Vertebrate Exam 3 Study Guide
Vertebrate Exam 3 Study Guide 81463 - BIOL 3030 - 001
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This 96 page Study Guide was uploaded by Abigail Towe on Thursday November 5, 2015. The Study Guide belongs to 81463 - BIOL 3030 - 001 at Clemson University taught by Richard W. Blob in Fall 2015. Since its upload, it has received 243 views. For similar materials see Vertebrate Biology in Biological Sciences at Clemson University.
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Lecture 16 Reptile Diversity - Part 1 Quick review: ● Amniotes- of tetrapod lineage but NOT dependent on aquatic habitations → they can live/reproduce anywhere! ○ features: amniotic egg + [astragalus + more sacral bones in vertebrae to help them move on land] ● Synapsid= mammals (like humans) ○ example: cats ● Sauropsids = turtles, lepidosaurs, and archosaurs ■ lepidosaurs= tuatara, lizards, snakes ■ archosaurs= crocodiles, birds, non-avian dinosaurs ○ has two types of fenestra (holes in skull) ■ anapsids = no temporal fenestra ● this is primitive and all extinct ■ diapsids = two temporal fenestrae (on each side) ● there are living species ● one example: crocodiles- risk of being extinct ● and TURTLES Turtles are unique: ● in relation to other sauropsids- there are two hypothesis over turtles ○ 1) the phylogeny shows that turtles are anapsids (sister group to all reptiles) - based on lack of temporal fenestrae ○ 2) more widely accepted= turtles are diapsids and the “outgroup” ■ the are part of diapsid clade but lost temporal fenestrae as the skull modified Fossil Turtle: ● looks like a lizard but the ribs are expanded and positioned like a turtle's ● most fossil turtles have basic turtle body design (shell) Turtle facts: ● about 310 species that range in how they eat, live, etc ○ can be: terrestrial, freshwater, marine ● Another difference between turtles is the mode of neck retraction (when they are scared they want their head inside their shell) ○ Clade Cryptodira= hidden-necked turtles that bends neck in vertical plane to completely hide head ■ however some extant cryptodires have lost ability to retract head (sea turtles and snapping turtles) ○ Clade Pleurodires - side neck turtles that bends head in a horizontal plane so it doesn’t hide head completely Distribution of the two clades of turtles: - Cryptodire turtles are found on every continent EXCEPT Antarctica - Pleurodires - only found in Gondwanaland distribution Other Major Clades of Turtles: chelydridae snapping turtles forceful bite; cannot hide head in shell completely cheloniidae sea turtles cannot hide head in shell completely carettochelyidae carettochelys limbs have evolved into flippers trionychidae trionychidae softshells (like skin) emydidae emydidae pond turtles testudinidae tortoises Turtle Synapomorphies: 1. shell a. bony skeleton + covering i. covering made from keratinized scutes or skin 1. keratin scutes = overlap of bony sutures to add strength b. carapace- upper shell= vertebrae is fused to shell → cannot move body side to side, can only move their limbs i. flattened shells = aquatic species 1. to streamline to reduce drag and cost of swimming a. river has lower drag (faster flow) b. lake has higher drag (slow flow) ii. domed shells = terrestrial species 1. adaptation against predators because it makes it harder for predators to get mouth around entire shell iii. excepts to general pattern of having flat or domed shell: 1. African pancake tortoise has shell that flat, but soft and flexible to help them cram their body in rocks to hide from predators. Once crammed inside, it brings in their limbs and inflates body so that it wedges itself in there. 2. shell kinesis- shell moves = box turtle has a flap on underside that allows the entire body (legs and head) to be placed inside shell and closes until it’s completely safe a. plastron= lower shell b. shell shape varies - 2. limb girdles deep to ribs a. ribs deflect laterally as they develop, grow i. the ribs continue to grow until they grow over the shoulder girdle → the shoulder girdle becomes inside ribs 3. no teeth -- keratin beak only -- but still provides forceful bite Turtle Locomotion: ● terrestrial = tortoises ○ walks on digits (but has fat pad) - “elephantine (club) feet” ● aquatic : ○ freshwater turtles ■ forefoot paddle with different degrees of webbing ■ aquatic locomotion: “rowing swimmers” ● good for accelerating and low-speed maneuvering ● uses forelimbs and hindlimbs ○ sea turtles ■ forelimbs = flippers ■ locomotion: “flapping swimmers” ● aquatic flight - lift-based thrust = up-down movements ● continuous thrust - good for long distance swimming (beneficial since they migrate and travel long distances) ○ not good for maneuvering at low speeds or accelerating ● only use forelimbs Turtle Feeding: ● can be carnivorous, herbivorous, or omnivorous ○ tortoise = herbivores ○ sea turtles = mostly carnivorous ● aquatic turtles can catch food on land but can only feed if they go into water ● Example: ○ alligator snapping turtle: uses tongue to act as a worm to attract fish Turtle Circulation: ● heart = two atria but with 3 chamber ventricle ● Typically the heart-lung relationship is two circuit system (pulmonary- blood goes to lungs and systemic - blood goes to body) and it’s a sequential process. ● But turtles can choose to shunt - which shifts blood between circuits ○ turtles dive so they don’t send deoxygenated blood to lungs because it’s not like it can become reoxygenated. ○ use intracardiac shunt to move blood from pulmonary circuit to systemic circuit Respiration: ● contracts muscles and moves lungs to facilitate breathing because they don’t have diagram. The movement of limbs and girdles change the body cavity volume. ● has cloacal respiration: to allow oxygen uptake while diving in water ○ water enters cloaca to pump water in, uptake oxygen and then exchange for new water ○ this allows them to dive for much longer times (20x longer time periods) reproduction and nesting: ● internal fertilization: ○ for terrestrial males- males have penis and their plastron is concave to fit over females to reach cloaca ● nesting behavior: ○ majority of females lays eggs on land because embryos die if below water ● can use embryonic diapause: ○ a pause in development until environmental trigger (temperature good, or ready food) Temperature-dependent sex determination (TSD) ● this process occurs in most turtles, all crocodilians, some lizards, and tuatara ● effects of global warming: ○ as temperatures increase, the sex determines one sex over another and leads to extinction imprinting: ● females return to their natal beach because sea turtles imprint on that specific beach ● hatchlings are very small and hardly survive because predator saturation Orientation and Navigation: ● sea turtles use 3 primary cues at different life stages: 1. light and elevation gradient - to enter ocean 2. waves - movement away from coastline 3. magnetic field- used during migration through North Atlantic Gyre to help them come back to where they were born (homing ability) Conservation: ● endangered of extinction ○ one reason: they don’t reproduce right when they are born - takes about 15 years to reach maturity ○ other reasons: ■ habitat destruction ● logging, developments, beach development (brings in more lights to distract them) and vehicles ■ pollution ● leatherback confuse jellyfish with balloons (trash) ■ over-collection for food and pets Lecture 17 Reptile Diversity Part 2 Two divisions: lepidosaurs and archosaurs ● lepidosaurs: ○ includes: tuatara, lizards, and snakes ■ snakes are a subclade of lizards! ● if you don’t include snakes, lizards are a group, not a clade. characteristics of lizards: ● synapomorphy of lepidosaurs: orientation of cloaca ○ it’s perpendicular/transverses cloacal slit (vent) in lepidosaurs ■ different from salamanders= they have longitudinal/parallel vents ● their scaly skin is impermeable to water ○ it’s skin sheds in sheets ■ usually shed skins are from snakes ■ lepidosaurs do it in distinct fashion: comes off in sheets ● mostly terrestrial, but some are freshwater and marine. but mostly terrestrial. ● many species have reduction of limbs ○ snakes are prime example, but there are lizards that have reduced limbs also. Spenodontids (Tuatara) ● if you don’t look close enough, you would think it’s a lizard. but NOT a lizard ● historically, very diverse clade. but now only two species left. relatively uncommon. live in tiny islands off the coast of New Zealand. ○ so low diversity and low abundance in the few diverse species. ● make their living: live in burrows & highly nocturnal so they are specially . ○ suggestive that you need to be adapted for the cold temperatures of living in ground (and at night it’s colder) ○ and they do have the highest level of adaptation to cool temperatures ● primary insectivorous= eats insects. in order to eat insects they have interesting dentition: ○ they have 2 rows of upper rows but one row of bottom teeth that fits between the two upper teeths. aids in shearing motion. ■ they two upper rows are on two separate bones ■ one row of lower teeth that fit in between two upper rows of teeth ■ 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 ● reproduction: slower than most vertebrates ○ females mate every 4 years ○ lay 5-15 eggs ○ incubate for a very long time to hatch (11-16 months) ■ unusual for reptiles ○ has temperature sex-determination (TSD) ● so they have a lot of risk factors that are leading to their extinction Squamates: (all remaining lepidosaurs belong to this group) ● two divisions: Iguania and Scleroglossa ● know difference between two groups ^^ and a few key members of each division (analyzed below) ● note: serpentes = snakes ● synapomorphy of squamate: ○ Hemipenes (bifurcated penis) ● bifurcated = means divided into two branches/forks ■ 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) ■ asymmetry of use- ● even though penis is paired, only one half is used at a time (so there is left/right preference) ■ show along of ornamentation: ● example: extravagantly ornamented ○ used in systematics ○ allow species specificity ○ and allow reproduction between male and female of same species ● other fun facts: ○ Determinate growth ■ their growth reaches a maximum size ■ grows a lot, then stops (tops out) ○ Limb reduction evolved many times ■ Almost always occurs reptiles with body elongation ● with the 8,000 species of squamate, there is of course diversity of reproduction: ○ Oviparity to Viviparity: ■ 20% of squamates are viviparous ■ Viviparity trait is often associated with cooler climate ● because the temperature is too cool for young to survive ■ so mostly are oviparous - hatch out an egg ○ Parthenogenesis: ● parthenogenesis- a type of asexual reproduction in which the offspring develops from unfertilized eggs ○ occurs in 6 families of lizards and 1 family of snakes. ■ in all females- so all are female because it creates more females with this reproduction ○ offspring are genetically identical to mother ● cost/disadvantage: 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. ○ higher reproductive potential ○ temperature sex determination (as opposed to genetics) ■ applies to some lizards, but never to snakes. ● squamate anti-predator behavior: ○ tail autotomy- ■ auto =self ■ tomy= separate ■ 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 time-regeneration 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 - ○ original tail- have separate vertebrate along axis ○ new tail- has fibrous rod ■ also: discolored and thickness may not match as before ○ cryptic coloration ■ the colors hide from predators ■ fence lizard- brown colors to blend in with earthy background ○ aposematic coloration ■ poisonous animal shows off bright colors to inform predators they have toxins ■ in groups where you have aposematic coloration, there are individuals that except: mimicry ○ mimicry ■ similar colors, slightly different, still brightly colored but no toxins. but most predators will leave it alone to be safe, rather than sorry. ■ example: coral snake vs king snake ● coral is poisonous , king snake mimics ○ “play dead” - unusual behavior, less common ■ 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. ● 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. ○ run on water: ■ the “Jesus Christ” Lizard (Basiliscus plumifrons) ■ seeks out water when confronted by predator so that it can use the water to run away from and confuse the predator. ■ can run up to 4.5 meters over water ■ 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 ■ uses all 4 legs Lizards: ● lizards = GRADE without snakes ● most have 4 limbs ○ but there are leg loss/ reduction seen in several legless lizards ● generally: insectivorous (applies to the 80% that is small in size) ○ however, there is a transition that as lizards get larger become herbivores ○ exception: Komodo drag is still herbivorous ● wide range of sizes ○ Komodo dragon = huge ○ but some lizards as small as a quarter ● in general, the social behavior in Iguania And Scleroglossa: ○ social behavior is limited- but there are sexual interactions and territorial actions between individuals of same species or between different species over territories. ○ sexual interactions-- sexual dimorphism ■ typically males are larger ● exception: often in fishes, the females are bigger ○ signals used have multiple uses: ■ same signal used for everything (sexual interaction, warn off predators, etc) ● example: for agonistic interactions & species/sex recognition ○ social cues: ■ Scleroglossans (including snakes) use pheromones (chemical cues) to leave a trail, or cue in a potential mate ● in order to perceive chemical cues- need tongue to sense pheromones and send signal to brain ■ in contract - Iguanas: use visual cues ● body movements to show off where your bright colors are ● example: anole: small lizards, mainly from caribbean but one species is located in Carolinas (green anole) ○ males use flap of skin that extends down from throat = “dewlap” = which contrasts in color from rest of skin. ■ different species have different colored/ shaped dewlaps ■ by flaring this out- they are trying to court or scare off enemies Iguanian Diversity: ● mainly herbivorous ○ tendency of herbivores becomes higher frequency as body size increases ○ this is a problem for lizards because: ■ 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. ■ 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. ● Iguanidae ○ Marine Iguana: ○ in the Galapagos islands the Iguanas feed on algae and seaweed ■ 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 ● Chameleons ○ Specialized arboreal lizard: ○ has zygodactylous (crab-claw) feet ■ allows them to grab onto branches very strongly ○ prehensile tail ■ strong tail that curls/wraps around branches to allow aid in stability/support ○ 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 move/rotate eyes around separately ■ but also has binocular vision ● vision using two eyes with overlapping fields of view, allowing good perception of depth. ○ diurnal (daytime active) ○ primarily insectivorous Scleroglossa Diversity: Geckos ● no eyelids ● toe pads to allow dry adhesion to help them stick to vertical or upside down surfaces ○ pads have setae- projections of highly modified scales ■ on the tips of each setae- there is spatulate tips (widened tips) ■ allows for increased surface area ■ van der Waal’s force can have an affect because acts at 60-90 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 ● now viewed as type of lizard ● have a highly ossified skull to use their head as a plow to move soil/sand to burrow in ground ○ most eyes are reduced or covered → light detection is limited ● most are legless ● elongate body with short tails ○ reduce of right lung to achieve this long, tubular shape ■ 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 lock-grip to maintain food in mouth ● integument (skin) around their bodies is loose, moves independent of skeleton to allow telescoping ○ 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”) ■ skin and vertebrae move separately ● secretive, poorly known Scleroglossa Diversity: Helodermatids ● 2 species Beaded lizard and Gila monster ● body shape: stout and 2 ft + ● tail is blunt (made from fat deposits) ○ 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) ○ teeth have grooves where they venom is released. as they bite down and gnaw on prey, the venom is released. ■ 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 ● location: africa, asia, australia ● size: 25 cm to 3 meters ○ fossil records of them being even bigger than that ● fast moving active predators: ○ 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.). ○ 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 ● Komodo dragon is the largest living lizard ○ feeds on bats: ■ doesn’t really sneak up on bats, climbs up wall and attacks bat. Scleroglossa Diversity: Snakes: features: ○ limbless - what makes a snake a snake? ○ englonate body with short tail ■ 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 pre-cloacal vertebrae to help with flexibility/coiling ○ 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 ■ insects, worms, snakes, eggs, large prey ○ not all snakes are venomous! ○ wide range of diet ○ wide range of habitats: ■ under ground, in trees, ocean Scleroglossa has two major divisions: Scolecophidia and Alethinophidia ● Scolecophidia: ○ about 500 species ○ small, fossorial snakes ○ burrowing snakes ○ blind snakes or reduced eyes ○ shiny scales ○ eat subterranean insects: ■ mouth is ventral, not terminal. ■ eats soft foods like larvae ■ traces of insects in pelvic girdle ● Alethinophidia: ○ Macostromata: ■ stoma = mouth ■ macro= big ■ so big mouth. ● they specialize in eating big prey (it’s their adaptation) ○ adaptation because it always them to not eat as often. ■ sensory systems: ● sight and smell are well developed ○ there are NO ciliary muscles = no changing the lens shape in any snake ■ possibly from burrowing ancestors , along with leglessness ○ they have a forked tongue to aid in chemoreception ■ tines (halves of tongue) move independently ● only has inner ear ○ don’t have external opening or ear drums or stapes ○ but they have sensory nerves of inner ear so they detect vibrations/sounds through ground or inner jaws ● infrared-detecting pit organs ○ Detect rapid & very small changes in heat (as little as 0.0003° C!!!) ○ Evolved twice independently: ■ Boids (multiple pits) ■ Crotaline vipers (=pit vipers, single pits) ● this group is within Viperidae, (true vipers) do not have pits ■ feeding: ● highly kinetic skulls and jaws ○ lower jaw symphysis loose to open mouth really wide ○ the kinetic skull allows for bigger food items ● swallow slow and puts animal in head first ● prey is usually alive. eats through two strategies: ○ constriction helps ○ Boidae ■ grabs prey with jaws, then coils around prey to keep it from moving or harming the snake ■ constrictors: boas, pythons, colubrids ● they have short vertebrate and short trunk muscles to allow contraction ● but these characteristics limits speed ○ envenomation: ■ the process by which venom is injected into some animal by the bite (or sting) of a venomous animal. ● Ophiophagy: snake seating ● Oophagy: egg eating ○ reduction of number of teeth ○ vertebrate have ventral projections to aid in breaking shells of egg once snake moves body side to side as the egg passes through. ■ note: once shell is cracked - it is expelled out of mouth. ■ Largest-bodied extant species ■ 3 subfamilies ● Boas (Boidae) ● Sand Boas (Erycinae) ○ lack pits ● Pythons (Pythonidae) ■ All boas are viviparous ■ All pythons are oviparous ● Egg brooding (raise inc. temp) ○ curls around eggs ■ Infrared pits ● Multiple pits in Boines & many pythons ● Sand boa (erycinae) lack pits ■ Anaconda: ● Contenders for “World’s Largest Snake” ○ Green anaconda (Eunectes murinus, a boa) ○ Reticulated python (Python reticulatus) ■ Both can reach over 9 meters ● Anacondas are heavier ● Pythons are longer ● ○ Colubroidea: ■ synapomorphies: ● lose all traces of pelvic girdle ● 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: sit-and-wait predators (cryptic colors) ■ 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 c. Important defensive behavior d. Tail shaker muscle i. One of fastest sustained movements of any vertebrate 1. Very energetically expensive ii. High levels of myoglobin for aerobic respiration ii. true vipers (viperines) 2. Elapids: ● Cobras, mambas, coral snakes & sea snakes ○ Slim-bodied with small heads ○ All venomous, active foragers ● Example: King Cobra ○ Longest venomous snake, eats snakes! ● Example: Sea snakes ○ laterally compressed tail, dorsal nostrils with valves, viviparous, helpless on land Venomous Snakes: ● 305 Viperidae, 347 Elapidae, many Colubrids ● Venom kills prey, safer for snake to not have their skull damaged ● venom Secreted by Duvernoy’s gland of upper jaw that contracts muscles to squeeze out venom ○ Complex mix of proteins and other ● molecules that differ among species ■ Elapid venoms: neurotoxic ● attacks neurons ■ Viper venoms: proteolytic and hemolytic ● break down proteins and blood ● Fang morphology (shape of fangs): ○ Opisthoglyphous (colubrids) ■ Rear-fanged ■ grooved teeth ○ Proteroglyphous (elapids) ■ Hollow fangs in front ■ smaller teeth also ○ Solenoglyphous (vipers) ■ Hollow fangs in front are the only teeth, foldable ■ 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 ○ so that they can eat and breath at same time ■ something lizards can’t do ● hepatic piston = “diaphragmatic” muscle ○ this muscle pulls back on liver to increase chest volume ■ moves the liver back and forth like a piston ○ 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 ○ uses foramen of panizza- a shunt between right and left area of heart ■ located outside the heart ● different from turtles where shunt was inside heart ■ used during basking and diving ● reproduction and parental care: ○ all oviparous: lays eggs ○ TSD in all species ○ builds nest fro vegetation or soil ○ extensive parental care: ■ the nest is guarded ■ carries young to water ■ stays with young for weeks to months when first born ● can tell species apart by snout ○ alligators: ■ teeth of lower jaw fit into pits in upper jaw ● so you can’t see lower jaw teeth with mouth closed ○ crocodiles ■ 4th tooth in lower jaw fits into notch in the outside of upper jaw ● you can see this 4th tooth when jaw is closed ○ gavials ■ has a very long, narrow snout that is specialized for feeding on fish Reptiles: ● unique features among organisms allow for different lifestyle When we are talking about: ● Mesozoic period - divided into three periods ○ Cretaceous - 65-146 MYA ○ Jurassic - 146-200 MYA ○ Triassic - 200-251 MYA ● during this time period, Pangea began to divide into separate land masses. ○ from Triassic to Cretaceous ■ in Triassic: AFrica and south america was joined but separated by Cretaceous period ■ antarctica ● During Mesozoic - overall, the world climate was very different- several degrees warmer ○ no ice caps ○ more ocean ○ 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. ○ Another example, the south carolina coast was underwater - so you can find marine fossils (cretaceous sharks) Who? ● Diapsids in Mesozoic: ○ Marine reptiles ○ Pterosaurs ■ pter/o= greek for wing ■ saurs = lizards ● but these aren’t actually lizards ■ sister group to dinosaurs ○ Dinosaurs ■ din/o = greek for terrible ■ saur= lizard ● but not lizards either ■ dinosaurs are a specific clade of vertebrates. they have different defining features. ● not all fossils are dinosaurs ● Note: Pterosaurs, dinosaurs, and crocodiles are all ARCHOSAURS- ○ they are all sister taxa ○ 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 (3-10 m) c. very diverse taxa (over 20 genera) d. long propulsive tail & 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 intramandibular joint → 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 → 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 1. Ichthyosaurus a. “fish” “lizards” b. not clear what they are related to because they are so different from other taxa we see c. they have a reptile, dinosaur version of a dolphin d. distinctive features: i. they have an elongated snout ii. very large eyes 1. it’s not just decoration, it's 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 → 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 movement/flexibility 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 side-to-side tail beats/swimming. not movement entire body. 1. this type of swimming is used by high-speed 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 1-11 3. Plesiosaurs a. “Nessie” shape but diverse in variation of size/shape/form i. sea monster body shape- long neck , smaller body shape ii. 2-14 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 → paddles 2. radius and ulna reduced iii. tail short, so that means that the limbs would have been used for thrust/propulsion 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 ● these two groups belong together because: ○ they share common chances in the ankle that simplify it to a simple flexing hinge ■ allows foot to point very directly forward (as opposed to diagonal/to the side) ■ function: easier to dinosaurs and pterosaurs- can now stand with upright limb posture ● aid their ability to run quickly (can be on two legs- some dinosaurs) ● for pterosaurs: allows them to grip surfaces (possibly for roosting) Pterosaurs: ● distinctive features: ○ WINGS - ■ different structure than in birds and bats ● bird: has short hand and wing surface is made out of feathers ● bats: fingers become highly elongated and a membrane of skin stretches to hand, arm, and sometimes hind leg ● but in pterosaurs: there is skin membrane but only supported by the elongated digit 4! ○ has some stiffness ○ digit 4 is a mobile joint - allowed it to be folded back to avoid injury ○ keeled sternum: ■ sternum is a broad plate with downward crest for origin of pectoralis ■ similar to birds - provides broad attachment sight for pectoralis muscles to help pulling down (to push air down and fly) ● this helps with flapping flight, rather than gliding ○ powered flight ○ thin-walled limb bones with internal struts ■ struts- thin bones that run from one wall to the other wall to aid in support and stiffness ■ limb bones are light because no solid core but stiff with struts ■ allows for minimum about of body weight to be supported in air ■ one example: Quetzalcoatlus ● has 12 meter wingspan ● bone walls are 2 mm thick ● Grade: Rhamphorhynchoids ○ has early lineages ○ typically small ○ short neck ○ head with several medium-large teeth ■ usually used their big spiky teeth to grab fish near shore. ● 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) ● Grade: Pterodactyloids ○ co-existed with Rhamphorhynchoids ■ 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) ■ 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 ■ dipped into water and filters with long teeth ○ †Gnathosaurus (L. Jurassic, Germany): long teeth on both jaws ○ Pteranodon Idae: large, diverse rear head crests (display structures) ■ diverse head crests would be from sexual dimorphism ■ toothless ○ Dsungaripterus: ■ also had diverse crests on face and jaws ● this would help stabilize the fish as it skimmed the water for fish ○ Quetzalcoatlus ■ largest and last pterosaur ever known ■ largest flying animal ever ■ probably only gliding because weight was close to 200 pounds ● amount of muscle was limited with their body structure so it would prevent true powered flight. ● 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) & larger optic lobes (vision) compared to other reptiles ■ this is prob related to flight ■ had an endocast around brain ○ there are some well preserved specimens that show wings, and also throat structure. fossils show a throat pouch ■ could function like pelicans to feed young- exhibiting parental care Dinosaurs: ● at beginning: dinosaurs were fairly rare out of all fauna (make up 1-2% fauna) but then ● but then they reach majority of 50-90% fauna make up dinosaurs ● average size: small (1-3 m long) ● similar body shapes ● bipedal and upright limb posture ○ some species shift later to walking on 4 feet ● no flying or swimming (except bird) Dinosaur synapomorphies: ● 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: ● they differ in the structure of hip: ○ anatomical labels for hip: ■ top is ilium ■ front bone: pubis ■ back bone: ischium (what you sit on) ● Ornithischia: ○ pubis points backwards - primitive in dinosaurs ○ “bird-hipped” ● Saurischia: ○ “lizard hipped” - primitive condition (so not a synapomorphy) ○ pubis points forward ○ this condition is related to skull allows for expanded access for jaw muscles on top of head Ornithischians: all herbivorous ● 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 → 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 1. 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 bones were arranged to resist forces of head-on collisions a. head-banging plausible b. ceratopsians- i. big heads ii. 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 a. large size b. quadrupeds c. long tail and necks - extra vertebrae d. herbivores e. gizzard stones - preserved in abdomen (gastroliths) i. helped to grind food f. mass death assemblages g. herd structure because multiple parallel trackways discovered suggest sociality and herding h. for this animal of this size to be endotherm the heart would have to weigh 2 tons i. this would take 60% of resting metabolisms 1. so prob ectotherm 2. theropods a. only dinosaur predators - carnivores b. huge diversity in size Theropods: ● Dilophosaurus: ○ spitter from Jurassic park ■ smaller in body size ■ no evidence that they spat ● Tyrannosaurus rex ○ reduction of forelimbs ● Ornithomimus ○ active runners so most likely endothermic ● deinonychus ○ had a large retractable claw used to kill prey ● some in a pack end of Cretaceous Extinction • Major vertebrate extinctions at end Cretaceous (65 million years ago), ~1/2 all tetrapods • Birds make it through; rest dinos, pterosaurs, marine reptiles take hits • Solid evidence for asteroid impact (e.g. crater structure off Yucatan, Mexico) Review: Dinosaurs = two major groups = Ornithischians + Saurischians ● orinthisicna hip pointed backwards ○ “bird-hipped dinos” ● saurischian - pubic bone points forward ○ “lizard-hipped dinos” Asteroid hit and killed most dinosaurs. The Aves (birds) survived. Birds are part of the theropod lineage of dinosaurs. Theropods are the meat eating lineage ( T. Rex). Recognize that birds are part of the lizard-hipped dinosaur lineage. Birds are part of Saurischians! The name ornithischian was named after what is seen in birds- because they do look like birds. But birds are traced back to saurischian lizard- hipped dinosaurs. so birds but not bird-hipped dinosaurs. Birds---- Clade Aves Theropod Dinosaurs include birds (saurischians) ● The features that unite birds with theropod dinosaurs are FEATHERS ○ they have downy feathers ○ microraptor had complex feathers on forelegs and hind legs. implying that it used all appendages for gliding- but probably not flapping all 4 limbs at same time. but from evolutionary standpoint, the features were actually present in a wide range of animal species in the theropod lineage well before birds. ○ so feathers are not unique to only birds ● But the features that distinguish birds from theropod dinosaurs: 1. birds have a shorter tail a. it has less than 25 vertebrae 2. their feet has a fully reversed hallux a. hallux = big toe b. so they have toes forward and then their hallux is pointed backwards ● These two qualities are different from theropods that have a long tail and forward big toe ○ Archaeopteryx was the specimen analyzed for bird, while Deinonychus was observed for theropod non-bird specimens. ■ Deinonychus - used the forward big toe to dig and injure prey further. Additional specializations of modern birds to allow flight: A closer look at feather construction: ● feathers are a special type of integumentary body covering ● feathers are made from mostly Beta keratin ● made up of: ○ shaft- central structure that includes= rachis + quill ■ it’s long and tapering ○ quill - “calamus” ■ it’s the basal (bottom) portion anchored to skin ■ this portion is hollow and cylindrical ○ rachis - solid, squarish ending portion ---- supports parallel branches ○ barbs - the parallel branches that comes off of the rachis ○ barbules - they come off each bar and interlock of the barbules - helps produce continuous surface on either side of rachis ○ vane - the collection of bars that interlock and form a continuous surface on each side of rachis ■ function: ● provide flight surface to make for a aerodynamic structure that allows flight ● sheds water ● protects against sun Feather types: ● Contour- form outline of body ■ large firm vane ■ downy base ○ primary flight feathers - grow off the hand ○ secondary feathers- grow off the arm (making up the base of the wing close to the body) ○ primary + secondary = flight feathers and covers body and tail ● down = small, fluffy layer found beneath and between contour feathers. The bars do not interlock so they can trap air-- this provides insulation. ○ rachis is shorter than bars ● semiplumes- loosely webbed contour feathers. ○ has loose vane, rachis is longer than bars ○ helps to insulate body and aid in buoyancy of water birds ● bristles- vaneless feather, consist only of shaft ○ filter dirt near eyes and nose ○ also has tactile sensory function ○ filoplumes- hairlike feathers ■ lack vane ■ mainly shaft ■ widely distributed ■ found between contour feathers ■ function: decorative and sensory ● in addition to have nerve supply, they can serve as tactile receptor structures (sort of like whiskers) because they stick out from body ● feathers are replaced through molting - replaces old with new Bird foreflight specialization: ● bones are hollow/air-filled (neumatic) ○ reinforced with internal struts ○ the hollowness is pneumaticity ■ this is ancestral from theropods ■ however, birds add to this condition - they had the internal struts to add stiffness of bones. so light weight but allows bone to withstand forces from flapping in flight ■ this condition is lost in diving birds because they want to be heavy so they can dive well. so they lose the pneumaticity and have thicker, denser limb bones Skeletal features of derived birds: 1. has keel on sternum a. it’s like a keel of boat (large keel) b. serves for origin of pectoralis muscles i. muscles of chest that when they contract they pull limbs toward midline to flap in air (downstroke) 2. synsacrum - fusion of previously separate pelvis bones of sacrum a. function: absorbs impact forces of landing from flight 3. pygostyle- the defining shortening of tail that occurs in modern birds a. the short fused tail → helps with reducing drag b. functions to reduce tail feathers, thus reducing drag 4. the collar bones (clavicles) - in birds they are fused into a single U-shaped structure = furcula a. this structure makes a spring in the bird's chest b. so when they flap their wings, they create energy c. helps to save energy in upstroke d. energy is stored in the U-shaped furcula e. keep in mind that bone doesn’t like to be bent against it’s shape so it will naturally want to go back to normal position 5. uncinate processes on ribs - a. function: allows consecutive bones of ribs to overlap i. keeps the bones stiff and stable so that they don’t roll while they move ii. stiffens tunk for stability iii. compresses length of trunk, overlaps ribs to make it more solid and prevent side to side movement. 6. several bones in arms and legs that fuse together (from previously separate centers) a. serves to add stability b. in the forelimb- the bones of wrist and hands fusese down to one bone (carpometacarpus) c. in hindlimb- bones of ankles (tarsals) will fuse onto bones of foot (metatarsals) to be a single bone (tarsometatarsus bone) i. also: tibiotarsus = fusion of tibia and tarsus (ankle) 7. reduction of total number of digits in hand (we have 5, birds have 3 digits) ● indirectly to flight, the impact of this structure is more related to terrestrial locomotion. so tail is short to reduce drag, birds walk with their trunk pointed down (looking at down) and their thigh bone is horizontal (forwards). ○ if thigh were not pointing forwards (pointed straight up and down) -- it would place all the weight in front of hips. not advantageous for survival because it would not be sturdy enough to support the weight. ○ but with the thigh being shift to horizontal, now the weight is shifted to counteract gravity ● when birds pick up their feet, they are picking up their knee (whereas we move our hips to move our feet) ● the thigh is located really high so when a bird walks they just pick up their knee and move their ankle 8.large acromion - it’s a process that comes off of shoulder ● it’s enlarged in birds ● forms shoulder joint ● forms channel that runs through the junction of 3 bones - these form the triosseal canal ○ bones: scapula, clavicle, and triosseal canal How flight works: ● the pectoralis muscle powers the downstroke ○ it’s exactly in the part of the body where you think it’s located based on its function ○ origin: keel ○ insertion: humerus ○ so when in contracts- it pulls humerus toward midline to produce midline ● supracoracoideus powers upstroke ○ another ventral muscle ○ this muscle is deep to pectoralis muscle ○ so it’s located below the wing- but trying to pull the wing up…. how do you pull the wing up when the muscle for that is located below it? ○ the supracoracoideus is connected to a tendon ○ the acromion acts like a pulley to take force and and apply it to on top of wings to pull them downward ● all of the muscles for wing are located below wing ○ so it saves their energy to allow them to fly in a straight, level line. ○ it's a stabilizing and energy-saving feature ○ archaeopteryx had these structures too, so it’s believed they had flight also ● the muscles that make up flight are the light and dark meat you eat. ○ the color difference is related to the myoglobin ■ lots of myoglobin = use aerobic respiration - used for behaviors that require endurance . dark meat muscles ■ little myoglobin - anaerobic - used for quick bursts of activity- tire quickly and experience high fatigue. white meat. ○ birds that tend to fly long distances (like for migrations) have mostly dark meat muscles. ○ birds that only run/fly to escape (chickens) have mostly white meat muscles to allow burst of flight) If a bird uses flight then they need to have respiration specializations ● flight demands efficient oxygen extractions ● air sacs are holding chambers without gas change ○ they are just location where air is held ○ they functionally allow birds to achieve unidirectional flow of air through respiratory system ■ different from humans ■ this is functionally advantageous for birds- you prevent mixing of stale and new air. ● this mixing occurs in any animal, including humans, with bidirectional flow ○ air sacs allow unidirectional flow by doing 2 cycles of inspiration and expiration cycles. ○ air sac - lung expansion/ compression coupled with wingbeats ● cross-current exchange - allows blood to extract more oxygen from air ○ every blood vessel is low in oxygen, so each can extract it from air even as oxygen gets depleted ○ rather than paring one oxygen containing vessel with one blood vessel--- the oxygen vessel runs through where many blood vessels run perpendicular to allow all of them to extract oxygen as it passes through the vessel. ● also: they have a 4 chambered heart to prevent blood from mixing Excretory system specializations: ● NO urinary bladder! that’s just more weight that isn’t needed that hinders flight. ● so waste is excreted as uric acid (white paste) Reproductive: ● females only have 1 ovary ● males have gonads regress inside of them so that they don’t have excess drag when they aren’t needed How flight works: the mechanics ● flight = thrust and lift ○ forwards directed thrust and stay aloft in the air ○ so they need to produce forces in two directions - forward and upward ● they generate these two forces by using their surrounding environment (air) to use reaction forces ● how to produce upward lift: ○ partly do to downstroke of wings ○ primary reason of light is due to airflow over wing ■ bird wings have particular shape: cambering ● wing is convex on top ● longer distance for fluid to travel ● upper surface is convex, under surface is concave ■ the difference of air flow because of the convex/concave sides of wings decreases pressure to generate a lift ■ a couple of ways to add to advantage of that shape: they tip their wings to increase angle of attack ● this improves lift until it rotates past 15 degrees - this creates a stall because this angle
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