Koparion
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''Koparion'' 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 small
coelurosauria Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyrann ...
n
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 c ...
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 ...
s (probably
troodontids Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil discov ...
), from the late
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 ...
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 ...
(
Kimmeridgian In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxfordian ...
stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...
), of
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 ...
. It contains the single named species ''Koparion douglassi'' which is known only from a single isolated tooth.


Discovery

In 1993, Daniel Chure and
Brooks Britt Brooks may refer to: Places ;Antarctica *Cape Brooks ;Canada *Brooks, Alberta ;United States *Brooks, Alabama * Brooks, Arkansas *Brooks, California *Brooks, Georgia * Brooks, Iowa * Brooks, Kentucky * Brooks, Maine *Brooks Township, Michigan * ...
reported the discovery of small theropod remains, found by screenwashing large amounts of earth in the
Rainbow Park A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows cau ...
near
Dinosaur National Monument Dinosaur National Monument is an American national monument located on the southeast flank of the Uinta Mountains on the border between Colorado and Utah at the confluence of the Green and Yampa rivers. Although most of the monument area is in ...
in
Uintah County Uintah County ( ) is a county in the U.S. state of Utah. As of the 2020 United States Census the population was 35,620. Its county seat and largest city is Vernal. The county was named for the portion of the Ute Indian tribe that lived in the b ...
,
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 ...
. In 1994, Chure named and described a unique tooth as the
type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...
of the new species ''Koparion douglassi''. The generic name ''Koparion'' comes from the
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
κοπάριον, "small surgical knife", in reference to the small size of the tooth. The specific name honors
Earl Douglass Earl Douglass (October 28, 1862 – January 13, 1931) was an American paleontologist who discovered the dinosaur ''Apatosaurus'', playing a central role in one of the most important fossil finds in North America. By 1922 Earl had unearthed and shi ...
, who, in the early twentieth century, excavated the Dinosaur National Monument quarry. 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 ...
specimen, DINO 3353, was found in the
Brushy Basin Member The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone, ...
of the
Morrison Formation The Morrison Formation is a distinctive sequence of Late Jurassic, Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandsto ...
dating from the late
Kimmeridgian In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxfordian ...
, about 151 million years old. The taxon is thus present in stratigraphic zone 6 of the Morrison Formation.Foster, J. (2007). "Appendix." ''Jurassic West: The Dinosaurs of the Morrison Formation and Their World''. Indiana University Press. pp. 327-329. The specimen consists of a single maxillary (upper cheek) tooth crown (the root is missing). It cannot be determined whether it represents a left or a right tooth.


Description

The tooth is two millimeters tall and very recurved, with a strongly convex front edge and a nearly vertical back edge. The tooth is stout, with a maximum fore-aft length of 1.9 millimeters. Both edges are serrated, showing low rectangular denticles (individual serrations). The twelve denticles on the rear edge are much higher than the fourteen on the front edge, which cover only the nearly horizontal upper part of the front edge. The tooth base, though very wide, is constricted. The base is asymmetrical, with the right side in front view protruding much further than the left side; because it is not known whether it is a left or right tooth, it cannot be established what is the inner and what the outer side. The denticles are separated by "blood grooves", and "blood pits" are also present. The back denticles point obliquely upwards but have no hooked upper corners.


Classification

Chure assigned ''Koparion'' to the
Troodontidae Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil disco ...
based on the anatomy of the tooth. At that time, it was the oldest known troodontid, and is the first of that group discovered from the Jurassic. A troodontid presence in the Jurassic was predicted by the standard theory regarding the
origin of birds The scientific question of within which larger group of animals evolution of birds, birds evolved has traditionally been called the "origin of birds". The present scientific consensus is that birds are a group of maniraptoran Theropoda, theropod ...
, claiming that birds and troodontids are closely related (Chure suggested that they may even have been sister taxa, though this is not currently supported).Chure, D. J. (1994). "''Koparion douglassi'', a new dinosaur from the Morrison Formation (Upper Jurassic) of Dinosaur National Monument; the oldest troodontid (Theropoda: Maniraptora)." ''Brigham Young University Geology Studies'', 40: 11-15. Within this context, ''Koparion '' could be used to refute the
temporal paradox A temporal paradox, time paradox, or time travel paradox is a paradox, an apparent contradiction, or logical contradiction associated with the idea of time and time travel. The notion of time travel to the future complies with current understanding ...
argument, that such a close relationship were unlikely because the then oldest known bird, ''
Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
'', lived much earlier than the
Deinonychosauria Deinonychosauria is a clade of paravian dinosaurs which lived from the Late Jurassic to the Late Cretaceous periods. Fossils have been found across the globe in North America, Europe, Africa, Asia, South America, and Antarctica,Case, J.A., Martin ...
, i.e. the Troodontidae and the
Dromaeosauridae Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...
; later also non-fragmentary Jurassic troodontid material was reported, from China.Xu X., Ma Q. & Hu D., 2010, "Pre-''Archaeopteryx'' coelurosaurian dinosaurs and their implications for understanding avian origins", ''Chinese Science Bulletin'' 55: 3971–3977


See also

*
List of dinosaurs A ''list'' is any set of items in a row. List or lists may also refer to: People * List (surname) Organizations * List College, an undergraduate division of the Jewish Theological Seminary of America * SC Germania List, German rugby unio ...
* ''
Hesperornithoides ''Hesperornithoides'' (meaning "western bird form"; nicknamed "Lori") is a genus of troodontid theropod dinosaur that lived in North America during the Late Jurassic period. Discovery Although several Troodontid teeth were found, with the trood ...
'' - Another troodontid reported from the Jurassic. *
Timeline of troodontid research This timeline of troodontid research is a chronological listing of events in the History of paleontology, history of paleontology focused on the troodontids, a group of bird-like theropod dinosaurs including animals like ''Troodon''. Troodontid re ...


References

{{Taxonbar, from=Q1821811 Late Jurassic dinosaurs of North America Troodontids Dinosaurs of the Morrison Formation Fossil taxa described in 1994 Paleontology in Utah