Ankylorhiza is the largest known Oligocene toothed whale and is one of the most completely known early members of this group, with characteristics intermediate between basal and derived cetaceans.

The holotype of Ankylorhiza (cataloged under specimen number AMNH 10445) consists of a partial snout fossil discovered in the Ashley Formation of South Carolina, United States.

[1] In 1887, zoologist Joel Asaph Allen attributed AMNH 10445 to the extinct river dolphin Squalodon—now considered a wastebasket taxon—as a new species he named Squalodon tiedemani.

[1] Ankylorhiza had a 97.2-centimeter (38.3 in) long skull that measured 42.5 centimeters (16.7 in) at its widest point, and a total body length of around 4.8 meters (16 ft), making it the largest known toothed whale from the Oligocene epoch.

Waipatia maerewhenua Squalodon calvertensis Prosqualodon davidis Phoberodon arctirostris Notocetus vanbenedeni Xiphiacetus bossi Zarhachis flagellator Physeteroidea Platanista gangetica Ziphiidae Inioidea Delphinoidea The jaws were shorter and more well-built than those of earlier toothed whales, indicating an overall stronger snout.

Known skull remains of Ankylorhiza often show severe breakage of the postcanine teeth, possibly caused during impacts with solid bone when the animal was feeding.

[1] The unique forward-pointing incisors of Ankylorhiza were potentially used for intraspecific combat, though Boessenecker and colleagues note that use for ramming, a method used by living orcas to injure whales,[4] may be more likely.

After the genus became extinct around the beginning of the early Miocene epoch, its niche was probably reoccupied successively by Squalodon, macroraptorial sperm whales, and extant orcas.