April 4, 2022 Scott Kraus

Hypsilophodon Was A Cretaceous Ornithopod

Hypsilophodon, pronounced hip-sih-LO-fuh-don, was a prehistoric ornithopod dinosaur that lived in primarily in the Early Cretaceous period of what is today known as England.  This was a small bipedal dinosaur that for some time has been misunderstood; recent findings and analyses have changed the picture we now have of Hypsilophodon.

Quick Facts

About Hypsilophodon

Being of the order Ornithischia, Hypsilophodon comes from a line of reptilian dinosaur that began as a small bipedal running and grazing group.  The group’s strongest evolutionary attribute was its ever progressive snout with chewing mechanisms, which allowed the group to adapt to almost any feeding option.  Over time, ornithopods became one of the most successful groups of herbivores in the Cretaceous Period and they took over the North American landscape.  Ornithischian fossils have been found on all seven continents.

What Did Hypsilophodon Look Like?

Hypsilophodon was a small dinosaur, about waist-high to the adult human.  Its estimated weight would have been about 40—50 pounds.  The body of Hypsilophodon was built for running, and the species resembles the much larger carnivorous runners.  Its skeleton was light-weight and its posture was low and aerodynamic in nature.  Hind limbs were much longer than the forelimbs, and the tail was proportionally large to the rest of the body.  In the case of Hypsilophodon—just as other aerodynamic bipedal racers—the tail was heavy and stiff to aid balance.

The head of Hypsilophodon was small and the snout ended in a beak.  There were teeth, but it is uncertain how exactly or if they teeth were used.  The number of teeth correlates to the size of the animal found, and teeth were at rear of mouth away from the beak.  The lower jaw tends to turn up more teeth than the upper, with 16 and 11 being respective averages.  P.M Galton, in The Ornithischian Dinosaur (1974), notes that rearmost teeth were fan-shaped.

Hypsilophodon, of the Early Cretaceous, was one of those ornithischian dinosaur species that retained four-toed feet on the rear and five-fingered hands on the forelimbs, as opposed to the later 4/3 combination seen on later ornithischian dinosaurs, as they tended toward herbivorous habits.

What Did Hypsilophodon Eat?

It is believed that Hypsilophodon ate plant material primarily, with the possibility that other food sources were taken advantage of as well.  It would make sense that this genus exhibited ornithischian polyphage tendencies, especially considering the snout of Hypsilophodon, with its anterior beak and posterior teeth.  Hypsilophodon probably ate plants, small animals, insects and fungi.

More is being learned with time regarding Hypsilophodon, and some still believe that Hypsilophodon ate only plants, using its beak to break and scrape foliage.   As ornithischian groups developed, it is believe that they gained more teeth to aid the changing available food sources, and Hypsilophodon would have been of the first groups to see the change.  The real question is, while ornithischian dinosaurs as a group adapted well to life throughout the Cretaceous Period, how well did the ornithischian Hypsilophodon itself adapt?

How Did Hypsilophodon Move?

Hypsilophodon is regarded to be the fastest ornithischian species to have existed.  Small, light and still bipedal—the body and carriage of Hypsilophodon adapted to the grass-feeding opportunities that arose as the Cretaceous Period moved on.  Hypsilophodon was probably exhibiting quadrupedal characteristics as well as bipedal and eventually most ornithischian dinosaurs would exist as primarily quadrupedal animals.

Where Did Hypsilophodon Live?

Hypsilophodon would have called the Early (lower) Cretaceous home, and a likely predator could have been the famous Utahraptor, also found in North American lower Cretaceous layers.  Other plant-eaters beside Hypsilophodon could have been Iguanodon, Cedarosaurus, Brachiosaurus and Stenopelix.

As far as the actual habitat of Hypsilophodon, associated fossil fauna of the Hypsilophodon Bed consists only of a few scutes from a crocodylomorph (archosaur) and a turtle.   Crocodylomorphs were plentiful during the Late Jurassic—Early Cretaceous Periods and known to have existed in significant numbers as early as the Triassic Period.

The Discovery of Hypsilophodon

Fossilized remains of Hypsilophodon were first found almost 200 years ago in 1849 (Mantell-Bowerbank block).  Hypsilophodon foxii was subsequently named, yet still misunderstood, in 1869.  Paleontologist Thomas Henry Huxley is primarily responsible for correctly taking Hypsilophodon out of the realm of Iguanodon (the original supposed origination and description of Hypsilophodon).  Subsequent to his own studies, Huxley spent 1869 in lecture to promote his finding, which were eventually published officially (1870).

*Note that this publication, which determines the origination of Hypsilophodon, is the same one which also determines that the hip bone (pubic bone) was in some such species pointed backward—“…like that of birds”. 

“High-ridge tooth” is a name that does not apply to Hypsilophodon.  When Huxley named the type species Hypsilophodon foxii, he intended that foxii represent the name of the original fossil-finder, Reverend William Fox.  Hypsilophodon is taken from the Greek hypsilophos, which means “high-crested” and refers to the back frill of a lizard.

Major Hypsilophodon related findings were the skull found by Fox (the holotype specimen) and the Mantell-Bowerbank block (the paratype specimen, a.k.a. Hypsilophodon Bed).  In the two centuries of Hypsilophodon-related fossil findings since 1849, several occasions have prompted studies to the origin of Hypsilophodon—and whether Hypsilophodon should in fact be Iguanodon.  While there is still some doubt to this day (as often happens in the prehistoric—modern world of paleontology), for now, the Hypsilophodon genus remains Hypsilophodon, the ornithopod.

“Hypsilophodon in the modern view thus simply is a basal ornithopod. Though not forming a separate branch together, such forms lasting from the late Jurassic to the end of the Cretaceous shared the common design of a small running herbivore that apparently was very successful.”

Hypsilophodon—tongue in cheek and beak

It is thought that Hypsilophodon likely gave rise to the later duck-billed dinosaur species, such as Pachycephalosaur.  Its feature of posterior teeth incorporated into its beaked snout over time lent to its herbivorous ability.  Over time, increased teeth and habits of chewing lent to the eventual development of the flattened snout feature of the duck-bills.