Geology 110; Exam 2
Terms in this set (54)
Who are Thyreophora?
-"shield bearing or carrying" "armor-bearers"
-categorized by a parallel row of special bones called osteoderms
-great with defense
-around for 100 million years on earth with 50 species
What are osteoderms?
"bone skin" that run down the necks, backs, and tails
What two clades was the Thyreophora (Eurypoda) group dominated with?
Stegosaur "Roof" and Ankylosauris "fused"
What is the clade known as Eurypoda?
-Stegosaur and Ankylosaur make up this monophyletic clade
Derived characteristics of Thyreophora include?
-broad process of the juggle
-parallel rows of keeled scutes on the back surface of the body
What are the primitive thyreophorans besides Ankylosauria and Stegosaur?
Scutellosauris, Emausaurus, and Scelidosaurus
Which of the primitive thyreophorans were quadrupedal?
What are some characteristics of the Scelidosaurus?
-Jurassic Period (from England)
-maybe a sister taxon with scutellosauris
what is the most primitive thyreophora?
What are some physical characteristics of the stegosaur?
-osteoderms (spines and plates)
-hindlimbs longer than forelimbs so their profiles sloped strongly toward the ground
-all tails end in long spikes
What are some locomotion characteristics of the stegosaur?
-lived in the late jurassic
-uncommon dinosaurs yet had a global distribution (evolved and migrated within the northern hemisphere)
-not fast because of their hindlimb
-leisurely (6.5-7 km\h)
-took their time to grow
-limited movement to walk at a slow gate
-does not suggest life in the fast lane
What are some eating characteristics of the stegosaur?
-not very effective chewers
-no efficient grinding
-little advantage of the jaw
-the way they digested food and ate is very poorly understood
-irregularly worn teeth (small triangular teeth; grind and chew a lot)
-large gut capacity
-cropping rhamphothecae (a little beak to crop and strip vegetation)
-weak jaw muscles
-soem say they could have gastroliths
What are gastroliths?
stones within the muscular part of the stomach to grind food (they have never been found in Stegosaur remains)
What did Stegosaurs eat?
-head was held near the 1m level
-consuming ground-level plants such as ferns, cycads, and other herbaceous gymnosperms
-if they got on their strong hind legs they could reach 6m vegetation
What are the characteristic of the Stegosaurs brain?
-They were not all that bright
-0.001% of the body
-dinosaur with two brains: a small on in the head and another in pelvis, presumably to pick up the slack left by the first brain
-brains were long, flexed, small, somewhat large olfactory bulbs
What are lifestyle characteristics of the stegosaur?
-relatively uncomplicated range of behaviors
-proposed that their is some sexual dimorphism (number of ribs in the pelvis)
-little is also known about their degree of socialization
-hint of gregarious (kentrosaurus, Tanzania)
-little evidence (no nest, eggs, or hatchlings)
What is sexual dimorphism?
differences between the sexes
What is gregarious?
exhibited herding and other social behaviors (kentrosaurus was interactive. Tanzania)
Spines and plates of the Stegosaurs?
-had at least one row of osteoderms along the dorsal margin of each side of the body
-shapes and patterns of the hot plates are all species specific
-their visual effect is maximized from the side therefore they might have served as a visual display (both for predators and other stegosaurus) -to gain dominance, to tell each other apart, territorial disputes, libido-enhancers during breeding season
-can't tell much because fossil record isn't rich enough
What do we know about the plates of the stegosaurus?
-the plates were grooved for blood vessels and nerves
-thermoregulation (regulate the body temp)
-protection? species recognition? color defense?
Summary of the Stegosaurus
• Quadrapedal herbivores
• Chewers that didn't chew
• Thermoregulators that moved slowly and had small brains
• Display features but not gregarious
What are some physical characteristics of an Ankylosauria?
-art of defense
-encased with bony plates and spines
-spines embedded in skin and interlocked with adjacent plates
-covered from top of head, cheeks, and eyelids
-complex nasal passageways (smell was an important sense for these dinosaurs)
-mid-sized (5m length)
-hind limbs exceeding length of forelimb
-triangular spikes along its length
-head is broader and shorter (than nodesauridae)
-agressive frontal spine based defense
Location of Ankylosauria?
globally distributed but predominantly found in north America and Asia
Social behavior of Ankylosauria?
-only one bone bed known
-animal had solidarity habits or lived in very small groups
-didn't enjoy the company of a large heard
What are the two great clads of the Ankylosauria?
Nodosauridae and Ankylosauridae
What are some physical characteristics of the Nodosauridae?
-muscular shoulder blade
-tall spines at the shoulders
-principally from northern hemisphere
-fought with their head first keeping their spines at the predator
What are some characteristics of an Ankylosaurs eating style?
-very low browsing range
-plants no more than a meter or so above the ground
-diff beak shapes suggest different feeding preferences
-less selective feeding in which plant parts they bite off or pulled from the ground
-teeth are small but not particularly elaborate
-grinding took place
-long flexible tongue
-inset tooth rows
-large and strong jaw bones
-reasonably adapt chewers
-enormous abdominal region
-huge guts (fermentation compartments)
What are some characteristics of an ankylosaurs brains and senses?
-brain power close to the bottom of the range
-enlarged nasal passages
-slowest moving Dinos in their size
-ran no faster than 10km\h
-built for digestion, not speed
defense mechanism of the ankylosaurian?
-powerful tail club
-equipped with spikes along the length
-base of tail is ossified
-swung their tail at opponents legs and feet during battle
Who were the best defended fortresses in the Mesozoic?
nodosaurids and ankylosaurids
Evolution of Thyreophora
-started at gracile, small, bipedal creatures and evolved to larger, quadrupedal Dinos
-Ankylosauria (Ankylosauridae & nodosauridae)
Who were marginocephalia?
"edge head" two major groups of dinosaurs- pachycephalosaurs and ceratopsians
What is the unique characteristic of the Cerapoda?
space between the front and back teeth
What is the unique characteristic of the Marginocephalia?
ridge along the back of the skull
Who were Pachycephalosauria?
-North American forms high domes
-Asian forms flattened thicken skulls
Asian species of pachycephalosauria
- Desert environment
- Articulated skeletons
- Found close to where they lived
Northern American species of pachycephalosauria
- Coastal plain, temperate
- Isolated skull caps (found wear and tear on them)
- Found far from where they lived
What are characteristics of the feeding of pachycephalosauria?
-jaw contained simple peg-like gripping teeth
-sometimes enlarged in canine like fashion
-surrounded by small rhamphotheca
-cheek teeth (shaped with small, triangular crowns w/ coarse serrations, for cutting plants)
-very broad with a large stomach (broke down vegetation with bacterial fermentation)
-enlarges olfactory lobes (better than average sense of smell)
-back half of the brain angled downward (head butt; internal bone structure is very dense
-Fibrous columns perpendicular to outside surface (shock absorber)
Socializing pachycephalosaur style
-social behavior is strongly implied and some degree of sexual dimorphism is expected
-sexual selection (canine like teeth, knobby and spiny osteoderms, spikes, and domes)
What is Sexual selection?
practice of establishing dominance hierarchies, selection within one gender (generally males) rather than among members of a single species
Evolution of Pachycephalosauria
-derived features (most of them cranial)
-most primitive from Asia
-tendency to thicken the roof skull (forms may reflect head butting, then to ritualized display)
-broad girth from narrower girth before
-chewing and fermentation lead to increase in nutrition from plants
physical characteristics of the ceratopsians?
-Great Plains of North America in the late cretaceous (rhino-like)
-Asia (smaller, lighter, non-horned)
-most outstanding dinosaur group
-primitively small bipedal, evolved into powerful quadrepedals
-thick hooves on all toes
-sized of small tanks
-skulls were narrow, hooked beak in front
-frill (size, ornamentation and shape)
characteristics of a ceratopsians mouth?
-blocks of cheek teeth in both upper and lower jaws
-study coronoid process
-inset jaws (evidence of fleshy cheeks)
-narrow hooked beak tip snout (careful selection of food)
-great mass of jaw musculature
-digestive tract was small so didn't rely on fermentation to get plants nutrients
-never browsed high above the ground
What is a dental battery?
grew stacked overlapping together into a single functional slicing block in each jaw; batteries continually refurbished
some say they have four erect legs which would make them faster runners and walkers and some say they have more of a sprawling posture which would make them slower
Ceratopsia horns and frills
-horns were once thought to be used to warn off predators at close quarters but now show they might be used as display, ritualized combat, defense of territories, and establishment of social ordering
-instraspecific identification and intraspecific dominance
Social life of ceratopsians
-lived in large herds
-competed with members of the same species
Brains of the ceratopsians
-brains were not particularly large
-brains less than the size of a similarly sized crocodile
-bigger than the Dinos before them but smaller than the Dinos after them
evolution of ceratopsians
-primitive ones: yin long and psittacosaurus (asian)
-adopted a quadrupedal stance
-migrated from Asia to America
-more derived the more elaborate frills and horns
when you change from when you were born to when you're a grown up; adult
What are sister taxon of ceratopsians?
centrosauriae (protection) and chasmosauridae (display)
Ornithopod; who are they?
-cows, deer, and bison of the mesozoic era
-one of the most numerous, diverse, and longest lived groups in all Dinos
-100 species present count
-lived in quite diverse habitats and in a wide range of climates
-small to large body sizes
-Isolated bones and bonebeds
ornithopods have what two specialized structures?
hip and jaw structure
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