the holotype of "agorophius pygmaeus", mcz 8761, was first mentioned in an 1848 report on the geology of south carolina by michael tuomey. it was eventually described as "zeuglodon pygmaeus" by johannes peter müller in 1849. louis agassiz coined the name "phocodon holmesii" for the same specimen, classifying it as an odontocete. later authors considered "zeuglodon pygmaeus" a species of either "dorudon" or "squalodon", and in 1895 edward drinker cope eventually recognized it as being a distinct genus, which he named "agorophius".