I Know Dino Podcast: Hypsilophodon

Episode 28 is all about Hypsilophodon, a fast-running dinosaur.

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In this episode, we discuss:

The dinosaur of the day: Hypsilophodon, an ornithopod, whose name means “Hypsilophus-tooth”

Almost 100 specimens have been found on the Isle of Wight (over 20 dinosaur species found there)
20 Hypsilophodon specimens have been found in one place, where they died together (may have been in quicksand)
Reverend William Fox, discovered the 1868 specimen (with skull), so the type species is named after him

Small, bipedal, about 5.9 feet (1.8 meters) long, weighed about 45 pounds (20 kg)
Agile runner, and had a sharp beak it used to bite off vegetation
Herbivore, and possibly an omnivore

Lots of misconceptions: scientists used to think Hypsilophodon climbed trees and was armored
First found in 1849, and two pieces were sold (one to naturalist James Scott Bowerbank); at the time, they thought it was the bones of a young Iguanodon (Mantell described it as an Iguandon in 1849, as did Richard Owen in 1855)
Paleontologist Thomas Henry Huxley wrote a more comprehensive description in 1870 (after studying the skull); Huxley was the first to note that Ornithischians had pubic bones that pointed backwards, like birds

Huxley chose the name Hypsilophodon because he wanted it to be similar to Iguanodon’s name (means iguana-tooth) so he chose named the dinosaur after an “extant herbivorous lizard”
Richard Owen still thought Hypsilophodon was not a different genus, and renamed it in 1874 Iguanodon foxii, but scientists rejected it (John Whitaker Hulke had more specimens from Fox)
In 1874 Hulke described Hypsilophodon as armored, but in 2008 Galton wrote the armor was actually from the torso, “an example of internal intercostal plates associated with the rib cage. It consists of thin mineralized circular plates growing from the back end of the middle rib shaft and overlapping the front edge of the subsequent rib”

In 1882 Hulke said Hypsilophodon was probably quadrupedal, but also climbed rocks and trees (because of its grasping hand). In 1912 paleontologist Othenio Abel said it was a aroboreal animal, and in 1916 Gerhard Heilmann said it lived like a modern tree kangaroo. But in 1926 Heilmann changed his mind and said the first toe was not opposable because it was “firmly connected to the second”. In 1927 Abel denied this description, and in 1936 Swinton said even though the first metatarsal was forward pointing it might have a moveable toe. In 1969 Peter M. Galton analyzed the skeleton, and described Hypsilophon as not being able to climb, but instead a bipedal runner.
Most Hypsilophodon specimens were found between 1849 and 1921, and are now in the Natural History Museum in London (about 20)
1967 Peter Malcolm Galton published his thesis on Hypsilophodon, starting modern research on the dinosaur

In 1978-79, Galton and James Jensen named another Hypsilophodon species, Hypsilophodon wielandi, after George Reber Wieland found a thigh bone in South Dakota. They thought Hypsilophodon wielandi was proof of a land bridge between North America and Europe, but now the specimen is considered an “indeterminate basal ornithopod”
Hypsilophodon had primitive features, such as five digits on each hand and four digits on each foot (its fifth finger was opposable and could grab food); had a beak like other ornithischians, but also had five teeth in its premaxilla (front of the upper jaw)–most other herbivores in its time no longer had these front teeth)
Had a large eye socket, and thin, pointy bones over the top half of its eyes to give it shade (and make it look fierce)

May have had cheeks, to help it chew food
Because it was small, at low-growing plants (probably liked shoots and roots, like modern deer)
May have been semi-quadrapedal when eating low growing plants

Possible predators: Eotyrannus, Neovenator, Baryonyx
Related species had neatly arranged nests (no Hypsilophodon nests have been found), so may have cared for eggs before hatching
One of the fastest types of dinosaur, probably

Had a body built for running; light weight, long legs, stiff tail (for balance); may be the best ornithischian adapted to running
When running, kept its spine horizontally level to the ground (long tail would help counterbalance)
Can see a mounted skeleton at Dinosaur Isle, “Britain’s first purpose built dinosaur museum and visitor attraction; based in Sandown on the Isle of Wight”

Hypsilophodonts were small, long, bipedal herbivores (some made burrows for their young, like Oryctodromeous (episode 2)
Lived in the middle Jurassic to late Cretaceous
Fossils have been found in Asia, Australia, Europe, New Zealand, North America, and South America

Fun Fact: All dinosaurs laid eggs. About 40 kinds of dinosaur eggs have been discovered. (there are ~1,000 discovered so far, so there are still a lot of unknowns [including ceratopsians])

I Know Dino Podcast Show Notes: Hypsilophodon (Episode 28)