{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}
{{Taxobox
| name = Hypsilophodonts
| fossil_range =
Middle JurassicThe Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age age called the Dogger...
–
Late CretaceousThe Late Cretaceous is the youngest of two epochs in which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
, {{Fossil range|165|66}}
| regnum =
AnimalAnimals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...
ia
| image = Hypsilophodon Melb Museum email.jpg
| image_width = 250px
| image_caption =
Hypsilophodon
| phylum =
ChordataChordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail...
| classis =
ReptiliaReptiles, or members of the class Reptilia, are air-breathing, generally "cold-blooded" amniotes that generally have skin covered in scales or scutes. They are tetrapods and lay amniote eggs, whose embryos are surrounded by the amnion membrane...
| superordo =
Dinosaur{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}{{Taxobox|name = Dinosaurs|fossil_range = {{Fossil range|230|65|earliest=230|latest=0|PS=
Descendant taxon Aves survives to present.}}|image = field_dinos_2.jpg...
ia
| ordo =
OrnithischiaOrnithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
| subordo =
CerapodaCerapoda is a clade or suborder of the order Ornithischia. They are the sister group of the Thyreophora within the clade Genasauria. Cerapods are united by having a thicker layer of enamel on the inside of their lower teeth...
| infraordo = Ornithopoda
| familia =
Hypsilophodontidae
| familia_authority = Dollo, 1882
| subdivision_ranks =
GeneraIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
| subdivision =
See text.
}}
Hypsilophodonts (named after the
Hypsilophus genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
of
iguanaIguana is a genus of lizard native to tropical areas of Central and South America and the Caribbean.. The genus was first described by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena in 1768...
lizardLizards are a very large and widespread group of squamate reptiles, with nearly 5,000 species, ranging across all continents except Antarctica as well as most oceanic island chains...
, literally meaning "high-crested
toothTeeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to tear, scrape, and chew food. Some animals, particularly carnivores, also use teeth for hunting or defense. The roots of teeth are covered by gums...
") were small
ornithopodOrnithopods are a group of bird-hipped dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American landscape...
dinosaur{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}{{Taxobox|name = Dinosaurs|fossil_range = {{Fossil range|230|65|earliest=230|latest=0|PS=
Descendant taxon Aves survives to present.}}|image = field_dinos_2.jpg...
s, regarded as fast, herbivorous
bipedBipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
s on the order of 1-2 meters long (3.3-6.6 feet). They are known from
AsiaAsia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...
,
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
,
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
,
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
, and
South AmericaSouth America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere...
, from
rocksThis is a List of rock formations, meaning isolated, scenic, or spectacular surface rock outcrops. These are usually the result of weathering and erosion sculpting the existing rock...
of
Middle JurassicThe Middle Jurassic is the second epoch of the Jurassic Period. It lasted from 176-161 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age age called the Dogger...
to
late CretaceousThe Late Cretaceous is the youngest of two epochs in which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
age. The group traditionally has included almost all bipedal
bird-hipped dinosaursOrnithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
other than
iguanodontIguanodonts were herbivorous dinosaurs that lived from the mid-Jurassic to Late Cretaceous. Some members include Camptosaurus, Callovosaurus, Iguanodon, and Ouranosaurus. Iguanodonts were one of the first groups of dinosaurs to be found. They are among the best known of the dinosaurs, and include...
s, and some early
phylogenetic analysesCladistics is a form of biological systematics which classifies living organisms on the basis of shared ancestry...
found it to be a natural group, but recent studies have found that the group is mostly paraphyletic and the taxa within represent a series leading up to Iguanodontia. Some of these studies have moved some traditional hypsilophodonts out of the Ornithopoda. Thus, the only certain member at this time is
HypsilophodonHypsilophodon is an ornithopod dinosaur genus from the Early Cretaceous period of Europe. It was a small bipedal animal with an herbivorous or possibly omnivorous diet...
. This area of the dinosaur family tree is complicated by a lack of research.
Relationships
The following
cladogramCladistics is a form of biological systematics which classifies living organisms on the basis of shared ancestry...
of hypsilophodont relationships depicts the
paraphyleticIn phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all the descendants of that ancestor.- Relation to monophyletic groups :...
hypotheses; the "natural Hypsilophodontidae" hypothesis has been falling out of favor since the mid-late 1990s. It is after Boyd
et al (2009), the most recent analysis of hypsilophodonts. Ornithischia, Ornithopoda, and Iguanodontia were not designated in their result, and so are left out here. Additional ornithopods beyond
Tenontosaurus are omitted. Dinosaurs traditionally described as hypsilophodonts are found from
Agilisaurus or
Hexinlusaurus to
Hypsilophodon or
Gasparinisaura.
{{clade| style=font-size:100%;line-height:80%
|label1=
unnamed
|1={{clade
|1=
ScutellosaurusScutellosaurus is a genus of herbivorous dinosaur that lived in North America around 200 to 196 million years ago, in the Early Jurassic times....
|label2=
unnamed
|2={{clade
|1=
LesothosaurusLesothosaurus is an herbivorous ornithischian dinosaur. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from Lesotho". The genus is monotypic, having only one valid species, Lesothosaurus diagnosticus, within the genus....
|label2=
unnamed
|2={{clade
|1=
HeterodontosaurusHeterodontosaurus is a genus of small herbivorous dinosaur with prominent canine teeth which lived in the Early Jurassic of South Africa. It was similar to a hypsilophodont in shape, and ate plants, despite its canines.Heterodontosaurus is currently known from specimens of the SAFM from South...
|label2=
unnamed
|2={{clade
|1=
AgilisaurusAgilisaurus is a genus of ornithischian dinosaur from the Middle Jurassic Period of what is now eastern Asia. The name is derived from the Latin agilis meaning 'agile' and the Greek sauros meaning 'lizard', and refers to the agility suggested by its lightweight skeleton and long legs...
|label2=
unnamed
|2={{clade
|1=
HexinlusaurusHexinlusaurus is a genus of basal ornithischian dinosaur from the Middle Jurassic of China. The holotype , consists of an almost complete, articulated skull and some postcranial material, collected from a terrestrial sandstone within the Lower Shaximiao Formation at the...
|label2=
unnamed
|2={{clade
|1=
OthnielosaurusOthnielosaurus 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...
|label2=
unnamed
|2={{clade
|label1=
unnamed
|1={{clade
|label1=
unnamed
|1={{clade
|label1=
unnamed
|1={{clade
|1=
OryctodromeusOryctodromeus was a genus of small ornithopod dinosaur, the fossilized remains of which have been found in rocks dating from the middle Cretaceous Blackleaf Formation of southwestern Montana , roughly 95 million years ago...
|label2=
unnamed
|2={{clade
|1=
OrodromeusOrodromeus was a genus of hypsilophodont dinosaur from Late Cretaceous North America . It was a small herbivore that probably coexisted with dinosaurs such as Daspletosaurus and Einiosaurus. It lived in what is now Montana some 75 million years ago...
|2=
ZephyrosaurusZephyrosaurus is a genus of hypsilophodont ornithopod dinosaur. It is based on a partial skull and postcranial fragments discovered in the Aptian-Albian-age Lower Cretaceous Cloverly Formation of Carbon County, Montana...
}}
}}
}}
|label2=
unnamed
|2={{clade
|1=
ParksosaurusParksosaurus was a genus of hypsilophodont ornithopod dinosaur from the early Maastrichtian-age Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull, showing it to have been a small, bipedal, herbivorous dinosaur...
|2=
Thescelosaurus
}}
}}
|label2=
unnamed
|2={{clade
|1=
HypsilophodonHypsilophodon is an ornithopod dinosaur genus from the Early Cretaceous period of Europe. It was a small bipedal animal with an herbivorous or possibly omnivorous diet...
|label2=
unnamed
|2={{clade
|1=
GasparinisauraGasparinisaura is the name of an extinct genus of dinosaur from the Late Cretaceous. Its fossils were found in Argentina. The type species, Gasparinisaura cincosaltensis, was described in 1996 by Coria and Salgado. Originally classified as an iguanodont, recent research indicates it was a...
|label2=
unnamed
|2={{clade
|1=
TenontosaurusTenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. It was formerly thought to be a 'hypsilophodont', but since Hypsilophodontia is no longer considered a clade, it is now considered to be a very primitive iguanodont.-Description:...
|2=Other ornithopods
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
}}
In the most recent review of hypsilophodonts, by Norman
et al. (2004), the following genera were known well enough to include in a
phylogenetic analysisCladistics is a form of biological systematics which classifies living organisms on the basis of shared ancestry...
:
- Agilisaurus
Agilisaurus is a genus of ornithischian dinosaur from the Middle Jurassic Period of what is now eastern Asia. The name is derived from the Latin agilis meaning 'agile' and the Greek sauros meaning 'lizard', and refers to the agility suggested by its lightweight skeleton and long legs...
- A. multidens (now Hexinlusaurus
Hexinlusaurus is a genus of basal ornithischian dinosaur from the Middle Jurassic of China. The holotype , consists of an almost complete, articulated skull and some postcranial material, collected from a terrestrial sandstone within the Lower Shaximiao Formation at the...
)
- Bugenasaura (now regarded as a junior synonym of Thescelosaurus)
- Gasparinisaura
Gasparinisaura is the name of an extinct genus of dinosaur from the Late Cretaceous. Its fossils were found in Argentina. The type species, Gasparinisaura cincosaltensis, was described in 1996 by Coria and Salgado. Originally classified as an iguanodont, recent research indicates it was a...
- Hypsilophodon
Hypsilophodon is an ornithopod dinosaur genus from the Early Cretaceous period of Europe. It was a small bipedal animal with an herbivorous or possibly omnivorous diet...
- Orodromeus
Orodromeus was a genus of hypsilophodont dinosaur from Late Cretaceous North America . It was a small herbivore that probably coexisted with dinosaurs such as Daspletosaurus and Einiosaurus. It lived in what is now Montana some 75 million years ago...
- Othnielia
Othnielia is a genus of hypsilophodont dinosaur, named after its original describer, Professor Othniel Charles Marsh, an American paleontologist of the 19th century...
(now OthnielosaurusOthnielosaurus 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...
)
- Parksosaurus
Parksosaurus was a genus of hypsilophodont ornithopod dinosaur from the early Maastrichtian-age Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull, showing it to have been a small, bipedal, herbivorous dinosaur...
- Thescelosaurus
Thescelosaurus was a genus of small ornithopod dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was a member of the last dinosaurian fauna before the Cretaceous-Tertiary extinction event around 65.5 million years ago...
- Zephyrosaurus
Zephyrosaurus is a genus of hypsilophodont ornithopod dinosaur. It is based on a partial skull and postcranial fragments discovered in the Aptian-Albian-age Lower Cretaceous Cloverly Formation of Carbon County, Montana...
The following genera were regarded as valid, but weren't classified:
- Anabisetia
Anabisetia is a genus of ornithopod dinosaur from the Late Cretaceous Period of Patagonia, South America. It was a small bipedal herbivore, almost seven feet long....
- Atlascopcosaurus
Atlascopcosaurus is the name given to a genus of hypsilophodont dinosaur. It lived in what is now Australia; the type specimen, Atlascopcosaurus loadsi, was found at Dinosaur Cove in Victoria. It was about 2–3 metres long and weighed roughly 125 kg...
- Drinker
Drinker was a genus of hypsilophodont dinosaur from the late Jurassic period of North America. Although based on good remains, it remains obscure due to a lack of post-naming publications.-Description:...
- "Gongbusaurus
Gongbusaurus is a genus of ornithischian dinosaur that lived between about 160 and 155 million years ago, in the Late Jurassic period. A small herbivore, it is very poorly known...
" wucaiwanensis (= "Eugongbusaurus"Eugongbusaurus" is the informal name given to a genus of dinosaur that lived about 160 to 155 million years ago, in the Late Jurassic. It was either a hypsilophodont, or a less-derived ornithischian...
")
- Fulgurotherium
Fulgurotherium is the name given to a genus of dinosaur from the Early Cretaceous. It lived in what is now Australia. It was a hypsilophodont, a primitive ornithopod. The type species, Fulgurotherium australe, was formalized by Huene in 1932, but the animal may be a chimera based on multiple...
- Jeholosaurus
Jeholosaurus is the name given to a genus of dinosaur from the Early Cretaceous Period. It lived in what is now China and its fossils have been found in the Yixian Formation. It was a hypsilophodont, a primitive ornithopod...
- Leaellynasaura
Leaellynasaura was a small herbivorous ornithopod dinosaur of about 60-90 cm in length from the earliest Cretaceous, first discovered in Dinosaur Cove, Australia. It was an Australian polar dinosaur. At this period in time, Victoria would have been well within the Antarctic Circle, which is...
- Notohypsilophodon
Notohypsilophodon was a genus of hypsilophodont ornithopod dinosaur. It was described as the only hypsilophodont known from South America, although this assessment is not universally supported, and Gasparinisaura is now believed to have been a hypsilophodont as well...
- Qantassaurus
Qantassaurus is a genus of fast two-legged, plant-eating dinosaur that lived in Australia about 115 million years ago, when the continent was still south of the Antarctic Circle. It was the size of a small grey kangaroo, and had huge eyes to help it see in the polar night...
- Yandusaurus
Yandusaurus is a genus of hypsilophodontid dinosaur from the Bathonian age of China.A fast-moving biped, Yandusaurus had four toes on each foot and five fingers on each hand...
- "Proctor Lake hypsilophodont"
Several other genera belong here somewhere, but are very poorly known or outright dubious:
- Laosaurus
Laosaurus is a genus of hypsilophodont 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...
- Nanosaurus
Nanosaurus is the name given to a genus of dinosaur from the Late Jurassic. Described by Othniel Charles Marsh in 1877, it is a poorly-known ornithischian of uncertain affinities. Its fossils are known from the Morrison Formation of Colorado and possibly Wyoming...
- Phyllodon
Phyllodon was a genus of small ornithopod dinosaur from the Kimmeridgian-age Upper Jurassic Guimarota Formation of Leiria, Portugal. It may have been closely related to contemporaneous dinosaurs in North America....
- Siluosaurus
Siluosaurus is a genus of ornithopod dinosaur from the Barremian-Albian-age Lower Cretaceous Xinminbao Group of Gansu, China. It is based on IVPP V.11117 , two teeth...
The only new hypsilophodont genera named since this publication are
ChangchunsaurusChangchunsaurus was a genus of small herbivorous ornithopod dinosaur from the Early Cretaceous Quantou Formation of Gongzhuling, Jilin, China. It is known from a skull and skeleton and additional skull fragments...
and
OryctodromeusOryctodromeus was a genus of small ornithopod dinosaur, the fossilized remains of which have been found in rocks dating from the middle Cretaceous Blackleaf Formation of southwestern Montana , roughly 95 million years ago...
Alternate versions and new data
Several recent studies on the base of Ornithischia, such as Butler (2005), Barrett
et al. (2005), Xu
et al. (2006), and Butler
et al. (2007) have found different arrangements of basal Ornithischia and basal ornithopods that have some bearing on the tree, but each has found different relationships. Given the lack of work on this area since the 1980s, this is not unexpected. One aspect is the reclassification of several genera outside of Ornithopoda, such as
AgilisaurusAgilisaurus is a genus of ornithischian dinosaur from the Middle Jurassic Period of what is now eastern Asia. The name is derived from the Latin agilis meaning 'agile' and the Greek sauros meaning 'lizard', and refers to the agility suggested by its lightweight skeleton and long legs...
and
OthnielosaurusOthnielosaurus 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...
(=
OthnieliaOthnielia is a genus of hypsilophodont dinosaur, named after its original describer, Professor Othniel Charles Marsh, an American paleontologist of the 19th century...
).
Varricchio
et al. (2007) found that their new genus,
OryctodromeusOryctodromeus was a genus of small ornithopod dinosaur, the fossilized remains of which have been found in rocks dating from the middle Cretaceous Blackleaf Formation of southwestern Montana , roughly 95 million years ago...
, forms a
cladeA clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[The term "monophyletic group" is used in this article...]
with two other genera from Montana,
Orodromeus and
Zephyrosaurus. This relationship was also found by Boyd
et al. (2009), who also recovered a
Parksosaurus–
Thescelosaurus clade more closely related to it than to other ornithopods, which would unite all North American Cretaceous hypsilophodonts in one clade.
Paleobiology
Hypsilophodonts were small (often 1-2 m [3.28 to {{convert|6.56|ft|m|abbr=on}}] long),
bipedBipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
al,
cursorialCursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation...
herbivores. The typical informal comparison has been to
gazelleA gazelle is any of many antelope species currently or formerly in the genus Gazella. Six species are included in two genera which were formerly considered subgenera...
s. However, there is evidence that at least some of them made
burrowA burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...
s as places to rear their young. While so far only known for
OryctodromeusOryctodromeus was a genus of small ornithopod dinosaur, the fossilized remains of which have been found in rocks dating from the middle Cretaceous Blackleaf Formation of southwestern Montana , roughly 95 million years ago...
, additional possible hypsilophodont burrows have been found in slightly older rocks in
VictoriaVictoria is the second most populous state in Australia. Geographically smallest mainland state, Victoria is bordered by New South Wales to the north, South Australia to the west, and Tasmania to the south, across the Bass Strait. Victoria is the most densely populated state, with over 70% of...
,
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
.