''Claosaurus'' ( ;

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

κλάω, ''klao'' meaning 'broken' and , ''sauros'' meaning 'lizard'; "broken lizard", referring to the odd position of the

fossils 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 ...

when discovered) is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

hadrosauroid Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or Hadrosauridae, and all dinosaurs more closely related to them than to ''Iguanodon''. Their remains have been recovered in Asia, Euro ...

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

that lived during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

Period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

(

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya ( million years ago) and 83.6 ± 0.7 m ...

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

). Traditionally classified as an early member of the family

Hadrosauridae Hadrosaurids (), also hadrosaurs 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 fam ...

, a 2008 analysis found ''Claosaurus agilis'' to be outside of the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

containing ''

Hadrosaurus ''Hadrosaurus'' (; ) is a genus of hadrosaurid ornithopod dinosaurs that lived in North America during the Late Cretaceous Period in what is now the Woodbury Formation in New Jersey about 83.6 to 77.9 Ma. The holotype specimen was found in flu ...

'' and other hadrosaurids, making it the closest non-hadrosaurid relative of true hadrosaurids within the clade Hadrosauromorpha.

Description

Because of the insufficient fossil remains ("minority of skull and partial skeleton"), the size of an adult ''Claosaurus'' remains uncertain. However, Thomas Holtz gave a length estimate of and a mass estimate as that of a lion. Like other hadrosaurs, it was an

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

History

Evidence of its existence was first found in the

Niobrara Formation The Niobrara Formation , also called the Niobrara Chalk, is a geologic formation in North America that was deposited between 87 and 82 million years ago during the Coniacian, Santonian, and Campanian stages of the Late Cretaceous. It is com ...

near the

Smoky Hill River The Smoky Hill River is a river in the central Great Plains of North America, running through Colorado and Kansas. Names The Smoky Hill is named from the Smoky Hills region of north-central Kansas through which it flows. American Indians li ...

Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...

, United States in the form of partial skull fragments and as an articulated postcranial skeleton both found in 1871.Marsh, O. C. (1872). Notice of a new species of ''Hadrosaurus''. ''American Journal of Science'', Series 3, 16: 301. Originally named ''Hadrosaurus agilis'' (Marsh, 1872), it was placed in a new genus and renamed ''Claosaurus agilis'' in 1890 when major differences between the specimen and ''Hadrosaurus'' came to light.Carpenter, K., Dilkes, D., & Weishampel, D. B. (1995). The Dinosaurs of the Niobrara Chalk Formation (Upper Cretaceous, Kansas). Journal of Vertebrate Paleontology, 15(2), 275–297. https://doi.org/10.1080/02724634.1995.10011230 In 1892, Marsh named a second species, ''C. annectens''. It was later reassigned to ''Anatosaurus'' and then ''

Edmontosaurus ''Edmontosaurus'' ( ) (meaning "lizard from Edmonton"), with the second species often colloquially and historically known as ''Anatosaurus'' or ''Anatotitan'' (meaning "duck lizard" and "giant duck"), is a genus of hadrosaurid (duck-billed) din ...

'', where it is currently. G. R. Wieland named third species ''C. affinis'' in 1903, which he compared to ''C. annectens''. ''C. affinis'' was founded on remains from the

Pierre Shale The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico. The Pierre Shale was described by Fielding Bradford Meek, Meek a ...

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state, state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Dakota people, Dakota Sioux ...

, found in association with remains of the giant sea turtle ''

Archelon ''Archelon'' is an extinct marine turtle from the Late Cretaceous, and is the largest turtle ever to have been documented, with the biggest specimen measuring from head to tail and in body mass. It is known only from the Pierre Shale and ...

''. At some point after its description, the fragmentary remains were mixed up with the original remains of ''C. agilis'', and a toe bone from ''C. agilis'' was accidentally thought to be the only part of the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

remains that could be located. This was corrected by Joseph Gregory in 1948, who found three toe bones from the right foot of a large hadrosaur in the Yale collections that had comparable preservation to the Pierre Shale turtle remains and were associated with labels in Wieland's handwriting. Gregory found the toe bones to be very similar in size to the corresponding bones of Marsh's ''Claosaurus annectens'', but did not reassign the species due to its much older age and fragmentary remains. ''C. affinis'' was considered a dubious hadrosaur in the 2004 review by Jack Horner and colleagues. They reported its type material as lost, although they also reported the remains as only including a single toe bone, instead of the three toe bones described by Gregory. Reports of

gastrolith 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 ...

s, or stomach stones, in ''Claosaurus'' are actually based on a probable double misidentification. The specimen thought to have gastroliths is actually of ''Edmontosaurus annectens''.

Barnum Brown Barnum Brown (February 12, 1873 – February 5, 1963), commonly referred to as Mr. Bones, was an American paleontologist. He discovered the first documented remains of ''Tyrannosaurus'' during a career that made him one of the most famous fossil ...

, who discovered the specimen in 1900, referred to it as ''Claosaurus'', because ''E. annectens'' was thought to be a species of ''Claosaurus'' at the time. Additionally, it is more likely that the supposed gastroliths represent gravel washed in during burial.

References

{{Taxonbar, from=Q133801 Hadrosauroidea Dinosaur genera Santonian dinosaurs Fossil taxa described in 1890 Taxa named by Othniel Charles Marsh Dinosaurs of the United States

Description

History

See also

References