lecture 17 & 18
lecture 17 & 18 81463 - BIOL 3030 - 001
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81463 - BIOL 3030 - 001
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This 22 page Class Notes was uploaded by Abigail Towe on Friday October 30, 2015. The Class Notes belongs to 81463 - BIOL 3030 - 001 at Clemson University taught by Richard W. Blob in Fall 2015. Since its upload, it has received 54 views. For similar materials see Vertebrate Biology in Biological Sciences at Clemson University.
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Date Created: 10/30/15
Lecture 17 Notes Reptile Diversity Part 2 Two divisions lepidosaurs and archosaurs o lepidosaurs 0 includes tuatara lizards and snakes I snakes are a subclade of lizards o if you don t include snakes lizards are a group not a clade characteristics of lizards o synapomorphy of lepidosaurs orientation of cloaca 0 it s perpendiculartransverses cloacal slit vent in lepidosaurs I different from salamanders they have longitudinalparallel vents o their scaly skin is impermeable to water 0 it s skin sheds in sheets I usually shed skins are from snakes I lepidosaurs do it in distinct fashion comes off in sheets 0 mostly terrestrial but some are freshwater and marine but mostly terrestrial o many species have reduction of limbs o snakes are prime example but there are lizards that have reduced limbs also Spenodontids Tuatara o if you don t look close enough you would think it s a lizard but NOT a lizard o historically very diverse clade but now only two species left relatively uncommon live in tiny islands off the coast of New Zealand 0 so low diversity and low abundance in the few diverse species o make their living live in burrows amp highly nocturnal so they are specially o suggestive that you need to be adapted for the cold temperatures of living in ground and at night it s colder o and they do have the highest level of adaptation to cool temperatures o primary insectivorous eats insects in order to eat insects they have interesting den on 0 they have 2 rows of upper rows but one row of bottom teeth that fits between the two upper teeths aids in shearing motion I they two upper rows are on two separate bones I one row of lower teeth that fit in between two upper rows of teeth I this set up of teeth helps to tear through insects these reptiles are large in size 60 cm almost 2 feet live for about 50 years old which is helpful because they have a slow reproductive system Lecture 17 Notes o reproduction slower than most vertebrates 0 females mate every 4 years 0 lay 515 eggs 0 incubate for a very long time to hatch 1116 months I unusual for reptiles o has temperature sexdetermination TSD o so they have a lot of risk factors that are leading to their extinction Squamates all remaining lepidosaurs belong to this group o two divisions lguania and Scleroglossa 0 know difference between two groups quotA and a few key members of each division analyzed below note serpentes snakes synapomorphy of squamate o Hemipenes bifurcated penis o bifurcated means divided into two branchesforks I in this specific amniote penis is a PAIRED copulatory organ but in all other amniotes the penis is single unbranched organ This change in structure makes copulation specific because it s shape is specific for these females penis is stores in tail therefore males have longer tails only everted during copulation turns outwards I asymmetry of use even though penis is paired only one half is used at a time so there is leftright preference I show along of ornamentation 0 example extravagantly ornamented 0 used in systematics 0 allow species specificity o and allow reproduction between male and female of same species 0 other fun facts 0 Determinate growth I their growth reaches a maximum size I grows a lot then stops tops out o Limb reduction evolved many times I Almost always occurs reptiles with body elongation o with the 8000 species of squamate there is of course diversity of reproduction Lecture 17 Notes 0 Oviparity to Viviparity I 20 of squamates are viviparous I Viviparity trait is often associated with cooler climate 0 because the temperature is too cool for young to survive I so mostly are oviparous hatch out an egg 0 Parthenogenesis o parthenogenesis a type of asexual reproduction in which the offspring develops from unfertilized eggs 0 occurs in 6 families of lizards and 1 family of snakes I in all females so all are female because it creates more females with this reproduction offspring are genetically identical to mother costdisadvantage removes variability through sexual recombination advantage you don t need to go find a mate so reproduction in general is easier less cost and effect so higher potential to have more young 0 higher reproductive potential 0 temperature sex determination as opposed to genetics I applies to some lizards but never to snakes o squamate antipredator behavior 0 tail autotomy I auto self I tomy separate I they self separate their tail but the tail will still flip around because it still has muscle and nerves this forms a decoy distracts predator and run away the tail can regrow over timeregeneration a version of the tail because it is useful but just convenient to remove it as an escape plan when it grows back it is different 0 original tail have separate vertebrate along axis 0 new tail has fibrous rod I also discolored and thickness may not match as before 0 cryptic coloration I the colors hide from predators I fence lizard brown colors to blend in with earthy background Lecture 17 Notes 0 aposematio coloration I poisonous animal shows off bright colors to inform predators they have toxins I in groups where you have aposematio coloration there are individuals that except mimicry o mimicry I similar colors slightly different still brightly colored but no toxins but most predators will leave it alone to be safe rather than sorry I example coral snake vs king snake o coral is poisonous king snake mimics 0 play dead unusual behavior less common I hognose snake many predators only eat live prey so sometimes the snake will flip over and play dead so that it doesn t appeal the predator o but problem the predator will flip it over but the snake will flip itself back over destroying the illusion that it s dead so then it s eaten 0 run on water I the Jesus Christ Lizard Basiliscus plumifrons I seeks out water when confronted by predator so that it can use the water to run away from and confuse the predator I can run up to 45 meters over water I doesn t really walk on water their foot comes through the water with an air pocket trapped under their feet to prevent them from sinking I uses all 4 legs Lizards o lizards GRADE without snakes o most have 4 limbs 0 but there are leg loss reduction seen in several legless lizards o generally insectivorous applies to the 80 that is small in size 0 however there is a transition that as lizards get larger become herbivores o exception Komodo drag is still herbivorous o wide range of sizes 0 Komodo dragon huge 0 but some lizards as small as a quarter Lecture 17 Notes in general the social behavior in Iguania And Scleroglossa 0 social behavior is limited but there are sexual interactions and territorial actions between individuals of same species or between different species over territories 0 sexual interactions sexual dimorphism I typically males are larger o exception often in fishes the females are bigger o signals used have multiple uses I same signal used for everything sexual interaction warn off predators etc o example for agonistic interactions amp speciessex recognition 0 social cues I Scleroglossans including snakes use pheromones chemical cues to leave a trail or cue in a potential mate o in order to perceive chemical cues need tongue to sense pheromones and send signal to brain I in contract Iguanas use visual cues 0 body movements to show off where your bright colors are 0 example anole small lizards mainly from caribbean but one species is located in Carolinas green anole 0 males use flap of skin that extends down from throat dewlap which contrasts in color from rest of skin I different species have different colored shaped dewlaps I by flaring this out they are trying to court or scare off enemies Iguanian Diversity mainly herbivorous o tendency of herbivores becomes higher frequency as body size increases 0 this is a problem for lizards because I if you eat plants plant cell wall is made up of cellulose but can t digest on our own so like many other species they have gut bacteria to break down this nutrient I but in juvenile doesn t have this gut bacteria therefore they eat feces from an adult so that they can get their own gut bacteria to break down the plant material for it s diet lguanidae 0 Marine Iguana o in the Galapagos islands the Iguanas feed on algae and seaweed Lecture 17 Notes I but since they dive up to 10 feet they have to come back on land to bask on land to warm up so that they can actually digest it o Chameleons O O Specialized arboreal lizard has zygodactylous crabclaw feet I allows them to grab onto branches very strongly prehensile tail I strong tail that curlswraps around branches to allow aid in stabilitysupport their body shape is laterally compressed they walk slow to mimic a leaf so that they aren t easily seen by predators and can sneak up on prey specialized tongue and hyoid bone that supports the tongue that allow tongue projection independently mobile eyes they can moverotate eyes around separately I but also has binocular vision 0 vision using two eyes with overlapping fields of view allowing good perception of depth diurnal daytime active primarily insectivorous Scleroglossa Diversity Geckos o no eyelids a toe pads to allow dry adhesion to help them stick to vertical or upside down sunaces O O pads have setae projections of highly modified scales I on the tips of each setae there is spatulate tips widened tips I allows for increased surface area I van der Waal s force can have an affect because acts at 6090 microns much stronger than any sticky glue because of the molecular interactions that are occurring lead to type of engineering bio inspired design that tries to mimic life to create products Scleroglossa Diversity Amphisbaenians a now viewed as type of lizard Lecture 17 Notes have a highly ossified skull to use their head as a plow to move soilsand to burrow in ground 0 most eyes are reduced or covered gt light detection is limited most are legless elongate body with short tails 0 reduce of right lung to achieve this long tubular shape I but snakes reduce the left lung to achieve elongation dentition unique because they have a single tooth in the middle top of their mouth that fits between two teeth in lower mouth to have a lockgrip to maintain food in mouth integument skin around their bodies is loose moves independent of skeleton to allow telescoping 0 put head in ground pull their body up behind them they can coil up there back bone in an S shape then uncoils to propel body deeper into ground by straightening out their vertebral column telescoping I skin and vertebrae move separately secretive poorly known Scleroglossa Diversity Helodermatids 2 species Beaded lizard and Gila monster body shape stout and 2 it tail is blunt made from fat deposits 0 if they get a big meal they store extra energy in tail so they use the fat deposits in tail to have energy until next big meal best known venomous lepidosaur besides in snakes o teeth have grooves where they venom is released as they bite down and gnaw on prey the venom is released I unlike snakes they don t have muscles around the venom glands to squeeze the venom out the venom just slides down the grooves of teeth when they bite down so that s why they tend to bite down on something and gnaw on it to release the venom prey on mammals birds eggs lizards sometimes insects location southwest of US to Guatemala Scleroglossa diversity Varanids lizardy monitor lizards about 70 species Lecture 17 Notes location africa asia australia size 25 cm to 3 meters 0 fossil records of them being even bigger than that o fast moving active predators 0 monitors use gular pumping to inflate and deflate the throat region and use the throat as a pump instrument to bring oxygen in and out independent from their lung function being squeezed or not 0 so it allows them to maintain stamina despite limb posture and locomotion varied carnivorous diet because it s scleroglossa uses tongue to sample outside environment sticks tongue out every couple of seconds while walking and pumps out throat also o Komodo dragon is the largest living lizard o feeds on bats I doesn t really sneak up on bats climbs up wall and attacks bat Scleroglossa Diversity Snakes features 0 limbless what makes a snake a snake o englonate body with short tail I they are able to elongate body because they reduce or lose left leg and shift kidneys around right kidney moves to be anterior to left so in a row as opposed to side to side has about 120 precloacal vertebrae to help with flexibilitycoiling no eyelids just has clear scale that covers eyes large range in body size 10 cm to 10 meters can be oviparous or viviparous little sexual dimorphism diverse diet I insects worms snakes eggs large prey not all snakes are venomous wide range of diet wide range of habitats I under ground in trees ocean OOOOOO Scleroglossa has two major divisions Scolecophidia and Alethinophidia o Scolecophidia 0 about 500 species 0 small fossorial snakes o burrowing snakes Lecture 17 Notes 0 blind snakes or reduced eyes 0 shiny scales 0 eat subterranean insects I mouth is ventral not terminal I eats soft foods like larvae I traces of insects in pelvic girdle o Alethinophidia o Macostromata I stoma mouth I macro big I so big mouth a they specialize in eating big prey it s their adaptation o adaptation because it always them to not eat as often I sensory systems a sight and smell are well developed 0 there are NO ciliary muscles no changing the lens shape in any snake I possibly from burrowing ancestors along with leglessness 0 they have a forked tongue to aid in chemoreception I tines halves of tongue move independently a only has inner ear 0 don t have external opening or ear drums or stapes 0 but they have sensory nerves of inner ear so they detect vibrationssounds through ground or inner jaws o infrareddetecting pit organs 0 Detect rapid amp very small changes in heat as little as 00003 C o Evolved twice independently I Boids multiple pits I Crotaine vipers pit vipers single pits c this group is within Viperidae true vipers do not have pits I feeding a highly kinetic skulls and jaws 0 lower jaw symphysis loose to open mouth really wide 0 the kinetic skull allows for bigger food items 0 swallow slow and puts animal in head first a prey is usually alive eats through two strategies 0 constriction helps Lecture 17 Notes I grabs prey with jaws then coils around prey to keep it from moving or harming the snake I constrictors boas pythons colubrids a they have short vertebrate and short trunk muscles to allow contraction a but these characteristics limits speed 0 envenomation I the process by which venom is injected into some animal by the bite or sting of a venomous animal a Ophiophagy snake seating o Oophagy egg eating 0 reduction of number of teeth 0 vertebrate have ventral projections to aid in breaking shells of egg once snake moves body side to side as the egg passes through I note once shell is cracked it is expelled out of mouth 0 Boidae I Largestbodied extant species I 3 subfamilies o Boas Boidae o Sand Boas Erycinae 0 lack pits o Pythons Pythonidae I All boas are viviparous I All pythons are oviparous o Egg brooding raise inc temp o curls around eggs I Infrared pits 0 Multiple pits in Boines amp many pythons o Sand boa erycinae lack pits I Anaconda o Contenders for World s Largest Snake 0 Green anaconda Eunectes murinus a boa o Reticulated python Python reticulatus I Both can reach over 9 meters o Anacondas are heavier o Pythons are longer 0 o Colubroidea I synapomorphies o lose all traces of pelvic girdle Lecture 17 Notes 0 single carotid artery to brain we have 2 also very kinetic skull and many are venomous stout thick bodies wide heads eats large prey feeding sitandwait predators cryptic colors I 1 vipers a species i pit vipers crotalinae 1 includes rattlesnakes a Viviparous some stay with young until first shed b Tip of tail modified into a rattle i Interlocking segments of keratin Important defensive behavior Tail shaker muscle i One of fastest sustained movements of any vertebrate 1 Very energetically expensive ii High levels of myoglobin for aerobic respka on 90 ii true vipers viperines 2 Elapids o Cobras mambas coral snakes amp sea snakes o Slimbodied with small heads 0 All venomous active foragers o Example King Cobra o Longest venomous snake eats snakes 0 Example Sea snakes o laterally compressed tail dorsal nostrils with valves viviparous helpless on land Venomous Snakes o 305 Viperidae 347 Elapidae many Colubrids o Venom kills prey safer for snake to not have their skull damaged 0 venom Secreted by Duvernoy s gland of upperjaw that contracts muscles to squeeze out venom 0 Complex mix of proteins and other o molecules that differ among species I Elapid venoms neurotoxic Lecture 17 Notes 0 attacks neurons I Viper venoms proteolytic and hemoytic o break down proteins and blood o Fang morphology shape of fangs o Opisthoglyphouscolubrids I Rearfanged I grooved teeth 0 Proteroglyphouselapids I Hollow fangs in front I smaller teeth also 0 Solenoglyphous vipers I Hollow fangs in front are the only teeth foldable I fold down so it allows them to be elongated Archosaurs SYNAPOMORPHY Hindlimb modifications to 1 Direct foot forward 2 More upright limb posture Crocodilian Diversity ancestrally upright posture strong eyesight good hearing and smell very strong jaw closing but weak jaw opening indeterminate growth stronger as they get older because they keep growing as they age has bony palate in mouth to separate food and air passageway 0 so that they can eat and breath at same time I something lizards can t do hepatic piston diaphragmatic muscle 0 this muscle pulls back on liver to increase chest volume I moves the liver back and forth like a piston 0 therefore they do not struggle with breathing and side to side walking because this hepatic piston muscle aids in inspiration of both lungs when walking have 4 chambered heart prevents blood mixing of oxygenated and deoxygenated blood 0 uses foramen of panizza a shunt between right and left area of heart I located outside the heart 0 different from turtles where shunt was inside heart I used during basking and diving Lecture 17 Notes o reproduction and parental care 0 all oviparous lays eggs 0 TSD in all species 0 builds nest fro vegetation or soil 0 extensive parental care I the nest is guarded I carries young to water I stays with young for weeks to months when first born c can tell species apart by snout o alligators I teeth of lower jaw fit into pits in upper jaw a so you can t see lowerjaw teeth with mouth closed 0 crocodiles I 4th tooth in lower jaw fits into notch in the outside of upper jaw c you can see this 4th tooth when jaw is closed 0 gavials I has a very long narrow snout that is specialized for feeding on fish Reptiles 0 unique features among organisms allow for different lifestyle When we are talking about o Mesozoic period divided into three periods 0 Cretaceous 65146 MYA o Jurassic 146200 MYA o Triassic 200251 MYA 0 during this time period Pangea began to divide into separate land masses 0 from Triassic to Cretaceous I in Triassic AFrica and south america was joined but separated by Cretaceous period I antarctica 0 During Mesozoic overall the world climate was very different several degrees warmer o no ice caps o more ocean 0 An example the Gulf of Mexico was under ocean during this period The best place to find fossils from Mesozoic is Kansas because the fossils were preserved under water 0 Another example the south carolina coast was underwater so you can find marine fossils cretaceous sharks Who o Diapsids in Mesozoic 0 Marine reptiles o Pterosaurs I ptero greek for wing I saurs lizards 0 but these aren t actually lizards I sister group to dinosaurs 0 Dinosaurs I dino greek for terrible I saur lizard 0 but not lizards either I dinosaurs are a specific clade of vertebrates they have different defining features c not all fossils are dinosaurs o Note Pterosaurs dinosaurs and crocodiles are all ARCHOSAURS 0 they are all sister taxa 0 except for birds crocs are the closest living relative to dinosaurs Mesozoic Marine Reptiles 1 Mosasaurs a marine lizards i are actually lizards ii closely related to varanids b large animals 310 m c very diverse taxa over 20 genera d long propulsive tail amp feet modified into paddles for steering i limbs change 1 the limb bones are shortened and flat 2 hyperphalangy digits lengthened with extra bones a each bone in finger or toe phalanx b in hyperphalangy extra phalanges c it makes the fingers longer by the addition of bones d increase the SA used for paddle to use for steering body in specific direction e they also have intramandibularjoint gt bigger mouth gape open mouth wider i helps to eat large prey 1 mostly aquatic fish based on food in stomach of fossils f pelvis poorly attached to spine gt their structure would not have supported their weight on land i since they can t support their own body weight so they most likely gave live birth since they couldn t go on land to lay eggs 1 following sea snake pattern 2 as opposed to sea turtle pattern that lays eggs on shores ii there is some evidence embryo bones in abdomen of mother 2 lchthyosaurus a fish lizards b not clear what they are related to because they are so different from other taxa we see they have a reptile dinosaur version of a dolphin d distinctive features i they have an elongated snout ii very large eyes 0 1 it s notjust decoration it39s a very interesting of bones in the sclera that forms structure called sclerotic ring the function of these bones in this eye is unknown a another example of the scelerotic ring found in chicken but the function wouldn t be the same since chicken is not similar at all iii short blocky bones that modified limbs gt fins 1 bones formed continuous surface that would have been great for steering 2 paddles increase surface area 3 if you look at the bones you see it s hyperphalangy because some phalanges have up to 20 bones it has increased bones but also increase in fingers hyperdactyly a dactyl digit iv narrow vertebrate with reduced processes 1 so it allows more movementflexibility e the fossils were preserved in certain areas that preserve soft tissue to show what body shape was especially in places without vertebrate f early species from Triassic i primitive 1 little bend in tail 2 small tail fin 3 large pelvic girdle and fin ii these primitive features has anguilliform swimming propel by movement of entire body axis g Later species Jurassic i derived 1 BIG bend in tail 2 large tail fin 3 small pelvic girdle and fin ii these derived features carangiform swimming just sidetoside tail beatsswimming not movement entire body 1 this type of swimming is used by highspeed fish today like tuna 2 helps to travel long distances quickly to capture large prey h live birth evidence i fossil that you can see the juvenile emerging out of birth canal 1 babies born tail first a embryos are oriented this way in fossil specimens of mothers giving birth ii the number of young ranges from 111 3 Plesiosaurs a Nessie shape but diverse in variation of sizeshapeform i sea monster body shape long neck smaller body shape ii 214 m long b distinctive features i nostrils close to eyes even though there is an elongation of snout 1 helped them to be able to just pop their head up to breath without being seen ii hyperphalangy 1 limbs gt paddles 2 radius and ulna reduced iii tail short so that means that the limbs would have been used for thrustpropulsion 1 would look like underwater flight c 3 main body shapes i primitive 1 medium head medium neck ii elasmosaurid 1 tiny head LONG neck 2 this variety evolves twice iii Pliosauroidea 1 large head short neck d plesiosaurus feeding diversity i elasmosaurid prey small fish ii pliosaurus prey anything pursuit predator Pterosaurs Dinosaurs Clade Ornithodira o these two groups belong together because 0 they share common chances in the ankle that simplify it to a simple flexing hinge I allows foot to point very directly forward as opposed to diagonalto the side I function easier to dinosaurs and pterosaurs can now stand with upright limb posture o aid their ability to run quickly can be on two legs some dinosaurs o for pterosaurs allows them to grip surfaces possibly for roosting Pterosaurs o distinctive features 0 WINGS I different structure than in birds and bats o bird has short hand and wing surface is made out of feathers o bats fingers become highly elongated and a membrane of skin stretches to hand arm and sometimes hind leg 0 but in pterosaurs there is skin membrane but only supported by the elongated digit 4 o has some stiffness 0 digit 4 is a mobile joint allowed it to be folded back to avoid injury 0 keeled sternum I sternum is a broad plate with downward crest for origin of pectoralis I similar to birds provides broad attachment sight for pectoralis muscles to help pulling down to push air down and fly 0 this helps with flapping flight rather than gliding 0 powered flight o thinwalled limb bones with internal struts I struts thin bones that run from one wall to the other wall to aid in support and stiffness I limb bones are light because no solid core but stiff with struts I allows for minimum about of body weight to be supported in air I one example Quetzalcoatlus c has 12 meter wingspan 0 bone walls are 2 mm thick 0 Grade Rhamphorhynchoids has early lineages typically small short neck head with several mediumlarge teeth I usually used their big spiky teeth to grab fish near shore 0 OOO O c this is based on gut contents and preservation in lagoonal deposits like Solnhofen where the first bird fossil was found Archaeopteryx frame very long tail with a flared end similiar to kite like a rudder o Grade Pterodactyloids O coexisted with Rhamphorhynchoids I ut outlasted them early ones were small less than 2 meters but over time then became giant sized 12 meters longer head with many small teeth and later ones became toothless I easiest features that distinguishes them from rhamphorhynchoids tiny tail long neck vertebrates more diverse than rhamphorhynchoids Pterodaustro had elongated teeth on lower jaw from sieve I dipped into water and filters with long teeth TGnathosaurus L Jurassic Germany long teeth on both jaws Pteranodon ldae large diverse rear head crests display structures I diverse head crests would be from sexual dimorphism I toothless Dsungaripterus I also had diverse crests on face and jaws c this would help stabilize the fish as it skimmed the water for fish Quetzalcoatlus I largest and last pterosaur ever known I largest flying animal ever I probably only gliding because weight was close to 200 pounds o amount of muscle was limited with their body structure so it would prevent true powered flight 0 so they would jump off higher surfaces and glide around for locomotion some pterosaurs had fine hairs indicating body covering endotherm pterosaurs brains show large cerebellum motor control amp larger optic lobes vision compared to other reptiles I this is prob related to flight I had an endocast around brain there are some well preserved specimens that show wings and also throat structure fossils show a throat pouch I could function like pelicans to feed young exhibiting parental care Dinosaurs 0 at beginning dinosaurs were fairly rare out of all fauna make up 12 fauna but then but then they reach majority of 5090 fauna make up dinosaurs average size small 1 3 m long similar body shapes bipedal and upright limb posture 0 some species shift later to walking on 4 feet o no flying or swimming except bird Dinosaur synapomorphies o serve to aid in hindlimb stabilization and upright posture 1 increase to 3 or more sacral vertebrae a that connect pelvic to backbone to help stabilize the body for upright posture and locomotion 2 bone in ankle astragalus now has ascending process an upward ascending flange that covers front of tibia a this ascending process helps to reinforce the connect of tibia to foot to stabilize limbs in upright locomotion Major groups within Dinosaurs o they differ in the structure of hip o anatomical labels for hip I top is ilium I front bone pubis I back bone ischium what you sit on o Ornithischia o pubis points backwards primitive in dinosaurs o birdhipped o Saurischia o lizard hipped primitive condition so not a synapomorphy o pubis points forward 0 this condition is related to skull allows for expanded access for jaw muscles on top of head Ornithischians all herbivorous o 3 major groups 1 Thyreophorans both have wimpy teeth a stegosaurus i has two rows of bony armour on backs 1 grde from plates to spikes ii their vertebrate has high arch gt neural arches are stretched 1 legs make up for this arch hindlegs are a lot longer than forelegs iii has spike at end of the tail serves to knock knees of potential predators b ankylosaurus i armour scutes over whole body ii the hindlimbs are about the same length as forelimbs iii tail club also used as a weapon against predators 2 Ornithopods a large animals b represent 25 of diversity in late Cretaceous c features i snout flattened at tip 1 enlarges nostrils 2 pushes eyes back ii teeth proliferate to dental battery grinding plants 1 helps with grinding teeth and oral processing iii many have crest on head 1 display and or hollow resonating chamber for sound production 2 indicate some sort of social interaction d paleobiology nesting also suggests social interaction i communal herd structure with nests located close together about a body length distance between nests ii fossils show juvenile skeletons are found in the vicinity to suggest parental care kids stay around 3 Marginocephalia a pachycephalosaurus i very thick skull bone suggests behavior of running into something or butting heads 1 possibly social interactions or male fighting 2 skull had knobs and bosses 3 cross section of skull shows that boens were arranged to resist forces of headon collisons a headbanging plausible b ceratopsians i big heads i diversity of frill and horn configurations 1 frills and horns to display and defensive weaponry iii herbivores iv herding herding indicated from mass deaths Saurischians 1 sauropods 07quot a large size b quadrupeds c d e long tail and necks extra vertebrae herbivores gizzard stones preserved in abdomen gastroliths i helped to grind food mass death assemblages herd structure because multiple parallel trackways discovered suggest sociality and herding for this animal of this size to be endotherm the heart would have to weigh 2tons i this would take 60 of resting metabolisms 1 so prob ectotherm 2 theropods a b Theropods only dinosaur predators carnivores huge diversity in size Dilophosaurus o spitter from Jurassic park I smaller in body size I no evidence that they spat Tyrannosaurus rex 0 reduction of forelimbs Ornithomimus 0 active runners so most likely endothermic deinonychus 0 had a large retractable claw used to kill prey some in a pack end of Cretaceous Extinction Major vertebrate extinctions at end Cretaceous 65 MyrBP 12 all tetrapods Birds make it through rest dinos pterosaurs marine reptiles take hits Solid evidence for asteroid impact eg crater structure off Yucatan Mexico
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