Claosaurus
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''Claosaurus'' ( ;
Greek Greek may refer to: Greece 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 ...
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 in ...
when discovered) is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
hadrosauroid Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or hadrosaurids, and all dinosaurs more closely related to them than to ''Iguanodon''. Their remains have been recovered in Asia, Eu ...
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 ...
that lived during the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', the ...
Period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...
(
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 mya. The ...
-
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. Campanian s ...
). Traditionally classified as an early member of the family
Hadrosauridae 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 includ ...
, a 2008 analysis found ''Claosaurus agilis'' to be outside of the
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
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 about 80 million to 78 million years ago. The holotype specimen was found in f ...
'' and other hadrosaurids, making it the closest non-hadrosaurid relative of true hadrosaurids within the clade Hadrosauria.


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 adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
.


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 compose ...
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.Smoky Hill River. (2009). In Encyclopædia Britannica. Retrieved July 22, 2009, from Encyclopædia Britannica Online: http://www.br ...
in
Kansas Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...
, United States in the form of partial skull fragments and as an articulated postcranial skeleton. 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") is a genus of hadrosaurid (duck-billed) dinosaur. It contains two known species: ''Edmontosaurus regalis'' and ''Edmontosaurus annectens''. Fossils of ''E. regalis'' have been found in rocks ...
'', 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 Meek and Hayden in 1862 in th ...
of
South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. 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 Lakota people, Lakota and Dakota peo ...
, found in association with remains of the giant sea turtle '' Archelon''. 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 is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
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 Doubt is a mental state in which the mind remains suspended between two or more contradictory propositions, unable to be certain of any of them. Doubt on an emotional level is indecision between belief and disbelief. It may involve uncertainty ...
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 othe ...
s, or stomach stones, in ''Claosaurus'' are actually based on a probable double misidentification. The specimen though 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. Named after the circus showman P. T. Barnum, he discovered the first documented remains of ''Tyrannosaurus'' during a career ...
, 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.


See also

*
Timeline of hadrosaur research A timeline is a display of a list of events in chronological order. It is typically a graphic design showing a long bar labelled with dates paralleling it, and usually contemporaneous events. Timelines can use any suitable scale representin ...


Notes

This species is not accepted as representing ''Claosaurus'' in reviews of the genus, but has not been given its own genus and is unlikely to receive one.


References

{{Taxonbar, from=Q133801 Late Cretaceous dinosaurs of North America Hadrosaurs Fossil taxa described in 1890 Taxa named by Othniel Charles Marsh Paleontology in Kansas Ornithischian genera