Page 46 - Dinosaur (DK Eyewitness Books)

Artery brings hot blood from the interior of the overheated Vein takes cooled
Plates and sails animal into the plate to lose heat to the cool air blood down into
the body

Iȯ ȵȩȦ ȭȢȵȦ ȫȶȳȢȴȴȪȤ ȸȰȰȥȭȢȯȥȴ, massive Stegosaurus
with its distinctive rows of plates on its back must have
been quite a sight! Features such as plates, sails, and
humps ran down the backs of many other dinosaurs.
We know this from rows of tall bony spines, blades,
and slabs found on the fossil backbones of these
animals. Strange arrays of these structures were
present in stegosaurs and some unusual sauropods,
ornithopods, and theropods. They were covered with
HEATED DEBATE
either horny sheaths, skin, or fatty tissue. But scientists Some scientists believe that Stegosaurus’s plates may have
still argue about the exact purpose been covered in skin. The blood vessels below the skin
of these structures. would adjust the body temperature by absorbing heat if
Sail or ridge the plates faced the Sun, and shedding heat if not. But
others believe that the plates were covered in dead tissue
like horn, which contains no blood vessels, and so the
plates couldn’t have functioned as heat exchangers.
Slender
snout
Dorsal plate
(plate on back)

SAIL BACK
Spinosaurus (“spine lizard”) was an immense theropod
with a long snout and may have fed on fish as well as
other dinosaurs. Neural spines (spiny pieces of bone
rising from the vertebrae) up to 6 ft (1.8 m) long jutted
from its backbone like sword blades. These spines
formed a bony scaffolding that held up a skin sail
or fatty ridge. Spinosaurus perhaps used it as
an eye-catching display to attract mates, as
a food store for body fat, as a radiator to
cool its body, or as a heat shield.

Rib
Cervical plate
(neck plate)
Small skull

PLATED DINOSAUR
Stegosaurus (“roof lizard”) was the largest of all the
plated dinosaurs, or stegosaurs. These were four-legged Long hind limb
ornithischians with a tiny head and toothless beak. Most
kinds of stegosaur sported a double row of tall spikes,
but alternating plates ridged Stegosaurus’s neck, back, and
tail. These spikes and plates helped members of different Short forelimb
species of stegosaur to recognize others of their own
kind. Stegosaurus was about 30 ft (9 m) long, and the
plates made it look even bigger, probably forcing even
larger theropods to think twice before attacking it.