Dryosaurus (/ˌdraɪoʊˈsɔːrəs/ DRY-o-SAWR-əs; meaning 'tree lizard', Greek δρυς/drys meaning 'tree, oak' and σαυρος/sauros 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 of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont (formerly classified as a hypsilophodont). Fossils have been found in the western United States (and supposedly the Marnes de Bleville locality in Europe), and were first discovered in the late 19th century. Valdosaurus canaliculatus and Dysalotosaurus lettowvorbecki were both formerly considered to represent species of Dryosaurus.[1][2][3]

Temporal range: Late Jurassic, 155–145 Ma
Beneski Museum of Natural History Dryosaurus altus
D. altus, Beneski Museum of Natural History
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Ornithopoda
Clade: Iguanodontia
Genus: Dryosaurus
Marsh, 1894
Type species
Dryosaurus altus
(Marsh, 1878 [originally Laosaurus altus])
Other species
  • D. elderae Carpenter & Galton, 2018


Restoration of D. altus

Dryosaurus had a long neck, long, slender legs and a long, stiff tail. Its arms, however, with five fingers on each hand, were short. Known specimens were about 8 to 14 feet (2.4 to 4.3 m) long and weighed 170 to 200 pounds (77 to 91 kg). However, the adult size is unknown, as no known adult specimens of the genus have been found.[4]

Dryosaurus had a horny beak and cheek teeth and, like other ornithopods, was a herbivore. Some scientists suggest that it had cheek-like structures to prevent the loss of food while the animal processed it in the mouth.

A quick and agile runner with strong legs, Dryosaurus used its stiff tail as a counterbalance.[5] It probably relied on its speed as a main defense against carnivorous dinosaurs.

The teeth of Dryosaurus were, according to museum curator John Foster, characterized by "a strong median ridge on the lateral surface."[6]

Discovery and naming

Dryosaurus limb
Pelvis, leg, and tooth of D. altus, 1878

In 1876, Samuel Wendell Williston in Albany County, Wyoming discovered the remains of small euornithopods. In 1878, Professor Othniel Charles Marsh named these as a new species of Laosaurus, Laosaurus altus. The specific name altus, meaning "tall" in Latin, refers to it being larger than Laosaurus celer.[7] In 1894, Marsh made the taxon a separate genus, Dryosaurus.[8] 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 remains Laosaurus altus, the combinatio nova is Dryosaurus altus.

The holotype, YPM 1876, was found in a layer of the Upper Brushy Basin Member of the Morrison Formation, dating from the Tithonian. It consists of a partial skeleton including a rather 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, Earl Douglass discovered Dryosaurus remains at the Dinosaur National Monument. 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.[9] Other fossils were found in Colorado. 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.[10]

Dryosaurus skull dinosaur national monument
Cast of the D. elderae holotype skull

Gregory S. Paul in his 2010 field guide to dinosaurs (2nd edition published in 2016) suggested that the Utah material represented a separate species,[11] which was confirmed by Carpenter and Galton (2018), who described the Dinosaur National Monument Dryosaurus as a new species, D. elderae.[12]

Apart from Dryosaurus altus, several other species have been named in the genus. The first of these was created accidentally when in 1903 Giuseppe de Stefano renamed Crocodilus phosphaticus Thomas 1893 into Dryosaurus phosphaticus;[13] he had intended to call it Dyrosaurus phosphaticus. This was only emended by Éric Buffetaut in 1981.[14]


Dryosaurus subsisted primarily on low growing vegetation in ancient floodplains.[6]

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.[6] As the animal grew, its eyes became proportionally smaller and its snout proportionally longer.[6]


Ceratosaurus & Dryosaurus
D. elderae holotype skeleton (front) with Ceratosaurus, Carnegie Museum

The Dryosaurus holotype specimen YPM 1876 was discovered in Reed’s YPM Quarry 5, in the Upper Brushy Basin Member, of the Morrison Formation. In the Late Jurassic Morrison formation of Western North America, Dryosaurus remains have been recovered from stratigraphic zones 2-6.[15] A spectacular digsite near Uravan, Colorado held hundreds of D. altus fossils which represented multiple stages of the animal's life cycle. This formation is a sequence of shallow marine and alluvial sediments which, according to radiometric dating, ranges between 156.3 million years old (Ma) at its base,[16] to 146.8 million years old at the top,[17] which places it in the late Oxfordian, Kimmeridgian, and early Tithonian stages of the Late Jurassic period. In 1877 this formation became the center of the Bone Wars, a fossil-collecting rivalry between early paleontologists Othniel Charles Marsh and Edward Drinker Cope. The Morrison Formation is interpreted as a semiarid environment with distinct wet and dry seasons. The Morrison Basin where dinosaurs lived, stretched from New Mexico to Alberta and Saskatchewan, and was formed when the precursors to the Front Range of the Rocky Mountains started pushing up to the west. The deposits from their east-facing drainage basins were carried by streams and rivers and deposited in swampy lowlands, lakes, river channels and floodplains.[18] This formation is similar in age to the Solnhofen Limestone Formation in Germany and the Tendaguru Formation in Tanzania.

The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Barosaurus, Diplodocus, Apatosaurus and Brachiosaurus. Dinosaurs that lived alongside Dryosaurus included the herbivorous ornithischians Camptosaurus, Stegosaurus and Othnielosaurus. Predators in this paleoenvironment included the theropods Saurophaganax, Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus, and Ornitholestes[19] and Allosaurus, which accounted for 70 to 75% of theropod specimens and was at the top trophic level of the Morrison food web.[20] Other vertebrates that shared this paleoenvironment included bivalves, snails, ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphans, and several species of pterosaur. 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, fungi, mosses, horsetails, cycads, ginkgoes, and several families of conifers. Vegetation varied from river-lining forests of tree ferns, and ferns (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum.[21]

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.[6]

See also


  1. ^ Tom R. Hübner; Oliver W. M. Rauhut (2010). "A juvenile skull of Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia), and implications for cranial ontogeny, phylogeny, and taxonomy in ornithopod dinosaurs". Zoological Journal of the Linnean Society. 160 (2): 366–396. doi:10.1111/j.1096-3642.2010.00620.x.
  2. ^ McDonald AT, Kirkland JI, DeBlieux DD, Madsen SK, Cavin J, et al. (2010). Farke AA (ed.). "New Basal Iguanodonts from the Cedar Mountain Formation of Utah and the Evolution of Thumb-Spiked Dinosaurs". PLoS ONE. 5 (11): e14075. doi:10.1371/journal.pone.0014075. PMC 2989904. PMID 21124919.
  3. ^ Galton, P.M., 1977. "The Upper Jurassic dinosaur Dryosaurus and a Laurasia-Gondwana connection in the Upper Jurassic", Nature 268(5617): 230-232
  4. ^ Horner, John R.; de Ricqlés, Armand; Padian, Kevin; Scheetz, Rodney D. (2009). "Comparative long bone histology and growth of the "hysilophodontid" dinosaurs Orodromeus makelai, Dryosaurus altus, and Tenontosaurus tillettii (Ornithischia: Euornithopoda)". Journal of Vertebrate Paleontology. 29 (3): 734–747. doi:10.1671/039.029.0312.
  5. ^ Marshall (1999) pp. 138-139
  6. ^ a b c d e "Dryosaurus altus," Foster (2007) pp. 218-219.
  7. ^ O.C. Marsh, 1878, "Principal characters of American Jurassic dinosaurs. Part I", American Journal of Science and Arts 16: 411-416
  8. ^ O.C. Marsh, 1894, "The typical Ornithopoda of the American Jurassic", American Journal of Science, series 3 48: 85-90
  9. ^ Gilmore C.W., 1925, "Osteology of ornithopodous dinosaurs from the Dinosaur National Monument, Utah. Camptosaurus medius, Dryosaurus altus, Laosaurus gracilis", Memoirs of the Carnegie Museum 10: 385-409
  10. ^ Galton, P.M. & Jensen, J.A., 1973, "Small bones of the hypsilophodontid dinosaur Dryoraurus altus from the Upper Jurassic of Colorado", Great Basin Nature, 33: 129-132
  11. ^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 281
  12. ^ Kenneth Carpenter; Peter M. Galton (2018). "A photo documentation of bipedal ornithischian dinosaurs from the Upper Jurassic Morrison Formation, USA". Geology of the Intermountain West. 5: 167–207.
  13. ^ G. de Stefano, 1903, "Nuovi rettili degli strati a fosfato della Tunisia", Bollettino della Societa Geologica Italiana 22: 51-80
  14. ^ R.T.J. Moody and E. Buffetaut, 1981, "Notes on the systematics and palaeoecology of the crocodiles and turtles of the Metaloui Phosphates (Eocene) of southern Tunisia", Tertiary Research 3(3): 125-140
  15. ^ "Appendix," Foster (2007) pp. 327-329.
  16. ^ Trujillo, K.C.; Chamberlain, K.R.; Strickland, A. (2006). "Oxfordian U/Pb ages from SHRIMP analysis for the Upper Jurassic Morrison Formation of southeastern Wyoming with implications for biostratigraphic correlations". Geological Society of America Abstracts with Programs. 38 (6): 7.
  17. ^ Bilbey, S.A. (1998). "Cleveland-Lloyd Dinosaur Quarry - age, stratigraphy and depositional environments". In Carpenter, K.; Chure, D.; Kirkland, J.I. (eds.). The Morrison Formation: An Interdisciplinary Study. Modern Geology 22. Taylor and Francis Group. pp. 87–120. ISSN 0026-7775.
  18. ^ Russell, Dale A. (1989). An Odyssey in Time: Dinosaurs of North America. Minocqua, Wisconsin: NorthWord Press. pp. 64–70. ISBN 978-1-55971-038-1.
  19. ^ Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329.
  20. ^ Foster, John R. (2003). Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. New Mexico Museum of Natural History and Science Bulletin, 23. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. p. 29.
  21. ^ Carpenter, Kenneth (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus". In Foster, John R.; Lucas, Spencer G. (eds.). Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 131–138.


  • Foster, J. (2007). Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. 389pp.
  • Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. pp. 138–139. ISBN 1-84028-152-9.

External links

1894 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1894.


Aralosaurini is a tribe of basal lambeosaurine hadrosaurs endemic to Eurasia. It currently contains Aralosaurus (from the Aral sea of Kazakhstan) and Canardia (from Toulouse, Southern France).

Arundel Formation

The Arundel Formation, also known as the Arundel Clay, is a clay-rich sedimentary rock formation, within the Potomac Group, found in Maryland of the United States of America. It is of Aptian age (Lower Cretaceous). This rock unit had been economically important as a source of iron ore, but is now more notable for its dinosaur fossils. Although often considered a formation, it may be only oxbow swamp facies within the Potomac Group. It is named for Anne Arundel County, Maryland.

Como Bluff

Como Bluff is a long ridge extending east-west, located between the towns of Rock River and Medicine Bow, Wyoming. The ridge is an anticline, formed as a result of compressional geological folding. Three geological formations, the Sundance, the Morrison, and the Cloverly Formations, containing fossil remains from the Late Jurassic of the Mesozoic Era are exposed. Nineteenth century paleontologists discovered many well-preserved specimens of dinosaurs, as well as mammals, turtles, crocodilians, and fish from the Morrison Formation. Because of this, Como Bluff is considered to be one of the major sites for the early discovery of dinosaur remains. Among the species discovered is the only known specimen of Coelurus. Significant discoveries were made in 22 different areas scattered along the entire length of the ridge. It is included on the National Register of Historic Places as well as the National Natural Landmark list.


Dryosaurids were primitive iguanodonts. They are known from Middle Jurassic to Early Cretaceous rocks of Africa, Europe, and North America.

Dryosaurus grandis

"Dryosaurus" grandis is a dubious species of ornithomimosaur dinosaur known from remains found in the Arundel Formation of Maryland.


Dysalotosaurus (meaning 'uncatchable lizard') is a genus of herbivorous iguanodontian dinosaur. It was a dryosaurid iguanodontian, and its fossils have been found in late Kimmeridgian age-rocks (Late Jurassic) of the Tendaguru Formation, Tanzania. The type and only species of the genus is D. lettowvorbecki. This species was named by Hans Virchow in 1919 in honour of the Imperial German Army Officer, Paul von Lettow-Vorbeck. For much of the 20th century the species was referred to related and approximately contemporary genus Dryosaurus, but newer studies reject this synonymy. In 2016, Gregory S. Paul estimated its length at 2.5 metres (8.2 ft), its weight at 80 kilograms (180 lb).

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 shipped more than 700,000 pounds of material including nearly 20 complete skeletons of Jurassic dinosaurs such as Diplodocus, Dryosaurus, Stegosaurus, Barosaurus, Camarasaurus and Brontosaurus.


Eousdryosaurus ("eastern Dryosaurus") is a genus of basal iguanodontian dinosaur known from a partial skeleton discovered in Upper Jurassic rocks in western Portugal.


Hypsilophodontidae (or Hypsilophodontia) is a traditionally used family of ornithopod dinosaurs, generally considerd invalid today. It historically included taxa from across the world, and spanning from the Middle Jurassic until the Late Cretaceous. This inclusive status was supported by some phylogenetic analyses from the 1990s and mid 2000s, although there have also been many finding that the family is an unnatural grouping which should only include the type genus, Hypsilophodon, with the other genera being within clades like Thescelosauridae. A 2014 analysis by Norman recovered a grouping of Hypsilophodon, Rhabdodontidae and Tenontosaurus, which he referred to as Hypsilophodontia. All other analyses from around the same time have instead found these latter taxa to be within Iguanodontia.


Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include Camptosaurus, Dryosaurus, Iguanodon, Tenontosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodontians were one of the first groups of dinosaurs to be found. They are among the best known of the dinosaurs, and were among the most diverse and widespread herbivorous dinosaur groups of the Cretaceous period.


Kangnasaurus (meaning "Farm Kangnas lizard") is a genus of iguanodontian ornithopod dinosaur found in supposedly Early Cretaceous rocks of South Africa. It is known from a tooth and possibly some postcranial remains. At times, it has been considered dubious or a valid genus. It was probably similar to Dryosaurus.


Laosaurus (meaning "stone or fossil lizard") is a genus of neornithischian dinosaur. The type species is Laosaurus celer, first described by O.C. Marsh in 1878 from remains from the Oxfordian-Tithonian-age Upper Jurassic Morrison Formation of Wyoming. The validity of this genus is doubtful because it is based on fragmentary fossils. A second species from the Morrison Formation, L. gracilis, and a species from the late Cretaceous of Alberta, Laosaurus minimus, are also considered dubious.

Marnes de Bleville

The Marnes de Bleville is a geological formation in France. It dates back to the Late Jurassic.


Othnielosaurus is a genus of ornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age Morrison Formation of the western United States. It is named in honor of famed paleontologist Othniel Charles Marsh, and was formerly assigned to the genus Laosaurus. This genus was coined to hold fossils formerly included in Othnielia, which is based on remains that may be too sparse to hold a name. O.C. Marsh named several species and genera in the late 19th century that have come to be recognized as hypsilophodonts or hypsilophodont-like animals, including Nanosaurus agilis, "N." rex (Othnielia), Laosaurus celer, L. consors, and L. gracilis. This taxonomy has become very complicated, with numerous attempts at revision in the years since; Othnielosaurus is part of decades of research to untangle the taxonomy left behind by Marsh and his rival Edward Drinker Cope from the Bone Wars. Othnielosaurus has usually been classified as a hypsilophodont, a type of generalized small bipedal herbivore or omnivore, although recent research has called this and the existence of a distinct group of hypsilophodonts into question.

Palpebral (bone)

The palpebral bone is a small dermal bone found in the region of the eye socket in a variety of animals, including crocodilians and ornithischian dinosaurs. It is also known as the adlacrimal or supraorbital, although the latter term may not be confused with the supraorbital in osteichthyan fishes. In ornithischians, the palpebral can form a prong that projects from the front upper corner of the orbit. It is large in heterodontosaurids, basal ornithopods such as Thescelosaurus (as Bugenasaura) and Dryosaurus, and basal ceratopsians such as Archaeoceratops; in these animals, the prong is elongate and would have stuck out and over the eye like a bony eyebrow. As paleoartist Gregory S. Paul has noted, elongate palpebrals would have given their owners fierce-looking "eagle eyes". In such cases, the expanded palpebral may have functioned to shade the eye.


Talenkauen (meaning "small skull" in Aonikenk, referring to the proportionally small skull) is a genus of basal iguanodont dinosaur from the Cenomanian-age Late Cretaceous Cerro Fortaleza Formation, formerly known as the Pari Aike Formation of Patagonian Lake Viedma in the Austral Basin of Santa Cruz, Argentina. It is based on MPM-10001, a partial articulated skeleton missing the rear part of the skull, the tail, and the hands. Its most unusual feature is the presence of several thin mineralized plates along the sides of the ribs.

The Ballad of Big Al

The Ballad of Big Al (distributed in the North American market as Allosaurus: a Walking with Dinosaurs Special) is a two episode series of Walking with Dinosaurs specials following the real-world Allosaurus (Allosaurus fragilis) specimen "Big Al". It first aired on BBC One in the United Kingdom during Christmas 2000.


Valdosaurus ("Weald Lizard") is a genus of bipedal herbivorous iguanodont ornithopod dinosaur found on the Isle of Wight and elsewhere in England. It lived during the Early Cretaceous.


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