miniature mammals have not always burned out so quickly. Researchers recently analyzed a pair of fossilized skeletons belonging to a mouse-size mammal relative that lived among dinosaurs during the Jurassic period. Their findings, published in the journal Nature, reveal that these critters lived much longer and grew more slowly than their similarly sized descendants.
The two specimens were discovered decades apart on Scotland’s Isle of Skye. This island was home to swampy lagoons fringed by dense forests 166 million years ago. Sauropod dinosaurs stomped across the mud as pterosaurs flew overhead. Scurrying underfoot was a menagerie of Mesozoic mammal relatives.
Krusatodon kirtlingtonensis was among these ancestral mammals. The two newly described specimens provide a picture of Krusatodon, which resembled a pint-size possum and weighed less than a hockey puck.
The larger of the Krusatodon specimens was found in the 1970s. The smaller Krusatodon was discovered in 2016 by Elsa Panciroli, a paleontologist at National Museums Scotland and the lead author of the new study, and her team.
Panciroli said she was delighted “to realize that the two of them were an adult and a juvenile of the same species.”
The team took high-resolution CT scans to compare the two fossil skeletons. To gauge how old each Krusatodon was when it died, the researchers analyzed rings of mineralized dental tissue called cementum. The cementum bands revealed that the adult Krusatodon was about 7 years old when it died — a ripe old age compared with living mammals of similar size. The juvenile, which was roughly half as large as the adult, was somewhere between 7 months and 2 years old. Surprisingly, this Krusatodon was still in the process of replacing its baby teeth when it died.
“We didn’t expect it to be such an old juvenile,” Panciroli said. Based on its size, “you would expect it to replace its teeth within weeks or months, not two years.” — JACK TAMISIEA/NYT