( ; meaning 'oak lizard', due
to the vague oak shape of its cheek teeth (Greek δρυο/dryo
meaning 'oak' and σαυρος/sauros
'lizard') is a genus
of an ornithopod dinosaur
lived in the Late Jurassic
was an iguanodont
(formerly classified as
). Fossils have been
found in the western United States and Tanzania and were first
discovered in the late 19th century.
The Tanzanian site
proved to be an especially fertile hunting ground for
fossils, this specimen was previously called
(meaning "lost wood reptile"). An
expedition led by German paleontologist Werner Janensch
found a great many fossils
that represented Dryosaurus
at many stages of
had a long neck, long, slender legs and a long,
stiff tail. Its 'arms', however, with five 'fingers' on each
'hand', were short. Known specimens were about long and weighed .
However, the adult size is unknown, as no known adult specimens of
the genus have been found.
had a horny beak and cheek teeth
and, like other ornithopods, was a
. Some scientists suggest that it
had cheek-like structures to prevent the loss of food while the
animal processed it in the mouth.
A quick and agile runner with strong legs, Dryosaurus
its stiff tail as a counter-balance. It probably relied on its
speed as a main defense against carnivorous
D. lettowvorbecki skeleton in
Diet and dentition
from the Morrison Formation subsisted primarily
on low growing vegetation in the ancient floodplain.
was a dinosaur genus contemporary to
, although smaller and with more primitive
dentition. The more highly derived teeth of Dryosaurus
were, according to museum curator John Foster, characterized by "a
strong median ridge on the lateral surface."
Growth and development
exhibited high rates of growth that were
both continuous and independent of seasonal weather
hatchling found at Dinosaur National Monument
in Utah confirmed that Dryosaurus
patterns of craniofacial development to other vertebrates; the eyes
were proportionally large while young and the muzzle proportionally
short. As the animal grew it's eyes became proportionally smaller
and its snout proportionally longer.
D. altus (previously Laosaurus altus)
was originally described as
D. lettowvorbecki (previously Dysalotosaurus
The African Dryosaurus
, D. lettowvorbecki
originally described as the type species of a separate genus called
Paleobiogeography and fossil distribution
In the Late Jurassic Morrison formation of Western North America,
Dryosaurus remains have been recovered from stratigraphic zones
2-6. A spectacular digsite near Uravan, Colorado held hundreds of
fossils which represented multiple stages of the
animal's life cycle. Other sites that have produced
material include Bone Cabin Quarry, the Red
Fork of the Powder River in Wyoming and Lily
- Marshall (1999) pp. 138-139
- "Dryosaurus altus," Foster (2007) pp. 218-219.
- "Appendix," Foster (2007) pp. 327-329.
- Foster, J. (2007). Jurassic West: The Dinosaurs of the Morrison
Formation and Their World. Indiana University Press. 389pp.