Paleontology

Hierarchical Classification of Life

• The order from most general to most specific is: Domain, Kingdom, Phylum, Subphylum, Class, Order, Family.
• A common mnemonic is: King Phillip Came Over For Good Soup.

Taphonomy- fossil preservation

• Taphonomy refers to the changes an organism undergoes from death to discovery as a fossil.
• It controls the fidelity of the fossil record and provides important environmental information.
• Paleoecology studies fossilized organisms including their life, and their environment as fossils..

Fossils

• Fossils are any object that provides evidence of prehistoric life.
• Fossils can be physical remains like shells, bones, and hardparts.
• Fossils can be mineral replacements where bodies/skeletons are replaced by minerals.
• Fossils can be biological impressions include tracks, trails, burrows, or chemical signatures like biomarkers, indicating life.

Modes of Fossil Preservation

• The modes of fossil preservation from least to most information loss are:
• Unaltered soft parts
• Altered soft parts
• Unaltered hard parts
• Altered hard parts
• Leached fossils
• Biogenic structures
• biomarkers

Soft Part Preservation

• Unaltered soft parts experience no change to organic tissues except for water loss.
• Preservation methods are freezing, mummification (dehydration/desiccation), and conservation traps.
• Altered soft parts involve carbonization or mineralization of organic tissues.
• Anoxia, or oxygen depletion, and obrution, or rapid burial, are important.
• Fossil Lagerstätten are “motherlodes” of fossils with great preservation of soft tissues and articulated hard parts.
• Examples of this occur through the Phanerozoic.

Hard Part Preservation

• Unaltered hard parts: original mineral composition remains intact.
• Various minerals are associated with certain organisms.
• Calcite (LMC): Brachiopods, bryozoans, paleozoic corals, echinoderms.
• Aragonite: Molluscs, modern corals.
• Silica: Radiolaria, diatoms, some sponges.
• Phosphate: Vertebrate bones, conodonts, inarticulate brachiopods.
• chitin/collagen: Arthropods, grapolites.
• cellulose: Wood, plant material.
• Altered hard parts can undergo recrystallization, where there is a change in crystal structure but no change in chemical composition.
• Recrystallization can be accompanied by loss of water in the mineral with aragonite (CaCO3) converting to LMC (CaCO3) and silica changing to quartz (with water loss)
• Any mineral (fine crystals → coarse crystals) can be altered, but only heat and pressure remove volatile elements during Carbonization leaving a carbon film,
• What is left includes resistant and stable parts of molecule such as in coal (black) or graphite (silver).
• Permineralization (Petrification) occurs when pores of the skeleton infilled with minerals that precipitate out of fluids thereby turning something into stone that won’t burn.
• Fossil wood and Permineralized dinosaur bones are examples of this.
• Replacement occurs when the original skeleton dissolves while precipitating a new mineral through common minerals like dolomite, silica, pyrite, or limonite/goethite.
• Leached Fossils: Original shell dissolves, leaving a void or filling with minerals.
• Common in molluscs because Aragonite dissolves easily.

Fossil Molds

• There are different types of fossil molds.
• Steinkern (core) has only internal features such as muscle attachments. It the most common type, pops out in 3D.
• Casts have internal and external features (full replica 3D)
• Replica show external features only, and are 3D.
• Molds show external features only, preserves shell structure and is 2D.

Biogenic Structures

• Biostratification is when the orientation of plant or animal remains are used to determine relative ages of rock strata.
• Stromatolites are a fossilized bacterial structure built by cyanobacteria in environments where grazers are excluded, with high salinity, high water temperature and strong currents.
• Abundant before grazing animals evolved (Precambrian).
• Bacteria cover the sediment surface trapping carbonate mud and/or precipitates to build low domes where High areas grow faster than low areas.
• Reliably increases upward to form stromatolite.
• Thrombolites: unlaminated, clotted microbial build ups.
• 2. Trace fossils are tracks, trails, burrows, and borings.
• 3. Coprolites are fossilized animal excrement.

Biomarkers

• Biomarkers are chemical evidence of life.
• Diagenesis, hopanepolyol (organic compound from the cell walls of bacteria), hopane (organic compound derived from hopanepolyol), and cholesterol (indicate animal kingdom).

Biostratinomy

• Biostratinomy occurs from death to final burial, where biological information may be lost, but information from the depositional environment can be gained.
• Processes involved are disarticulation (the removal of joints): complete arthropods and echinoderms can only be preserved through obrution (burying)
• Progressive crinoid disintegration due to scavenging, complete calyces and stems, partial stems and disarticulate columnals, and disarticulated columnals
• Abrasion is wear from transport that result in Fossil hash.
• Bivalves hold up stronger and are measured using Mohs Harness Scales

Transport of Shells

• Transport of shells via traction currents (bedload) = extensive abrasion.
• Transport of shells in suspension = minimal abrasion.
• Example: Storm beds, turbidites (current flow with higher density)
• Reorientation is when currents/waves align shells.
• Unimodal Orientation: all apices point in the same direction if there is current flowing in one direction, but you can't identify the direction.
• Bimodal Orientation: apices pointing in two directions (180 apart) points to an Oscillating current.

Shell orientation

• During shell orientation Shells flip after a threshold.
• Concave-down orientation = wave or current activity when current threshold flipped them over if no preferred horizontal orientation when waves/currents were strong enough to flip the shells, but too weak to orient them, however Strong bimodal orientation if there were strong wave action

Transportation

• Dissolution occurs when shells dissolve in cold/freshwater and can also occur prior to burial.
• Transportation: occurs through several ways
• Indigenous materials are found in the same environment they lived in shuffled in order but close, and are used in paleoecology and biostratigraphy
• Exotic materials are transported from a different (but same time) environment, mixing diff communities is deposited by storms, used in biostratigraphy only
• Reworked (remanie) materials are fossils from older rocks mixed with new sediments can mislead age dating.

Paleoecology

• Paleoecology: evolution of ecosystems.
• Considers Environmental changes (big and small) and helps understands ecosystem evolution and limiting factors.
• Used to:Explain how modern ecosystems respond to climate change; Show how ecosystems become complex over time; Understand Limiting factors that control species presence and abundance.
• Limiting Factor Categories include sedimentologic, metabolic and combination.
• Sedimentologic: grain size; substrate consistency (how cohesive the grains are is the most important factor affecting benthic organics); turbulence (water agitation) that favours filter-feeders in shallow environments, but is harmful to fragile/branching organisms; turbidity (suspended sediment) that is harmful to filter-feeders and clogs respiratory/feeding systems.
• Metabolic: light that affects photosynthesis and vision, sunlight diminishes in quantity and wavelength spectrum with depth influences distribution of organisms; salinity where freshwater and euryhaline environments have the most diverse life -shelly animals are diverse in freshwater and normal marine environments but are approaching a limiting factor.
• Decrease in oxygen affects shelly fossils (affect ability to respire/metabolize).
• Light zones influence what can be seen regarding photosythesis and vision and oxygen abundance
• Grain size: influences type and abundance of organisms; epifauna (surface) sand which makes it mobile (moves with waves); mud and gravel make it less mobile (easier to attach).

Substrate Consistency

• Most important factor affecting benthic organics.
• Considers Category which can be: -Hardground (rock/shell)
• Firmground (stiff mud)
• Softground (loose sediment)
• Superground (soupy mud)
• It is easiest for sand burrowing but hardest for burrowing in gravel.

Oxygen Levels

• Oxic (>1 ml/L): abundant fossils, predators coomon.
• Disoxic (0.1-.1ml/L): few fossils, burrows (soft-bodied animals) only, predators are rare (require lots of E), few shelly fossils (affect ability to respire/metabolize) ;
• Anoxic (<0.1ml/L) and decreases as oxygen decreases
• Light zones affects photosynthesis, vision and animal/plant life

Ecological concepts:

• Individual – single organisms.
• Population - group of same species area/time.
• Community: all Populations areatime.
• Ecosystem- interaction living and nonliving.
• Trophic chains and webs:
• Trophic chain: energy and matter flow from one organism to another ex chemoautorophs get E from breaking down organic matter or organisms beginning.
• Trophic levels :organism that same # of steps of E & matter.

Marine Paleoecology

Categories:

• Pelagic- live in the water column, Neustonic Surface floater , Planktonic floaters, Nektonic swimmers.
• Benthic -Live on/in bottom.

• Bumbach-Bush ecospace Cube:
• Motility, Feeding type, Relative location to sea floor, tiering, 216 categories total

Paleoecology - Features in Marine settings

• Limiting Factors, fossil record , ecosystem completion, and Herbivory
• Trace fossils- Preserved behavior of organism in lock/ sediment - ichno=footprint

History of Ichology - trace fossils classified based on behavior

• Originators- can be identified through trace fossil formation through different types of traces

Universal ichnofacies: -

• Ichnofacies are classified as
• Two Main types, substrate controlled, depth controlled

Paleontology questions on taphonomy, fossilization, trace fossils, and mineral replacement. Explore fossil types and the information they provide about ancient environments and organisms.