The term was coined by Charles Darwin in his On the Origin of Species from 1859, when discussing Ornithorhynchus (the platypus) and Lepidosiren (the South American lungfish): ...
O termo foi acuñpado por Charles Darwin na súa obra A orixe das especies de 1859, cando discutía o caso do Ornithorhynchus (ornitorrinco) e Lepidosiren (peixe pulmonado suramericano): ...