Fossil Terminology Flashcards
Benthonic
Organism that lives in the sediment substrate of the sea floor
Pelagic
Organism that lives in the water column, typically in the surface layers.
Epifaunal (rem: position of movement, example)
Position: Organism which lives on the sediment substrate.
E.g. A bivalve oyster
Infaunal (rem: position or movement, example)
Position: Organism which lives in the sediment, usually in a burrow.
Many will filter feed.
E.g. A bivalve clam, certain types of trilobite
Vagrant (rem: position or movement, example)
Movement: Organism moves around on the sea floor and is usually a scavenger or a predator.
E.g. Echinoid, certain types of trilobite
Sessile (rem: position or movement, example)
Movement: Organism does not move around on the sediment substrate. Some are attached to the seafloor, whereas others may just lie on the seafloor.
Most will filter feed.
E.g. A bivalve mussel
Planktonic (rem: position or movement, example)
Movement: Floats in the water column to wherever the currents will take the organism.
Usually a filter feeder
E.g. A graptolite
Nektonic (rem: position or movement, example)
Movement: Actively swims in the water column. Most are scavengers or predators.
E.g. An ammonite
Extant
Organisms that are still alive today
Death assemblage
A collection of organisms found in a different place and position than they occupied in life.
E.g. a collection of disarticulated shells
Life assemblage
A collection of organisms found within sediments in the same position as they would have been when they were alive.
E.g. a bivalve in a burrow
Geopetal structures
Allow us to see the way up of a rock
E.g. a coral or a bivalve in life position
Derived fossils
Weathered out of one rock and re-deposited into another. Different fossils may give conflicting dates
Ornament
Expressed on the surface of a fossil, such as ribs, tubercles, spines and growth lines
Robustness
The ability of the fossil to resist abrasion.
Robust forms are more likely to be preserved whole or with slight damage only
Articulated
Organisms found whole, or connected, as in life
Littoral zone
The high-energy area between high and low tide
Disarticulated
Organisms found as fragments, such as separate shells or parts of trilobites
Trace fossils
Formed by benthonic infaunal, benthonic epifaunal and benthonic vagrant.
They preserve the activity of an organism, NOT the organism itself
They include tracks, trails, burrows, borings and excrement (coprolites)
Tracks
Footprints of an organism made when it moved along the sediment
Trails
Impressions of animals which were travelling
Could have been formed due to part or all of the animal dragging along the surface of the substrate
E.g. a trilobite trail
Resting traces
A type of trail as the whole body of the animal had stopped moving/rested
Bioturbation
The burrowing or working the sediment in a way that disrupts the bedding
This is caused by the activity of living organisms
Substrate
The name given to the sediment or rock on the sea floor
Strophic (Brachiopods)
A straight hinge line (these are sometimes extended as wings)
Commisure (Brachiopods)
The margin between the valves at the posterior (may be folded, curved or zig-zagged)
Folds and sulcus (Brachiopods)
A fold in the central or middle part of valves
Separates currents of water entering and leaving the animal
Prevents the mixing of fresh water and waste
What time periods were Brachiopods present? (Long hinged and short hinged)
Long hinged = Cambrian to Permian. Most prominent in the Carboniferous
Short hinged = Triassic (most prominent) to Today, but as of today they are not very common
