The smallest

The smallest vertebrate anyone has described is a frog you could stand on a fingernail. It has a skull, a spine, four legs and lungs, at a size most people assume belongs to insects.

Each group is ranked separately, because the groups are not measured the same way. A frog is measured snout to vent and that is very nearly the whole animal. A snake is measured snout to vent as well, and its tail — sometimes a third of it — is not in the figure.

Ranked on snout-to-vent length, which 15,251 species carry. 6,321 have no figure recorded at all and cannot appear here. Nobody has published a body length for them; they are not small, they are unmeasured.