BrowseStories
The stories from the TST Timelines.
The significant idea of the bilaterian body plan is directionality. By moving from a radial (circle) to a bilateral (line) symmetry, life transitioned from a passive state of “being” to an active state of “doing.”
Fri 3 Apr 2026
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Before, during, and after the K–Pg extinction: a thriving Late Cretaceous world of dinosaurs, pterosaurs, birds, and flowering plants gives way to the asteroid strike and global collapse that ended the age of non-avian dinosaurs.
Sun 22 Mar 2026
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The Permian-Triassic extinction was not just the end of many species. It was a planetary reset that destroyed the old synapsid-dominated world and opened the door for the archosaur line that would later give rise to dinosaurs.
Sun 22 Mar 2026
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About 255 million years ago, during the late Permian, our mammalian ancestory, the synapsids ruled the land.
Sun 22 Mar 2026
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The Cenozoic era starts with the K–Pg extinction 66 million years ago. That event marks the sudden end of the reign of dinosaurs and the rise of mammals and birds.
Sun 22 Mar 2026
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U. 2 weeks ago
The Mesozoic era starts with the end-Permian mass extinction 252 million years ago. Dinosaurs ruled over all, including us. It ends the reign of dinosaurs with the K–Pg extinction 66 million years ago.
Sun 22 Mar 2026
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The start of the Paleozoic era is marked by burrowing life 538.8 million years ago. The era includes the dominant rise of our ancestors. It ends 252 million years ago with the end-Permian mass extinction, a volcanic cascade global warming event.
Sun 22 Mar 2026
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This trilobite reminds us that early animal life was already complex, varied, and successful hundreds of millions of years before dinosaurs, birds, or mammals ever appeared.
Sat 21 Mar 2026
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Argentinosaurus shows how far the sauropod body plan could go. By the Late Cretaceous, some titanosaurs had become the largest land animals known, turning the long-necked dinosaur design into one of evolution’s most extreme achievements.
Sat 21 Mar 2026
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The diplodocid story likely began with an earlier shared ancestor we have not yet found by name, reminding us that evolution is often reconstructed from branching clues rather than a single perfect fossil.
Sat 21 Mar 2026
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U. 2 weeks ago