An Early Pliocene Fish Assemblage from the Southern Appalachians: Ichthyofauna of the Gray Fossil Site
Location
Culp Center Rm. 304
Start Date
4-25-2023 1:40 PM
End Date
4-25-2023 2:00 PM
Faculty Sponsor’s Department
Geosciences
Name of Project's Faculty Sponsor
Joshua Samuels
Additional Sponsors
Joshua Samuels, Blaine Schubert, Steven Wallace
Competition Type
Competitive
Type
Oral Presentation
Project's Category
Ecology
Abstract or Artist's Statement
Pre-Pleistocene freshwater fish assemblages in the eastern United States are exceedingly rare, limited to only a handful of localities. The Gray Fossil Site, an early Pliocene sinkhole fill in northeast Tennessee, has yielded an abundance of vertebrate remains, including fish. Comparison with extant and fossil fish taxa reveals a depauperate ichthyofauna consisting of only two centrarchid genera: Micropterus cf. M. salmoides (black bass) and Lepomis sp. (sunfish). This material includes hundreds of specimens and represents the oldest centrarchid material from the eastern United States; it has potential to inform our understanding of centrarchid evolution and diversification. Fishes of the genus Micropterus are opportunistic predators that feed increasingly on fish and even terrestrial vertebrates as they increase in size. Lepomis, smaller Micropterus, and terrestrial vertebrates such as frogs and salamanders likely formed a major food source for Gray Fossil Site Micropterus. Extant fishes in the genus Lepomis are generally predators of aquatic insect larvae, small crustaceans, zooplankton, and other aquatic invertebrates and prey occasionally on small fish. Lepomis from the Gray Fossil Site were likely non-specialized predators of aquatic invertebrates – they are “short-jawed,” indicating low levels of piscivory and lack the robust pharyngeal jaws associated with extensive feeding on mollusks. Extant species of Micropterus and Lepomis occupy a wide variety of freshwater habitats but typically only spawn in shallow, open water with soft substrate overlying gravels. This suggests these conditions were present in the sinkhole pond. The absence of other fish species that are ubiquitous in streams and rivers in the southeastern United States today suggests that the sinkhole pond was not connected to surrounding waterways by surface hydrology. In addition to large numbers of isolated bones, several articulated and partially articulated fish specimens have also been recovered and show minimal evidence of postmortem disarticulation or scavenging. This suggests a cold and/or anoxic hypolimnion within the sinkhole pond as well as an absence of scavengers such as crayfish, which have not been documented from the site. Osteological thin sectioning of fish atlantes suggests slow growth rates in Gray Fossil Site fishes and small overall size for their age, possibly due to high competition or limited surface area of the pond they inhabited.
An Early Pliocene Fish Assemblage from the Southern Appalachians: Ichthyofauna of the Gray Fossil Site
Culp Center Rm. 304
Pre-Pleistocene freshwater fish assemblages in the eastern United States are exceedingly rare, limited to only a handful of localities. The Gray Fossil Site, an early Pliocene sinkhole fill in northeast Tennessee, has yielded an abundance of vertebrate remains, including fish. Comparison with extant and fossil fish taxa reveals a depauperate ichthyofauna consisting of only two centrarchid genera: Micropterus cf. M. salmoides (black bass) and Lepomis sp. (sunfish). This material includes hundreds of specimens and represents the oldest centrarchid material from the eastern United States; it has potential to inform our understanding of centrarchid evolution and diversification. Fishes of the genus Micropterus are opportunistic predators that feed increasingly on fish and even terrestrial vertebrates as they increase in size. Lepomis, smaller Micropterus, and terrestrial vertebrates such as frogs and salamanders likely formed a major food source for Gray Fossil Site Micropterus. Extant fishes in the genus Lepomis are generally predators of aquatic insect larvae, small crustaceans, zooplankton, and other aquatic invertebrates and prey occasionally on small fish. Lepomis from the Gray Fossil Site were likely non-specialized predators of aquatic invertebrates – they are “short-jawed,” indicating low levels of piscivory and lack the robust pharyngeal jaws associated with extensive feeding on mollusks. Extant species of Micropterus and Lepomis occupy a wide variety of freshwater habitats but typically only spawn in shallow, open water with soft substrate overlying gravels. This suggests these conditions were present in the sinkhole pond. The absence of other fish species that are ubiquitous in streams and rivers in the southeastern United States today suggests that the sinkhole pond was not connected to surrounding waterways by surface hydrology. In addition to large numbers of isolated bones, several articulated and partially articulated fish specimens have also been recovered and show minimal evidence of postmortem disarticulation or scavenging. This suggests a cold and/or anoxic hypolimnion within the sinkhole pond as well as an absence of scavengers such as crayfish, which have not been documented from the site. Osteological thin sectioning of fish atlantes suggests slow growth rates in Gray Fossil Site fishes and small overall size for their age, possibly due to high competition or limited surface area of the pond they inhabited.