Sperm whale, 19th century illustration. Physeter is a genus of toothed whales. There is only one living species in this genus, the sperm whale (Physeter macrocephalus, here as Cachalot whales). Two fossil species are currently known that are placed in the same genus. Copperplate engraving from the Encyclopaedia Londinensis, or Universal Dictionary of Arts, Sciences, and Literature; Volume XX; Edited by Wilkes, John. Published in 1825.