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Glossary

Every term on DinoAtlas explained twice: one plain sentence, then the detail if you want it.

Naming things

Taxon: Any named group of living things — a species, a genus, or a whole branch like Dinosauria.; A taxon (plural: taxa) is a named unit in classification, at any level. Tyrannosaurus rex is a taxon, so is the genus Tyrannosaurus, so is Theropoda, and so is Dinosauria. When we say DinoAtlas holds ~12,900 taxa, we mean every named unit at every level, not 12,900 kinds of dinosaur.; also: taxa
Genus: The first half of a scientific name — the group a species belongs to, like Tyrannosaurus.; Scientific names have two parts: the genus (capitalised) and the species epithet (lower case), both italicised — Tyrannosaurus rex. Most famous dinosaurs are known to the public by their genus alone. A genus can hold one species or dozens.; also: genera
Species: The narrowest kind of named animal — the 'rex' in Tyrannosaurus rex.; For living animals a species is usually defined by which populations interbreed. Fossils cannot be tested that way, so paleontologists define fossil species by consistent differences in bone shape. That makes species boundaries in the fossil record a matter of expert judgement, and they get revised often.
Clade: An ancestor plus every single one of its descendants — a complete branch of the family tree.; A clade is a branch cut cleanly from the tree of life: one ancestral species and all of its descendants, with nothing left out. Dinosauria is a clade, which is why birds are inside it — they descend from dinosaurs, so leaving them out would break the branch. 'Reptiles' in the everyday sense is not a clade, because it excludes birds.
Phylogeny: The family tree of a group, worked out from shared features.; Phylogenetics reconstructs relationships by scoring hundreds of anatomical characters and finding the tree that requires the fewest evolutionary changes. Different data sets give different trees, which is why the dinosaur family tree is redrawn every few years — including a serious 2017 proposal to rearrange its deepest branches.; also: cladistics, phylogenetic
Synonym: A second name given to an animal that already had one — the older name usually wins.; When two researchers name the same animal, the names are synonyms and, by the rules of zoological nomenclature, the earliest published name has priority. This is why Brontosaurus spent a century folded into Apatosaurus (a 2015 study argued it deserves its own genus again). DinoAtlas keeps synonyms searchable so an old name still finds the right page.
Nomen dubium: A name based on fossils too scrappy to tell apart from anything else — a 'doubtful name'.; Literally 'doubtful name'. If the original specimen lacks any feature unique to it, the name cannot be reliably applied to new finds, so it is set aside as a nomen dubium. Many 19th-century dinosaur names based on a single tooth ended up here.
Extinct / extant: Extinct means none are left; extant means the group is still alive today.; In DinoAtlas, records are flagged extinct or extant. Dinosauria as a whole is extant — because birds are dinosaurs — while every non-avian branch inside it is extinct.

Rocks & time

Formation: A named layer of rock that can be traced across the landscape — dinosaurs are found inside them.; A geological formation is a body of rock distinctive enough to be mapped and named, usually after a place: the Morrison Formation, the Hell Creek Formation. Formations are the address of a fossil. Because a formation was laid down over a known span, knowing the formation usually tells you roughly how old the fossil is.
Ma: Short for 'millions of years ago' — 66 Ma means 66 million years ago.; Ma is the standard abbreviation for mega-annum, a million years. Fossil ages are given as ranges (say 68–66 Ma) because dating brackets a specimen between two datable layers rather than pinning it to a date.; also: mya, million years ago
Mesozoic: The age of dinosaurs: the Triassic, Jurassic and Cretaceous together, 252 to 66 million years ago.; The Mesozoic Era spans 252–66 Ma and is bounded by the two largest extinctions of the last half-billion years: the end-Permian event that opened it, and the asteroid impact that closed it. Non-avian dinosaurs occupy roughly its last two-thirds.
Radiometric dating: Reading a rock's age from the steady decay of radioactive atoms inside it.; Certain unstable isotopes decay at fixed, measured rates. Uranium-lead dating of zircon crystals in volcanic ash can date a layer to within a few tens of thousands of years, even hundreds of millions of years back. It dates the ash, not the fossil, so paleontologists bracket a fossil between dated layers above and below.
Biostratigraphy: Dating rocks by which fossils they contain.; Some species existed briefly and spread widely — pollen, microfossils, ammonites. Finding one pins a layer to that species' known window. Biostratigraphy is how most dinosaur-bearing rocks are dated, since datable volcanic ash is not always present.
Paleolatitude: Where a place sat on the globe back then, before the continents drifted to where they are now.; Plate motions are reconstructed from seafloor magnetic stripes and rock magnetism, so any site's ancient coordinates can be calculated for a given age. DinoAtlas's map can switch to paleo-coordinates, which is why a Wyoming quarry slides south and a Mongolian site moves once you flip the toggle.

Fossils

Holotype: The one specimen that officially carries a species' name.; When a new species is named, one specimen is designated the holotype and permanently anchors the name. Every later identification is a comparison back to it. Holotypes live in museum collections with a catalogue number — for Tyrannosaurus rex it is CM 9380, now in Pittsburgh.; also: type specimen
Occurrence: One record of one kind of fossil found at one place.; An occurrence is the basic unit of a fossil database: this taxon, at this locality, in this rock unit, dated to this interval. It is not one bone and not one animal — a single skeleton is one occurrence, and so is a bone bed of a hundred individuals. DinoAtlas maps ~37,800 of them.
Matrix: The rock a fossil is stuck in, which preparators chip and grind away.; Matrix is the sediment surrounding a fossil. Removing it is slow, skilled work with air scribes, needles and sometimes acid baths, and it routinely takes longer than the excavation did — thousands of hours for a large skeleton.
Taphonomy: Everything that happens to a body between death and discovery.; Taphonomy studies the filter between life and the fossil record: scavenging, transport by water, burial, chemical alteration, erosion. It explains the record's biases — big bones in river sediments preserve well, small forest animals hardly at all — so the fossil record is never a fair census of the living world.
Trace fossil: A footprint, burrow, nest or dropping — evidence of behaviour rather than a body part.; Trace fossils record what an animal did. Because you can rarely match a track to a skeleton, tracks get their own parallel names, called ichnotaxa (for example Grallator). DinoAtlas flags these separately so trackway names do not get mistaken for animals.; also: ichnotaxon, ichnotaxa, ichnogenus
Coprolite: Fossilised dung — surprisingly informative about diet.; Coprolites preserve bone fragments, plant tissue and even muscle, giving direct evidence of what an animal ate. A famous Saskatchewan specimen, over 40 cm long and full of crushed bone, is widely attributed to a tyrannosaur.

Dinosaur groups

Theropod: The mostly meat-eating, two-legged dinosaurs — Tyrannosaurus, Velociraptor and every bird.; Theropoda is defined by hollow bones and three main weight-bearing toes. Diets ran the full range: hypercarnivores, fish-eaters, insectivores and plant-eating therizinosaurs. Birds are theropods, making this the only dinosaur branch alive today.
Sauropod: The giant long-necked plant-eaters on four legs — Brachiosaurus, Diplodocus, Argentinosaurus.; Sauropods evolved air-filled neck vertebrae, small heads and a fast-cropping, no-chewing feeding style, which let them reach body masses no land animal has matched since — the largest are estimated near 60–70 tonnes.
Ornithischian: The bird-hipped plant-eaters: horned, armoured, plated and duck-billed dinosaurs.; Ornithischia includes ceratopsians, ankylosaurs, stegosaurs, hadrosaurs and pachycephalosaurs. The name means 'bird-hipped' after a backwards-pointing pubis bone — a confusing label, since birds evolved from the other branch, the saurischians.
Saurischian: The 'lizard-hipped' half of the family tree: theropods plus sauropods.; Saurischia has traditionally united the theropods and the long-necked sauropodomorphs, split from Ornithischia by hip anatomy. A 2017 analysis proposed regrouping theropods with ornithischians instead; the debate is unresolved and DinoAtlas follows the Paleobiology Database's current classification.
Avian: Bird. 'Non-avian dinosaurs' means the dinosaurs that died out 66 million years ago.; Since birds are dinosaurs, paleontologists say 'non-avian dinosaurs' for the ones that vanished at the end of the Cretaceous. DinoAtlas tags avian taxa so you can include or exclude ~11,000 living species from the counts.