Hoplocetus

The teeth of Hoplocetus are massive (95–150 mm in length; 27–47 in maximum diameter), robust and have a short enamel cap on the crowns.^[3] They are somewhat larger than those of modern orcas^[4] but considerably smaller than those of macroraptorial sperm whales, such as Zygophyseter, as well as those of Scaldicetus caretti.^[5] They display a large degree of abrasion, suggesting a highly predatory niche comparable to that of modern orcas.^[3] The genus of the latter, Orcinus, first appears in the middle Pliocene and it may have eventually replaced Hoplocetus.^[3]

These teeth features also characterize the other extinct toothed whale genera, Diaphorocetus, Idiorophus and Scaldicetus, sometimes placed with Hoplocetus in the subfamily Hoplocetinae.^[6] However, some of these taxa are fragmentary and have been used as wastebasket taxa for non-diagnostic material of stem physeteroids. The estimated length range of Hoplocetus, based on its teeth and vertebrae, was about 6–8 m (20–26 ft).^[7]This body length suggests that it was a large predator similar in size to modern orcas.