as teeth grind together, enamel is sharpened; creates 'self sharpening blade'
expanded nasal openings: who? function?
iguanodontids and hadrosaurs
making sounds/visual display?
dental batteries: who? function?
iguanodontids and hadrosaurs
numerous teeth stacked on top of one another; get ground down quickly but new teeth are constantly growing
thumb spike: who? function?
used in defense?
duckbills: who? function?
highly modified upper anterior mouth so that it looks like a flattened bill
margin of bone at back of skull: who? function?
thickened (domed) skulls: who? function?
what do we think the bizarre enlarged nasal bones of hadrosaurs were for?
making mating noises or visual display
what's the evidence for parental care in hardosaurs?
nests, skeletons of young hadrosuards - not hatchlings
why did pachycephalosaurs have such thick skulls?
for head butting
novelty: rostral bone
psittacosaurs, "protoceratopsids", ceratopsids
sister group of ceratopsids and psittacosaurs, part of the ceratopsian clade
novelties: neck vertebrae lengthened, semi-opposable thumb
sauropodomorphs and therapods
novelties: claw on thumb, extremely long neck, small heads, peg-like teeth
"prosauropods" and sauropods
smaller bodied, hind limb dominated, widespread
novelties: stumpy hands and feet, short distal limb bones, nostrils migrate to top of skull
diplodocids, brachiosaurs, camarasaurs
rostral bone: who? function?
beak like bone, covered in keratinous layer, forms a beak like a bird
frill: who? function?
"protoceratopsids" and ceratopsids
large margin at back of skull; visual display; attachment for jaw muscles
long neck: who? function?
carried to extreme in sauropodomorphs; each individual vertebra elongated, no new vertebrae added
semi-opposable thumb: who? function?
thumb offset from rest of hand, for grabbing?
thumb claw: who? function?
large size: who? function?
quadrupedal: who? function?
horns: who? function?
used in defense/combat
what is a challenge of a vegetarian diet? how do sauropodomorphs solve this problem?
gastroliths -- swallow rocks
what's the evidence for parental care in psittacosaurs? what about evidence that all dinosaurs exhibited parental care?
34 juveniles clustered together in an area of 0.5 meter square with one adult
the only living archosaur lineages exhibit extensive parental care, if it's homologous then it means it was present in last common ancestor of archosaurs and is primitive in dinosaurs
what are examples of convergent evolution between ceratopsians and ornithopods?
give two lines of evidence that Margin-heads were social animals
travel in herds
novelties: teeth like steak knives, '123' hand, splint like fibula, hollow bones
ceratosaurs and tetanurans
point of tooth points backwards
laterally compressed - not round but flattened
even more extreme than in sauropodomorphs
more likely to be broken
e.g. eating chicken leg you're holding onto tibia and little splinter of bone sticking out is the fibula
why do scientists now think that sauropods did not hold their necks up vertically?
they would need a 900 lb heart in order to pump blood up the height of the neck, so they think they held their necks parallel to the ground only occasionally lifting their heads up high to feed
what are the adaptations that sauropods evolved to deal with their really long necks?
vertebrae in neck filled with holes - makes neck lightweight
v-shaped notch in vertebrae where cables of ligaments ran, helping to hold up neck like a suspension bridge
list two differences that help distinguish diplodocids, camarasaurs, and brachiosaurs
diplodocids: nostrils top of head, still tiny ; hind limb dominant, forelimbs shorter than hind limbs
camarasaurs: nostrils bigger ; hind limbs and forelimbs about the same length
brachiosaurs: even larger nostrils ; forelimbs longer than hindlimbs
which of the following dinosaur clades includes the largest creatures ever to walk on Earth: theropods, ceratopsians, sauropods, stegosaurs, ankylosaurs?
there are estimates that the dinosaur Amphicoelus may have been as much as 60 m long and 150 tons. some scientists question this. Why? What evidence is this based on?
larger size tends to increase efficiency of digesting food; have longer digestive system so food is kept in gut for longer periods of time so can survive on lower quality food
evidence: dominant in jurassic - before flowering plants evolved so probably ate conifers (have much lower nutritional value); evidence that they lived in semi-arid, seasonally dry areas
one idea for the large size of sauropods relates to their diet. what's the explanation?
see previous slide
when did flowering plants first appear?
how does a change in size affect the generation and loss of body heat? what about the need for and acquistion of oxygen in insects? why were insects able to get so big in the carboniferous period?
heat generation correlated with volume, heat loss correlated with surface area; small things lose heat more easily than big things cause have a greater relative surface area; large animals don't need to eat so many calories to maintain heat
oxygen levels were higher in paleozoic era so insects could get larger
how does a change in body size affect skeletal strength?
strength of a bone proportional to cross sectional area; body weight scales with volume so when a dinosaur increases in size, its weight increases at a faster rate than the strength of bones.. same relative size/shape bones wont be able to hold up body so femurs become relatively thicker compared to length
why do scientists no longer think that sauropods lived in swampy environments, using their long neck as snorkels?
the water pressure would be too great, they wouldn't be able to breathe, lungs would be 10 m below water surface, at a pressure 2 times that at sea level
they also possessed limb bones that were sturdy enough to support weight on land and their body shapes are more like that of elephants and rhinos
what were sauropods like? migratory? herding behavior? did they take care of their children?
many may have moved in herds (single species mass of bones beds, vast assemblages of footprints)
a heard would have devastated local vegetation so we assume that they would've needed to keep moving to find food
large size good defense
thumb claw well developed at young age for defense
nesting grounds --- liked to hang out with each other but no adults found at site so probably left eggs behind
T/F: sauropod diversification coincided with the diversification of flowering plants
what were early theropods like? sweet and cuddly? slow-moving and vegetarian? efficient hunting and killing machines?
efficient hunting and killing machines
why is the fossil record of theropods not as good as that of other dinosaurs?
late cretaceous of Mongolia, about the size of a wolf
specimen is part of one of the most amazing fossil discoveries ever: velociraptor killed and fossilized in act of killing a protoceratops
tail simplification; results from interlocking parts of vertebrae
allows wrist to be bent from side to side
important in flight stroke of birds
bent bone in order to accommodate muscles that allow hand to be moved side to side
reverse pubis (observed in which two groups of dinos?)
maniraptors and ornithischia
maniraptors have a pubic boot
big claw on digit #2
had to walk on only two toes, kept this toe up while walking
ideal for disemboweling prey
what is thought to be the reason T. Rex arms are so tiny?
to make up for increased head size; beed to balance front and back half of bodies over two feet; one idea is that their arms are used to lift their body up from a belly-down position
Who came first, Ceratosaurs or Tyrannosaurids?
is large size of carnosaurs and tyrannosaurids convergent or homologous
"ostrich dinosaur" is common name for what group of dinos?
ornithomimids because of superficial similarities with ostriches
birds are members of which theropod clades?
list three characteristics that are present in birds but which evolved much earlier, in their theropod ancestors. which if any of these, were coopted later for use in flight?
no teeth, semilunate carpus, reverse pubis
semilunate carpus helped flight
toothless with prominent crest containing large nasal cavity within (similar to hadrosaurs?)
warm blooded? proving own body heat to keep eggs warm
very large plant eaters
3 foot long claw on hands
used to pull branches to mouth?
long neck similar to prosauropods
reverse pubis like ornithischians
several features of hands indicate that they are maniraptors
small, rare, poorly know
possess largest brain of any dinos, large centers for hearing and seeing
not all theropods are meat eaters. list three examples of herbivorous theropods
teeth were lost on at least three independent occasions within the theropods. list three of these.
make sure you know how to use phylogenetic bracketing to reconstruct characteristics of extinct groups. why can't we use phylogenetic bracketing with crocodiles and birds to determine whether extinct dinosaurs had feathers?
crocodiles don't have feathers but all birds do
what might have been the original function of feathers in the earliest feathered dinosaurs? did feathers evolve for flight? explain.
feathers did not evolve for the purpose of flight
--->transfer or function
what's up with archaeoraptor?
are feathers a novelty of dinosaurs? what's the evidence? in which clade do we think feathers evolved?
yes, all coelosaurs have feathers. shown in less than 12 taxa
list at least three lines of evidence that maniraptors may have been warmblooded.
oviraptors sitting on eggs to provide warmth through body heat
troodontids 'tuck in' posture for heat conservation
birds are warm blooded
birds are an amalgam of different characteristics that evolved at different times in their ancestry. indicate the order in which they appeared in the ancestry of birds
loss of tail
fused hand and wrist bone
loss of teeth
ground up vs. trees down
ground up - fast running, then jump to flight (avoid predator, catch prey)
tree-down - climb up trees and jump off to glide down
where in the tree of mammals did milk production evolve? what about nipples? placenta?
when do mammals appear?
dicuss four trends in synapsid evolution
improved food processing
changes in hearing
changes in locomotion
changes in physiology
give an example of transfer of function in mammals
hearing - two new bones (malleus and incus)
three characters that are convergent between mammals and dinosaurs
double pump heart
erect posture, narrow track gait
teeth embedded in sockets
study of how the position of land influences the distribution and evolution of life
northern continents colliding with gondwana
super continent of southern continents
4 reptile groups that independently evolved an aquatic habit
did the ancestor of ichthyosaurs and plesiosaurs live on land or in the sea?
compare/contrast the ways ichthyosaurs, plesiosaurs, penguins, and dolphins swim
plesiosaurs - fly through water
ichthyosaurs - move side to side while they swim
mammals have three ear bones. what are they and where did they come from?
stapes, malleus, incus * come from jaw
give two examples of how preservational differences can influence the pattern of dinosaurs in the fossil record
rock volume varies through time
different dinos have different preservability
how do differences in rock volume influence patterns of fossil diversity
rock volume varies through time
give two examples of collection bias
1. why so few dinos in antartica?
--inaccessible: ice sheets
what about North Korea? Libya? Afghan?
--inaccessible: political instability
2. lots of dinos in North America
--nationalities of paleontologies. not a lot of African paleontolgist
what is the relationship between endemism and geographic isolation?
endemism = distinct faunas found nowhere else in the world
lots of geographic isolation = high endemism, less=less
high endemism in turn means higher global diversity
---each isolated area has different species
what was the climate like in the mesozoic? how did climate change through the meozoic? what about geography? biogeography? vegetation? vertebrate biota? which dinosaurs lived during the triassic? jurassic? cretaceous?
why were the continent partly flooded during the cretaceous? give two reasons
no glaciers *continents breaking apart
lots of mid-ocean ridges, displace water
non avian dinosaurs went extint at KT boundary
end of mesozoic era, beginning of cenozoic
high levels of iridium found in clays deposited right at KT boundary
rare on earth, only found in significat levels in extraterrestrial rocks like meteorites/asteroids
fractures in quartz only form in response to extremely high pressures
found in KT boundaries
likely formed by force of impact
tiny round or tear drop shaped rock pieces
formed by molten rock thrown into the atmosphere
common in meteorites
chicxulub impact crater
the smoking gun
found off the yucutan peninsula, mexico
found at exact time of KT boundary
background vs. mass extinction
background = there has always been a low level rate of extinctions throughout life history; species go extinct for a variety of reasons
mass extinctions are different from background extinctions in that they involve a lot of species going extinct within a very short period of time
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