Acrophyseter, an extinct genus of toothed whale. Despite its resemblance to modern dolphins, Acrophyseter belonged to the spermwhale family and likely behaved like a killer whale. For a relative of the spermwhale, this whale was quite modest in size—4-5 meters in length, about the size of a great white shark. However, its weight is comparable to that of a modern killer whale—approximately 3.2-4.5 tons