Glossary

Plain-language definitions for the terms and clades used across the guide.

What is (and isn't) a dinosaur

Dinosaurs are terrestrial archosaurs with an upright stance. Birds are dinosaurs — the only branch that survived.
Pterosaurs (flying reptiles), plesiosaurs, ichthyosaurs, and mosasaurs (marine reptiles) are close cousins, not dinosaurs.
Dimetrodon is a synapsid — closer to mammals — and lived before any dinosaur.

How this guide works

Period vs. epoch: The Mesozoic splits into three periods — Triassic, Jurassic, Cretaceous — and each into Early / Middle / Late epochs.
Known vs. guess: Known is read from the bones (size, teeth, where it lived). Guess is the artist's call — skin color, feather coverage, behavior.
Detail tiers: Curated entries carry the full known/guess split and a scale silhouette; Limited are fragmentary finds (flagged as such); Brief are index stubs whose reconstruction notes aren't written up yet.

Terms

These are the words that pop up across the guide. They also appear as tap-to-read popovers inside featured entries.

ankylosaur: An armoured, low-slung plant-eater; many had a bony tail club.
bipedal: Walking on two legs.
caudal vertebra: A tail bone.
ceratopsian: A horned, frilled plant-eater like Triceratops.
cervical vertebra: A neck bone. Sauropods stacked dozens into enormous necks.
clade: Clades nest inside clades. A tyrannosaurid is also a coelurosaur, a theropod, and a dinosaur — all at once.
cladistics: Classifying life strictly by shared ancestry, drawn as nested branches.
coelurosaur: The theropod branch closest to birds — raptors, tyrannosaurs, ornithomimids.
convergent evolution: Unrelated animals independently evolving similar features.
coprolite: Fossilised dung — a direct window into diet.
dromaeosaurid: A 'raptor' — a feathered theropod with a big sickle claw on each foot.
femur: The thigh bone — often the best clue to an animal's size.
frill: The bony shield extending back over the neck in ceratopsians.
gastrolith: A 'stomach stone' swallowed to help grind up plant food.
hadrosaur: A 'duck-billed' dinosaur with batteries of grinding teeth; often crested.
holotype: The single specimen that formally defines a species' name.
ilium: The main blade of the hip that the leg muscles anchor to.
integument: The body covering — skin, scales, feathers, or quills.
K-Pg extinction: The asteroid-driven mass extinction 66 Mya that ended the non-bird dinosaurs.
keratin: The tough protein in beaks, claws, horn sheaths, and feathers.
lagerstätte: A fossil site with exceptional preservation, sometimes including soft tissue.
Mesozoic: The 'age of dinosaurs', 252–66 million years ago: Triassic, Jurassic, Cretaceous.
Mya: Million years ago.
nomen dubium: A 'doubtful name' — a species too poorly known to be diagnosed.
ornithischian: Ornithischians had a backward-pointing pubis bone. Despite the name 'bird-hipped', birds are NOT ornithischians — they are saurischian theropods.
ornithopod: A beaked, plant-eating dinosaur group that includes the duck-bills.
osteoderm: A bony plate or stud set in the skin — natural armour.
pachycephalosaur: A 'thick-headed' dinosaur with a domed, bony skull roof.
paleoart: Scientific reconstruction art — the artist's best guess at a living animal.
quadrupedal: Walking on four legs.
raptor: Informal name for a dromaeosaurid: a sickle-clawed, feathered predator.
saurischian: One of the two great dinosaur divisions. Confusingly, birds (true dinosaurs) descend from this 'lizard-hipped' group, not the 'bird-hipped' one.
sauropod: Sauropods were the largest animals ever to walk on land, with pillar legs, long necks and tails, and small heads.
sauropodomorph: The long-necked plant-eater lineage — sauropods and their early relatives.
sclerotic ring: A ring of bone in the eye; its size hints at day- or night-activity.
stegosaur: A plated dinosaur with back plates and a spiked tail (the 'thagomizer').
thagomizer: The cluster of tail spikes on a stegosaur, used in defence.
theropod: Theropods walked on two legs and had hollow bones and three main toes. The group runs from tiny Microraptor to Tyrannosaurus — and to every bird alive today.
titanosaur: A late, often armoured sauropod group; includes the largest dinosaurs.
trace fossil: Evidence of behaviour (tracks, burrows, nests) rather than the body itself.
type specimen: The reference fossil a species is officially based on.
tyrannosaur: A large-headed, small-armed predatory theropod lineage (T. rex and kin).

Clades

Dot color marks the broad family. Names link to that clade's page.