Figure 3. Representative examples of hypostyle conditions in Oligocene horses of the Turtle Cove assemblage of Oregon. Hypostyle condition follows the terminology of Prothero and Shubin (1989). (1) Type 1 hypostyles (UOMNH F-58207) are thin ridges that have no cusps or spurs projecting anteriorly; (2) Type 2 hypostyles (JODA 1086) exhibit a small spur, which projects anteriorly from the hypostyle ridge; (3) Type 3 hypostyles (UCMP 75274) are characterized by a small distinct ovoid or triangular pocket between a posterior ridge and an anterior spur; I have added the additional condition, (4) none (UCMP 75279), which Idefine as the lack of hypostyle in heavily worn teeth. Note that there are multiple hypostyle conditions contained within an individual tooth row. Arrows point to exemplar hypostyles on each tooth row that exhibit the specific condition. Line drawings of exemplar teeth are to the right of the photographs with the hypostyle highlighted in blue. Scale bars = 1 cm.