This year is the 10th anniversary of the discovery of the Gray Fossil Site near Gray Tennessee. In honor of the event, East Tennessee State Natural History Museum and the Don Sundquist Center of Excellence in Paleontology co-hosted a one-day symposium on the current state of research at the site.
The seven talks in the morning session focused on geology, paleobotany and paleoclimatology at the site. Michael Whitelaw, Aaron Shunk, and Cynthia Liutkus looked at the basic underlying geology of the site (in an oversimplified form, Gray is basically a Cenozoic lake-sediment infill of karst/cave cavities in Paleozoic sediments). One interesting technique they used, which could have applications at Carmel Church, is to map the deposit by using gravity maps to determine the depth to the bedrock.
The rest of the morning talks described the vegetation, and used various techniques to try to get at paleotemperature, rainfall variation, canopy cover, and other ecological issues. The data here seems to be somewhat inconsistent, and the discussion became heated at times. Based on the presence of charcoal and the make-up of the plant communities (talks by Michael Zavada, and Diana Ochoa-Lozano and Yu-Sheng Liu) and isotopic ratios in the sediments (Yongli Gao, Taylor Burnham, and Michael Whitelaw, and Aaron Shunk) there are strong indications that there were drier periods and wetter periods at Gray, and at least some of these authors believe the climatic variations were seasonal. However, Larisa DeSantis and Steven Wallace presented (I think) very compelling isotopic data from herbivore tooth enamel that indicate that the Gray climate was seasonally very uniform, even though there could be longer-term variations. This seems a small point, but it results pretty significant differences in the ultimate interpretation of the paleoclimate.
Several talks (Yu-Sheng Liu with plants, DeSantis and Wallace based on isotope ratios in gomphothere teeth, and Steven Wallace in the afternoon session with red pandas) suggested that Gray may have been a relatively limited ecological refugium.
The afternoon was devoted to talks on vertebrates. Trying to identify fish remains from Gray, A. Brett Woodward discovered the same thing I’ve found working on Carmel Church fish – good fish skeletal references are practically nonexistent. He has been able to identify Micropterus (bass, like the one below left) and Lepomis (
breems bream/sunfish below right):
Greg McDonald and Steven Wallace discussed the even more rare sloth remains (4 bones), apparently a megalonychid, and the timing of the arrival of sloths in North America (sloths migrated from South America long before the Isthmus of Panama formed). Blaine Schubert, Steven Wallace, and Leopoldo Soibelzon presented on the yet more rare (3 bones) tremarctine bear Plionarctos.
Steven Wallace’s talk, as mentioned above, was on the red panda Pristinailurus bristoli (below), for which a relatively large amount of material is now known:
The last four talks (by Richard Hulbert, Aaron Abernethy, Matthew Gibson, and Patrick Hawkins, with Steven Wallace as a co-author on all of them), were all on the Gray Site tapir Tapirus polkensis (top of page). Gray has the world’s largest collection of fossil tapirs, with at least 80 individual animals so far. Such a large sample from (apparently) a single species allows for population level studies that are normally impossible with fossil vertebrates, including individual variation and ontogenetic studies.
Congratulations to Gray Fossil Site on their tenth anniversary, and for the excellent and informative symposium.