The Gray Fossil Site is an

Early Pliocene Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * Early ...

assemblage of fossils dating between 4.5 and 4.9 million years old, located near the town of

Gray Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...

Washington County, Tennessee Washington County is a county located in the U.S. state of Tennessee. As of the 2020 census, the population was 133,001. Its county seat is Jonesborough. The county's largest city and a regional educational, medical and commercial center is ...

. The site was discovered during road construction on Tennessee State Route 75 by the

Tennessee Department of Transportation The Tennessee Department of Transportation (TDOT) is a multimodal agency with statewide responsibilities in roadways, aviation, public transit, waterways, and railroads. The mission of TDOT is to provide a safe and reliable transportation syste ...

in May 2000, after which local officials decided to preserve the site for research and education. The site became part of

East Tennessee State University East Tennessee State University (ETSU) is a public research university in Johnson City, Tennessee. Although it is part of the State University and Community College System of Tennessee, the university is governed by an institutional Board of Tr ...

, and the Gray Fossil Site & Museum was opened on the site in 2007. The ancient habitat of the Gray Fossil Site was a

pond A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from ...

formed within a

sinkhole A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openi ...

surrounded by a warm, wet forest. The fossils found at the site represent the ancient plants and animals that lived and died in and around the sinkhole pond. As the first site of its age known from the Appalachian region, the Gray Fossil Site is a unique window into the past. Research at the site has yielded many surprising discoveries, including new species of

red panda The red panda (''Ailurus fulgens''), also known as the lesser panda, is a small mammal native to the eastern Himalayas and southwestern China. It has dense reddish-brown fur with a black belly and legs, white-lined ears, a mostly white muzzle ...

rhinoceros A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant species (or numerous extinct species) of odd-toed ungulates in the family Rhinocerotidae. (It can also refer to a member of any of the extinct species ...

, pond turtle,

hickory tree Hickory is a common name for trees composing the genus ''Carya'', which includes around 18 species. Five or six species are native to China, Indochina, and India (Assam), as many as twelve are native to the United States, four are found in Mex ...

, and more. The site also hosts the world's largest known assemblage of fossil

tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a pig, with a short, prehensile nose trunk. Tapirs inhabit jungle and forest regions of South and Central America, with one species inh ...

Formation

The Gray Fossil Site is a deposit of laminated clay and silt sediments laid down in an ancient lake that formed within a sinkhole. The deposit is oval in shape, covering an area of roughly 220 meters by 180 meters and ranging in depth from about 7 meters to 39 meters deep. The fossils within this deposit are abundant and often exceptionally well-preserved. Stratigraphic ranges of mammals from the Gray Fossil Site, TN

Stratigraphic ranges of mammals from the Gray Fossil Site, TN

The site is situated within the Knox Group formation, a series of Cambrian-

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

s. Groundwater flowing through joints in these rocks creates caves and sinkholes, forming a region of karst topography. The sinkhole that contains the fossil-rich deposits of the Gray Fossil Site is the result of a series of overlapping collapse events that ultimately formed one large basin. Sizable boulders deposited within the lake sediments indicate that the edge of the sinkhole once featured high walls or overhangs where chunks of rock could occasionally break off. Based on the assemblage of mammal fossils uncovered at the site, the main deposit is estimated to date between 4.5 and 4.9 million years old, during the Early

Pliocene Epoch The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Hemphilian and Blancan Land Mammal Ages. There is some evidence from drill cores for more ancient deposits deeper within the site, resulting from earlier stages of sinkhole collapse.

History

In late May 2000, this fossil-rich deposit was discovered during a

road construction project on the outskirts of Gray, TN. As it became clear that the fossils were unusual for this part of the country, members of the local community began an effort to preserve the site. In September 2000, Tennessee Governor

Don Sundquist Donald Kenneth Sundquist (born March 15, 1936) is an American businessman and politician who served as the 47th Governor of Tennessee from 1995 to 2003. Prior to his governorship, he represented Tennessee's 7th congressional district in the Uni ...

announced that the construction project would be moved so the fossil site could be saved and dedicated to research and education. The Gray Fossil Site then became a project of East Tennessee State University, which began hiring paleontologists and geologists to oversee the site and ultimately to create a new Department of Geosciences. The university founded the Don Sundquist

Center of Excellence A center of excellence (COE or CoE ), also called excellence center, is a team, a shared facility or an entity that provides leadership, best practices, research, support or training for a focus area. Due to its broad usage and vague legal prec ...

in Paleontology and began construction of an on-site museum to house research facilities and educational exhibits. The museum first opened in August 2007, originally known as the East Tennessee State University and General Shale Brick Natural History Museum and Visitor Center, but now known more simply as the Gray Fossil Site & Museum.

Paleoenvironment

The Gray Fossil Site was once a lake or pond surrounded by forest. The ancient lake was home to a diverse community of aquatic animals, including fish, pond turtles, aquatic salamanders, beavers, and alligators. Plant fossils found at the site, particularly pollen, indicate that the dominant vegetation of the forest was oak, hickory, and pine trees, along with various herbaceous species. Estimates for the density of this forest have varied; earlier research suggested a moderately dense forest, while later study indicated that the site might have been more of an open woodland where disruptive factors such as large herbivores, frequent fire, and drought limited the development of a closed

canopy Canopy may refer to: Plants * Canopy (biology), aboveground portion of plant community or crop (including forests) * Canopy (grape), aboveground portion of grapes Religion and ceremonies * Baldachin or canopy of state, typically placed over an ...

. A 2020 study used fossil mammal teeth as a proxy to estimate the ancient climate conditions of the Gray Fossil Site, estimating a mean annual temperature of 16.8 °C, or 62.2 °F (similar to modern-day

Atlanta, GA Atlanta ( ) is the capital and most populous city of the U.S. state of Georgia. It is the seat of Fulton County, the most populous county in Georgia, but its territory falls in both Fulton and DeKalb counties. With a population of 498,715 ...

), and an annual precipitation of 1,343mm, or 52.9in (similar to modern-day

Tampa, FL Tampa () is a city on the Gulf Coast of the U.S. state of Florida. The city's borders include the north shore of Tampa Bay and the east shore of Old Tampa Bay. Tampa is the largest city in the Tampa Bay area and the seat of Hillsborough Count ...

), with the minimum temperature of the coldest month reaching 2.6 °C, or 36.7 °F. These results line up with earlier hypotheses that the site had a warmer and wetter climate than modern East Tennessee based on the presence of warm-climate animals and plants like

alligator An alligator is a large reptile in the Crocodilia order in the genus ''Alligator'' of the family Alligatoridae. The two extant species are the American alligator (''A. mississippiensis'') and the Chinese alligator (''A. sinensis''). Additiona ...

tupelo Tupelo , genus ''Nyssa'' , is a small genus of deciduous trees with alternate, simple leaves. It is sometimes included in the subfamily Nyssoideae of the dogwood family, Cornaceae, but is placed by other authorities in the family Nyssaceae. In ...

, and '' Corylopsis''. Many of the fossil fauna and flora of the Gray Fossil Site are closely related to modern-day species in Europe and Asia, including red pandas, European badgers, Chinese moonseed, and ''Corylopsis''. This indicates that during the Early Pliocene, eastern North America maintained a biogeographic link with

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...

Fossils

The Gray Fossil Site is a

Lagerstätte A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These f ...

that boasts a rich assemblage of well-preserved fossils. It is the only fossil site in the Appalachian region dating near the boundary between the Miocene and Pliocene Epochs, and therefore offers a unique window into this region at this time.

Fish

So far, all of the

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...

fossils identified at the Gray Fossil Site belong to the family

Centrarchidae Centrarchidae, better known as sunfishes, is a family of freshwater ray-finned fish belonging to the order Perciformes (formerly belonging to the deprecated order Centrarchiformes), native only to North America. There are eight universally i ...

Amphibians

Salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...

s. Several taxa have been identified, including ''Ambystoma, Desmognathus, Notophthalmus,'' and ''Plethodon.'' These are the oldest known members of their families in the Appalachian mountains, a region well-known for its modern salamander diversity. *

Frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...

s. Numerous taxa, including ''Rana.'' Top and bottom shell fossil Cf Chrysemys picta 01

Reptiles

Alligator An alligator is a large reptile in the Crocodilia order in the genus ''Alligator'' of the family Alligatoridae. The two extant species are the American alligator (''A. mississippiensis'') and the Chinese alligator (''A. sinensis''). Additiona ...

s. Several well-preserved specimens have been identified to the genus ''Alligator'', but these appear to be distinct from known alligator species. * Lizards. Identified lizards include skinks, anguids, and helodermatids. *

Snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...

s. The most common snakes are

colubrid Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ev ...

s, of which several species have been identified, including the endemic fossil species ''Zilantophis schuberti.''

Viperids The Viperidae (vipers) are a family of snakes found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, and various other isolated islands. They are venomous and have long (relative to non-vipers), hinged fangs t ...

are also present. *

Turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked t ...

s. These are the most diverse group of reptiles at the site, including several taxa of

box turtle Box turtle is the common name for several species of turtle. It may refer to those of the genus '' Cuora'' or '' Pyxidea'', which are the Asian box turtles, or more commonly to species of the genus '' Terrapene'', the North American box turtles. ...

s, painted turtles,

slider turtle ''Trachemys'' is a genus of turtles belonging to the family Emydidae. Members of this genus are native to the Americas, ranging from the Midwestern United States south to northern Argentina, but one subspecies, the red-eared slider (''T. script ...

snapping turtle The Chelydridae is a family of turtles that has seven extinct and two extant genera. The extant genera are the snapping turtles, ''Chelydra'' and '' Macrochelys''. Both are endemic to the Western Hemisphere. The extinct genera are '' Acherontem ...

s, and

tortoise Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like oth ...

s. Among these are two species only known from the Gray Site, the musk turtle ''Sternotherus palaeodorus'' and the slider turtle ''Trachemys haugrudi.'' ''T. haugrudi'' was named after Shawn Haugrud, the site's lab and field manager and lead preparator.

Birds

A preliminary study in 2011 identified several families of birds at the Gray Fossil Site, the most common of which were

duck Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form ...

Mammals

Perissodactyls Odd-toed ungulates, mammals which constitute the taxonomic order Perissodactyla (, ), are animals—ungulates—who have reduced the weight-bearing toes to three (rhinoceroses and tapirs, with tapirs still using four toes on the front legs) o ...

(odd-toed hoofed mammals) *'' Tapirus polkensis'' (dwarf

). The Gray Fossil Site has the largest tapir population of any known fossil site, including fossil tapirs of all ages, from very young juveniles to old adults. *'' Teleoceras aepysoma'' (

). Several specimens are known, including two nearly complete skeletons. In 2019, the Gray Fossil Site rhinos were identified as a new species, named the "high-bodied" ''Teleoceras'' for their longer front legs compared to other species. *'' Cormohipparion emslei'' (three-toed horse)

Artiodactyls The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...

(even-toed hoofed mammals) *

Peccaries A peccary (also javelina or skunk pig) is a medium-sized, pig-like hoofed mammal of the family Tayassuidae (New World pigs). They are found throughout Central and South America, Trinidad in the Caribbean, and in the southwestern area of North ...

. Two species have been identified: '' Mylohyus elmorei'' and ''Prosthennops serus.'' * '' Pediomeryx''. * Camel, possibly ''

Megatylopus ''Megatylopus'' (also known as the North American camel) is an extinct genus of large camel, endemic to North America from the Late Miocene to the Pliocene, existing for approximately . Fossil distribution ranged from North Carolina to Califor ...

.''

Carnivora * '' Pristinailurus bristoli'' (

). Named as a new species in 2004. Two nearly complete skeletons make this one of the best-known fossil pandas in the world. * ''Arctomeles dimolodontus'' (Eurasian

badger Badgers are short-legged omnivores in the family Mustelidae (which also includes the otters, wolverines, martens, minks, polecats, weasels, and ferrets). Badgers are a polyphyletic rather than a natural taxonomic grouping, being united by ...

). This species was named alongside the Gray Fossil Site panda in 2004. * ''Gulo sudorus'' (

wolverine The wolverine (), (''Gulo gulo''; ''Gulo'' is Latin for " glutton"), also referred to as the glutton, carcajou, or quickhatch (from East Cree, ''kwiihkwahaacheew''), is the largest land-dwelling species of the family Mustelidae. It is a muscul ...

). The oldest known fossil wolverine. Named the "sweaty wolverine" since the ancient climate of Gray was much warmer than modern wolverine habitats. * ''

Plionarctos ''Plionarctos'' is an extinct genus of bear endemic to North America from the Miocene to the Pliocene, ~10.3—3.3 Mya, existing for about 7 million years. ''Indarctos'' (10.7—9.2 Mya) preceded ''Plionarctos'' by only a few thousand years ...

'' (short-faced bear). *

Saber-toothed cat Machairodontinae is an extinct subfamily of carnivoran mammals of the family Felidae (true cats). They were found in Asia, Africa, North America, South America, and Europe from the Miocene to the Pleistocene, living from about 16 million ...

, possibly ''

Machairodus ''Machairodus'' (from el, μαχαίρα , 'knife' and el, ὀδούς 'tooth') is a genus of large machairodontine saber-toothed cats that lived in Africa, Eurasia and North America during the late Miocene. It is the animal from which the su ...

''. * ''Buisnictis breviramus'' ( skunk). * ''

Borophagus ''Borophagus'' ("gluttonous eater") is an extinct genus of the subfamily Borophaginae, a group of canids endemic to North America from the Middle Miocene epoch through the Early Pleistocene epoch 12—1.8 Mya. Evolution ''Borophagus'', like o ...

'' (bone crushing dog). Proboscidea (elephants) *

Mastodon A mastodon ( 'breast' + 'tooth') is any proboscidean belonging to the extinct genus ''Mammut'' (family Mammutidae). Mastodons inhabited North and Central America during the late Miocene or late Pliocene up to their extinction at the end of th ...

. Likely a new species, represented by several specimens, including one nearly complete and very large skeleton. Early findings of proboscidean fossils at Gray were originally believed to belong to a gomphothere.

Rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

s * Several species, including beavers, packrats, and mice. Lagomorphs * ''Alilepus vagus'' ( rabbit). * ''Notolagus lepusculus'' (rabbit)

Bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most ...

s * Two species of

vespertilionid Vespertilionidae is a family of microbats, of the order Chiroptera, flying, insect-eating mammals variously described as the common, vesper, or simple nosed bats. The vespertilionid family is the most diverse and widely distributed of bat familie ...

bats.

Eulipotyphla Eulipotyphla (, which means "truly fat and blind") is an order of mammals suggested by molecular methods of phylogenetic reconstruction, which includes the laurasiatherian members of the now-invalid polyphyletic order Lipotyphla, but not the ...

* Several species of shrews and moles.

Xenarthra Xenarthra (; from Ancient Greek ξένος, xénos, "foreign, alien" + ἄρθρον, árthron, "joint") is a major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and armadillos. ...

* An unknown species of

megalonychid Megalonychidae is an extinct family of sloths including the extinct ''Megalonyx''. Megalonychids first appeared in the early Oligocene, about 35 million years (Ma) ago, in southern Argentina (Patagonia). There is actually one possible find dating ...

sloth.

Invertebrates

Aquatic invertebrates of the Gray Fossil Site include

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typi ...

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class G ...

s, and small

clam Clam is a common name for several kinds of bivalve molluscs. The word is often applied only to those that are edible and live as infauna, spending most of their lives halfway buried in the sand of the seafloor or riverbeds. Clams have two shel ...

s. Insects are also known from fossilized exoskeletal remains and trace fossils, including at least four different families of

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

Plants

Plant fossils at the Gray Fossil Site include pollen, leaves, wood, fruits, seeds, and other structures which represent a diverse flora of

angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants ...

, conifers,

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...

lycophyte The lycophytes, when broadly circumscribed, are a vascular plant (tracheophyte) subgroup of the kingdom Plantae. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldes ...

s, and

bryophyte The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and mosses. Bryophyta s.s. consists of the mosses only. They are characteristically limited in s ...

s. The forest flora was dominated by a variety of trees and shrubs, of which the most common were hickory,

oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...

, and

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanical Garden accepts ...

. Several previously unknown extinct plant species have been identified at the Gray Fossil Site: * ''Carya tennesseensis'' (hickory) * ''Sinomenium macrocarpum'' (moonseed) * ''Staphylea levisemia'' (bladdernut) * Three species of ''Vitis'' (grapes) * ''Corylopsis grisea'' (witch hazel) * ''Cavilignum pratchettii,'' the first extinct genus of plant identified at the Gray Fossil Site.

Algae

Algal Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mi ...

microfossils have been identified as numerous freshwater species, including one previously unknown extinct species, ''Stigmozygodites grayensis,'' named after the Gray Fossil Site in 2013.

Fungi

Several types of

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

have been identified from microfossil remains of fungal tissue and fruiting bodies.

References

External links

ETSU Gray Fossil Site & Museum websiteResearch at the Gray Fossil SiteETSU Natural History Museum & Gray Fossil Site YouTube Channel

The Paleobiology Database: Gray Fossil Site Taxonomic ListHands On! Discovery Center

Early photos and activities

{{authority control East Tennessee State University Natural history of Tennessee Miocene paleontological sites of North America Protected areas of Washington County, Tennessee Museums in Washington County, Tennessee Natural history museums in Tennessee Fossil parks in the United States Paleontology in Tennessee 2000 in paleontology