Zygophyseter varolai

Zygophyseter is an extinct genus of sperm whale that lived during the Tortonian age of the Late Miocene 11.2 to 7.6 million years ago. The genus contains a single species, Zygophyseter varolai, known from a single specimen from the Pietra Leccese Formation in Italy. It was a member of a stem group of fossil macroraptorial sperm whales (often shortened to "raptorial") also including Brygmophyseter, Acrophyseter, and Livyatan. It probably grew to be around in length and shared some characteristics with other raptorials, such as large teeth with tooth enamel that were functional in both the upper and lower jaws which the modern sperm whale (Physeter macrocephalus) lacks. It also had a beak, the ability to echolocate prey, and could have probably swum faster than the modern-day sperm whale which can reach . These were probably used in the capture of large prey, such as large fish, seals, and whales. In fact, its common name, the killer sperm whale, refers to its feeding habits that would have had a resemblance to the modern-day killer whale (Orcinus orca).

==Discovery and naming== The type and only specimen, labelled MAUL 229/1, is of an almost complete skeleton discovered in southern Italy by geologist Angelo Varola in the marine lime mudstone of the Pietra Leccese Formation near the city of Lecce. It was described in 2006 by geologists Giovanni Bianucci and Walter Landini from the University of Pisa. The genus name Zygophyseter comes from the Latin word zygomaticus, which emphasizes the elongation of the zygomatic process of the only known species Z. varolai, and the term physeter refers to the modern-day sperm whale (Physeter macrocephalus) of the family Physeteridae. The species name honors the discoverer. ==Description== ===Skull=== thumb|left|Digital reconstruction showing the proposed Rostrum (anatomy)|beak A characteristic of related raptorials, Zygophyseter had buccal exostoses, bony outgrowths in the alveolar ridge in the mouth, which are thought to have increased their bite force. Like other raptorials, it had large temporal fossae, probably for supporting strong temporal and masseter muscles, the strongest muscles between the skull and the jaw, meaning this adaptation allowed it to shut its jaws harder. The zygomatic bone (cheekbone) projects outward (anteriorly), indicating it had a beak, which featured an abrupt narrowing; this may have allowed it to clamp down on prey more effectively.