Because his father, Cronus, wanted to hide his affair with the nymph Philyr
Because his father, Cronus, wanted to hide his affair with the nymph Philyra from Rhea, he slept with her in the form which gave rise to this creature's shape. The husband of Chariclo and father of Endeis, he was poisoned with the blood of the Hydra,  and gave his immortality to Prometheus to escape the pain. FTP, identify this archer, healer, and teacher of Asclepius, Achilles, and Jason, the best known of the centaurs.
Because his father, Cronus, wanted to hide his affair with the nymph Philyra from Rhea, he slept with her in the form which gave rise to this creature's shape.
Chiron