Week 12

Question 1

What characters do the ornithiscians have in common?

Answer 1

• predentary bone
• toothless and rough tip of snout
• narrow bone that crosses the outside of the eye socket (palpebral)
• jaw joint set below upper tooth row
• cheek teeth with low, subtriangular crowns
• at least 5 sacral vertebrae
• ossified tendons above the sacral region
• backward pointing pubis
• internal room for digestion

Question 2

What kind of food did the ornithiscians eat? How can we know this?

Answer 2

Large amounts of tough plant matter

Fossils with flared ribs reveal they would have had lots of room for internal digestion which may have been accommodated for by the backward pointing pubis,

a predentary bone for ripping plant matter,

the toothless rough tip of the snout,

a jaw joint that is positioned below the tooth row for chewing,

and triangular-shaped cheek teeth with low crowns.

Question 3

Were primitive ornithiscians bipedal or quadrupedal?

Answer 3

Primitive ornithiscians were bipedal.

Question 4

The genosauria had well developed, muscular

Answer 4

cheeks.

Question 5

The genosauria were subdivided into groups based on efficiency of chewing, what were the groups?

Answer 5

Thyreophora

Cerapoda: marginocephelia and ornithopods

Question 6

Define thyreophorans

Answer 6

Genasaurs with dermal armour-boney plates embedded in the skin-along the back surface of the body.

Question 7

Define ornithiscia

Answer 7

Genosaurs with a pronounced diasterma.

Question 8

The cerapoda is split into two groups:

Answer 8

marinocephalia

ornithopoda

Question 9

Define marginocephalians

Answer 9

A group united by having a shelf of bone extending over the back of the skull.

Question 10

Define ornithopoda

Answer 10

Iguanadon, “duckbilled dinosaurs”, and other excellent chewers.

Question 11

As we make our way up the cladogram of ornithiscians we get better

Answer 11

chewers.

Question 12

Why doesn’t a beak fossilize well?

Answer 12

The beak would be made of keratin, the same stuff that makes up hair or finger nails, keratin does not fossilize well.

Question 13

Why is the term “duckbilled dinosaur” misleading?

Answer 13

The hadrosaur’s beak is actually massively downturned and unlike a duck’s. It would have been used for gripping, ripping, and breaking vegetation rather than anything duck like.

Question 14

What character do thyreophorans have in common?

Answer 14

They are shield bearers. They have spikey bones in common.

Question 15

Thyreophornas began as small and ____ but quickly evolved into larger, ____ dinosaurs.

Answer 15

Thyreophorans began as small and bipedal but quickly evolved into larger, quadrupedal dinosaurs.

Question 16

Osteoderms

Answer 16

Armour is not attached to the skeleton, instead, it is embedded into the skin.

Question 17

How were the thyreophora as chewers?

Answer 17

Okay

• jaw joint positioned a little below tooth row
• teeth slightly inset
• cropped and stripped foliage with rhamphotheca (beak)
• spaced out and pointy teeth
• no large coronoid process

Question 18

The thyreophora separate into two clades…

Answer 18

the stegosauria (not armoured all over body) and the ankylosauria (full back is entirely covered, like a turtle)

Question 19

Stegosaurs fossil location

Answer 19

• few fossils
• global distribution
• limited fossils means limited knowledge
• none in Alberta (none for you gretchen wieners), because our rocks are cretaceous and the stegosaurs were alive around the Jurassic to early cretaceous periods.

Question 20

How do we know stegosaurs were slow walkers?

Answer 20

Despite being quadrupedal, they had long hind limbs and short forelimbs.

Question 21

Why do most stegosaurs have at least one row of osteoderms on each side of their back? And how can we know?

Answer 21

Osteoderms were likely for defence, we know this from finding broken and healed spikes, which heal in a deformed way.

Question 22

Stegosaurs have plates that are thin and visually impactful only from the side, what might they have been for?

Answer 22

Plates were different shapes and sizes, if they were for defence they should have been all the same size and shape. They could have been for

• identifying different species
• identifying different sexes
• thermoregulation: plates have vessels, the arrangement would help dissipate heat (this was proved wrong in 2005)

Question 23

Where/when did we find Ankylosauria?

Answer 23

Canada, China, and Mongolia

Early Jurassic-late cretaceous

Question 24

The Ankylosaurs were mid-sized and encased in

Answer 24

armour.

Question 25

Two main groups of the Ankylosauria

Answer 25

1. Ankylosauridae: tail club and no shoulder spikes

2. Nodosauridae: no tail club and big shoulder spikes

Question 26

Ankylosauridae

Answer 26

• shorter, broader head/beak
• large triangular plates attached to rear corners of skull
• well-armoured but fewer tail spikes along body
• tail with massive boney club

Question 27

Nodosauridae

Answer 27

• longer narrow snouts/beak
• well-muscled shoulders
• tall spikes at the shoulder
• no tail club

Question 28

Ankylosaurs were built for ____, not ____.

Answer 28

Ankylosaurs were built for digestion, not speed.

Question 29

While the ____ beak of the nodosauridae suggests more selective feeding methods, the ____ beak of the ankylosauridae suggests they were less selective.

Answer 29

While the narrow beak of the nodosauridae suggests more selective feeding methods, the broader beak of the ankylosauridae suggests they were less selective.

Question 30

The anlylosauridae had short front arms and long back legs, they were slow moving and __pedal.

Answer 30

The ankylosauridae were slow moving and quadrupdeal.

Question 31

Like stegosaurs, ankylosaurs were not very smart but they were good at

Answer 31

smelling. They had an enlarge olfactory lobe/convoluted nasal passages.

Question 32

Nodosauridae: ___first defence
Ankylosauridae: ___first defence

Answer 32

Nodosauridae: head first defence
Ankylosauridae: tail first defence