Name: Dryosaurus
(Oak
lizard).
Phonetic: Dry-o-sore-us.
Named By: Othniel Charles Marsh - 1894.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Cerapoda, Ornithopoda, Dryosauridae.
Species: D. altus (type), D. elderae.
Type: Herbivore.
Size: 2.4 - 4.3 meters long, though possibly more
for large adults.
Known locations: USA, Morrison formation.
Time period: Late Jurassic.
Fossil representation: Numerous specimens
illustrating different life stages.
The
maximum
adult size of Dryosaurus is difficult to estimate
as all of the known
specimens seem to represent animals that were still growing. What is
known is that Dryosaurus was a bipedal dinosaur of
the bird hipped
group. It had a light build with long legs, long neck and a stiff tail,
but no known defensive features, so it probably relied upon speed and
agility to escape predators.
Dryosaurus
earned its name
from the oak shaped teeth of its mouth, a marked characteristic of
herbivorous dinosaurs that fed on lush vegetation. It also featured a
beak at the front of the mouth which would have been used for cropping
off parts of plants. Some palaeontologists have also considered the
presence of cheeks to prevent food from spilling out of the sides of
its mouth.
Study
of Dryosaurus remains
show that the skull underwent considerable change as it grew, the eyes
of the smaller juveniles being proportionately larger than the larger
specimens. As the animal grew, the skull would extend forwards
resulting in a larger snout.
Further reading
- The typical Ornithopoda of the American Jurassic. - American Journal
of Science, series 3 48:85-90. - O. C. Marsh - 1894.
- The Upper Jurassic dinosaur Dryosaurus and a
Laurasia-Gondwana
connection in the Upper Jurassic. - Nature 268(5617): 230-232. - P. M.
Galton - 1977.
- Comparative long bone histology and growth of the "hysilophodontid"
dinosaurs Orodromeus makelai, Dryosaurus
altus, and Tenontosaurus
tillettii (Ornithischia: Euornithopoda). - Journal of
Vertebrate
Paleontology 29 (3): 734–747. - John R. Horner, Armand de Ricql�s,
Kevin Padian & Rodney D. Scheetz - 2009.