Lecture 21

Question 1

• Primitive thyreophorans

Answer 1

• Scutellosaurus
• Scelidosaurus

Question 2

Stegosaurs

Answer 2

Kentrosaurus
* Stegosaurus

Question 3

Thyreophora key evolutionary novelty:

Answer 3

the presence of one or more
rows of osteoderms above or
alongside the vertebral column.

Question 4

Osteoderms have bony external shield-like plates overlain with a keratin sheath called

Answer 4

scutes

Question 5

Primitive Thyreophora tails are

Answer 5

especially long as a
counterbalance on the posterior end to all
that added weight on the anterior end.

Question 6

The most basal member known from the primitive thyreophorans is

Answer 6

Scutellosaurus

Scutellosaurus (“little-shielded lizard”) that lived in what is now
Arizona during the Early Jurassic, 196 Ma.

Question 7

The primitive Thyreophora are represented by

Answer 7

rare Early Jurassic
fossils from North America and Europe.

Question 8

primitive thyreophoran that’s name means (“limb lizard”)

Answer 8

Scelidosaurus

it lived in England during the
Early Jurassic, around 191 Ma.
It was discovered in the 1850’s and
named by Richard Owen. The
initial find was a limb bone, but
then most of the skeleton was
located. Scelidosaurus was the
first find of a dinosaur found
preserved as mostly complete.

Question 9

“plated lizards”

Answer 9

Stegosaurs: medium to large quadrupedal
dinosaurs with the following key evolutionary novelty:
vertical bony plates and spikes arranged in single or double rows
along the neck, back, and tail.

Other characteristics:
small head
short, massive forelimbs
small, ridged triangularshaped teeth

Question 10

Stegosaurids

Answer 10

advanced stegosaurs
with flatter (wider) skulls and much
longer hind limbs than forelimbs.

Question 11

A very close relative to the North American Stegosaurus is

Answer 11

Kentrosaurus (“sharp point lizard”), found within the Late
Jurassic Tendaguru Formation of Tanzania.

Two paired rows of small plates
cover the neck and back, merging
into tall spikes above the hips and
tail. Also note the robust shoulder
girdle and huge shoulder spikes.

Question 12

“roof lizard”

Answer 12

The Late Jurassic Stegosaurus from the western U. S. had two rows of thin offset plates running mid-line
from neck to tail, and two pairs of spikes at the tail tip (four in total)

Question 13

Stegosaurus lived in the Late Jurassic
during North America’s:

Answer 13

‘Golden Age
of Dinosaurs’. It lived alongside
these well-known dinosaurs:
Apatosaurus
Diplodocus
Camarasaurus
Brachiosaurus
Allosaurus
Ceratosaurus

Question 14

Stegosaurid Defense

Answer 14

Stegosaurids used an erect limb posture for locomotion, while using
a sprawled forelimb pose for defensive behavior.

The sprawled pose would allow them to tolerate the large lateral forces used
in swinging the spiked tail as a clubbing device

Question 15

Stegosaurs Suffer Extinction

Answer 15

Happened at the start of the
Late Cretaceous (~100 Ma). for being picky eaters, they ate plants called sycads and as they became less abundant so did the stegosaurs.