Lecture 13 Flashcards
What group did the marginocephalians belong to?
Cerapoda
What are the two main groups of margincephalians?
Pachycephalosauria
Ceratopsia
What were the Pachycephalosauria commonly referred to? were they bipedal or quadrapedal, what kind of skull roofs did they have?
The dome-heads, they were bipedal with thickened skull roofs
What were the pachycephalosauria thickened skull roofs good for?
Flank butting
Where are the pachycephalosauria found and when?
Only in northern hemisphere (asia and north america), mostly late cretaceous but some early cretaceous forms in asia
What are the differences between domes in north american versus asian forms? What recent studies dispute this?
North American forms tend to
have high domes
Asian forms tend to have both high domes and flattened, thickened skulls.
- recent studies show
that at least some of the flattened
skulls may just be juvenile forms
of fully adult, dome-headed
pachycephalosaurs
What were the pachycephalosaurs brains characteristics? (3)
Had enlarged olfactory lobes, the brain was tilted down towards the back of the skull, the bones at the back of the skull were rotated downwards
What evidence lead people to believe that the pachycephalosaurs head butted?
- The structure of the dome is
very dense - Bone fibres are oriented
perpendicular (at right angles)
to the external surface of the
dome - This may help distribute
forces around the brain like a
built-in helmet.
How was it tested that the dome of pachycephalosaurs reacted to head butting?
A plastic model of a small pachycephalosaur was built and stress lines mimicked the orientation of the columnar bone, reinforcing idea that the fibrous columns evolved to resist head butting
How does the rotated bones at the back of the pachycephalosaurs skull serve as evidence for head butting?
rotation of bones at the back of
the skull minimizes the potential for
violent rotation or dislocation of the head
In the spine of pachycephalosaurs, what features made it rigid and limited rotation?
Further down the spine, the vertebrae are uniquely linked with a tongue and groove articulation that made the spine very rigid and limited lateral rotation
Where are injuries concentrate din pachycephalosaurs?
concentrated near the apex, due to it being wear direct head on collison occur
DO flat headed pachycephalosaurs have injuries?
no
How many percent of pachycephalosaurs skulls have injuries representing infections from trauma?
22%
Is there a difference in rate of injurt amongst diff genera of pachycephalosaurs?
no
How does stygimoloch support evidence that head-butting is only adult behaviour of pachycephalosaurs?
Because it’s skull cap contains blood vessels, so it prob wouldn’t head but- but if it’s juvenile then maybe juveniles didn’t head but but adults did
What features did pachycephalosaurs have for visual display? (4)
- Dome
- Canine-like teeth (threat display/biting combat with rivals)
- Knobby/spiny osteoderms on the snout/side of the face and
marginocephalian shelf - Likely, the male with the best looking domes, knobs and spikes got to
perpetuate the family line (but he perpetually had to defend that position)
What kind of fossils for pachycephalosaurs can we find in north america? Asia?
North america: Mainly Water-worn skull caps, isolated bones
Asia: Complete skulls and articulated
skeletons.
What can we say about the transport distances of pachycephalosaurs after looking at their anatomical fidelity of fossils in north america versus asia? ON TEST
North America:
* Water-worn skull caps,
isolated bones
* Lots of transport before burial
* Lived in/near the mountains
Asia:
* Complete skulls and articulated
skeletons.
* Buried close to where they died
* Lived in a Sahara-desert with
ephemeral streams.
All ceratopsians have what features? (5)
- a rostral bone
- Narrow skulls with a hooked beak
- the jugal horns
- a frill
-thick hooves on all toes
Did all ceratopsians have horns? Were they all quadrapedal?
nope and nope
Where were ceratopsia found?
In northern hemisphere
What did the horns of certaposia consist of? What does that mean for the preservation of ceratopsia?
- The horns consist of a bony core
with a sheath of keratin, but only the
core gets preserved. - Therefore, the horn was much
larger than what is preserved in
fossils
Did primitive forms of ceratopsia have facial horns?
No
The primitive forms of ceratopsia were what? What did their transtion to ceratopsidae (larger qudrapedal more ornamented dinos suggest)?
small, bipedal, and without horns, the transition suggests that display and competition were important
Where do we find primitive forms of ceratopsia? Where do we find ceratopsidae?
asia, north america
Which ceratopsia migrated to north america first and how?
a ceratopsia similar to proceratops migrated to to the new world through the bering straits
Once in northamerica, the clade ceratopsiadae split into what?
chasmosaurines and the centrosaurines
What’s the difference between the centrosaurines and the chasmosaurines?
the chasmosaurines:
had long frills, long horns over the orbit and a short horn over the nasal, elongated snouts, and variation in frill
The centrosaurines:
Had typically short frills, typically short horns over the orbitals, and more ornamented frills, big horn near nose
Horns were used for what purposes in ceratopsia? (5)
- Display
- ritualized combat
- defense of territories
- maturity
- species identification
Centrosaurs competed in what type of combat?
Have few injuries to skull, focused on flank attacks- avoided eyes, ears and snout
Chasmosaurines competed in what type of combat?
face to face combat (had mor einjuries around face)
What evidence do we have the ceratopsians were herders and competed with each other?
Bone beds with healed wounds
