Animal groups
Every species in the catalogue belongs to one of these nine groups. Each page explains what actually separates the group from the others — not just the field marks, but the biology underneath — and lists where its species turn up across the 32 regions.
Mammals
Mammals are defined by hair and by feeding their young on milk, and those two things underwrite most of what else is distinctive…
613 species · 68 profiles →Birds
Birds are living dinosaurs, the surviving branch of the theropod lineage, and almost everything about them is organised around…
1,714 species · 9 profiles →Fish
Fish are not a single natural group so much as everything vertebrate that stayed in the water, and the category covers animals as…
782 species · 4 profiles →Reptiles
Reptiles regulate their temperature using the environment rather than by burning food, which is the single fact that explains…
440 species · 5 profiles →Amphibians
Amphibians live across two worlds and are exposed in both. Most begin as aquatic larvae with gills and metamorphose into…
131 species · 1 profiles →Insects
Insects are the most numerous and diverse animals on Earth by an enormous margin — more described species than all other animal…
2,368 species · 0 profiles →Arachnids
Arachnids have eight legs, two body sections and no antennae, which separates them cleanly from insects however often the two get…
305 species · 1 profiles →Mollusks
Mollusks are the second most diverse animal group after the arthropods, and they include animals with almost nothing visibly in…
130 species · 1 profiles →Other animals
This group collects the animals that sit outside the familiar vertebrate and arthropod classes used elsewhere in the catalogue —…
202 species · 2 profiles →