Acrophyseter

Acrophyseter deinodon Temporal range: Late Miocene
Acrophyseter deinodon skull
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Superfamily:	Physeteroidea
Family:	incertae sedis
Genus:	†Acrophyseter Lambert, Bianucci & Muizon, 2008
Species:	† A. deinodon
Binomial name
Acrophyseter deinodon Lambert, Bianucci & Muizon, 2008

Acrophyseter is a genus of stem-sperm whales that lived around 6 million years ago, found in the Pisco Formation in Peru.^[1]

Description

Teeth

Acrophyseter is derived from the Greek akros, meaning acute, which describes the short, pointed upturned snout, and Physeter, the scientific name for sperm whales. But unlike today's sperm whales, A. deinodon was relatively small at around 4 m (13 ft) and had teeth on both the upper and lower jaws; 12 pairs in the upper jaw and 13 pairs in the lower. These teeth were large, sharp, and set firmly in deep sockets; the species epithet deinodon is from the Greek deinos, meaning terrible, and odon, tooth. The lower back teeth were close together suggesting they were used for shearing, unlike the suction feeding used by today's sperm whales, which don't even have teeth on their upper jaws. These differences imply that Acrophyseter fed on comparatively large prey, such as the smaller whales like Piscolithax, pinnipeds like Acrophoca, and penguins like Spheniscus urbinai that lived in the area at that time.

Various skull characteristics such as the size of the teeth and presence of tooth enamel which living sperm whales don't have indicate that Acrophyseter is probably a sister group to the Brygmophyseter and Zygophyseter group and to the group comprising Aulophyseter and living physeteroids, the kogiids and physeterids.^[1]

References

1. Lambert, Olivier; Bianucci, Giovanni; Demuizon, Christian (2008). "A New Stem-Sperm Whale (Cetacea, Odontoceti, Physeteroidea) from the Latest Miocene of Peru". Comptes Rendus Palevol (Elsevier Masson SAS) 7: 361–369. doi:10.1016/j.crpv.2008.06.002.