Fossils

TYPES OF FOSSILS

• BODY FOSSILS - USUALLY HARD SKELETAL MATERIAL (SHELLS, BONES, TEETH); RARELY SOFT TISSUE (DUE TO FREEZING OR MUMMIFICATION)
• TRACE FOSSILS - TRACKS & TRAILS, BURROWS, BORINGS, NESTS, OR ANY OTHER INDICATION OF ACTIVITY BY ORGANISMS
  • useful for deducing environments of deposition, & life style of organisms
  • coprolites - fossilized feces

PRESERVATION

• SURPRISING ANYTHING IS EVER PRESERVED
  • organic materials are easily destroyed & rapidly scavenged
• HARD PARTS HAVE A BETTER CHANCE OF PRESERVATION
  • soft tissues rarely are
• RAPID BURIAL INCREASES CHANCES THAT SOMETHING WILL BE PRESERVED
  • marine invertebrates with shells stand the best chance of fossilization
  • soft-bodied terrestrial organisms have the least
  • more complete record for marine organisms with hard parts
  • less complete record for soft-bodied terrestrial organisms

TYPES OF FOSSILIZATION

• UNALTERED BODY FOSSILS
  • soft tissue can be preserved in amber or tar, or by mummification or freezing
  • hard parts may be preserved without change - usually shells (calcium carbonate & silica), bone/teeth (calcium phosphate), or pollen & spores
• ALTERED BODY FOSSILS
  • Carbonization: soft tissues preserved as thin carbon films
  • Permineralization: porous material filled with secondary minerals
  • Recrystallization: conversion of a mineral polymorph to another
    • E.G. ARAGONITE -> CALCITE, OR OPAL -> QUARTZ
  • Replacement: dissolution of original material, precipitation of new mineral, equal in volume to that dissolved
    • CAN PRESERVE FINEST DETAILS
  • Petrification: replacement or permineralization of wood
• MOLDS (DISSOLUTION OF SHELL) & CASTS (FILLING OF MOLD)
• TRACE FOSSILS - SEE ABOVE

USES OF FOSSILS

• BIOSTRAGRAPHY - stratigraphic correlation
• PALEOECOLOGY - relationships of fossil organisms to each other & to environment
• PALEOBIOGEOGRAPHY - restriction of fossils to particular geographic areas

Study Questions

1. Summarize the differences between trace & body fossils & give examples of each.

2. What factors control whether any fossil is preserved?

3. Summarize the types of fossilization.

Biological Classification (Taxonomy)

KINGDOM, PHYLLUM, CLASS, ORDER, FAMILY, GENUS, SPECIES

• DEVELOPED BY C. LINNAEUS & referred to as the Linnaean System
  • two names - Genus (General Group) + species (specific group)
    • examples: Canis latrans = coyote, Canis lupus = wolf, Homo sapiens = human
• 6 KINGDOMS - ARCHAEBACTERIA, EUBACTERIA, PROTISTA, FUNGI, ANIMALIA, PLANTAE
  • Phyla (& Classes)/Divisions
    • ARCHAEBACTERIA- primitive prokaryotes [1-CELLED, NO NUCLEUS] = Many anaerobic bacteria (including sulfate-reducing and methanogenic forms) & bacteria that tolerate extreme environments
    • EUBACTERIA - advanced prokaryotes [1-CELLED, NO NUCLEUS] = Most aerobic bacteria & Cyanobacteria (Blue-green algae)
    • PROTISTA - unicellular eukaryotes [1-CELLED, NUCLEUS]; Most Algae (diatoms, coccoliths & dinoflagellates) & Protozoans (foraminifers & radiolarians)
    • PLANTAE - photosynthetic, multicelled eukaryotes [multicelled plants]
      • Seaweeds (RODO-, PHAEO-, & CHLOROPHYTA)
      • Mosses (BRYOPHYTA) & other nonvascular plants
      • Primitive vascular land plants (PSILOPHYTA, LYCOPODOPHYTA, & SPHENOPHYTA)
      • Ferns (FiLICINOOPHYTA)
        • mosses, primitive vascular land plants, & ferns are spore-bearing
      • GYMNOSPERMS [non-flowering seed plants] = extinct seed ferns, plus conifers, cycads, & ginkoes
      • ANGIOSPERMS [flowering seed plants]
    • ANIMALIA - nonphotosynthetic, multicelled eukaryotes [multicelled animals] that ingest
      • sponges (PORIFERA)
      • corals/sea anemones & jellyfish (CNIDARIA)
      • BRYOZOA [how do they differ from corals?]
      • BRACHIOPODA [how do they differ from clams?]
      • snails/slugs, clams/oysters/mussels, & squids/octopi (MOLLUSCA)
      • segmented worms (ANNELIDA)
      • insects, spiders/scorpions, crustaceans, millipedes/centipedes & trilobites (ARTHROPODA)
      • starfish/brittle stars, sand dollars/urchins, & crinoids (ECHINODERMATA)
      • vertebrates, including fish, amphibians, reptiles, birds, mammals (CHORDATA)