What is Paleontology Applications Biostratigraphy Systematics Functional Morphology

What is Paleontology?

Applications • • • Biostratigraphy Systematics Functional Morphology Paleoenvironment Reconstruction Paleoecology

Types of Fossils -a fossil is evidence of 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)

Modes 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.

Preservational 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 level Biological activity (predators/scavengers) Water chemistry (ex. oxygen level) at burial site and impact on biological activity Rate of burial Diagenesis/mineralization Tectonic “reworking” of strata Erosion of strata

Lagerstätten 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

Extinction • Background Extinction: Extinction is occurring all the time. The averate 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 interval The Big Five are the five universally recognized mass extinctions. End Ordivician Late Devonian Permain-Triassic-Jurassic Cretaceous-Tertiary We are currently in a period of human driven extinctions that some consider the sixth big event.

Biostratigraphy CHARACTERISTICS OF A GOOD INDEX FOSSIL: • • • * * * • • • IMPORTANT INDEX FOSSILS IN DIFFERENT TIME PERIODS Cenozoic: planktonic microorganisms, especially forams Mesozoic: Ammonoids predominate Late Paleozoic: Ammonoids and conodonts Ordovician - Devonian: Conodonts and graptolites Cambrian - Ordovician: Trilobites Abundant Geographically widespread Easily preservable Diagnosable Found in multiple environments (when dead) Short species duration

Paleoenvironment • Depth: 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 distinguish lacustrine and marine settings • Direction of flow: Orientation of fossils indicates direction. Randomly oriented fossils may indicate autochthonous deposit. Parellel oriented long bones, tree trunks, and similar fossils will give indication of directionality of flow

Evolution 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.

The 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.

Cladistic Method • Choose 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 outgroups • Group 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.

Phylogeny of Life http: //www. mansfield. ohio-state. edu/~sabedon/campbl 26_files/image 009. jpg

Simplified Phylogeny of Plants http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/plantrelat. gif

Simplified Phylogeny of Animals http: //www. cnrs-gif. fr/cgm/evodevo/enindex. html

Simplified Phylogeny of Vertebrates http: //www. mun. ca/biology/scarr/Vertebrate_Classifications. htm

A brief tour of the Phanerazoic

Ediacaran The first body fossils of metazoas (animals) occur 575 mya- these animals were soft bodied jellyfish, worms, and echinoderms. Predation appears to have been very rare or non-existant.

Cambrian The Cambrian Explosion occurs. Mineralized skeletons appear and life rapidly diversifies. The majority of living phyla appear by the end of this period. Agronomic Revolution- burrowing Organisms disrupt algal matt ecosytem Trophic Escalation - Predator/Prey interactions lead to increase in complexity

Ordovician • Marine 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.

Silurian • • First truly large scale reefs form. The first jawed fishes appear. First vascular plants - Cooksonia First land animals - arachnids, myriapods and mites. These feed on decaying plant and animal material.

Devonian • This 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 20 m • Mass 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 algae • Cause of extinction debatable - may have involved sea level / climate change. Asteroid impact has also been proposed but compelling evidence is lacking

Carboniferous • First amniote fossils - Hylonomus • Insects radiate • Large plants and lack of herbivores to consume them leads to massive coal deposits.

Permian • Gymnosperms largely replace ferns and lycopsids. • Two main lineages of amniotes - the diapsids (reptile line) and synapsids (mammal line) radiate

The end-Permian Mass Extinction • This was the largest mass extinction in Earth’s history • 90% of all species wiped out • The leading explanation is the extinction is related to the massive negative C 13 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 CH 4 release • This 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

Triassic • The 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

Jurassic • Dinosaurs attain dominance of terrestrial ecosystems and the first truly large dinosaurs appear. • Archaeopteryx, the first bird, evolves in the Late Jurassic.

Cretaceous • Faunas become increasingly provicial. • Angiosperms (flowering plants) appear and become widespread • Ornithischian 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 nonavian dinosaurs, plesiosaurs, pterosaurs, and ammonites.

R. H. Tschudy, C. L. Pillmore, C. J. Orth, J. S. Gilmore, J. D. Knight, Science, 1984

From: http: //www. museum. hu-berlin. de/min/forsch/csdp. html

K-T Environmental Stress Time scale Air blast near impact site Heat from reentering ejecta (melt) Tsunamis near impact site Continent-scale wildfires Interruption of photosynthesis Nitric acid rain Cooling from dust H 2 O greenhouse Sulfate aerosol Destruction of ozone layer Methane greenhouse CO 2 greenhouse Modified from Pope et al. , 1994 hours to weeks days to months to years months to years > decades > +decades

K-T Conclusions 1. 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.

K-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 km 3). 8. K-T boundary is within Deccan Traps. 9. Extinction of the dinosaurs opened up ecological space allowing ascent of mammals.

Cenozoic • 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 high • Pleistocene - First Anatomically Modern Humans

The latest news in paleontology • The discovery of feathered dinosaurs has ended debate on 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!

That just ain’t right! Hu et al, 2005

Past 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.