Dietary Habits and Tusk Usage of Shovel-Tusked Gomphotheres from Florida: Evidence from Stereoscopic Wear of Molars and Upper and Lower Tusks

SIMPLE SUMMARY: The shovel-tusked gomphotheres have long intrigued paleontologists and the general public as they are one of the most notable of all elephant ancestors. This is due to their highly distinctive and broad, flattened lower tusks that look remarkably like the head of a shovel. There has been much speculation regarding how these bizarre mammals lived as well as the possible functions of their tusks. This study aims to provide evidence as to their ancient diet as well as the likely functions of their upper and lower tusks by examining scars left in their molar as well as the scratch patterns left on their tusks. We show that the Florida shovel-tusked gomphotheres browsed on leaves and twigs, and thus, most likely occupied a dietary niche similar to living forest elephants. We demonstrate that they used their tusks for a wide variety of purposes. Upper tusks were used for scraping and slicing, whereas lower tusks were used for shoveling in some forms and scraping in others. The obvious importance of tusks in the life of proboscideans such as the shovel-tuskers underscores the vital importance of saving modern elephant populations from poachers that callously steal their tusks for profit. ABSTRACT: The paleodiet of the shovel-tusked gomphotheres from Florida (Amebelodon floridanus, Konobelodon britti, and Serbelodon barbourensis) was assessed via microwear analysis of molar dental enamel and compared to a large database of both extant proboscideans and ungulates. Scratch and pit results show a consistent browsing signal in A. floridanus, K. britti and S. barbourensis. Fossil results are more similar to those of the extant Loxodonta cyclotis than to Loxodonta africana or Elephas maximus, the latter two taxa exhibiting a mixed feeding result. Scratch width scores are high in all three shovel tuskers as well as in the extant proboscideans indicating the ingestion of some coarse vegetation, most likely bark, and twigs. Gouging is relatively low in A. floridanus and S. barbourensis. Only K. britti has levels of gouging approximating that seen in extant elephants. Large pitting is relatively low in both fossil and extant forms although L. cyclotis has higher levels of large pitting including more puncture-like pits seen with fruit and/or seed consumption. A variety of scratch patterns indicating variation in tusk usage behavior was found. Some Serbelodon and Konobelodon mandibular tusks exhibited digging behavior, although Konobelodon digging behavior was much more common and obvious, whereas Amebelodon mandibular tusks did not exhibit digging behavior and were more likely used for stripping and scraping. Unusual distal tusk wear was found in Amebelodon and Serbelodon most likely due to stripping off tree bark. Upper tusk usage varied with all three fossil species exhibiting scraping and/or cutting behavior. Results indicate that shovel-tusked gomphotheres from Florida occupied a narrow dietary niche but employed a variety of strategies to obtain the vegetation that they consumed.