The Brasilodon is an early mammal/mammaliaform threshold at 225 million years ago. The more conservative textbook marker is the Morganucodon at 205 million years ago. The Natural History Museum notes that Brasilodon dates to 225 million years ago and predates Morganucodon, which is usually considered the first mammal, by about 20 million years.
STORY
First Mammaliaforms
By Michael Alan Prestwood
Thu 21 May 2026
Published 14 hours ago.
Updated 14 hours ago.
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First Mammaliaforms
~215 Million years ago (+/- 10 million)
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Prestwood writes on science-first philosophy, with particular attention to the convergence of disciplines. Drawing on his TST Framework, his work emphasizes rational inquiry grounded in empirical observation while engaging questions at the edges of established knowledge. With TouchstoneTruth positioned as a living touchstone, this work aims to contribute reliable, evolving analysis in an emerging AI era where the credibility of information is increasingly contested.
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