from lamprey to bird · and why "fish" and "reptiles" are not groups
Built as a memo rather than a table: the thing worth hanging it up for reads across the room, with the full reference in smaller type below it.
Three sizes in one archive — from a sheet on the fridge to a poster on the wall.
A box is a clade: a group with all its descendants. Deeper shared box, closer kin. The dashes ring a hole — and a group with a hole is not a clade.
Crocodilians and birds are the two living branches of the archosaurs; dinosaurs and pterosaurs sit between them, which is exactly why the box they share is deeper than the one a crocodile shares with any lizard. A bird is not something standing beside the reptiles — a bird is a dinosaur that is still here.
"Reptiles" therefore becomes a real group only once birds are counted in. Without birds it is not a group but a remainder: what is left of a branch after its most successful part has been taken out. The same goes for "fish" — and the hole there is where you sit.
Why the numbers can be trusted. Every countable number here is computed from data rather than typed in, and the sheet must pass 5 independent checks before it is allowed to build — how many items there are, the order they come in, and the claim in the highlighted box itself. If one fails, there is no file.
from the Challenger Deep to the summit of Everest · one scale, nothing compressed
from the first synapsid to us · 320 million years on one axis
when each group appeared · five hundred million years on one axis
fifteen formulas · every letter explained beneath it