A PALEOECOLOGICAL ANALYSIS OF THE RED HILL SITE, PENNSYLVANIA, U.S.A., USING VERTEBRATE MICROFOSSILS

The Red Hill site located along a road cut near Hyner in Clinton County, Pennsylvania, represents a floodplain ecosystem during the late Famennian age of the Upper Devonian Period. Fossil vertebrates from the Red Hill site include those of palaeoniscid ray-finned and lobe-finned fishes, placoderms, acanthodians, freshwater sharks, and early tetrapods. Vertebrate microfossils are often used to assess the paleoecology of extinct ecosystems. Differences in species richness in similar geological sediments can indicate differences in the paleoecology between locations. Fossils were collected from two distinct strata: oxidized strata representing sediments from main river channel margins and reduced strata representing sediments from highly vegetated floodplain ponds. Four quarries were excavated at the Red Hill site with two quarries in each strata. Vertebrate fossils were identified and counted from each quarry. A total of 293 vertebrate fossils were recorded from the four quarries. These fossils included teeth and scales of Hyneria lindae, dermal bony plates of groenlandaspid placoderms, scales of megalichthyid sarcopterygian fish, Gyracanthus spines, teeth of Ageleodus pectinatus, and body impressions of Limnomis delaneyi. Quarries from the oxidized layers produced many more fossils compared to the reduced layers. A total of 17 H. lindae scales, 3 H. lindae teeth, 12 placoderm plates, 5 megalichthyid scales, 2 Gyracanthus spines, and 2 L. delaneyi partials were found in the reduced strata. A total of 128 H. lindae scales, 33 H. lindae teeth, 72 placoderm plates, 37 megalichthyid scales, 11 Gyracanthus spines, and 10 A. pectinatus teeth were collected from the oxidized strata. From these data, we concluded that the main river channel margin habitats contained higher densities of vertebrates than the still water ponded environments. Our findings also potentially indicate that the flowing water and ponded water types of habitats preserved at Red Hill supported different types of vertebrate communities.