Dryosaurus Altus
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''Dryosaurus'' ( , meaning 'tree lizard',
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 ...
' () meaning 'tree, oak' and () meaning 'lizard', (the name reflects the forested habitat, not a vague oak-leaf shape of its cheek teeth as is sometimes assumed) 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 ...
of an
ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...
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 in the
Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...
period. It was an
iguanodont Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivore, herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and rel ...
(formerly classified as a
hypsilophodont Hypsilophodontidae (or Hypsilophodontia) is a traditionally used family of ornithopod dinosaurs, generally considered invalid today. It historically included many small bodied bipedal neornithischian taxa from around the world, and spanning from ...
). Fossils have been found in the western
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
and were first discovered in the late 19th century. '' Valdosaurus canaliculatus'' and '' Dysalotosaurus lettowvorbecki'' were both formerly considered to represent species of ''Dryosaurus''.


Description

Based on known specimens, ''Dryosaurus'' has been estimated to have reached up to long and to have weighed up to . However, as no known adult specimens of the genus have been found, the adult size remains unknown. In 2018, the largest specimen (CM 1949) was concluded to be from another species; revising the identity of this specimen put the previous research on size and growth into question. ''Dryosaurus'' had a long neck, long, slender legs and a long, stiff tail. Their arms, however, with five fingers on each hand, were short. They had a horny beak and
cheek teeth Cheek teeth or postcanines comprise the molar and premolar teeth in mammals. Cheek teeth are multicuspidate (having many folds or tubercles). Mammals have multicuspidate molars (three in placentals, four in marsupials, in each jaw quadrant) and ...
. Some scientists suggest that it had cheek-like structures to prevent the loss of food while the animal processed it in the mouth. The teeth of ''Dryosaurus'' were characterized by a strong median ridge on the lateral surface."''Dryosaurus altus''," Foster (2007) pp. 218-219.


Discovery and naming

In 1876,
Samuel Wendell Williston Samuel Wendell Williston (July 10, 1852 – August 30, 1918) was an American educator, entomologist, and Paleontology, paleontologist who was the first to propose that birds developed flight Origin of birds#Origin of bird flight, cursorially (by ...
in Albany County,
Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...
discovered the remains of small euornithopods. In 1878, Professor
Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of paleontology. A prolific fossil collector, Marsh was one of the preeminent paleontologists of the nineteenth century. Among his legacies are the discovery or ...
named these as a new species of ''
Laosaurus ''Laosaurus'' (meaning "stone or fossil lizard") is a genus of neornithischian dinosaur. The type species, ''Laosaurus celer'', was first described by O.C. Marsh in 1878 from remains from the Oxfordian-Tithonian-age Upper Jurassic Morrison Form ...
'', ''Laosaurus altus''. The
specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...
''altus'', meaning "tall" in
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
, refers to it being larger than ''Laosaurus celer''. In 1894, Marsh made the taxon a separate genus, ''Dryosaurus''.O.C. Marsh, 1894, "The typical Ornithopoda of the American Jurassic", ''American Journal of Science, series 3'' 48: 85-90 The generic name is derived from the Greek δρῦς, ''drys'', "tree, oak", referring to a presumed forest-dwelling life mode. Later it was often assumed to have been named after an oak-leaf shape of its cheek teeth, which, however, is absent. The
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
remains ''Laosaurus altus'', the ''
combinatio nova In biological taxonomy, a combinatio nova (abbreviated comb. nov. or n. comb.) refers to the formal renaming of an organism's scientific name when it is transferred to a different genus, reclassified within a different species, or its taxonomic ...
'' is ''Dryosaurus altus''. The holotype, YPM 1876, was found in a layer of the Upper Brushy Basin Member of the
Morrison Formation 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, siltston ...
, dating from the
Tithonian In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...
. It consists of a partial skeleton including a mostly complete skull and lower jaws. Several other fossils from Wyoming have been referred to ''Dryosaurus altus''. They include specimens YPM 1884: the rear half of a skeleton; AMNH 834: a partial skeleton lacking the skull from the '' Bone Cabin Quarry''; and CM 1949: a rear half of a skeleton dug up in 1905 by William H. Utterback. From 1922 onwards in
Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
, Earl Douglass discovered ''Dryosaurus'' remains at the ''
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 River (Colorado River tributary), Green and Yampa River, Y ...
''. These include CM 11340: the front half of a skeleton of a very young individual; CM 3392: a skeleton with skull but lacking the tail; CM 11337: a fragmentary skeleton of a juvenile; and DNM 1016: a left ilium dug up by technician Jim Adams. Other fossils were found in
Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
. In Lily Park, Moffat County, James Leroy Kay and Albert C. Lloyd in 1955 recovered CM 21786, a skeleton lacking skull and neck. From 'Scheetz’ Quarry 1, at Uravan, Montrose County, in 1973 Peter Malcolm Galton and James Alvin Jensen described specimen BYU ESM-171R found by Rodney Dwayne Scheetz and consisting of some vertebrae, a left lower jaw, a left forelimb and two hindlimbs. Rodney D. Scheetz and his family discovered a fossil locality around five miles from Uravan, Colorado in the spring of 1972. This site, unintentionally exposed by a bulldozer, was found to contain fossil fragments, said to be in such condition they looked like unfossilized bone. The site was noted in a 1973 paper, and Scheetz continued to dig at the site annually until publishing a short note in 1991. By then around 2500 fragments had been excavated, almost all of which specimens are thought to have belonged to ''Dryosaurus''. At least eight individuals are represented, with ages ranging from juvenile to embryonic; finding specimens of embryonic age is exceptionally rare for dinosaur fossils. Eggshells were also represented in the sample. Scheetz voiced his intention to continue work at the site following the publishing of the note.
Gregory S. Paul Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology. He is best known for his work and research on theropoda, theropod dinosaurs and his detailed illustrations, both l ...
in his 2010 field guide to dinosaurs (2nd edition published in 2016) suggested that the Utah material represented a separate species,Paul, G.S., 2010, ''The Princeton Field Guide to Dinosaurs'', Princeton University Press p. 281 which was confirmed by Carpenter and Galton (2018), who described the Dinosaur National Monument ''Dryosaurus'' as a new species, ''D. elderae''. In 2003 remains from Portugal were tentatively referred to ''Dryosaurus'', possibly meaning it was more widespread.


Paleobiology

''Dryosaurus'' subsisted primarily on low growing vegetation in ancient floodplains. A quick and agile runner with strong legs, ''Dryosaurus'' used its stiff tail as a counterbalance.Marshall (1999) pp. 138-139 It probably relied on its speed as a main defense against
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...
dinosaurs.


Growth and development

A ''Dryosaurus'' hatchling found at Dinosaur National Monument in Utah confirmed that ''Dryosaurus'' followed similar patterns of craniofacial development to other vertebrates; the eyes were proportionally large while young and the muzzle proportionally short. As the animal grew, its eyes became proportionally smaller and its snout proportionally longer.


Paleoecology

The ''Dryosaurus''
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 ...
specimen YPM 1876 was discovered in Reed's YPM Quarry 5, in the Upper Brushy Basin Member, of the
Morrison Formation 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, siltston ...
. In the Late Jurassic Morrison formation of Western North America, ''Dryosaurus'' remains have been recovered from stratigraphic zones 2–6."Appendix," Foster (2007) pp. 327-329. This formation is a sequence of shallow marine and alluvial sediments which, according to
radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to Chronological dating, date materials such as Rock (geology), rocks or carbon, in which trace radioactive impurity, impurities were selectively incorporat ...
, ranges between 156.3 million years old ( Ma) at its base, to 146.8 million years old at the top, which places it in the late Oxfordian,
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 154.8 ±0.8 Ma and 149.2 ±0.7 Ma (million years ago). The Kimmeridgian follows the Oxfordian ...
, and early
Tithonian In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...
stages of the Late Jurassic period. In 1877 this formation became the center of the
Bone Wars The Bone Wars, also known as the Great Dinosaur Rush, was a period of intense and ruthlessly competitive fossil hunting and discovery during the Gilded Age of American history, marked by a heated rivalry between Edward Drinker Cope (of the Aca ...
, a fossil-collecting rivalry between early paleontologists
Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of paleontology. A prolific fossil collector, Marsh was one of the preeminent paleontologists of the nineteenth century. Among his legacies are the discovery or ...
and
Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontology, paleontologist, comparative anatomy, comparative anatomist, herpetology, herpetologist, and ichthyology, ichthyologist. Born to a wealthy Quaker fam ...
. The Morrison Formation is interpreted as a semiarid environment with distinct wet and
dry season The dry season is a yearly period of low rainfall, especially in the tropics. The weather in the tropics is dominated by the tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year. The t ...
s. The Morrison Basin where dinosaurs lived, stretched from New Mexico to Alberta and Saskatchewan, and was formed when the precursors to the
Front Range The Front Range is a mountain range of the Southern Rocky Mountains of North America located in the central portion of the U.S. State of Colorado, and southeastern portion of the U.S. State of Wyoming. It is the first mountain range encounter ...
of the Rocky Mountains started pushing up to the west. The deposits from their east-facing
drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
s were carried by streams and
river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...
s and deposited in
swamp 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 ...
y lowlands, lakes, river channels and
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
s. This formation is similar in age to the Solnhofen Limestone Formation in
Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
and the
Tendaguru Formation The Tendaguru Formation, or Tendaguru Beds are a highly List of fossiliferous stratigraphic units in Tanzania, fossiliferous Lithostratigraphy, formation and Lagerstätte located in the Lindi Region of southeastern Tanzania. The formation represe ...
in
Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...
. The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as ''
Brontosaurus ''Brontosaurus'' (; meaning "thunder lizard" from the Ancient Greek, Greek words , "thunder" and , "lizard") is a genus of herbivorous sauropod dinosaur that lived in present-day United States during the Late Jurassic period. It was describe ...
'', '' Camarasaurus'', ''
Barosaurus ''Barosaurus'' ( ) is a genus of giant, long-tailed, long-necked, herbivore, plant-eating Sauropoda, sauropod dinosaur closely related to the more familiar ''Diplodocus''. Remains have been found in the Morrison Formation from the Jurassic, Up ...
'', '' Diplodocus'', ''
Apatosaurus ''Apatosaurus'' (; meaning "deceptive lizard") is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, ''A. ajax'', in 1877, a ...
'' and ''
Brachiosaurus ''Brachiosaurus'' () is a genus of sauropod dinosaur that lived in North America during the Late Jurassic, about . It was first Species description, described by American paleontologist Elmer S. Riggs in 1903 in paleontology, 1903 from fossi ...
''. Dinosaurs that lived alongside ''Dryosaurus'' included the herbivorous ornithischians ''
Camptosaurus ''Camptosaurus'' ( ) is a genus of plant-eating, beaked ornithischian dinosaurs of the Late Jurassic Period (geology), period of western North America and possibly also Europe. The name means 'flexible lizard' (Ancient Greek, Greek (') meaning ...
'', ''
Stegosaurus ''Stegosaurus'' (; ) is a genus of herbivorous, four-legged, armored dinosaur from the Late Jurassic, characterized by the distinctive kite-shaped upright plates along their backs and spikes on their tails. Fossils of the genus have been fo ...
''and ''
Nanosaurus ''Nanosaurus'' ("small or dwarf lizard") is an extinct genus of neornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic in North America. Its fossils are known from the Morrison Formation of the south-we ...
''. Predators in this paleoenvironment included the
theropods Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
''
Torvosaurus ''Torvosaurus'' () is a genus of large Megalosaurinae, megalosaurine Theropoda, theropod dinosaur that lived approximately 165 to 148 million years ago during the Callovian to Tithonian ages of the late Middle Jurassic, Middle and Late Jurassi ...
'', ''
Ceratosaurus ''Ceratosaurus'' (from Greek 'horn' and 'lizard') is a genus of carnivorous theropod dinosaur that lived in the Late Jurassic period (Kimmeridgian to Tithonian ages). The genus was first described in 1884 by American paleontologist Othni ...
'', '' Marshosaurus'', ''
Stokesosaurus ''Stokesosaurus'' (meaning "Stokes' lizard") is a genus of small (around in length), carnivorous early tyrannosauroid theropod dinosaurs from the late Jurassic period of Utah, United States. History From 1960 onwards Utah geologist William ...
'', '' Ornitholestes'' and ''
Allosaurus ''Allosaurus'' ( ) is an extinct genus of theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period ( Kimmeridgian to late Tithonian ages). The first fossil remains that could definitively be ascribed to th ...
''.Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329. ''Allosaurus'' accounted for 70 to 75% of theropod specimens and was at the top
trophic level The trophic level of an organism is the position it occupies in a food web. Within a food web, a food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the ...
of the Morrison
food web A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Position in the food web, or trophic level, is used in ecology to broadly classify organisms as autotrophs or he ...
. Other animal taxa that shared this paleoenvironment included
bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...
s,
snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...
s, ray-finned fishes,
frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...
s,
salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...
s,
turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...
s, sphenodonts,
lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...
s, terrestrial and aquatic crocodylomorphs, and several species of
pterosaur Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earli ...
. Early mammals were present in this region, such as docodonts, multituberculates, symmetrodonts, and triconodonts. The flora of the period has been revealed by fossils of
green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...
,
fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
,
moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...
es, horsetails,
cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...
s,
ginkgo ''Ginkgo'' is a genus of non-flowering seed plants, assigned to the gymnosperms. The scientific name is also used as the English common name. The order to which the genus belongs, Ginkgoales, first appeared in the Permian, , and ''Ginkgo'' is n ...
es, and several families of
conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...
s. Vegetation varied from
river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...
-lining forests of
tree fern Tree ferns are arborescent (tree-like) ferns that grow with a trunk (botany), trunk elevating the fronds above ground level, making them trees. Many extant tree ferns are members of the order Cyatheales, to which belong the families Cyatheaceae ( ...
s, and
fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...
s (
gallery forest A gallery forest is one formed as a corridor along rivers or wetlands, projecting into landscapes that are otherwise only sparsely treed such as savannas, grasslands, or deserts. The gallery forest maintains a more temperate microclimate above th ...
s), to fern
savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...
s with occasional trees such as the ''
Araucaria ''Araucaria'' (; original pronunciation: .ɾawˈka. ɾja is a genus of evergreen coniferous trees in the family Araucariaceae. While today they are largely confined to the Southern Hemisphere, during the Jurassic and Cretaceous they were glo ...
''-like conifer ''
Brachyphyllum ''Brachyphyllum'' (meaning "short leaf") is a form genus of fossil coniferous plant foliage. Plants of the genus have been variously assigned to several different conifer groups including Araucariaceae and Cheirolepidiaceae. They are known from ...
''. Other sites that have produced ''Dryosaurus'' material include Bone Cabin Quarry, the Red Fork of the Powder River in Wyoming and Lily Park in Colorado.


See also

*
List of dinosaurs 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 annum, million years ago, although the exact origin and timing of the evolution of ...
* Paleobiota of the Morrison Formation


Footnotes


References

* Foster, J. (2007). ''Jurassic West: The Dinosaurs of the Morrison Formation and Their World''. Indiana University Press. 389pp. *


External links


Dryosaurus, from the Dinosaur Encyclopaedia at Univ. of Illinois at Urbana-Champaign
{{Taxonbar, from=Q131085 Ornithopoda Dinosaur genera Tithonian dinosaurs Morrison Formation Fossil taxa described in 1894 Taxa named by Othniel Charles Marsh Dinosaurs of the United States