''Arkansaurus'' (meaning "

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 ...

lizard") is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of ornithomimosaurian

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ...

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 ...

. It lived during the

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± ...

and

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

stages of 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 Pr ...

. The type and only species is ''Arkansaurus fridayi''.

History

In August 1972, Joe B. Friday, who owned a service station in Locksburg, Arkansas, noticed some

vultures A vulture is a bird of prey that scavenges on carrion. There are 23 extant species of vulture (including Condors). Old World vultures include 16 living species native to Europe, Africa, and Asia; New World vultures are restricted to North and S ...

circling above his land. Checking his cows, he noticed that fossil bones were visible in a ditch near the road where some gravel had been removed recently for the reconstruction of Arkansas Highway 24. He removed them and for some months displayed the fossils in his station. At the time, nobody recognised them for dinosaur bones.McDonnold, Paul, 2014, "Them Dry Bones", ''Arkansas Life'', September 2014, pp 80–85 A geology professor at the

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 ...

and former resident of the nearby town of Nashville, Doy Zachry Jr., took the bones to his colleague at the University of Arkansas, paleontologist Dr. James H. Quinn, to view. Quinn recognized the fossilized remains as dinosaurian and prepared the bones. He took the remains to the annual meeting of the Society of Vertebrate Paleontology in

Lincoln, Nebraska Lincoln is the capital city of the U.S. state of Nebraska and the county seat of Lancaster County. The city covers with a population of 292,657 in 2021. It is the second-most populous city in Nebraska and the 73rd-largest in the United St ...

in the fall of 1972. Once there, the bones were examined by experts from both the US and Europe. They were thought to be related to '' Ornithomimus''. Quinn first presented on the fossils in 1973 at the Geological Society of America Meeting in Little Rock, Arkansas. In March 1973, Dr. Quinn and Benjamin Clardy of the Arkansas Geological Commission went to the area on the Friday farm where the remains had been discovered, hoping to find more remains. The site was a pit that had been dug for road construction and the fossils had been taken from the

Trinity Group. Unfortunately, all the scientists were able to find was a toe bone. They speculated that the bones had either been scattered when they were buried or during the road construction. In all there were three metatarsals, four phalanges, and three claws found of ''Arkansaurus''. Four casts of the bones were made. These casts were given to the Friday Family, the University of Arkansas, the Arkansas Geological Commission, and the Arkansas Museum of Science and Natural History. The University cast is hanging in a classroom in Ozark Hall. The Museum of Science and Natural History actually had a large statue of the dinosaur constructed to go along with their cast, and it was on display for many years when the museum was located at the Tower Building. The original bones, donated to the university by Friday, currently reside at the University of Arkansas Museum Collections, now housed at the Arkansas Archaeological Survey in Fayetteville, Arkansas. Quinn intended to name the species "Arkansaurus fridayi" but in 1977 made a fatal fall when prospecting for fossils in Nebraska. The name ''Arkansaurus'' first appeared in print in a popular-science book by Helen Roney Sattler in 1983, remaining an invalid ''

nomen nudum In taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published with an adequate des ...

''. The full species name was first published by Angela K. Braden in 1998, mentioning that Quinn had informally used the combination "Arkansaurus fridayi". In January 2017 Rep. Greg Leding, D-Fayetteville, submitted a bill to the Arkansas Legislature to designate Arkansaurus the State Dinosaur, along with several cosigners. The original idea of the bill came from high school student Mason Cypress Oury, who, accompanied by Rep. Leding, presented a modified version of the bill to a House panel, and answered questions. Among his reasoning for adopting the Arkansaurus as the state dinosaur Oury pointed out that Oklahoma, Texas and Missouri all have listed state dinosaurs, and Arkansas already has 24 designated state symbols, and since it was the 25th state to be admitted to the union, it made sense to add one more. The bill was approved by the governor February 17, 2017. ''Arkansaurus'' was declared the official

state dinosaur in 2017. The

was discovered in

Lockesburg, Arkansas Lockesburg is a city in Sevier County, Arkansas, United States. The population was 739 at the 2010 census. History Though Lockesburg became the county seat on January 18, 1869, it was not incorporated until November 7, 1878. The land was donated ...

, and was a bipedal ornithomimosaur dinosaur. A near relative is the ornithomimosaur ''

Nedcolbertia ''Nedcolbertia'' is a genus of theropod dinosaur from the Early Cretaceous Period (geology), Period of North America. Discovery and naming Three skeletons of a theropod were discovered in 1993 by Christopher H. Whittle, Christopher Whittle near ...

''. It is named for the state of

and its discoverer Joe B. Friday, who found the dinosaur's fossilized foot on his land in 1972. It is the only dinosaur fossil currently described from Arkansas. The fossil was officially described in 2018 by paleontologists ReBecca Hunt-Foster and James Harrison Quinn in the

Journal of Vertebrate Paleontology The ''Journal of Vertebrate Paleontology'' is a bimonthly peer-reviewed scientific journal that was established in 1980 by Jiri Zidek (University of Oklahoma). It covers all aspects of vertebrate paleontology, including vertebrate origins, evol ...

. The official description of this dinosaur was published on March 19, 2018 in the Journal of Vertebrate Paleontology by paleontologists ReBecca Hunt-Foster and, posthumously, James H. Quinn. The study determined that the fossils contain a combination of unique anatomical details, such as differentiated pedal unguals, a laterally compressed third metatarsal that is ovoid in proximal view, and a distal ungual with a very weak flexor tubercle, lacking spurs. The condition of this third metatarsal suggests that ''Arkansaurus fridayi'' is more basal than Asiatic ornithomimosaurs of similar age, but consistent with older North American forms, such as ''

''.

Description

''Arkansaurus'' was probably a fast moving

omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...

between tall. Its long arms would likely have ended in three fingered grasping hands. A single

autapomorphy In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

, unique derived trait, was indicated: the strong curvature of the foot claws. These are normally rather flat with ornithomimosaurians.

Phylogeny

''Arkansaurus'' was placed in the

Ornithomimosauria 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 Nor ...

in a basal position, outside of the Ornithomimidae.

Paleobiology

Ornithomimisaur tracks of similar age are known from north of Moab, Utah, at the Mill Canyon Dinosaur Tracksite, in the Ruby Ranch Member of the

Cedar Mountain Formation The Cedar Mountain Formation is the name given to a distinctive sedimentary geologic formation in eastern Utah, spanning most of the early and mid-Cretaceous. The formation was named for Cedar Mountain in northern Emery County, Utah, where Willia ...

(Early Cretaceous). This tracksite also preserves the tracks of

ankylosaur Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. ...

hadrosaur Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which inclu ...

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 ...

and several size classes of

dinosaurs, along with crocodiles and birds. A similar fauna has been noted from the Trinity Group in Arkansas.

References

External links

The Arkansas Dinosaur "Arkansaurus fridayi"

{{Portalbar, Dinosaurs, Cretaceous Ornithomimosaurs Albian life Aptian life Early Cretaceous dinosaurs of North America Cretaceous Arkansas Paleontology in Arkansas Fossil taxa described in 2018