The Triassic–Jurassic extinction cleared ecological space for dinosaurs to become the dominant land animals of the Jurassic.
Triassic–Jurassic Extinction: Volcanoes Open the Age of Dinosaurs Read More »
Snowball Earth was a time when our planet may have frozen nearly from pole to pole, testing life and setting the stage for later biological change.
Snowball Earth: When Ice Reached the Equator Read More »
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.”
Bilaterian Split: The Origin of Agency Read More »
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.
The K-Pg Extinction Read More »
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.
Cenozoic Era: Age of Mammals & Birds Read More »
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.
Mesozoic Era: Age of Dinosaurs Read More »
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.
Paleozoic Era: The Age of Synapsids Read More »
At the K–Pg boundary, birds were already diverse, but most of that Late Cretaceous variety died out, leaving only a small toothless slice of the bird world to continue.
Toothed Birds Go Extinct Read More »
Proceratosaurus had the same general tyrannosaur-style look: a big head, long tail, strong hind legs, short forelimbs, and a built-for-biting predator shape: D-shaped front teeth and a crest on top of the skull.
Proceratosaurus (T.Rex ancestor) Read More »
Before the famous branches split into predators, long-necks, horned giants, and birds, there was one early ancestral species. One population eventually led to all dinosaurs: Allosaurus, Styracosaurus, and Diplodocus.
Dinosauria Emerge: True Dinosaurs! Read More »
Neoaves is the enormous living bird branch that includes all birds that are not part of the ostrich-tinamou branch and not part of the duck-chicken branch.
Neoaves Birds Emerge (from Neognathae) Read More »
Galloanserae is the living bird branch that includes landfowl and waterfowl: chickens, turkeys, pheasants, ducks, geese, and swans.
Galloanserae Birds Emerge (from Neognathae) Read More »
Palaeognathae is the living bird branch that includes ostriches, emus, cassowaries, rheas, kiwis, and tinamous.
Palaeognathae Birds Emerge Read More »
Three branches of modern birds evolved from within neornithes: Struthio camelus (the ostrich), Gallus gallus (chickens), and Passer domesticus (the house sparrow is a good one).
Neornithes (Crown Birds) emerge Read More »
Hesperornithiformes were early, highly specialized diving birds that evolved before modern birds.
Hesperornithiformes Birds Emerge (Now Extinct) Read More »
Enantiornithes were one of the most successful early bird branches of the Cretaceous, but unlike Confuciusornithiformes, they generally kept their teeth and often looked a bit more like small, sharp-faced bird-dinosaurs than beaked proto-birds.
Enantiornithes Birds Emerge (Now Extinct) Read More »
Weird carryovers and side experiments: clawed wings, elaborate ribbon-like tail feathers, and a mix of advanced beak features with a still primitive dinosaurian body.
Confuciusornithiformes Birds Emerge (Now Extinct) Read More »
Archaeopteryx, from about 150 million years ago, is an early bird that still looked strikingly dinosaurian, with feathers and wings alongside teeth, clawed hands, and a long tail.
First True Bird: Archaeopteryx Read More »
Sauropodomorphs, in their early forms, were lightly built, often partly bipedal, with long necks, small heads, leaf-shaped teeth, and grasping hands.
Sauropodomorph Line Diverges Within Dinosaria (from Saurischia) Read More »
Theropods were the agile, sharp-toothed dinosaur branch that refined the classic predator body plan. They stood fully upright on two legs and balanced with long tails.
Theropod Line Diverges Within Dinosaria (from Saurischia) Read More »
