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 »
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.
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.
Diplodocid LCA: The Age of Giant Necked Sauropods Read More »
Brontosaurus, in the revived interpretation, looks broadly similar to Apatosaurus but is argued to be less massive and less robust. A bit lighter-built overall.
Apatosaurus was the heavier, more robust sauropod — more muscular-looking, with a thicker, lower-set neck and a bulkier frame.
Diplodocus was the longer, slimmer, more stretched-out sauropod, famous for its especially long neck and whiplike tail. It is one of the longest land animals and generally more slender in build.
The last sauropods were titanosaurs—the final surviving long-necked dinosaurs, still ranging from giants to smaller and even armored forms at the end of the Cretaceous.
The Last Sauropods 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 »
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 »
LCA of crocodiles and birds — the larger archosaur branch that later gave rise to crocodilians, pterosaurs, dinosaurs, and birds.
Archosauria Diverge Within Reptiles Read More »
Ornithodirans were the early branch that later gave rise to both pterosaurs and dinosaurs, including birds.
Ornithischians Diverge Within Dinosauria “Bird Hipped” Read More »
Eoraptor reminds us that classification is not always neat at the beginning of a lineage. Early dinosaurs can be hard to classify because of a mix of traits.
Eoraptor lunensis. Read More »
In a testament to our understanding of evolution, archosaurs emerged around 255 million years ago, eventually giving rise to dinosaurs about 230 million years ago. Bridging this gap, the dinosauromorphs – a transitional group between archosaurs and dinosaurs – evolved approximately 245 million years ago. One notable early dinosauromorph is Asilisaurus kongwe, found in present-day
Bird-line Archosaurs: Asilisaurus kongwe (within Ornithodira) Read More »
One of the last bird-line archosaurs before true dinosaurs is the Nyasasaurus parringtoni, which lived during the Middle Triassic period, around 243 million years ago. Discovered in Tanzania, Nyasasaurus represents a key transitional form, showcasing features that are both dinosaurian and pre-dinosaurian, highlighting the evolutionary path leading to more well-known dinosaurs of the Late Triassic
Bird-line Archosaur: Nyasasaurus parringtoni Read More »
Before dinosauromorphs like Asilisaurus, the evolutionary lineage would include earlier archosaurs. One such early archosaur is Marasuchus lilloensis, which lived around 240 million years ago. Marasuchus exhibits several primitive features that are on the evolutionary path towards dinosaurs. Kingdom: Animalia > Phylum: Chordata > Class: Reptilia > Order: Dinosauriformes 30 to 40 cm (12 to
Marasuchus lilloensis Read More »
