Cerapoda
The Cerapoda were the main herbivores of the Cretaceous. The first Cerapods evolved in
the early Jurassic. They didn’t start getting bigger until the late Jurassic. They evolved to
lengths of 15m in the late Cretaceous, and lived in herds of hundreds of animals.
Cerapoda is divided into three groups: Ornithopoda, Pachycephalosauria, and Ceratopsia.
The latter two are sometimes grouped together as Marginocephalia because they share a few
features, including a bony shelf on the back of the skull.
Avaceratops
Ornithopoda
Ornithopods started out as small,
bipedal running grazers, and grew in
size and numbers until they became
one of the most successful groups of
herbivores in the Cretaceous world,
dominating the North American
landscape. They include one of
the earliest discovered dinosaurs,
Iguanodon, as well as the famous
crested and “duck-billed” hadrosaurs.
Iguanodon
Ornithopoda means “bird feet”; this refers to their characteristic three-toed feet, although
many early forms retained four toes. They also had no armour, a horny beak and a missing hole
in the lower jaw.
The early ornithopods were only about a metre long, but probably very fast. They had stiff tails
to help them balance as they ran on their back legs. Later ornithopods became more adapted
to grazing on all four legs and their spines curved, similar to ground-feeders we see today, such
as the bison. As they became more adapted to eating while bent over, they became semiquadrapedal - still running on two legs but spending most of their time walking or grazing
while on all four legs.
Pachycephalosauria
Pachycephalosauria is the infraorder of “thick-headed”
Marginocephalia dinosaurs. Most lived during the Late
Cretaceous Period, in what is now North America and Asia.
They were all bipedal, herbivourous/omnivorous animals
with thick skulls. Their skulls were up to 9 inches (23 cm)
thick, as in Pachycephalosaurus. By comparison, a human
skull is only ¼ inch (.64 cm) thick. In some fossils, the skull
roof is domed and several inches thick; in others it is flat or
wedge-shaped. The domes were often surrounded by nodes
and/or spikes.Their vertebrae also show strengthening
that would be of use if pachycephalosaurs used their
heads as battering rams, although this is widely debated.
Some example of Pachycephalosaurs include Stygimoloch,
Stegoceras and Wannanosaurus.
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Ceratopsia
Ceratopsia, meaning ‘horned face’, is a group of herbivorous
beaked dinosaurs that lived in what is now North America,
Europe and Asia during the Cretaceous Period, although ancestral
forms lived earlier in the Jurassic Period.
Early members of the ceratopsian group were small bipedal
animals. Later members became very large quadrapeds and
developed elaborate facial horns and frills extending over
the neck. The horns may have been used for defence against
predators such as Tyrannosaurus, and also for interacting with
members of its own species, in ways similar to the behaviour of
present-day deer or antelope.
Ceratopsians are easily recognized by features of the skull. On
the tip of a ceratopsian upper jaw is the rostral bone, a unique
bone found nowhere else in the animal kingdom. Along with
the predentary bone, which forms the tip of the lower jaw in all
ornithischians, the rostral forms a parrot-like beak.
Dracorex
Rubeosaurus
The most famous and largest member of the family was one of its last, the Triceratops, who had
three forward-facing horns: one above each eye and one projecting from its nose.
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