Hypsilophodon
Encyclopedia
Hypsilophodon is an ornithopod
dinosaur
genus
from the Early Cretaceous
period of Europe
. It was a small biped
al animal with an herbivorous
or possibly omnivorous
diet. Abundant fossil
remains found in England
indicate that Hypsilophodon reached about 2 metres (6.6 ft) in length.
The first remains of Hypsilophodon were recovered in the early days of paleontology
in 1849. However, at the time, the bones were thought to belong to a young Iguanodon
. It was not until 1870 that paleontologist
T. H. Huxley
was able to publish a full description of Hypsilophodon as we know it today. He had been provided with a number of skeletons by the Reverend William Fox
, after whom the first species of Hypsilophodon was named.
Early paleontologists modeled the body of this small, bipedal, herbivorous dinosaur in various ways. In 1882 some paleontologists suggested that, like a modern tree-kangaroo
, Hypsilophodon was able to climb trees in order to seek shelter. This was the accepted view for almost a century. However, Peter M. Galton finally performed more accurate analysis of the musculo-skeletal structure in 1974 and convinced most paleontologists that Hypsilophodon remained firmly on the ground.
Since then, three near-complete and over twenty minor finds have been made, especially on the Isle of Wight
, off the south coast of England. Other finds have been made in southern England and Spain
.
Another misconception concerning the anatomy of Hypsilophodon was that it was armoured. The putative armour, consisting of thin mineralized plates from the torso, instead appear to be examples of intercostal plates associated with the rib cage. Such plates are better known from Talenkauen
and Thescelosaurus
, and were probably cartilaginous
in origin.
There is only one known species of Hypsilophodon, Huxley's original H. foxii. Galton and Jensen named another species in 1979, H. wielandi, which is based on a thigh bone
from South Dakota
, USA, but it is now regarded as an indeterminate basal
ornithopod.
Hypsilophodon was a relatively small dinosaur. While not quite so small as, for example, Compsognathus
, Hypsilophodon was only around 2.3 metres in length. It would have reached approximately waist-height on a modern man and would have weighed about the same, at 50 to 70 kg (110.2 to 154.3 lb).
Like most small dinosaurs, Hypsilophodon was bipedal and ran on two legs. Its entire body was built for running; a light-weight, minimized skeleton, low, aerodynamic posture, long legs and stiff tail for balance all would have allowed it to travel remarkably fast for its size.
Due to its small size, Hypsilophodon fed on low-growing vegetation, most likely preferring young shoots and roots in the manner of modern deer
. The structure of its skull, with the teeth set far back into the jaw, strongly suggests that it had cheeks, an advanced feature that would have facilitated the chewing of food. There were twenty-eight to thirty ridged teeth in the animal's jaw which, due to their alternate arrangement, appear to have been self-sharpening. As in almost all dinosaurs and certainly all the ornithischia
ns, the teeth were continuously replaced.
The level of parental care in this dinosaur has not been defined, although a neatly-arranged nest has been found, suggesting that some care was taken before hatching.
Fossils of large groups have been found, so it is likely that the animals moved in herd
s. For these reasons, the hypsilophodont
s, particularly Hypsilophodon, have often been referred to as the "deer of the Mesozoic".
Despite living in the last of the periods in which dinosaurs walked the earth, the Cretaceous, Hypsilophodon had a number of primitive features. For example, there were five digit
s on each 'hand' and four on each foot. Most dinosaurs had lost these redundant features by the Cretaceous period. Also, although it had a beak like most ornithischia
ns, Hypsilophodon still had pointed triangular teeth in the front of the jaw. Most herbivorous dinosaurs had, by this stage, become sufficiently specialized that the front teeth had been altogether lost (although there is some debate as to whether these teeth may have had a specialized function in Hypsilophodon).
The group Hypsilophodont
idae remained remarkably static from the late Jurassic
to the end of the Cretaceous. It is possible that this was because the animals were almost perfectly adapted to their lifestyle, therefore selective pressure, it is assumed, was low.
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian 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...
dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
from the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
period of Europe
Europe
Europe 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 watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. It was a small biped
Biped
Bipedalism 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 animal with an herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
or possibly omnivorous
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
diet. Abundant fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains found in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
indicate that Hypsilophodon reached about 2 metres (6.6 ft) in length.
Discoveries and species
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
in 1849. However, at the time, the bones were thought to belong to a young Iguanodon
Iguanodon
Iguanodon is a genus of ornithopod dinosaur that lived roughly halfway between the first of the swift bipedal hypsilophodontids and the ornithopods' culmination in the duck-billed dinosaurs...
. It was not until 1870 that paleontologist
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
T. H. Huxley
Thomas Huxley
Thomas Henry Huxley PC FRS was an English biologist, known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution....
was able to publish a full description of Hypsilophodon as we know it today. He had been provided with a number of skeletons by the Reverend William Fox
William Fox
William Fox may refer to:* William Fox , Irish international footballer active in the 1880s.* William Fox , Paymaster of the Forces of England* William Johnson Fox , British politician* William F...
, after whom the first species of Hypsilophodon was named.
Early paleontologists modeled the body of this small, bipedal, herbivorous dinosaur in various ways. In 1882 some paleontologists suggested that, like a modern tree-kangaroo
Tree-kangaroo
Tree-kangaroos are macropods adapted for life in trees. They are found in the rainforests of New Guinea, far northeastern Queensland, and nearby islands. Although most are found in mountainous areas, several species also occur in lowlands, such as the aptly named Lowlands Tree-kangaroo...
, Hypsilophodon was able to climb trees in order to seek shelter. This was the accepted view for almost a century. However, Peter M. Galton finally performed more accurate analysis of the musculo-skeletal structure in 1974 and convinced most paleontologists that Hypsilophodon remained firmly on the ground.
Since then, three near-complete and over twenty minor finds have been made, especially on the Isle of Wight
Dinosaurs of the Isle of Wight
The Isle of Wight is one of the richest dinosaur localities in Europe, with over 20 species of dinosaur having been recognised from the early Cretaceous Period , some of which were first identified on the island, as well as the contemporary non-dinosaurian species of crocodile, turtle and...
, off the south coast of England. Other finds have been made in southern England and Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
.
Another misconception concerning the anatomy of Hypsilophodon was that it was armoured. The putative armour, consisting of thin mineralized plates from the torso, instead appear to be examples of intercostal plates associated with the rib cage. Such plates are better known from Talenkauen
Talenkauen
Talenkauen is a genus of basal iguanodont dinosaur from the Maastrichtian-age Upper Cretaceous Pari Aike Formation of Lake Viedma, 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...
and Thescelosaurus
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...
, and were probably cartilaginous
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
in origin.
There is only one known species of Hypsilophodon, Huxley's original H. foxii. Galton and Jensen named another species in 1979, H. wielandi, which is based on a thigh bone
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
from South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
, USA, but it is now regarded as an indeterminate basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
ornithopod.
Paleobiology
Compsognathus
Compsognathus was a small, bipedal, carnivorous theropod dinosaur. The animal was the size of a turkey and lived around 150 million years ago, the early Tithonian stage of the late Jurassic Period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany...
, Hypsilophodon was only around 2.3 metres in length. It would have reached approximately waist-height on a modern man and would have weighed about the same, at 50 to 70 kg (110.2 to 154.3 lb).
Like most small dinosaurs, Hypsilophodon was bipedal and ran on two legs. Its entire body was built for running; a light-weight, minimized skeleton, low, aerodynamic posture, long legs and stiff tail for balance all would have allowed it to travel remarkably fast for its size.
Due to its small size, Hypsilophodon fed on low-growing vegetation, most likely preferring young shoots and roots in the manner of modern deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...
. The structure of its skull, with the teeth set far back into the jaw, strongly suggests that it had cheeks, an advanced feature that would have facilitated the chewing of food. There were twenty-eight to thirty ridged teeth in the animal's jaw which, due to their alternate arrangement, appear to have been self-sharpening. As in almost all dinosaurs and certainly all the ornithischia
Ornithischia
Ornithischia 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'...
ns, the teeth were continuously replaced.
The level of parental care in this dinosaur has not been defined, although a neatly-arranged nest has been found, suggesting that some care was taken before hatching.
Fossils of large groups have been found, so it is likely that the animals moved in herd
Herd
Herd refers to a social grouping of certain animals of the same species, either wild or domestic, and also to the form of collective animal behavior associated with this or as a verb, to herd, to its control by another species such as humans or dogs.The term herd is generally applied to mammals,...
s. For these reasons, the hypsilophodont
Hypsilophodont
Hypsilophodonts were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 1–2 meters long . They are known from Asia, Australia, Europe, New Zealand, North America, and South America, from rocks of Middle Jurassic to late Cretaceous age...
s, particularly Hypsilophodon, have often been referred to as the "deer of the Mesozoic".
Despite living in the last of the periods in which dinosaurs walked the earth, the Cretaceous, Hypsilophodon had a number of primitive features. For example, there were five digit
Digit (anatomy)
A digit is one of several most distal parts of a limb, such as fingers or toes, present in many vertebrates.- Names:Some languages have different names for hand and foot digits ....
s on each 'hand' and four on each foot. Most dinosaurs had lost these redundant features by the Cretaceous period. Also, although it had a beak like most ornithischia
Ornithischia
Ornithischia 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'...
ns, Hypsilophodon still had pointed triangular teeth in the front of the jaw. Most herbivorous dinosaurs had, by this stage, become sufficiently specialized that the front teeth had been altogether lost (although there is some debate as to whether these teeth may have had a specialized function in Hypsilophodon).
The group Hypsilophodont
Hypsilophodont
Hypsilophodonts were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 1–2 meters long . They are known from Asia, Australia, Europe, New Zealand, North America, and South America, from rocks of Middle Jurassic to late Cretaceous age...
idae remained remarkably static from the late Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
to the end of the Cretaceous. It is possible that this was because the animals were almost perfectly adapted to their lifestyle, therefore selective pressure, it is assumed, was low.