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Date Created: 09/06/14
Historical Geology 3 Mesozoic Invertebrates Marine Invertebrates Back from the Brink 0 Groups that managed to persist after the mass extinction at the end of the Paleozoic only left a few surviving species 0 Bivalves I Common in Middle Triassic I Most successful oysters Gryphaea and Exogyra I Rudistids important components of Iurassic and Crestaceous reefs bivalves that grey conical shells o Corals I Large numbers of reef building corals in Tethys sea I Prefer depths under 50m and temper higher than 20 C I Food and shelter for other marine life many symbiotic relationships I Brachiopods bivalves bryzoans sponges etc lived there I Gastropods ate them crabs and shrimp fed off them I Shallower coral urchins starfish crinoids o Echinoids I Mobile relatives of crinoids not attached to sea oor by stem I More diverse and abundant than relatives I Regular echinoids 5 fold symmetry and spherical shell abundant during Iurassic I Irregular echinoids bilaterally symmetrical with a attened shell took over from regular in the Crestaceous Age of the Ammonoids 0 Very abundant and varied mollusks in the Mesozoic useful in stratagraphic correlation o Cephalopods I Nautiloidea relatively straight sutures I Ammonoidea wrinkled sutures I Sutures lines on cephalopods formed on the inside of the shell where the edge of each chamber s partition or septum meets the inner wall I Three groups of ammonoids Goniatites Ceratites Ammonites 0 Not abundant during Iurassic and Cretaceous o Wrinkled septa and sutures I Wrinkled because they are uted and uted because it provides greater strength help animal withstand pressure differences I Another proposal folds served as attachments for tissue so tissue would be ripped away by predators and not main body I Had success adapting to marine environments but declines at end of Cretaceous only relatives survived o Belemnites I Groups of cephalopods squid like conch inside the animal I 10 tentacles and body form I successful in Iurassic and Cretaceous I Octopods have poor record because they were soft tissue Snails and Crustaceans o Gastropods were abundant during the Mesozoic o Colorful and beautiful form present in current descendants o Crustaceans abundant by Iurassic crayfish lobsters crabs shrimp ostracods some barnacles Protistans o Radiolarians Paleozoic lattice like skeleton made of opaline silica contribute to formation of chert beds and diatomite porous siliceous rock o Forminifera aka Forams Mesozoic fossil record important in petroleum exploration small size large quantity used to trace stratigraphic units from well to well sensitive indicators of past water temperature and salinity attained greatest number in Cretaceous became thick beds of chalk on sea oor along with planktonic species Terrestrial Invertebrates 0 Less is known because land dwelling groups were less likely to be preserved o Air breathing snails freshwater clams and snails ostracods in lake beds 0 Worms likely existed spiders millipedes scorpions centipedes fossils are rare 0 Best fossils come from the Solnhofen Limestone in Bavaria and those insects preserved in amber o Fleas did not appear until the Cenozoic when their mammal hosts began evolving Life in the Mesozoic Synapsids most numerous before Mesozoic and reptiles smaller numbers Extinction event and synapsids basically go extinct with the exception of the cynodonts o Cynodonts small and caniverous the successful therapsids and the last of the synapsids o Changes in jaw joint differentiation of teeth and formation of huge jaw closing muscles giving then a very powerful bite force Reptiles dominate throughout the Mesozoic o Especially the archosaurs Mammals 1 one set of adult teeth as opposed to replacing them continuously but this allowed them to specialize their teeth to do different jobs ex Front bite but back chew 2 23 mammal evolution occurs in the Mesozoic Archosaurs late Permian to today still exist today 0 crocodilians 0 birds dominate Triassic some were small predators some were large predators early middle Triassic some were aquatic and crocodile lice Mid late Triassic others became herbivorous late Triassic Archosaur locomotion o Bipedalism frees up front legs to do other things o Archosaurs reoriented their back limbs so they were underneath their body and not jutting out horizontally and then having a 45 angle at the elbow joint to walk Pterosaurs ying archosaurs adapt front limbs into wings form wing from hand elongate fourth finger to support wing structure hollow light weight bones trackways from pterosaurs prove they were no longer bipedal and they walked on all fours when they were on the ground Crocodylians late Triassic to present death roll to kill dismember prey early crocodylians were terrestrial long legged good runners with longer skulls some were completely marine with porpoise like tail Ichthyosaurs not reptile completely marine front and hind lips into paddles survived until cretaceous dorsal fin and tail fin looked similar to what dolphins now look like recently a 23m one was found in Canada have found fossils with embryos so some is known about reproductive process ex Come out tail first like dolphins today do so the offspring can immediately begin swimming alongside the mother very large eye indicated that they were very deep divers large eye to allow more light in to be able to see in very dim lighting Modern reptile late Triassic not archosaurs those are only crocodiles and birds sphenodontian tuatara lizards found only in New Zealand Snakes middle cretaceous 0 Major change is the quadrate bone upper jaw hinge can swing for and aft as well as laterally Turtles late Triassic recent bottom shell plastron tope shell carapace no one really knows where turtles fit in the scheme of life Frogs early Triassic recent Salamanders later urassic recent Triassic extinction a lot of archosaur groups go extinct dinosaurs ourish cynodonts become mammals but are small and evolve successfully throughout the Mesozoic Mesozoic Vertebrates The Ray Finned Bony Fish 0 Abundant since Devonian replaced by teleosts in Cretaceous o Teleosts today are more varied than any other group of vertebrate The Rise of Modern Amphibians o Temnospondyls I Survived extinction at end of Permian 2 out of 17 lineages I Frog like but skeleton not as adapted to jumping I One frog was as large as a squashed beachball o Salamanders and newts were less specialized o Caecilians oldest of modern amphibians worm like with vertebrate The Triassic Transition o Crustal unrest veriety of continental environments diversity 0 New reptilian groups appeared like the Turtle similar to modern turtle but with teeth 0 Rhynchocephalians new marine reptile represented by tuatara of New Zealand Basal Archosaurs 0 Diapsid reptiles two eye openings behind the eye orbits 0 Two groups Lapidosaurs lizards snakes and their ancestors amp Archosaurs dinosaurs pterosaurs crocodilians o Basal archosaurs archosaurs present during Triassic 0 Many were bipdal but some were four legged these because carnivores large aquatic reptiles called phytosaurs 0 Convergence evolutionary process of producing similar forms in unrelated organisms The Triassic urassic Extinction Event 0 1996 mya between Triassic and Iurassic periods 0 killed 20 of marine organisms o extinction of highly successful Crurotarsans which is believed to be the extinction which allowed the dinosaurs to ourish 0 cause of extinction is debatable possibly sea level uctuations and anoxia and climate change Dinosaurs Terrifying Lizards Dinosauria term coined by anatomist Richard Owen 1842 Harry G Seeley noticed differences in pelvic bones which divided dinosaurs into two groups 0 Saurischia lizard hipped I Ilium bone firmly clamped to spinal column I Three pelvic bones radiating in different directions I Teeth extended all the way around the jaws or were confined to the forward part of the jaw o Ornthischia bird hipped although not the ancestors of birds I Lacked teeth in the front became beak I Side teeth for crushing vegetation Saurischia are divided into Teropoda bipedal meat eaters and Sauropodomorpha usu large quadrupedal herbivores Theropods Nature Raw with Tooth and Claw 0 Dinosaurs quickly were widespread because Pangea lacked boundaries as it was still in the process of breaking apart Theropods dominant land predators of Mesozoic Known for teeth and claws desined for tearing esh Three functional fingers with one useless one Three major groups I Ceratosaurs small nimble I Carnosaurs largest huge head massive tooth jaws powerful hind limbs I Coelurosaurs include Tyrannosaurus rexbelieved to be the largest until 1995 Lizard Hipped Quadrupedal Plant Eaters The Saurischian Sauropodomorphs 0 Divided into prosauropods and sauropods close relatives but not descendants 0 Prosauropods I Quadrupeds with shorter forelimbs ability to balance on hind legs to reach trees or survey area I Late Triassic to Early Iurassic I Replaced by sauropods in Early Iurassic o Sauropods I Plant eaters tree top browsers with long necks I Forelimbs longer than hindlimbs OOOO I Heads were relatively small brain size of a clenched fist I Non serrated teeth I Possibly land and riverlake dwellers Bird Hipped Plant Eaters Ornithischians o Evolved near end of Triassic lasted until Cretaceous o Herbivores bipedal and quadrupedal o Ornithopods Mostly bipedal ornithischians I Early Iurassic to end of Cretaceous I Replaced sauropods as dominant terrestrial herbivores I Laid eggs in nest like structure I Had crests that were probably used to attract the opposite sex I Very diverse 4 most prominent Heterodontosauridae Hypsilophodontidae Iguanodontidae Hadrosauridae Thyreophorans Stegosaurs and Anklosaurs shield bearers bony armor not attached to skeleton o Stegosaurs I Best known Stegosaurus vertical plates along neck back and tail probably allowed for the regulation of body heat two spikes on tail as defense shorter forelimbs to feed on low lying vegetation large animal with small brain 0 Ankylosaurs Ankylosaurines and Nodosaurines I Two groups both heavily armored Ankylosaurines triangular skull with triangular horns on either side of rear of head bony club on tail Nodosaurines elongate head with lateral nasal passages to helo moisten the air or improve sense of smell no club on tail Marginocephalia Pachycephalosauria and Ceratopsia o rimmed head 0 Pachycephalosauria I thick headed lizards I bipedal herbivores in Late Cretaceous I engaged in head butting behavior for mates and territory I strong neck and backbone o Ceratopsia I Two groups Psittacosauridae short snout and beak parrot like beak thick skin of 25 collagen layers Neoceratopsia quadrupedal large heads prominent frills shark and pointed beaks I Ceratopsia are replace with rhino like dinosaurs like the Triceratops near the end of the Cretaceous I Some frills were hollow to alleviate weight off organism39s neck others had necks fused to backbones frills probably radiated excess heat or attracted mates