About

A walk through the Mesozoic — the 187 million years (252 to 66 Mya) when dinosaurs ran the planet. Inspired by a Scholastic Dinosaurs A to Z a kid once owned, dog-eared and underlined.

What we know vs. what we guess

Every entry has two sections: what we know (the part the bones really tell us) and what we guess (the part the artist had to fill in). Skin colors, feather coverage, hunting behaviour, social structure — those are usually guesses. Bone shape, tooth count, size, and where the animal lived — those are usually known.

The line keeps moving. Tyrannosaurs almost certainly had feathers as babies, but the adult body covering is still debated. Brontosaurus was a valid genus, then a synonym of Apatosaurus, then valid again (since 2015). When new bones come in, the page should change.

What is and isn't a dinosaur

• Dinosaurs are terrestrial archosaurs with an upright posture. Birds are dinosaurs.
• Pterosaurs (flying reptiles like Pteranodon) are close cousins of dinosaurs, but not dinosaurs.
• Plesiosaurs, ichthyosaurs, and mosasaurs are marine reptiles, not dinosaurs.
• Dimetrodon is a synapsid — closer to mammals than to dinosaurs — and lived long before any dinosaur.

Data sources

• Paleobiology Database — taxonomy, age range, geographic occurrences.
• PhyloPic — silhouettes (CC0 / CC-BY).
• Wikipedia: List of dinosaur genera — cross-checks, etymology, IPA pronunciations.
• Reconstructions (where shown) are attributed inline. Most are CC-BY paleoart by Nobu Tamura, FunkMonk, and other paleo-illustrators.

Built with

Astro 6, served from Cloudflare Pages. Open the source on GitHub. Part of too.foo.