He is remembered chiefly as the first ornithologist to propose a division of birds into Ratitae (
ratites or running birds, with a flat
sternum) and
Carinatae (carinates or flying birds, with a keeled sternum), which formed part of his classification of birds in
Tentamen Systematis Naturalis Avium, published in Berlin in 1816 (in
Abhandlugen Akad. Wiss. Berlin 1812–1813: Phys. Kl.). ==Herpetology==