May 24

New research shows that the evolution of ankles and feet helped mammals rise to take over the Earth


A study shows that the evolution of ankles and metatarsal bones into different shapes and sizes helped mammals adapt and thrive after the extinction of the dinosaurs.

The evolutionary boost following the great extinction 66 million years ago, the researchers say, allowed mammal species to diversify and prosper during a period of great Earth change.

Bone analysis suggests that mammals during this time (the Paleocene epoch) formed part of the ankle and heel, the researchers say.

Mesonychia is a taxon of medium to large extinct ungulates that are carnivores related to Artiodactyla. Mesonychia first appeared in the early Paleocene and died out completely when the last genus, Mongolestes, became extinct at the beginning of the Oligocene.

This was discovered by paleontologists at the University of Edinburgh, UK by comparing the anatomical structure of several Paleocene mammals with those from the Cretaceous and other animals. mammals that exist today.

They analyzed measurements of the feet and ankle bones – providing insights into the lifestyles and body sizes of the animals of more than 40 Paleocene species. The team then compared the results with data from mammals alive today and mammals that existed during the Cretaceous Period.

Their findings suggest that the Paleocene mammals had sturdier, more muscular bodies than those from the Cretaceous period or today.

Reconstruction of a Paleocene mammal that lived about 65 million years ago. Paleocene mammals still did not have the specialized teeth/limbs as present-day mammals, and their brain-to-body weight ratio was still very low. When compared to later forms of mammals, they are primitive. It was not until the Eocene that truly modern mammals developed. Fossil evidence of the Paleocene is quite rare and so little is known about the mammals of this period.

The joints of animals of this period were also very mobile – supported by ligaments and tendons instead of the bony features found in some mammals alive today. The team believes that it is this feature that helps them adapt and evolve faster than other species after the great extinction of the dinosaurs.

The ankles and feet of many species closely resemble the ankles and feet of terrestrial and burrowing mammals that exist today, suggesting that these lifestyles were key to survival. existed and evolved after a mass extinction caused by an asteroid impact.

For example, the ability to dig underground may have helped mammal species survive the initial devastation, while the loss of arboreal habitat following the extinction may have caused many species to die. Mammals evolved to live underground.

Mammals first appeared during the Triassic period and evolved adjacent to the dinosaurs, exploiting ecological niches untouched by these larger and more famous animals of the Cretaceous: in the low and high shrubs on trees of insectivorous forests. These tiny mammals (as well as birds, reptiles, amphibians, and insects) escaped the mass extinction that the dinosaurs were unable to avoid at the end of the Cretaceous period, allowing the animals to survive. Breasts have more opportunities to diversify and grow around the world. While early mammals were small and nocturnal, with a diet consisting of vegetables and insects, the extinction of the dinosaurs and the onset of the Paleocene suggest that they were extinct. get bigger, more ferocious and eventually become the dominant carnivores and spread around the world.

“The focus of our study was to understand how the Paleocene mammals anatomically evolved and what this had to do with aspects such as lifestyles and adaptations. their adaptation to the new environment when the dinosaurs became extinct,” said Dr Sarah Shelley,

In terms of the anatomical aspects of Paleocene mammals, they tended to have many of the “ancient” precursor features and lack the distinct features of today’s mammal groups. .

“What we found is amazing diversity – they are adapting and evolving to be stronger and more flexible in ways that are far different from today’s mammals. Their results. I think shows one of the many ways mammals evolved to be able to adapt and evolve after the late Cretaceous extinction,” added Dr Sarah Shelley.


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