Paleontology in Arkansas refers to paleontological research occurring within or conducted by people from the

U.S. The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

state of

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage ...

. The

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

record A record, recording or records may refer to: An item or collection of data Computing * Record (computer science), a data structure ** Record, or row (database), a set of fields in a database related to one entity ** Boot sector or boot record, ...

of Arkansas spans from the Ordovician to the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

. Nearly all of the state's fossils have come from ancient

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

life. During the early

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

, much of Arkansas was covered by seawater. This

sea The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...

would come to be home to creatures including ''

Archimedes Archimedes of Syracuse (;; ) was a Greek mathematician, physicist, engineer, astronomer, and inventor from the ancient city of Syracuse in Sicily. Although few details of his life are known, he is regarded as one of the leading scientists ...

'', brachiopods, and

conodonts Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...

. This sea would begin its withdrawal during the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...

, and by the

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

the entire state was dry land. Terrestrial conditions continued into the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

, but during the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

, another sea encroached into the state's southern half. During the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

the state was still covered by seawater and home to marine invertebrates such as ''

Belemnitella ''Belemnitella'' is a genus of belemnite from the Late Cretaceous of Europe and North America. ''Belemnitella'' was a squidlike animal, probably related to the ancestors of modern squids and cuttlefish. The shell was internal. The rostrum or gua ...

''. On land the state was home to long necked

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...

dinosaurs Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

, who left behind footprints and

ostrich dinosaurs Ornithomimosauria ("bird-mimic lizards") are theropod dinosaurs which bore a superficial resemblance to the modern-day ostrich. They were fast, omnivorous or herbivorous dinosaurs from the Cretaceous Period of Laurasia (now Asia, Europe and North ...

such as ''

Arkansaurus ''Arkansaurus'' (meaning "Arkansas lizard") is an extinct genus of ornithomimosaurian theropod dinosaur. It lived during the Albian and Aptian stages of the Early Cretaceous. The type and only species is ''Arkansaurus fridayi''. History In Augus ...

''. During the

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...

the state's seas were inhabited by marine invertebrates and sharks, although the waters were gradually shrinking away. During the

Ice Age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...

, the state's climate cooled. Local

grasslands A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natural ...

and forests spread that were inhabited by creatures such as

mammoths A mammoth is any species of the extinct elephantid genus ''Mammuthus'', one of the many genera that make up the order of trunked mammals called proboscideans. The various species of mammoth were commonly equipped with long, curved tusks and, ...

mastodons 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 ...

, and

giant ground sloths ''Megatherium'' ( ; from Greek () 'great' + () 'beast') is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene through the end of the Pleistocene. It is best known for the elephant-sized type species ' ...

Prehistory

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...

fossils are known from Arkansas, so the state's fossil record does not begin until the

. During the Paleozoic northern, central, and western Arkansas was covered by seawater. During the Ordovician, the life inhabiting modern Arkansas was diverse. Remains of life from this period fossilized in the East Lafferty Creek and Cushman areas of Independence County.

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

Arkansas was also home to a great diversity of life. Remains from this period, like the Ordovician, were preserved in the Cushman area of Independence County. During the ensuing

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

period,

and sporangites were preserved at Caddo Gap in Montgomery County.

Arkansas was home to ''

'' and a variety of brachiopods. This fauna was preserved in the West Fork area of Washington County and the Fayetteville area. The Habberton area also preserves a diverse invertebrate fauna from this time period. During the early part of the Carboniferous, the Mississippian, Arkansas was home to a variety of marine invertebrates. Later in the period, the northern region of the state was exposed as dry land by the gradual withdrawal of the sea. Rivers flowed across this area of the state. Pennsylvanian Arkansas was home to the

blastoid Blastoids (class Blastoidea) are an extinct type of stemmed echinoderm, often referred to as sea buds. They first appear, along with many other echinoderm classes, in the Ordovician period, and reached their greatest diversity in the Mississi ...

Pentremites ''Pentremites'' is an extinct genus of blastoid echinoderm belonging to the family Pentremitidae. Description These stalked echinoderms averaged a height of about but occasionally ranged up to about 3 times that size. They, like other blastoid ...

'', the brachiopods ''

Composita ''Composita'' is an extinct brachiopod genus that lived from the Late Devonian to the Late Permian.

'' and ''

Spirifer ''Spirifer'' is a genus of marine brachiopods belonging to the order Spiriferida and family Spiriferidae. Species belonging to the genus lived from the Middle Ordovician (Sandbian) through to the Middle Triassic (Carnian) with a global distribu ...

'', and other invertebrates. The sea had completely vanished by the start of the Permian. With the final retreat of the sea, local sedimentation had stopped and begun being eroded away. Northern and central Arkansas was a terrestrial environment during the

. However, by the early

seawater covered the southern region of the state. Southern and northeastern Arkansas were likewise covered by the sea into the

. Local life left behind many fossils. During the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

, the region of Arkansas southeast of the Ouachita Mountains was submerged by the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...

. The invertebrates of Arkansas's Cretaceous sea included

clams 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 ...

echinoids Sea urchins () are spine (zoology), spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard s ...

oysters Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not al ...

, and

snails 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 Gastrop ...

. During the Cretaceous, Arkansas was home to ''

'', ''

Exogyra ''Exogyra'' is an extinct genus of fossil marine oysters in the family Gryphaeidae, the foam oysters or honeycomb oysters. These bivalves grew cemented by the more cupped left valve. The right valve is flatter, and the beak is curved to one si ...

'', '' Ostrea'', '' Turritella'', and other marine invertebrates in the Arkadelphia area of Clark County.

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 li ...

of the same age left behind teeth in the area near Saratoga in

Hempstead County Hempstead County is a county located in the U.S. state of Arkansas. As of the 2010 census, the population was 22,609. As of the 2020 census, the population decreased to 20,065. The county seat is Hope. Hempstead County is Arkansas's fourth cou ...

. Other fossils in this area are similar to those of the preserved in contemporary deposits near Arkadelphia. During the Cretaceous Arkansas was home to the sea turtle ''

Bothremys ''Bothremys'' is an extinct genus of bothremydid pleurodiran turtle that was discovered near Gloucester, New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north ...

'', which may have fed on ancient

. During the Late Cretaceous the region now occupied by the Quachita Mountains of Arkansas may have attracted long necked plesiosaurs from hundreds of miles away as a source of

gastroliths A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In oth ...

. Other vertebrates included sharks. Exogyracostata

Southwestern Arkansas was part of the coastline to the Western Interior Seaway during the

. Dinosaurs roamed the ancient shorelines here both as individuals and in groups. Many footprints left by coastal sauropods have been preserved in the southwestern part of the state. The ornithomimosaur ''Arkansaurus fridayi'' lived at this time, known only from remains of its foot discovered in 1972. The seas of southern and eastern Arkansas began to shrink during the early

. Sharks and oysters were still present in its sea waters. During the

epoch, Arkansas was home to a marine invertebrate fauna that included

echinoderms An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea li ...

, ''Ostrea'', and ''Turritella''. The echinoderm fossils were preserved in the

Bradford Bradford is a city and the administrative centre of the City of Bradford district in West Yorkshire, England. The city is in the Pennines' eastern foothills on the banks of the Bradford Beck. Bradford had a population of 349,561 at the 2011 ...

area of Jackson County. The ''Ostrea'' fossils were preserved in the Bradford area of Jackson County and in the Forrest City area of

St. Francis County St. Francis County is a county in the U.S. state of Arkansas. As of the 2010 census, the population was 28,258. The county seat is Forrest City. St. Francis County comprises the Forrest City, Arkansas Micropolitan Statistical Area, which is ...

. The ''Turritella'' fossils were preserved in the Bradford area of Jackson County. The sea gradually and inconsistently retreated toward the south, leaving the state altogether by the mid-to-late

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

. By this time

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

s and

swamps A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

covered the southern half of the state. During the

, the state's climate cooled down. Most of Arkansas was covered by grasslands and forests. These were inhabited by creatures including

, and

History

In August 1972, J. B. Friday discovered

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

bones in a Sevier County

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

pit near Lockesburg. In 1973 the fossils Friday discovered were being cleaned and compared to related by dinosaurs by

University of Arkansas The University of Arkansas (U of A, UArk, or UA) is a public land-grant research university in Fayetteville, Arkansas. It is the flagship campus of the University of Arkansas System and the largest university in the state. Founded as Arkansas ...

professor James Harrison Quinn. In the course of his research, Quinn made hypothetical clay models of the missing bones in the animal's foot and duplicated the actual fossils with plaster cast in latex molds. Quinn published an abstract about the bones and nicknamed the animal "Arkansaurus fridayi". This abstract was the first scientific mention of any dinosaur bones ever found in Arkansas. A

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...

quarry in southwestern Arkansas preserves dinosaur tracks, which have hindered the quarry operations. This is called the Briar Site. Some areas of the quarry were rough due to what appeared to be large potholes, which frustrated the drivers of the excavation equipment. In 1983, however these "potholes" were recognized as

dinosaur footprints A fossil track or ichnite (Greek "''ιχνιον''" (''ichnion'') – a track, trace or footstep) is a fossilized footprint. This is a type of trace fossil. A fossil trackway is a sequence of fossil tracks left by a single organism. Over the year ...

. Jeff Pittman was responsible for the correct identification of the tracks. At the time he was studying the quarry's

sedimentology Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation (erosion and weathering), transport, deposition and diagenesis. Sedimentologists apply their understanding of mo ...

. After he visited the Purgatoire tracksite in

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

he noticed that the local

tracks resembled the "potholes" seen at the Briar site in Arkansas. Pittman later performed an aerial

survey Survey may refer to: Statistics and human research * Statistical survey, a method for collecting quantitative information about items in a population * Survey (human research), including opinion polls Spatial measurement * Surveying, the techniq ...

and found evidence for 10 parallel sauropod trackways on a rock surface that had also been extensively "trampled". The Briar quarry has two separate surfaces that each preserve thousands of dinosaur tracks. The operations of the quarry continue to both uncover and destroy dinosaur footprints. In 1989 Pittman successfully dated the dinosaur tracks of the Briar quarry as equal in age to the lower Glen Rose Formation's megatracksites, which are more than 200 miles away. In the fall of 1995 senior paleontologist of the Utah Geological Survey (then with Dinamation International), James Kirkland, examined the Arkansaurus foot and found it to be larger but otherwise nearly identical to a new species found two years prior in

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

rocks of Early Cretaceous age. Kirkland concurred that Arkansaurus was likely related to ''

Ornithomimus ''Ornithomimus'' (; "bird mimic") is a genus of ornithomimid dinosaurs from the Late Cretaceous Period of what is now North America. ''Ornithomimus'' was a swift bipedal theropod which fossil evidence indicates was covered in feathers, equipped w ...

''. Future clues about Arkansaurus may come from a similar dinosaur discovery in

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

that, as of 2007, has yet to be described. From 2001 to 2003, then University of Arkansas undergraduate, ReBecca Hunt, studied the fossils and presented on them at several meetings, including the 2002 Society of Vertebrate Paleontology Annual Meeting, the 2002 Geological Society of America Annual Meeting, and the 2003 Arkansas Undergraduate Research Conference. Hunt published a brief description of the fossils with the limited scientific research available at the time.

Paleontologists

Helen Frances James Helen Frances James (born May 22, 1956) is an American paleontologist and paleornithologist who has published extensively on the fossil birds of the Hawaiian Islands. She is the curator in charge of birds in the Department of Vertebrate Zool ...

was born in

Hot Springs A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circ ...

on 22 May,

1956 Events January * January 1 – The Anglo-Egyptian Sudan, Anglo-Egyptian Condominium ends in Sudan. * January 8 – Operation Auca: Five U.S. evangelical Christian Missionary, missionaries, Nate Saint, Roger Youderian, Ed McCully, Jim ...

Natural history museums

Museum of Discovery The Museum of Discovery, formerly the Arkansas Museum of Natural History and Antiquities, is located in downtown Little Rock, Arkansas. The museum is housed in a historic building in the River Market District (Little Rock, Arkansas), River Mark ...

Little Rock ( The "Little Rock") , government_type = Council-manager , leader_title = Mayor , leader_name = Frank Scott Jr. , leader_party = D , leader_title2 = Council , leader_name2 ...

* University of Arkansas Museum * Arkansas State University Museum - Jonesboro

Footnotes

References

* Hunt, ReBecca K., Daniel Chure, and Leo Carson Davis. 2003. "An early Cretaceous theropod foot from southwestern Arkansas." Pages 87–103 in Proceedings of the 2003 Arkansas Undergraduate Research Conference. * Braden, Angela K. "The Arkansas Dinosaur ''Arkansaurus fridayi''". ''Arkansas Geologic Survey''. 2007. * Everhart, M. J. 2005. ''Oceans of Kansas—A Natural History of the Western Interior Sea''. Indiana University Press, 320 pp. * Leslie, Stephen, Dale Springer, Judy Scotchmoor. July 1, 2005
"Arkansas, US"The Paleontology Portal
Accessed September 21, 2012. * Lockley, Martin and Hunt, Adrian. '' Dinosaur Tracks of Western North America''. Columbia University Press. 1999. *

External links

Geologic units in Arkansas

Paleoportal: Arkansas

The Encyclopedia of Arkansas History and Culture
{{Paleontology in the United States

Natural history of Arkansas Science and technology in Arkansas

Prehistory

History

Paleontologists

Natural history museums

See also

Footnotes

References

External links