Life: Diversity and Fossils Taphonomy Refractory versus volatile

Life: Diversity and Fossils Taphonomy Refractory versus volatile

Life: Diversity and Fossils Taphonomy Refractory versus volatile remains Destruction Modes of preservation Diversity Taphonomy - the study of the post-mortem history of organic matter. Building blocks of organic remains Post-mortem history Modes of preservation Chemical Composition of the Human Body PRIMARY ELEMENTS H 63.0% O 25.5% C 9.5%

SECONDARY ELEMENTS Ca 0.31% P 0.22% K 0.06% S 0.05% Na 0.03% Cl 0.03% Mg 0.01% (Frieden 1972) TRACE ELEMENTS (<0.01%) Cr Mn Co Mo Cu Se F Si I Sn Fe Zn Chemical Composition of the Human Body PRIMARY ELEMENTS H 63.0% O 25.5% C 9.5% (Frieden 1972)

SECONDARY ELEMENTS Ca 0.31% P 0.22% K 0.06% S 0.05% Na 0.03% Cl 0.03% Mg 0.01% TRACE ELEMENTS (<0.01%) Cr Mn Co Mo Cu Se F Si I Sn Fe Zn carbohydrates CnH2nOn amino acids C6H14N2O2 (lysine) Heme a

C49H56O6N4Fe Soft Parts and Hard Parts Volatile (soft)- easily and quickly digested e.g, sugars, starches, fats, simple proteins Refractory (hard)- tough to break down e.g., biominerals, wood Common Refractory Biomolecules Sporopollenin Cellulose Lignin Melanin Chitin Collagen (Allison and Briggs 1991)

oxidative polymer of carotenoid or carotenoid esters dinoflagellates, acritarchs, plant spores and pollen polysaccharide carbohydrate plant cell walls polyaromatic woody plants polyaromatic cephalopod ink, fungi pigment polysaccharide carbohydrate arthropod cuticle, fungi hyphae protein polymer chordate bone and skin, graptolite periderm Common Biominerals Aragonite CaCO3 scleractinian corals, some mollusks, some algae

Calcite CaCO3 rugose and tabulate corals, some brachiopods, bryozoans, some mollusks, echinoderms, calcareous nannofossils Carbonates Opalline Silica SiO2*(H2O) silicoflagellates, diatoms, radiolarians, some sponges Apatite Ca5(PO4)3(OH, F) Chordates, conodonts, some brachiopods (Allison and Briggs 1991) Cellulose and Lignin Apatite and Collagen Organisms

with readily identifiable hard parts have good Calcite and Aragonite fossil records, e.g. Calcite and Clams, snails, and other creatures with shells Aragonite Sporopollenin Corals and other organisms that make rocky skeletons Animals with bones Plants with wood Plant spores and pollen Calcite, Aragonite, Silica, Sporopollenin, and others Many microscopic organisms with hard parts microfossils

Post-Mortem Destruction The fossil record is biased specifically against organisms without hard parts. Preservation of these animals requires some kind of special conditions. The more robust remains are also more likely to be preserved than delicate bits. In a typical shallow water marine environment, approximately 40% of bottom-dwelling species have hard parts. Almost all of those species have fossil records. Of the remaining 60% of species, almost none are found as fossils. Post-Mortem Destruction Remains left on the surface tend to degrade

much more quickly than interred remains due to physical, chemical, and biological processes scavenging, decay, recycling, accidental destruction Preservation of fossil remains depends on relatively rapid and permanent burial. Post-mortem Decay A lot of energy goes into building and maintaining a living organism.

Post-mortem Decay As long as an organism is alive, it expends energy and resources to maintain its body. While disease can cause some deterioration, most carcasses are relatively whole before death. How an organism dies is important in determining whether or not it will be fossilized.

Post-mortem Decay Predators Predators and and scavengers scavengers will will strip strip even even the the hardiest hardiest carcasses, carcasses, removing removing some some parts parts and scattering

scattering others. others. Post-Mortem Decay C B D A Schaefer, W. 1972. Ecology and palaeoecology of marine environments. University of Chicago Press. A B C D

carcass sinks Bloat and Float carcass fills with decay gas, and floats decay continues, with pieces detaching gas escapes, allowing carcass to sink Post-Mortem Decay Bloat and Float Schaefer, W. 1972. Ecology and palaeoecology of marine environments. University of Chicago Press.. Large carcasses (especially of well-constructed animals like dolphins) can float for weeks or months before sinking Different parts fall off at different times, spreading the

remains over a wide area. Post-Mortem Destruction Organisms that lived (and died) in environments in which they were not likely to be buried before complete disintegration dont have good fossil records. (AP Photo/Damian Dovarganes) Burial requires relatively high sedimentation rates (at least periodically), and so fossils are most likely found in environments in which sediment is being accumulated. Since marine environments are more likely to accumulate sediment than terrestrial environments, the fossil record of ocean life is much better than that of land organisms.

Modes of Preservation Organism remains are frequently altered in one way or another before, during, and after burial. Both chemical and physical alterations are common, and the resulting fossil is frequently not composed of the same material as the original remain. Unaltered Remain Some fossils are essentially unaltered organic material. Such preservation is exceedingly rare for soft parts, but more common for hard parts. Distillation

Alteration of organic molecules leaving behind a carbon film. Can result in very fine scale preservation of soft parts. 300-million-year-old arachnid with what look like silk-spinning structures Permineralization Void spaces in remain fill with mineral crystals. The mineralogy of infill may or may not be the same as that of the remain.

Recrystalization The biominerals (plus any permineralized crystals) re-crystallize, maintaining the same bulk chemical composition of the original. This process usually destroys fine scale features. Replacement The remain is replaced by a mineral. The process can preserve very fine detail (especially in pyritization and phosphatization), or can obliterate details.

Common Replacement and Permineralization Minerals Pyrite (FeS) Hematite (Fe2O3) Common in stinky, reducing environments With limonite, the main kind of rust. Common Replacement and Permineralization Minerals Iron oxide

precipitation Manganese oxide precipitation Common Replacement and Permineralization Minerals Opalline silica (SiO2H2O) and chert (SiO2) Commonly precipitated where concentration of silica ions (derived from unstable silicates) is high (e.g., volcanic regions). Common Replacement and Permineralization Minerals Lime Scale Calcite (CaCO3) precipitation

scale build-up in water heaters and pipes Casts and Molds Molds form when a buried remain dissolves after (or during) lithification, leaving impressions of the remain and containing a void space. A cast is a secondary infilling of a mold. Diversity - measure of the number of taxa in a community or other group or area. Diversity is a somewhat slippery concept for several reasons, including:

Many taxa are over-split or overlumped Characterizing a complete community is very difficult Marine species known from the continental seas of the British Isles Scale differences are very problematic Most studies of diversity concentrate on a single taxon (e.g., birds) or a small number of ecologically related taxa (e.g., marine benthic organisms) in a single ecosystem (e.g., the Gulf Coast of the U.S. and Mexico) South Carolina Terrestrial Vertebrates Taxa Genera

Amphibians 23 Diversity 13% frogs/toads 7 salamanders 16 Reptiles 41

turtles 19 snakes 26 lizards 5 alligators 1 Birds

76 41% Mammals 45 24% Total: 185 22%

Taxa SC Div. Global Div. Amphibians 13% 19% Reptiles 22% 28% Birds 41%

35% Mammals 24% 18% Modern global tetrapod diversity = 25,654 Diversity tends to decrease with increasing environmental stress (more stressful environment = lower diversity), e.g.,: Environmental variability

Higher latitudes (toward poles) Increasing altitude Rocky Intertidal Zone Environmental variability is found at all scales from tiny to global. High Intertidal Zone Mid Intertidal Zone Gooseneck Barnacles Acorn Barnacles Limpets Mussels Perwinkles Snails

Brown Algae Gooseneck Barnacles White Cap Limpet Acorn Barnacles Keyhole Limpet Keyhole Limpet Periwinkles Mussel Snails Periwinkles Purple Sea Urchin Rocky Intertidal Zone Snails Red Sea Urchin Purple Sea Urchin

Ochre Sea Star Red Sea Urchin Brittle Star Ochre Sea Star Bat Star Anemone Green Anemone Crabs Aggregating Anemone Chitons Sea Hares Tunicate Nudibranch Sea Lettuce Chitons Algae Black Eyed Goby Kelp Fish

Sponges Red Algae Sub-tidal Zone Global Bivalve Diversity In general, diversity is highest at the equators and lowest at the poles. Hallam, A. 1994. An outline of Phanerozoic biogeography. Oxford Univ. Press. Pole high latitude low diversity marine

terrestrial Total Bird Species low latitude high diversity Cowan, R. 1995. History of Life. Blackwell Sci. Press. Equator Jack Sepkoskis Three Evolutionary Faunas Number of Families (Marine) Mass Extinctions O D

P/ Tr Tr K/T 600 400 Modern Fauna 200 Cambrian Fauna Paleozoic Fauna C

O S D Paleozoic C P Tr J K Mesozoic T Cenozoic

Cambrian Fauna Paleozoic Fauna Modern Fauna Group I: The Cambrian Fauna Tons of trilobites Extinct end of Permian Lots of inarticulate brachiopods Huge diversity loss at

end of Cambrian Many monoplacophorans Almost went extinct at end of Permian Group II: The Paleozoic Fauna Almost went extinct at end of crinoids Permian Extinct end of Permian

Almost went extinct at end of articulate brachiopods Permian rugose corals starfish Extinct end of Permian Slammed by two cephalopods mass extinctions

tabulate corals stenolaemate bryozoans Group III: The Modern Fauna malacostracans bivalves scleractinian coral echinoids chondrichtys osteichthys gastropods

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