L2 - Fossils & Fossilization

What are the conditions of preservation?

• Presence of Hard Parts (shells, bones, teeth)

• Rapid Burial by Sediment (removes most of oxygen, protection from scavengers)

What is preservation biased by?

• Geographic Environment

• Organisms

• Time

What are the types of preservation?

→ Permineralization

→ Recrystallization

→ Replacement

→ Carbon Films/Impressions

→ Casts/Molds

→ Trace Fossils

Permineralization

Minerals like quartz/calcite crystalize in pore spaces, filling them in.

→ minerals fill pores

Recrystalization

Still calcite, over time it recrystallizes and

• outside shape of fossil remains the same

• lose inside structure and information.

Replacement

Replacement of original hard part by a new material.

Carbon Films/Impression

When organic plant material decays, lots of carbon is left behind, often as a thin film.

Casts / Molds

Original material dissolves away leaving a mold

When that mold is filled in by a secondary material you have a cast

Trace Fossils

Do not represent the organism itself, but the activity.

Of the 12 plant phyla and 36 animal phyla there are only ____ classes in 6 phyla that are commonly found as fossils

8

→ Anthozoa

→ Articulata

→ Pelecypoda

→ Gastropoda

→ Cephalopoda

→ Trilobita

→ Crinoidea

→ Veretebrates

Which 6 Phylum did we discuss?

What are the classes within those phyla discussed?

Cnidaria - Anthozoa

Brachiopoda - Articulata

Mollusca - Pelecypoda(Bivalvia), Gastropoda, Cephalopoda

Artrhopoda - Trilobita

Echinodermata - Crinoidea

Phylum Chordata - Subphylum Vertebrata

Cnidaria = Phylum, what class did we discuss? What organism?

Anthozoa → Corals

• reef building organisms with calcite skeletons

Brachiopod = Phylum → What Class did we discuss? What Organism?

Articulata → Brachiopods

Mollusca = Phylum → What Classes did we discuss?

Pelecypoda (Bivalvia) → Clams

Gastropoda → Snails

Cephalopoda → Nautilus, Squid, Octopus

Pelecypoda (Bivalvia) = Class. What organism did we discuss?

Clams

Gastropoda = Class. What organism did we discuss?

Snails

Cephalopoda = Class → What organisms did we discuss?

Nautilus, Squid, Octopus

Arthropoda=Phylum. What class and organism did we discuss?

Trilobita → trilobites

Echinodermata = Phylum. What class and organism did we discuss?

Crinoidea → Crinoids

Phylum = Chordata, What subphylum and class did we discuss?

Vertebrata (subphylum) → vertebrates

Which of the following has a skeleton composed primarily of calcium phosphate?

a. Brachiopod

b. Crinoid

c. Trilobite

d. Vertebrate

d. Vertebrate

A fossil has two halves, each valve is symmetrical through it’s middle, but the two halves differ from one another. The fossil is most likely a

a. Clam

b. Brachiopod

c. Gastropod

d. Trilobite

b. Brachiopod.

T/F Brachiopods have a thick calcite shell that is easily preserved

True

Due to their ______ ________, bivalves (Pelecypoda) often preserved within rocks as molds

Aragonitic mineralogy

T/F Most snails have argonitic shells

True

The trilobite’s dorsal exoskeleton is reinforced by

Calcite

Echinoderms have a ______ endoskeleton

Calcite

What are the 3 Classes in Phylum Mollusca discussed in class?

Pelecypoda → clams

Gastropoda → snails (stomach foot)

Cephalopoda → nautilus, squid, octopus (head foot)

Taphonomy

• study of everything that happens to an organism between death and fossilization

• includes

  • decay

  • disarticulation

  • transport

  • fragmentation

  • accumulation

  • sorting

  • burial

  • disturbance

What allows for an organism to be spectacularly preserved?

→ buried rapidly after death, or buried alive

→ in environments discouraging scavenging and disturbance by burrowers

Exceptional Preservation

Lagerstatte

→ under burial conditions where physical & biological agents of destruction are absent,

Under burial conditions where physical, chemical, and biological agents of destruction are absent, it may be possible through a variety of processes to preserve exception remains of organisms in terms of _______ (______ ______) or _____ (_______ ________).

Quantity → Konzentrat-Lagerstatten

Quality → Konservat Lagerstatten

Fossil preservation is a race between

Decay and Fossilization

When can the organism’s soft tissues (or their outline) be preserved?

→ Special conditions where the chemistry surrounding and within the decaying organism can favour early precipitation of minerals

→ Pyrite, Calcium Carbonate, Calcium Phosphate

Extraordinary Fossil Preservation can

→ provide information on animals known only from their fossilized hard parts

→ reveal otherwise unknown organisms

→ provide more complete picture of ancient ecology

→ show evolutionary history of soft-bodied groups, and of soft-part characters of known groups

Trace Fossils are also known as

Ichnofossils

Trace Fossils (_______) are not the preserved remains of an organism, but the preserved _______ of an organism, often in the form of ____ and ______.

Ichnofossils

Activity

Molds

Casts

Examples of trace fossils

• burrows, footprints, trackways produced as an organism moves, rests, and feeds.

What can dinosaur trace fossils provide?

Information on

→ Anatomy

→ Social Behaviour

→ Feeding Strategies

→ How they moved & at what speed

Coprolites

• Fossil Dung

→ type of dinosaur fossil

Gastroliths

• Stomach stones

→ type of dinosaur fossil

T/F Skin impressions and eggs are types of dinosaur fossils

True,

What are the steps involved in collecting?

1. Planning

2. Prospecting

3. Collecting

4. Preparing & Curating.