Lecture 12 Flashcards
What are the shared characters of the Thyreophora?
they have parallel rows of bones that are embedded in the skin called osteoderms
How did thyreophorans begin? What did they evolve into?
small and bipedal, evolved into larger quadrapedal dinosaurs
What is the advantage of having armor like the thyrophorans?
protection
What other dinosaurs besides the thyreophorans had armour? How was it different?
Amaragasaurus, but it was extensions of the vertebrate called neural spines
Where are the plates in stegosaurs attached too?
They are embedded in the skin and not attached to the spine
What is dermal armor and in which dinosaur lineage do they develop?
In another dinosaur lineage- the saurapods- are osteoderms
What kind of chewers were thyreophora? Why?
They were okay chewers, they could crop and strip foliage with their rhampotheca’s (beaks) and had an inset tooth row, but the teeth were small, simple, triangular, and couldnt grind well, their coronoid process is small
What sis thyreophora eat?
ferns and cycads less than a metre off the ground
What were the two great clades of the thyreophora?
stegosauria
ankylosauria
Are there many fossils available for stegosauria?
No, juvenile fossils are rare, have no nests, eggshells or hatchling material, fossils are found globally
Why don’t we find fossils of stegosaurus in alberta?
Because the sediment rock we have in laberta is late cretacous, so the rocks to preserve the stegosaurus we don’t have
What were the characteristics of stegosauria? (2)
Had plates organized in rows down the neck, back, and tail.
Were 3-9 m long and 300-1500 kg
What was the issue with stegosaurs locomotion? What was the solution to this?
They had long hindlimbs which covered more distance per step than short forelimbs, the centre of mass was towards their head.
They either had to walk really slowly or lift the forelimbs up when running.
Did stegosaurs run? What was their max speed?
No, because their weight was distributed to their heads so they couldn’t run bipedally, so their max speed was 6.5-7 km/h
Was the stegosaurus smart?
no 1/1000 ratio of brain to body size
What were the stegosarias brains shaped like?
Had long tiny brains with a slightly enlarged olfactory lobe for smelling
Why did the stegosaurs have osteoderms in the form of spikes on their tails?
Defense, the splayed spikes (called thagomizers) were likely slashed from side to side
Why did stegosaurs have osteoderms in the form of plates?
Not really for defense, made them look scarier, identified them as diff species and sexes, and may have helped with thermoregulation
How did the plates of stegosaurs help with thermoregulation?
a study showed that the natural arrangement of plates in symmetrical pairs would dissipate heat, shaky as other studies showed they don;t have effect and grooves were used to supply nutrients
Why did juvenile stegosaurs not have plates or spikes?
because they had to devote more energy into growing
What sexual dimorphism existed in stegosaurs?
- Two distinct sizes and shapes of
plates - Equal numbers of both sizes
- No intermediate forms
What are the characteristics of ankylosaurs? (4 characteristics)
- Encased in an “armor” of osteoderms
- Wide girth so had a large gut
- Longer hindlimbs than forelimbs, but quadrupedal
- Mid sized (usually < 5 m, but up to 9 m), ~3500 kg (2 hippos!)
When did anklyosaurs appear?
late cretaceous
What are the two main groups of ankylosauria?
Ankylosauridae and nodosauridae
What are the characteristics of ankylosauridae and nodosauridae?
- Ankylosauridae:
* Shorter, broader head/beak
* Large, triangular plates attached to
rear corners of skull
* Well-armored, but fewer tall spikes
along body.
* Tail with a massive, bony club,
sometimes with paired tail spikes
or knobs - Nodosauridae:
* Longer, narrow snouts/beak
* Well-muscled shoulders
* Tall spikes at the shoulder
* No tail club
What is the differences in beaks of both Ankylosauria and Nodosauridae? What does this suggest?
- Narrow beak of nodosaurids
suggests selective feeding
(plucking fruits and foliage) - Broad beak of ankylosaurids
suggest that they were less
selective.
Were ankylosaurs smart?
no, had a small ratio of brain to body size
Were ankylosaurs good at smelling?
yes, had enlarged olfactory lobes/convoluted nasal passages
Were ankylosaurs slow moving? What was their max running speed? walking speed?
yes, max running speed was 10 km/h, walking was 3 km/h
What kind of defense did Nodosaurids have?
head-first defense- had no club
What kind of defense did ankylosaurids have?
tail-first defense, Base of tail was flexible, but rear became hard with
interlocking vertebrae and ossified tendons. Served as muscle attachment sites for a powerful swing.
