Hypsilophodon | Natural History Museum Dino Directory
Natural History Museum, London
Reviewed: 9/6/2026
Museum reference page documenting Hypsilophodon as a small herbivorous ornithopod and its plant-based feeding.
Open source
Hypsilophodon foxii
Hypsilophodon foxii was a small, lightly built plant-eating dinosaur that reached barely more than two metres in length, over half of which was a long, stiffened tail. It carried its body horizontally on strong hind legs, with the tail held straight out behind as a counterweight rather than dragging on the ground.
Hypsilophodon
Hypsilophodon foxii
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Quick facts
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Weight
20–28 kg
Length
1.5–1.8 m
Diet
Herbivore
Period
Cretaceous
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20–28 kg
1.5–1.8 m
Cretaceous
Bipedal
60–90 cm
40 km/h
Herbivore
3 recorded fossil finds in United Kingdom. First described in 1870 by Huxley.
Sites and counts from the Paleobiology Database
The timeline shows the whole age of dinosaurs – and how much time has passed since. The glowing part is when Hypsilophodon lived.
million years ago
Lived 130–125 million years ago
If the whole age of dinosaurs were a single day, Hypsilophodon lived at 16:04.
Chapter • Meet the dinosaur
Hypsilophodon foxii was a small, lightly built plant-eating dinosaur that reached barely more than two metres in length, over half of which was a long, stiffened tail. It carried its body horizontally on strong hind legs, with the tail held straight out behind as a counterweight rather than dragging on the ground. The arms were short with five fingers, while the foot had four functional toes. The skull was small and pointed, with large eye sockets, a horn-covered beak at the front and cheek teeth bearing prominent enamel ridges – the feature that gave the genus its name, "high-ridged tooth".
Chapter • Where it lived
Hypsilophodon lived in the Early Cretaceous, during the Barremian stage about 130–125 million years ago. All secure fossils come from the Wessex Formation on the Isle of Wight in southern England, especially the cliffs at Cowleaze Chine. The setting was a floodplain crossed by meandering rivers, with temporary lakes, dry seasons and wildfires, and vegetation of conifers, ginkgos, cycads and ferns. It shared this landscape with Iguanodon, Neovenator, Eotyrannus and Polacanthus.
Chapter • Wild behavior
Diurnal
The so-called Hypsilophodon bed has yielded the remains of several individuals together, which has been read as evidence that the animals lived in groups. The interpretation remains uncertain: the bones could equally have been washed into one place by water, or record a group that died in a single event. Direct evidence of habitual herding, such as trackways with many parallel footprints, is lacking.
The name means roughly "high-ridged tooth", after the strong enamel ridges on its cheek teeth.
The species name foxii honours the Reverend William Fox, a keen fossil collector on the Isle of Wight.
Thomas Henry Huxley named the animal in 1869; before that its bones had been mistaken for young Iguanodon.
For nearly a century Hypsilophodon was drawn perching in trees with a supposedly grasping toe – Peter Galton showed in the 1970s that the toe was not opposable.
Its light frame and long lower legs make it one of the fastest of all small herbivorous dinosaurs.
Thin mineralised intercostal plates lie along its ribs, and palaeontologists still debate what they were for.
Almost every known specimen comes from a single horizon in the Wessex Formation, informally called the "Hypsilophodon bed".
Fossils from Spain, Portugal and the United States once assigned to Hypsilophodon have since been referred to other dinosaurs.
Chapter • Scientific place
Natural History Museum, London
Reviewed: 9/6/2026
Museum reference page documenting Hypsilophodon as a small herbivorous ornithopod and its plant-based feeding.
Open sourceProceedings of the Geologists' Association (Elsevier)
Reviewed: 9/6/2026
Extinct taxon; conservation status NE
Open sourceJournal of the Geological Society
Reviewed: 9/6/2026
Peer-reviewed reconstruction of the floodplain palaeoenvironment and taphonomy of the Hypsilophodon Bed at Cowleaze Chine.
Open sourcethedinosaurs.org
Reviewed: 9/6/2026
VERIFY:length_min_m: stored=1.8 suggested=1.5 confidence=medium — Following Galton's 2009 revision, typical Hypsilophodon specimens are estimated at about 1.5 m (4.9 ft) long, with 1.8 m being the largest known individual; a stored minimum of 1.8 m equals the maximum known size and excludes the typical adult range.
Open sourcethedinosaurs.org
Reviewed: 9/6/2026
VERIFY:length_max_m: stored=2.3 suggested=1.8 confidence=high — The 2.3 m figure derives from Galton's 1974 extrapolation from femur BMNH R 167, which Galton reassigned to Valdosaurus in 2009, downsizing Hypsilophodon to a maximum known length of about 1.8 m based on the largest specimen NHMUK PV R 5829 (femur 202 mm).
Open sourcewww.ebsco.com
Reviewed: 9/6/2026
VERIFY:weight_max_kg: stored=50 suggested=28 confidence=medium — Current mass estimates cluster around 20 kg for a 2 m animal (Paul, 2010) with upper published figures of roughly 25-28 kg; 50 kg is far above any supported estimate, especially after the 2009 downsizing of the taxon.
Open sourcefossil.fandom.com
Reviewed: 9/6/2026
VERIFY:height_max_m: stored=0.9 suggested=0.5 confidence=low — Reference summaries of the post-2009 literature give a standing height of up to about half a metre for Hypsilophodon, consistent with the reduced 1.8 m maximum body length; 0.9 m is not supported.
Open sourcePaleobiology Database
Reviewed: 9/6/2026
Paleobiology Database taxon page giving the accepted classification of Hypsilophodon foxii within Ornithischia, Neornithischia and Ornithopoda (Hypsilophodontidae).
Open sourceProceedings of the Geologists' Association (Elsevier)
Reviewed: 9/6/2026
Documents the stratigraphic and geographic setting of the Wessex Formation on the Isle of Wight, the only unit yielding secure Hypsilophodon material.
Open sourceBulletin of the British Museum (Natural History), Geology
Reviewed: 9/6/2026
Galton's monographic redescription of Hypsilophodon foxii, the standard authoritative overview of its anatomy, size and biology.
Open sourceBulletin of the British Museum (Natural History), Geology
Reviewed: 9/6/2026
Galton's monographic redescription of Hypsilophodon foxii, the standard authoritative overview of its anatomy, size and biology.
Open sourceBulletin of the British Museum (Natural History), Geology
Reviewed: 9/6/2026
Galton's monographic redescription of Hypsilophodon foxii, the standard authoritative overview of its anatomy, size and biology.
Open sourceBulletin of the British Museum (Natural History), Geology
Reviewed: 9/6/2026
Galton's monographic redescription of Hypsilophodon foxii, the standard authoritative overview of its anatomy, size and biology.
Open source