HYBODONT SHARKS AS LINKAGES BETWEEN TERRESTRIAL AND MARINE FOOD WEBS IN THE PERMIAN PERIOD

Acrodus olsoni, Acrodus sweetlacruzensis, and Lissodus zideki, are all hybodontiform sharks from the early Permian Period (Artinskian Stage: 283.5 - 290.1 million years ago), whose fossils been found in rocks corresponding to nearshore ecosystems in Permian Basin of Texas. We also report these species in deeper marine, cephalopod rich, carbonates of the Leuders Formation in Shackleford County, Texas. These new fossils indicate that Hybodonts from this time routinely traveled between fully marine and nearshore marine environments, and may have helped connect the well-understood terrestrial/freshwater food webs of the early Permian to the marine realm. This behavior may also be the cause of increased Hybodont diversity from the Shackleford County site, compared to fossil communities from the same age elsewhere, in that it allowed for these sharks to diversify their diets in ways that similarly sized marine sharks and other fishes from the Leuders Formation could not.