ABOVE: Left to right: CT scans of the skulls of a tuatara hatchling (modern reptile), offspring of the mammal-like Kayentatherium wellesi, and a 27-day-old opossum (modern mammal)

Apaper published August 29 in Nature describes the discovery of a mammal-like adult creature, named Kayentatherium wellesi, and 38 of its probable young, fossilized in the early Jurassic, 184 million years ago in present-day Arizona. These offspring are the youngest mammal-like creatures discovered in fossil form to date.

CT scans of the skulls of a tuatara hatchling (left) and a 27-day-old opossum (right)

E.A. Hoffman, T.B. Rowe, “Jurassic stem-mammal perinates and the origin of mammalian reproduction and growth,” Nature, doi:10.1038/s41586-018-0441-3, 2018.

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