How did Georges Cuvier change the classification of animals?

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Group of fallow deer (Dama dama) stags with large, palmate antlers standing alert in a green summer field. — Animal The fallow deer (*Dama dama*) has been introduced in many areas ever since the Neolithic Period.

Georges Cuvier significantly advanced the classification of animals by rejecting the 18th-century concept that all living things could be arranged in a single, continuous linear series from the simplest organisms up to humans.1

In his 1817 work, Le Règne animal distribué d’après son organisation ("The Animal Kingdom, Distributed According to Its Organization"), Cuvier argued that animals possess such diverse anatomical traits that they must be categorized based on their specific type of anatomical organization. He divided the animal kingdom into four distinct groups:1

Vertebrates
Mollusks
Articulates
Radiates

Cuvier believed that all animals within each of these groups were modifications of one particular anatomical type, and he insisted that these four types were entirely separate. By moving away from a linear hierarchy and emphasizing these distinct structural plans, Cuvier raised fundamental questions regarding why animals are anatomically different, ultimately helping to transition zoology toward the scientific views that emerged in the 19th century.1