Pliocene Pronghorns of Florida

Abstract

Two genera and species of Antilocaprinae occur in Hemphillian (middle Pliocene) deposits of Florida. Hexameryx simpsoni White bore three widely divergent horns above each orbit. The middle horn is more anteriorly directed in larger-horned individuals. This distinction, previously used to separate H. elmorei from H. simpsoni, is attributed to sexual dimorphism, and the two species are synonymized. Antilocapra (Subantilocapra) garciae, new subgenus and species, represents the ancestry of the Recent American pronghorn. It has a tall-based, laterally compressed horn core with a weak anterior as well as a strong posterior prong. The bifurcation of the horny sheath in Recent male pronghorns is thus a relict of an earlier bony bifurcation.