Page 102 - Ultimate Visual Dictionary (DK)

PREHISTORIC EAR TH
Marginocephalians 1 Thick, high-
domed cranium
Supraorbital ridge
MARGINOCEPHALIA Orbit
(“margined heads”) were
Naris
a group of bipedal and quadrupedal
Mandible
ornithischian dinosaurs with a narrow Neural spine
shelf or deep, bony frill at the back of
HEAD-BUTTING PRENOCEPHALES
the skull. Marginocephalians were
probably descended from the same ancestor as the ornithopods and
lived in what are now North America, Africa, Asia, and Europe during
the Cretaceous period (145–65 million years ago). They were divided Cervical
into two groups: Pachycephalosauria (“thick -headed lizards”), such rib
Humerus
as Pachycephalosaurus and Stegoceras, and Ceratopsia (“horned
faces”), such as Triceratops and Psittacosaurus. The thick skulls of Ulna
Pachycephalosauria may have protected their brains during possible Radius Pubis
head-butting contests fought to win territory and mates; their hips Wrist joint
and spines may also have been strengthened to withstand the shock. Metacarpal
The bony frill of Ceratopsia would have added to their frightening
Phalanx
appearance when charging; the neck was strengthened for impact Ilium
and to support the huge head, with its snipping beak and powerful Ischium
slicing toothed jaws. A charging ceratopsian would have been a
Metatarsals
formidable opponent for even the largest predators. Ceratopsians
Phalanges
were among the most abundant herbivorous dinosaurs of the
Late Cretaceous period (97–65 million years ago).
EXAMPLES OF SKULLS OF PACHYCEPHALOSAURS
Thickened dome
Thickened dome
of cranium
Thickened dome Orbit of cranium
Orbit of cranium
Bony spike
Maxilla
Bony
ridge
Bony
Maxilla nodule
Tooth Maxilla Bony
Mandible
SKULL AND MANDIBLE Orbit nodule
OF STEGOCERAS SKULL OF PRENOCEPHALE SKULL OF PACHYCEPHALOSAURUS
EXTERNAL FEATURES OF Bony nodule Thickened dome
PACHYCEPHALOSAURUS Scaly skin of cranium
Domed head
Eye Bony nodule
Bony spike
Neck
Snout
Tail Knee Forelimb
Hind limb Finger
Buccal cavity
Ankle Hand Brain cavity
Claw SECTION THROUGH SKULL OF
Foot PACHYCEPHALOSAURUS
Toe

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