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Hypsilophodon

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

             iHypsilophodon

                       Fossil range: Early Cretaceous

   Hypsilophodon skeleton at Oxford University Museum of Natural History.
   Hypsilophodon skeleton at Oxford University Museum of Natural History.
                         Scientific classification

   Kingdom:    Animalia
   Phylum:     Chordata
   Class:      Sauropsida
   Superorder: Dinosauria
   Order:      Ornithischia
   Suborder:   Ornithopoda
   Family:     Hypsilophodontidae
   Genus:      Hypsilophodon

                                Binomial name

   Hypsilophodon foxii
   Huxley, 1869

   Hypsilophodon ( IPA: /ˌhɪpsɪˈlɔfodɔn/; meaning 'high-crested tooth') 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. Abundant fossil remains found in England indicate that
   Hypsilophodon reached about 2  meters (6.5  feet) in length.

Discoveries and species

   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 Darwin 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, Portugal and South
   Dakota, USA.

   There is only one known species of Hypsilophodon, Huxley's original H.
   foxii. Galton and Jensen named another species, H. wielandi in 1979,
   but it now seems likely this was just a variant individual within H.
   foxii.

Paleobiology

   Mounted cast, Melbourne Museum.
   Enlarge
   Mounted cast, Melbourne Museum.

   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 50-70 kg.

   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 ornithischians, 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 herds. For these
   reasons, the hypsilophodonts, 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 digits 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
   ornithischians, 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 Hypsilophodontia 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.
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