Page 48 - Dinosaur (DK Eyewitness Books)

Arms and hands
Humerus
(upper arm bone)

DȪȯȰȴȢȶȳȴp ȢȳȮȴ Ȣȯȥ ȩȢȯȥȴ evolved in amazingly
ARMED AND DANGEROUS
Deinocheirus (“terrible hand”) had the varied ways. Early dinosaurs had flexible arms with
longest arms of any known theropod.
Each arm was longer than a man and grasping hands that seized prey. The first theropods
ended in a three-fingered hand with had five fingers on each hand, but most later kinds
large, curved claws. Little else is known
about this monster from Late Cretaceous had only three—during evolution the thumb and
Mongolia. Scientists suspect it was a little finger had gradually shrunk and vanished. Some
giant ostrichlike dinosaur with arms
that hooked leafy branches or fruits theropods had long, gangly arms, but other larger
down to its mouth.
theropods, such as Tyrannosaurus, managed with
tiny, two-fingered hands and absurdly short arms.
The forelimbs of some plant-eaters developed in other
ways. Iguanodon’s hands could be put to many different
uses, such as walking or standing, grasping leaves, or
stabbing an attacker. Sauropods’ arms and hands formed
pillarlike, weight-bearing props for their big, heavy bodies.

Phalanx
(finger
bone)
Ungual Upper arm
(claw)
Third finger ODD ONE OUT
Maniraptorans formed a group of theropods that
were related to birds and had long arms and hands.
Therizinosaurus (“scythe lizard”) was a strange,
plant-eating maniraptoran. As heavy as an
elephant, this Late Cretaceous oddity
was slow and pot-bellied, and yet
it had a maniraptoran’s distinctive
Fourth finger forelimbs, with special wrist and
shoulder joints that enabled the
animal to fold its arms and
hands close to its body.

Second finger
Flexible
fifth finger

Thumb spike

Hand bone $1 $//ʜ385326( +$1'
Like a Swiss Army knife, each part of
Iguanodon’s hand was shaped for a different
task. The thumb spike served as a weapon for
stabbing an attacker. The three middle fingers
ended in tiny hooves and bore the body weight
when Iguanodon walked on all fours. The fifth
finger was flexible, and could curl inward
to pull leafy twigs to the dinosaur’s mouth.

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