Final Exam 2 Flashcards
(44 cards)
What are the two main groups of Ankylosaurs?
Ankylosauridae
Nodosauridae
Ornithischia - Genosauria - Thyreophora - Eurypoda - Ankylosauria
Ankylosauridae
A sub group of Ankylosauria
Ornithischa - Genosauria - Thyreophora - Euryopoda - Ankylosauria
Characters that distinguish this group group from Nodosauridae:
Shorter broader head/beak
Large triangle plates attached to the rear corners of the skull
Well-armoured, but not many taller spikes along the body
Tail with a massive, bony club, sometimes paired with tail spikes or knobs (tail first defense)
Broader beak suggests that they were less selective in their diet than Nodosauridae
Nodosauridae
A family in the Ankylosauria group
Ornithischia - Genosauria (has cheeks) - Thyreophora - Euryopoda - Ankylosauria - Nodosauridae
Features that distinguish this group from Anklosauridae
- Longer, narrow snouts/beak
- Well-muscled shoulders
- Tall spikes at the shoulders
- No tail club
Their narrow beak suggests selective feeding (plucking fruits and foliage)
Head-first defense
Brain to body size ratio of Ankylosauria?
They had a small brain to body size ratio, like stegosaurs.
They were not terribly smart, but they were good at smeller (enlarged olfactory lobe/convoluted nasal passage)
Incredible slow- built for digestion, not speed
Tail club of Ankylosauridae
Paired masses of bones, most dense around the exterior
Base of the tail was flexible, but rear was stiffened with interlocking vertebrae and ossified tendons. Served as muscle attachment sites for a powerful swing.
Cerapoda
Genosaurs with cheeks AND a pronounced diastema
Ornithischia - Genosauria - Cerapoda
Major groups within Cerapoda include the Ornithopoda and the Marginocephalia
Marginocephalia
Edge - head
Two main groups = Ceratopsia and Pachycephalosauria
Have a ridge or shelf of bone that runs across the back of the skull.
the size is highly variable, obscures view of other bones at the back
Pachycephalosauria
The dome heads
Thick-head-lizard
They are BIPEDAL ornithishians with thickened skull roofs
Ornithischia – Genosauria – Cerapoda –> Marginocephalia –> Pachycephalosauria
They are only found in the northern hemisphere
Geographic distribution of Pachycephalosauria
Only found in the Northern Hemisphere
An earlier population was found in Asia and some think they travelled over to North America across a land bridge called Beringia
Differences between North American and Asian Pachycephalosauria forms?
NA - tend to have high domes
Asian - tend to have both high domes and flattened, thickened skulls.
Did Pachycephalosaurs have big brains?
Nope, smaller brains like other Ornithischians.
They had particularly large olfactory lobes
Brain was tilted down towards the back of the skull
The bones at the back of the skull are also rotated downwards. The bigger the bone, more downwards facing there was. Potentially for male to male competition.
Ceratopsians
Horn face (triceratops!)
Ornithischia - Genosauria - Cerapoda –Marginocephalia - Ceratopsia
A subgroup of marginocephalia
How to distinguish between Pachycephalosauria and Ceratopsia?
Ceratopsians have a well-developed frill, nasal horns, and more derived forms are quadrupedal (they were bigger)
ALL HAVE A ROSTAL BONE - NO OTHER GROUPS HAVE THIS BONE (tip of the upper jaw)
All ceratopsians have:
A rostral bone
Narrow skulls with thick beaks
A skull that flares in the cheek regions (jugal horns)
A bony shelf of variable size off the back of the head (FRILL)
Thick hooves on all toes
.. they DIDNT all have horns and they WEREN’T all quadrupedal
they did have lots of ornamentation however - the transition towards larger more ornamented frills suggests that display and competition were important
Ceratopsian geographical distribution
Only found in the Northern Hemisphere (alberta!)
Asia and North America
Psittacosaurus, Yinlong, and Archaeceratops, Protoceratops
These ones were small, bipedal, and without horns
Smaller ones from Asian
NA ones were mainly large and quadrupedal
A comparison suggests that early on, a neoprimitive ceratopsian similar to Protoceratops migrated to the new world likely via the Bering Straits (land briefly exposed) –> led to diff evolutionary trajectories
Did all Ceratopsians have facial horns
Most had facial horns, BUT primitive forms lacked them
Did all Ceratopsians have facial horns
Most had facial horns, BUT primitive forms lacked them
What does a horn consist of?
Bony core and a sheath of keratin
appear shorter than actual in the fossil record because only the core gets preserved in the fossil record
horns are NOT shed
What were the groups of Certopsidae that were split into in NA?
Centrosauridae, Chasmosauridae
Chasmosaurines
Ceratopsians found in NA
Typically had long frills, and long horns over the orbitals and a short horn over the nasals (BUT this is a primitive conditions also observed in basal centrosaurines)
The frill can widely vary in shape
Elongate snout
TRICERATOPS
tHE Centrosaurines
A sub group of Ceratopsidae that resided in NA
Typically had relatively Short frills and typically short horns over the orbitals
Typically have more ornamented frills, shorter snout, longer nasal bones
EX Centrosaurus
PURPOSE of horns?
originally thought to be defense weapons against predators but other things could be happening as well (as stated by more recent interpretations
Might have more to do with display, ritualized combat, defense of land, maturity, species identification
Intraspecies, interspecies
Deter predators, attract mates
Centrosaurines (Centrosaurus) vs Chasmosaurines (triceratops) in behaviour
Centrosaurus
- fewer injuries to the skull so they may have been flankers (evidence of broken ribs)
- May have locked horns in combat, but tried to avoid eyes, ears, snout
Triceratops
- tend to have more injuries around the face than Centrosaurus- may have participated in more face to face combat
INTRASPECIES combat is hypothesized to be more likely given the distribution of wounds. Healed wounds are common in ceratopsian bones - suggests intraspecies competition (damge inflicted is not the damage inflicted by a predator, for example)
Herding behaviour is Ceratopsians?
Bone beds found with Ceratopsians provide good evidence of herding behaviour –> many dinos of all ages all died together at the same time
Which group is referred to as the ‘cattle of the cretaceous’
Ornithopoda!
Iguanodon is an Ornithopod
We have got a great fossil record for them because they were common, widespread, and lived for a long time
