Midterm 2 Stegosaurs and Ankylosaurs

Question 1

Match the following dinosaurs with their name definition:

Stegosaurs
Ankylosaurs
Plated Dinosaurs
Armored dinosaurs

Answer 1

Stegosaurs = Plated dinosaurs
Ankylosaurs = Armored dinosaurs

Question 2

What does Thyreophora mean?

Answer 2

Shield bearers

Question 3

True or false: Thyreophorans were ornithischian.

Answer 3

True

Question 4

True or False: Thyreophorans were primarily bipedal.

Answer 4

FALSE. Primarily quadrupedal

Question 5

What is the key evolutionary novelty of thyreophorans?

Answer 5

The presence of one or more rows of armor plates in the skin above or alongside the vertebral column

Question 6

What are some of the characteristics of primitive ornithischian dinosaurs?

Answer 6

small skull and jaws, cheek teeth positioned on the jaw margins, short neck, hind limbs only slightly longer than forelimbs, long tail

Question 7

Examples of primitive ornithischian thyreophorans

Answer 7

Scutellosaurus and Scelidosaurus

Question 8

True or False: Stegosaurs and Ankylosaurs are the only clades in the group thyreophora.

Answer 8

False. There were also primitive thyreophorans

Question 9

Were stegosaurs quadrupedal?

Answer 9

Yes

Question 10

What are the evolutionary novelties of stegosaurs?

Answer 10

Small heads, short and massive forelimbs, long, columnar hind limbs, short stout feet with hooves on their toes, vertical bony plates and spines along the neck, back, and tail.

Question 11

Where were the most primitive Stegosaur skeletons found? And what were they?

Answer 11

CHINA
Huayangosaurus
Gigantspinosaurus

Question 12

Which two stegosaurs are the only ones left out of the family Stegosauridae?

Answer 12

Gigantspinosaurus and Huayangosaurus

Question 13

How large was the brain of a Stegosaurus?

Answer 13

70-80 grams.

Question 14

Why don’t we know if Stegosaurus had one row of plates or two?

Answer 14

Because the plates weren’t connected to the bone and often fell out/got separated before fossilization occurred.

We haven’t found a complete skeleton to show us. The skeletons we’ve found have created tension and diverse opinions.

Question 15

What is an endocast?

Answer 15

Short for endocranial cast. We make a replica of the inside of a dinosaur’s braincase. Usually use latex to form the cast because it reforms shape once it’s pulled out. We can see the overall shape and size of the brain cavity.

Question 16

True or False: A stegosaurus’ brain is smaller than a walnut or a kitten’s brain.

Answer 16

False. It’s a little bigger lol

Question 17

What covered the plates of stegosaurus?

Answer 17

Grooves and canals for blood vessels. They weren’t solid plates of bone.

Question 18

What was the main purpose of stegosaurus plates?

Answer 18

They acted as radiators and solar panels to help control body temperature.

Question 19

When were the stegosaurs most diverse?

Answer 19

Late Jurassic

Question 20

Were there stegosaurs in the Cretaceous?

Answer 20

Yes, but very few. They were past their prime and declining. They were entirely extinct by the beginning of the late Cretaceous

Question 21

What does Ankylosaur mean?

Answer 21

fused lizard, due to the rod of fused vertebrae in their backs

Question 22

Evolutionary novelties of ankylosaurs

Answer 22

Robust limbs, short stout feet with hooves, forelimbs were 2/3 the length of hind limbs, low skulls, closure of the fenestrae in front of the eyes and skull, added dermal bones on the skull, extensive body armor and modifications of the rib cage and hip girdle

Question 23

What is a low skull

Answer 23

the width between the eyes exceeds the height of the skull

Question 24

What time period were ankylosaurs most present?

Answer 24

Cretaceous

Question 25

Which two families make up the majority of ankylosaurs?

Answer 25

Nodosauridae and Ankylosauridae

Question 26

Evolutionary novelties of nodosaurid ankylosaurs

Answer 26

Narrow skulls that lacked armor and horns at the posterior corners, the presence of spines in the armor, lack of ossified tail tendons or tail club

Question 27

Examples of nodosaurids

Answer 27

Edmontonia, Nodosaurus, Sauropelta, Panoplosaurus

Question 28

Evolutionary Novelties of ankylosaurids

Answer 28

Wide armored heads (as wide as they were long), long triangular horns at posterior corners, lateral temporal fenestra completely covered with bony armor, complex nasal passage, few or no spines present in body armor, club on the tail, tail vertebrae braced by ossified tendons

Question 29

What shape is the ankylosaurs nasal passage?

Answer 29

S shaped

Question 30

What is one of the best known ankylosaurs (other than ankylosaurus)?

Answer 30

Euoplocephalus

Question 31

What military weapon is an ankylosaur compared to?

Answer 31

Tank

Question 32

Was the ankylosaur fast?

Answer 32

No, it was designed for slow, powerful walking

Question 33

What defense mechanism did the ankylosaur use when under attack?

Answer 33

It would squat down so that it couldn't get flipped over, and nothing could bite the armor. Using their tail to fight off attackers

Question 34

When were Ankylosaurids at their greatest level of diversity?

Answer 34

Late cretaceous

Question 35

When were nodosaurids the most diverse?

Answer 35

Early to middle cretaceous

Question 36

Know the two thyreophoran clades and the evolutionary novelty that distinguishes thyreophorans from other dinosaurs.

Answer 36

Armor Dermal ossicles, stegosauria, ankylosauria

Question 37

Know the evolutionary novelties of stegosaurs and explain how Huayangosaurus exemplifies them

Answer 37

Long, narrow skull - Standard ornithischian beaks - Rows of large spikes or plates along back - Stegosaurus: Late Jurassic. Plates and spikes. Largest of stegosaurids

Question 38

Huayanosaurus

Answer 38

Middle Jurassic - most primitive stegosaurid - Combination of spikes and plates.

Question 39

Explain the nature of dermal ossicles including the physical description, what covered them, how they were attached to the body, and what explains the presence of grooves and tubes.

Answer 39

Located within the skin, covered with keratinous sheath, in life they were covered by blood vessels Grooves created by the blood vessels

Question 40

Explain what paleontologists believe were the arrangement and function of the plates of Stegosaurus

Answer 40

Arrangement→ two separate rows (just staggered) Display (main and original hypothesis) and protection

Question 41

Know how the evolution of stegosaurs differs from that of ankylosaurs in terms of timing, distribution and amount of morphological change.

Answer 41

They evolved at around the same time but ankylosaurs were around for longer Skull shape