Temporal and Paleoenvironmental Distribution of Basilosaurus in the Southeastern United States: New Evidence from the Eocene of Southwest Georgia10th Annual North American Paleontological Convention (2014)
AbstractBasilosaurus is a fully aquatic archaeocete characterized by elongated posterior thoracic, lumbar, and anterior caudal vertebrae. The genus was present in North America by the late Eocene, with most occurrences within the Gulf Coastal Plain. In Georgia, there are only three confirmed reports of Basilosaurus, two of which are of isolated elements. Here we report a fourth Basilosaurus from Georgia, found on the banks of the Flint River in Albany. This specimen appears to be the most complete Basilosaurus known from Georgia, and upon initial discovery, consisted of a series of seven elongate vertebrae (five complete and two partial) and some probable rib fragments. Since the discovery, three vertebrae have been stolen, but excavation is ongoing, and there is potential for recovery of additional material beyond what has been identified. The specimen is encased in the Ocala Limestone, a fine-grained, white to cream-colored limestone that formed during the late Eocene (Priabonian: 37.2–33.9 Ma) in the shallow open waters of the continental shelf. The goal of this study is to investigate the facies, temporal, and geographic distribution of Basilosaurus in North America in order to identify paleoenvironmental and geographic limitations to its distribution. To address this goal, Basilosaurus occurrences and depositional environment for each site were plotted on a paleogeographic reconstruction of Eocene North America for four time intervals (middle to late Priabonian, early Priabonian, Bartonian/Priabonian boundary, and Bartonian). Occurrences of Basilosaurus are rare near the Bartonian/Priabonian boundary, which coincides with a sea-level lowstand. Following this lowstand, the Jackson Sea transgressed, and Basilosaurus dispersed from Florida to as far north as South Carolina and as far west as Louisiana. The North American Basilosaurus population reached its peak during the height of the Jackson transgression, just prior to the Eocene/Oligocene boundary, with specimens found as far north as Arkansas and Tennessee, and in abundance in Mississippi and Alabama. There are no apparent associations between geography and paleoenvironment, or time and paleoenvironment, as Basilosaurus fossils are typically found in nearshore, shallow-marine environments regardless of age or location. There is, however, some association between geography and age, as specimens track the movement of the shoreline through time. Basilosaurus fossils also indicate the presence of an embayment leading to Arkansas and Tennessee, a feature that is absent in many paleogeographic reconstructions of the Eocene. Continuation of this study will ultimately provide a better understanding of the habitat preference and timing of dispersal of Basilosaurus, with implications for the evolution of archaeocetes in southeastern North America.
- Southwest Georgia,
Citation InformationKathlyn M. Smith, Alexander Hastings, Ryan M. Bebej and Mark D. Uhen. "Temporal and Paleoenvironmental Distribution of Basilosaurus in the Southeastern United States: New Evidence from the Eocene of Southwest Georgia" 10th Annual North American Paleontological Convention (2014)
Available at: http://works.bepress.com/kathlyn_smith/2/