Evolution: very early pre-mammal found (Evolution)

by David Turell , Wednesday, November 04, 2020, 19:53 (1478 days ago) @ David Turell

220 million years old:

https://www.sciencedaily.com/releases/2020/11/201104001309.htm

"Fossilized jaw bone fragments of a rat-like creature found at the Petrified Forest National Park in Arizona last year by a Virginia Tech College of Science Ph.D. candidate are in fact a newly discovered 220-million-year-old species of cynodont or stem-mammal, a precursor of modern-day mammals.

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"'This discovery sheds light on the geography and environment during the early evolution of mammals," Kligman said. "It also adds to evidence that humid climates played an important role in the early evolution of mammals and their closest relatives. Kataigidodon was living alongside dinosauromorphs and possibly early dinosaurs related to Coelophysis -- a small bipedal predator -- and Kataigidodon was possibly prey of these early dinosaurs and other predators like crocodylomorphs, small coyote-like quadrupedal predators related to living crocodiles."

"Kligman added that finding a fossil that is part of Cynodontia, which includes close cousins of mammals, such as Kataigidodon, as well as true mammals, from Triassic rocks is an extremely rare event in North America. Prior to Kligman's discovery, the only other unambiguous cynodont fossil from the Late Triassic of western North America was the 1990 discovery of a braincase of Adelobasileus cromptoni in Texas. Note that 220 million years ago, modern day Arizona and Texas were located close to the equator, near the center of the supercontinent Pangaea. Kataigidodon would have been living in a lush tropical forest ecosystem.

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"Along with the jawbone fossils, Kligman found incisor, canine, and complex-postcanine teeth, similar to modern day mammals. Given the pointed shape of its teeth and small body size, it likely fed on a diet of insects, Kligman added. (Why are jaw fossils commonly found, even among small specimens? According to Kligman, the fossil record is "biased" toward only preserving the largest and most robust bones in a skeleton. The other smaller or more fragile bones -- ribs, arms, feet -- disappear.)"

Comment: So our branch goes way back showing how one cannot chop up evolution into segments. Everything present and past relates.