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dino midterm 2


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How fossilization works
bones in a deposition area, animal dies and bones are left in newly lithified rock
most/least likely to be fossilized
most likely: animals in deposition environment, larger animals least: smaller, more fragile animals
kinds of fossils
bones, sedimentary structures, trace fossils (trackways, etc), soft structures (freezing, drying, etc), gastroliths and coprolites
what the fossil record tells us
size, morphology, time period, location, diet, synapomorphies, ecology, behavior
aka replacement; organic material in bone dissolves and is replaced by minerals
water with minerals comes through the sediment and holes in the bone are filled with these minerals
fossilized stomach stones
fossilized feces
relative dating
age in relation to something else
absolute dating
gives dates in years
radiometric dating
dates igneous rocks through radioactive decay, with parent product versus daughter product
age of the earth
about 4.5 billion years old
Phanerozioc sequence and boundary dates
Paleozoic (570 my-245 my) Mesozoic (245-65 my) Cenozoic (65 my-present)
sequence of Mesozoic periods
triassic, Jurassic, Cretaceous
issues in studying the origin of life
the conditions are impossible to replicate
lobe-finned fish
ancestor of all land vertebrates; had the pectoral fin
amniote egg
shelled eggs, like the ocean in a shell; teh shell protects, but is thin enough for oxygen to come in through pores, plus the babies can still get out
have skull with two openings, the diapsid skull
mammals and their ancestors; single, lower temporal skull opening
wastebasket term for primitive synapsids; ectotherms
erect posture; very small, early mammals; fur-like covering: endotherms
regulate body temperature internally; all mammalssince therapsids
animals who regulate their body temperature externally
mammry glands (identifies earliest mammals), small and nocturnal to start with, three bones in middle ear
only living mammals that still lay shelled eggs (ekidna and platypus)
syn: live birth
babies are born as embryos
syn: complex placenta
complex placenta
cushions fetus in fluid; blood vessel connection to mother; acts as endocrime gland (hormones); suppresses mother's immune response to fetus
reptiles, anapsid skull, carapace
no openings in the skull
the dorsal bone in the turtle's shell, covered in dermal scutes
ancestors of snakes; very small; ectotherms; kinetic skull
active in daytime (to stay warm: ectotherms)
active at night
kinetic skull
more flexibility in the skull; some bone loss for a more flexible lower jaw
pterygoid walk
snakes use inward-pointing teeth in roof of mouth to "walk" food into their mouths
water lizards; effective predators
lateral undulation
moving tail laterally to propel self forward under water
dolphin-like; carnivores; amniotes; found fossil of ichthyosaur giving live birth
short tails, propelled self with fins; lots of teeth; some: long neck; others: short nech and long head
group of species with similar foraging requirements
pursuit predators
fast swimmers with torpedo bodies; chase down prey; ichthyosaurs and short-necked plesiosaurs
ambush predators
lurk and wait for prey; mosasaurs and long-necked plesiosaurs
semi erect posture; sun: crurotarsal ankle
thecodont teeth
deep-rooted, strong teeth
semi-erect posture
legs can be pulled significantly under body; crocodiles' "high walk"
crurotarsal ankle
s-shaped ball and socket ankle joint that is more stable and makes semi-erect posture possible
small Crurotari with hind legs longer than front legs: facultative biped: could go on two legs sometimes
advanced crurotarsi, amphibious, parental care, at first (Triassic) they were more erect and more terrestrial, nostril on tip of nose, niche replacement from phytosaurs
advanced crurotarsi, Triassic, nostrils right in front of eyes, niche replacement because crocodiles took their niche
terrestrial herbivores, known for their body armor, only in Triassic
not dinosaurs, powered fliers with wings made of kerotin, fur-like body covering, hollow bones, syn: pterosaur wing
How do pterosaur skeletons show flight adapatations?
wings, hollow bones, short necks, shortened hind legs
How did pterosaurs move on the ground?
Why do we think pterosaurs were endothermic?
they had a fur-like body covering, flying takes more energy than just walking around, signs of parental care
determinate growth
growing to a reproductive age, and then not growing any more (endotherms)
syn: long tail with a vane on the end, used for steering
syn: tail short or gone, plus crest on back of head; two distinct morphs: one big with big crest, the other smaller with smaller crest and bigger hips (females)
habitual bipeds
animals that are built to be bipedal
mesotarsal ankle
a reinforced ankle that flexes straight up and down
Lagosuchus (underlined)
mid-Triassic, South America, hind legs longer than front legs
perforate acetabulum
bipedal femur isn't pushing straight into acetabulum, so it doesn't have to be as strong, so now there's a hole in it
opposable thumb
one finger able to work against the rest, showing that hands/arms aren't involved in locomotion, so that they can do other things
"bird-hipped", syn: backward pointing pubis, new lower predentary bone, leaf-shaped teeth, elongated ischium, elongated illium, oscified tendons along vertebral column (incr. stability)
competitive edge
all else being equal, if a group of animals develops a key feature, then they will be dominant
What does it mean adaptively to be a herbivore?
need a larger gut, so more room for that (back-turned pubis), need grinding mechanism (either teeth or gizzard)
How to digest plants:
need to break down teh cellulose: either mechanical (chewing) or chemical (with digestive enzymes (bacteria in digestive tract))
predentary bone
bone in front of teeth on lower jaw, chopping mechanism?, probably covered in keratin in life
How does the ornithischian skeleton show herbivorous features?
teeth for grinding, extended room for gut
"shield-bearing", syn: elaborate osteoderms, aka bony armor in the skin, especially on the back
bones in the skin
"wide foot", syn: short and stocky metacarpals/tarsals, plus shortened post-acetabular process of the illium, they are getting larger and heavier
syn: plates or spikes running along back bone, tall neural arches with highly angled transverse processes, loss of osciied bakc and tail tendons
glycogen body
can be broken down into sugars, "sugar store"
syn: closure of antorbital and suratemporal fenestrae, secondary palate, and shield-like dermal armor on back an sides
Defensive stragegies of ankylosaurids and nodosaurids
they were covered in armor, plus ankylosaurids had a bony club on their tails
syn: diastema
gap in the teeth
syn: relatively short pubis, plus bony shelf on back of skull
syn: dome head: maybe for head butting
sexual dimorphism
consitencies and differences in male/female actions in a single species
sexual selection
working to impress and get the best mate
"horn face", syn: frill at back of skull, plus half of their teeth being replaced by a rostral bone
rostral bone
a beak-like structure
Psittacosaurus (underlined)
most primitive ceratops
frill and horn functions
frill protects the neck, while the horn can be used for defense and fighting
herd plant eaters, facultative bipeds, syn: jaw articulation below the level of the teeth
syn: pre-pubis
small to medium in size, cursorial, social herd behavior
bipedial, maybe secondarily quadripedal, herd animals
syn: cheek-tooth battery, thought to be amphibious but they aren't, many had large crests (species recognition and sexual display
external and internal fertilization
external: primitive vertebrates such as fish, internal: amniotes
intromittent organs
male amniotes' structures to internally fertilize females
birds, turtles, crocodiles, probably dinosaurs
lepidosaurs and lizards
medullary bone
provides extra calcium for shells of eggs
egg laying habits and reproductive strategies
some have parental care, so babies might stay ing the nest for a while (trampling shell pieces); others: no parental care (shells untrampled); Maiasaura vs. Orodromeus
specialized herbivores, recurved claw, graviportal
thumb claw is twisted, smaller than Sauropodomorpha, gastroliths?
even longer neck
adults keeping some juvenile features
largest animals ever, nres fully retracted, all teeth in front of antorbital fenestrae
front legs longer than hind legs
smaller of the group, herd behavior
carnivorous skull and teeth, obligate bipeds, thin-walled hollow bones, hands redued to three functional digits
maxillary fenestra
hole in the skull between nares and antorbital fenestra
obligate biped
can't be quadripedal
fusion between bones to make pelvis stronger, then possibly kinetic skulls, sexual dimorphism, and head ornamentation
"still tail", walk with legs in straight line, complete loss of digit 4
pubic boot
bony plate at the end of pubis
semilunate carpal
half-moon shaped wrist bone, allows birds to fold outer section of wings
fusing of the clavicles, wish bone

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