3Types of Fossils Fossils -a fossil is evidence of life life Body fossils - elements of original body of ancient organisms (e.g., bones, shells, teeth)Trace fossils - traces and structures recording activity of ancient organisms (e.g., footprints, burrows, tooth marks, root marks, coprolites, egg shells)Chemical fossils - relics of biogenic organic compounds that may be detected geochemically in rocks (isotopically enriched carbon, sponge compounds)
4Modes of Fossilization Unaltered: simple burial, some weathering.Permineralized: Dissolved minerals precipitate in pore space. Seen in many vertebrate fossils.Recrystallization: Calcite crystals reorder and grow into each other. Original mineralogy remains, but structure is lost.Replacement: Partial to complete replacement of crystals of one mineralogy with another. Includes silicification, pyritization, phosphatization.Carbonization:carbon film left in place of tissues - this may preserve outlines of soft parts, seen in some lagerstatten deposits.
5Preservational Bias Hard parts preserve more easily than soft parts Marine environments preserve more easily than terrestrial (more prone to early erosion)Other factors:Post-mortem transport and fragmentation/energy levelBiological activity (predators/scavengers)Water chemistry (ex. oxygen level) at burial site and impact on biological activityRate of burialDiagenesis/mineralizationTectonic “reworking” of strataErosion of strata
6Lagerstätten Extremely important windows into past! Concentration-Lagerstätten: anomolously high amounts of fossil material * Condensation deposits (decreased rate of sedimentation) * Placer deposits (hydrodynamic concentration by currents, eddies) * Concentration traps (holes, pits, caves)Conservation-Lagerstätten: unusually well-preserved fossils * Often requires anoxic bottom conditions (so no scavenging), quiet water (so bodies are not disturbed), rapid burial (to reduce possibility of mechanical destruction of material) * Stagnation deposits (autochthonous conditions of anoxia, low currents, etc.) * Obrution deposits (assemblage is transported into such conditions) * Conservation traps (amber, for example)Examples: Burgess Shale, Mazon Creek, Green River, Yixian Formation
7Extinction Background Extinction: Extinction is occurring all the time. The averate rate of extinction over an extended time period is referred to as the background rate.Mass Extinction:A mass extinction occurs when a large number of taxa go extinct in a geologically rapid intervalThe Big Five are the five universally recognized mass extinctions.End OrdivicianLate DevonianPermain-TriassicTriassic-JurassicCretaceous-TertiaryWe are currently in a period of human driven extinctions that some consider the sixth big event.
9Biostratigraphy CHARACTERISTICS OF A GOOD INDEX FOSSIL: * Abundant * Geographically widespread* Easily preservable* Diagnosable* Found in multiple environments (when dead)* Short species durationIMPORTANT INDEX FOSSILS IN DIFFERENT TIME PERIODSCenozoic: planktonic microorganisms, especially foramsMesozoic: Ammonoids predominateLate Paleozoic: Ammonoids and conodontsOrdovician - Devonian: Conodonts and graptolitesCambrian - Ordovician: Trilobites
10PaleoenvironmentDepth: presence of benthic vs shallow water organisms can indicate water depth.Temperature: presence of different faunas suggest paleotemperature.Freshwater vs Marine: ostracods, molluscs, etc can distinguishlacustrine and marine settingsDirection of flow: Orientation of fossils indicates direction. Randomlyoriented fossils may indicate autochthonous deposit. Parellel oriented longbones, tree trunks, and similar fossils will give indication of directionalityof flow
11Evolution by Natural selection 1. There is heredity of most features 2. There is variation which itself is inherited 3. There is the capacity for growth in population that far exceeds the capacity of the environment 4. Variation leads to differential survival and reproduction rates in the struggle for existence. 5. Differential reproduction leads to the increase in the frequency of the traits that are responsible, leading over time to divergence in form.
12The Three Assumptions of Cladistics All organisms are related by descent from a common ancestor.There is a bifurcating pattern of cladogenesis.Change in characteristics occurs in lineages over time.The first and last assumptions are obviously critical parts of Darwins theory of evolution. The second has its problems but they are what they are.
13Cladistic MethodChoose the taxa whose evolutionary relationships interest you. Choose an outgroup, that is, a taxon closely related to the group you are studying.Determine the characters, or features, of the organisms and examine each taxon to determine the character states.Determine the polarity of characters by comparison to outgroupsGroup the organisms by synapomorphies - shared derived character states.Resolve conflict using the principle of parsimony - as in Occum’s Razor, we assume the simplest explanation is correct. The cladogram which requires the least evolutionary events is therefor prefereable.
19EdiacaranThe first body fossils of metazoas (animals) occur 575mya- theseanimals were soft bodied jellyfish, worms, and echinoderms.Predation appears to have been very rare or non-existant.
20Cambrian The Cambrian Explosion occurs. Mineralized skeletons appear and life rapidly diversifies.The majority of living phylaappear by the end of this period.Agronomic Revolution- burrowingOrganisms disrupt algal matt ecosytemTrophic Escalation - Predator/Preyinteractions lead to increase incomplexity
21The appearance of more complex animals with hard parts.
22OrdovicianMarine fauna continues diversifying: trilobites and brachiopods radiate.Tabulate and rugose corals dominant reef builders.First land plant fossils - spores.Glaciation lowers sea level and causes a severe mass extinction at the end of the Ordivician.
23Silurian First truly large scale reefs form. The first jawed fishes appear.First vascular plants - CooksoniaFirst land animals - arachnids, myriapods and mites. These feed on decaying plant and animal material.
24DevonianThis period is known as the Age of Fishes - armored jawless fish and armored jawed placoderms, and lobe-finned sarcopterygians are very diverse. The earliest well-preserved actinopterygians occur.The first tetrapods evolve.First seed plants, including the first tree: Archaeopteris - reached heights of 20mMass extinction in the Late Devonian- the stromatoporid sponge-algae rugose coral reef system is decimated and replaced by new reef systems that included bryozoas, new sponges, calcareous algaeCause of extinction debatable - may have involved sea level / climate change. Asteroid impact has also been proposed but compelling evidence is lacking
25Carboniferous First amniote fossils - Hylonomus Insects radiate Large plants and lack of herbivores to consume them leads to massive coal deposits.
26Permian Gymnosperms largely replace ferns and lycopsids. Two main lineages of amniotes - the diapsids (reptile line) and synapsids (mammal line) radiate
27The end-Permian Mass Extinction This was the largest mass extinction in Earth’s history90% of all species wiped outThe leading explanation is the extinction is related to the massive negative C13 anomaly at the boundary.The cause of the appears to be linked to flood volcanism associated with the formation of the Siberian trappes (largest Phanerazoic eruption event known), which may have raised temperatures enough to cause gas hydrate destabilization and massive CH4 releaseThis would have caused super greenhouse effects, a reduction in atmospheric oxygen levels, and widespread ocean anoxia.Evidence for an impact has been put forth butis controversial
28Luann Bekker - not duplicated. Crater, uncertain.
29TriassicThe Triassic is a time of very high diversity on land, with many groups that exist only in the Triassic.Most major groups of living groups of tetrapods appear during the Triassic- this includes turtles, lizards, frogs, crocodiles, dinosaurs and mammals.The first social insects evolve.The end of the Triassic is marked by a mass extinction that dramatically changes the ecosytem for the rest of the Mesozoic.Extinction linked to either CAMP flood basalts or Manicougan impact crater.Depsite the extinction, the early Triassic is not too different from the Late Permian on land.
31We are now in the Triassic world We are now in the Triassic world. You will notice that the land right where we are sitting was almost at the equator. It would be possible to walk right over to Africa.
33JurassicDinosaurs attain dominance of terrestrial ecosystems and the first truly large dinosaurs appear.Archaeopteryx, the first bird, evolves in the Late Jurassic.
34Cretaceous Faunas become increasingly provicial. Angiosperms (flowering plants) appear and become widespreadOrnithischian dinosaur herbivores replace sauropods as the dominant herbivores.There are still no permanent polar icecaps, but climate is relatively cooler than the Jurassic.The End Cretaceous extinction wipes out non-avian dinosaurs, plesiosaurs, pterosaurs, and ammonites.We are moving from a time were you find pretty much the same animals in South Africa, New Jersey, Colorado and Europe
35R. H. Tschudy, C. L. Pillmore, C. J. Orth, J. S. Gilmore, J. D R. H. Tschudy, C. L. Pillmore, C. J. Orth, J. S. Gilmore, J. D. Knight, Science, 1984
37K-T Environmental Stress Time scale Air blast near impact site hours Heat from reentering ejecta (melt) hoursTsunamis near impact site hours to weeksContinent-scale wildfires days to monthsInterruption of photosynthesis monthsNitric acid rain monthsCooling from dust months to yearsH2O greenhouse months to yearsSulfate aerosol yearsDestruction of ozone layer > decadesMethane greenhouse > +decadesCO2 greenhouse > +decadesModified from Pope et al., 1994
38K-T Conclusions1. There was a giant impact of an asteroid or comet, producing an essentially global impact layer enriched in Ir and having shocked quartz, and various other impact related materials.2. The impact site was Chicxulub.3. In oceans and on the continents the impact layer is at least coincidental with the mass extinction.4. On the continents a post-impact assemblage existed, dominated by ferns for hundreds to thousands of years.
39K-T Conclusions, cont’5. In Oceans, extinctions are directly followed by a large negative carbon isotopic shift suggesting a sudden mixing of the global oceans and a change in carbon cycling .6. Fullarenes with extraterrestrial He isotopic ratios have been reported.7. There was massive outpourings of basaltic lava to form the Deccan Traps (~106 km3).8. K-T boundary is within Deccan Traps.9. Extinction of the dinosaurs opened up ecological spaceallowing ascent of mammals.
40Cenozoic Paleocene - Mammals Radiate, large avian predators Eocene - First Whales. At the end of the Eocene, many “archaic” mammals go extinct.Miocene: Grasslands spread, primate diversity lower.Pliocene: NA-SA connected by land bridge: faunal interchange and some extinction.In Africa Bovids radiate and hominid diversity is highPleistocene - First Anatomically Modern Humans
41The latest news in paleontology The discovery of feathered dinosaurs has ended debate on the theropod ancestry of birds.Nesting dinosaurs discovered, proving dinosaurs exhibited bird-like parental care.Advances in histological methodology show that theropod dinosaurs had S-shaped growth curves, intermediate between marsupial mammals and placental mammals.The largest Mesozoic mammal ate dinosaurs!
43Past Questions Talk about early life. Talk about the history of vertebrates.Draw a cladogram of tetrapods. Talk about defining tetrapod characters.Draw cladogram of land plants. Define the characters.Give the age and locality of the oldest vertebrate, tetrapod, mammal.K/T mass extinction - what died, what survived? The plausible reasons for that.