Abstract
Hypercanines are here defined as hypertrophied caniniform teeth, that is, canine teeth that are elongated to serve specific functions in different clades of mammals and their synapsid ancestors. This article presents an overview of the occurrence of hypercanines, their growth, and their function across a broad range of clades. Sabertooth felids and felid-like taxa are found to be unique in having determinate growth (although some Dinocerata may also have this). The most common function of hypercanines among herbivores is found to be sexual display and male-male competition. Three clades of small ruminants have evolved hypercanines that can move within their sockets, although the evolutionary details behind this convergent adaptation have not been worked out.