Geology Reference
In-Depth Information
Ankylosaurs:
The most heavily armored dinosaurs were the
ankylosaurs.
Its entire
back, parts of its legs, and top of its head were covered in a thick, protective, bony
armor. It also had a large club-tail that could be used as a defensive weapon. This
armoring meant that the ankylosaurs could weigh up to 5 tons! Because they car-
ried this much weight, scientists estimate that they could travel only about 5 to 8
miles an hour.
Stegosaurs:
Stegosaurs
were quadrupedal and included the
Stegosaurus
from the
Jurassic period, approximately 150 to 200 million years ago. Stegosaurs had large
plate-like spines along their backs and spiked tails. While the spiked tails were
probably for defense, scientists think the plates along their spine may have helped
them regulate body temperature.
Ceratopsians:
The
ceratopsian
dinosaurs had sharp teeth for cutting down vegeta-
tion and large horns, presumably for defense, on their heads. They were also
quadrupedal and traveled in large herds. The most well-known ceratopsian dino-
saur is the
Triceratops.Triceratops
fossils are most common at the end of the
Mesozoic, around 70 million years ago.
Ornithopods:
The
ornithopod
dinosaurs were bipedal, with front legs that were de-
veloped enough to occasionally support them as quadrupeds. This group includes
the duck-billed dinosaurs, or
hadrosaurs.
The hadrosaurs (such as the Hypocro-
saurus) had a distinctive, thick, domed skull that in some species extended into a
bony crest. Scientists have yet to figure out what purpose (if any) these elaborate
bony crests served.
Figure 20-7:
Ornith-
ischian dinosaurs.
