page_title: Macroraptorial sperm whale
section_title: Taxonomy
hierarchical_section_title: Macroraptorial sperm whale / Taxonomy
caption_attribution_description: English: Zygophyseter varolai, a sperm whale from the Late Miocene of italy. Digital.
context_page_description: Macroraptorial sperm whales were highly predatory whales of the sperm whale family of the Miocene epoch that hunted large marine mammals, including other whales, using their large teeth. Likewise, they were all likely the apex predator of their habitats, comparable to the modern day killer whale, and achieved great lengths, with one species–Livyatan–measuring about 13.5–17.5 metres. The macroraptorial sperm whales–Albicetus, Acrophyseter, Brygmophyseter, Livyatan, Scaldicetus, and Zygophyseter–are an informal grouping of genera without a family designation. All species are known by at least a skull.
context_section_description: The macroraptorial sperm whales are a paraphyletic fossil group of hyper-predatory stem sperm whales comprising four genera: Acrophyseter, Brygmophyseter, Livyatan, and Zygophyseter. These macroraptorials all share large, functional, enamel-coated teeth on both the upper and lower jaws, which were used in capturing large prey. In contrast, the modern sperm whale (Physeter macrocephalus) lacks enamel, teeth in the upper jaw, and the ability to use its teeth to catch prey. However, Livyatan belongs to a different lineage than the other macroraptorials, and the development of large size and the spermaceti organ, an organ that is characteristic of sperm whales, are thought to have evolved independently from the other macroraptorials. The large teeth either evolved once in the group with a basilosaurid-like common ancestor, or independently in Livyatan. The large temporal fossa depressions on the skull of raptorials is probably descended from a common ancestor (plesiomorphy). The presence of enamel is thought to be an ancient and basal characteristic, as it is present on the teeth of fetal modern sperm whales. Macroraptorials appeared during an adaptive radiation event of baleen whales in the Miocene, an increase in whale populations and diversity, implying the macroraptorials evolved specifically to exploit baleen whales. A 30 cm (12 in) tooth found in Australia indicates macroraptorials still existed 5 mya in the Pliocene.
  Zygophyseter was discovered in the Pietra Leccese Formation in Italy from a skull, teeth, and vertebrae; Brygmophyseter was discovered in the Bessho Formation in Japan from a nearly-complete skeleton; and Acrophyseter and Livyatan both originate from the Pisco Formation in Peru and are known by only a skull.
  It has also been suggested that the macroraptorials be placed into the subfamily Hoplocetinae, a subfamily characterized by robust and enamel-coated teeth, alongside the genera Diaphorocetus, Idiorophus, and Hoplocetus, which are known from the Miocene to the Early Pleistocene. However, most of these whales are known from fragmentary remains or have been used as wastebasket taxa for indiscernible stem sperm whale remains.
caption: Restoration of Zygophyseter
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