Introductory Palaeontology (Fossils) Flashcards
What are three environments with a good chance of preservation?
Swamp on delta, Shallow marine, Deep marine
Define Actual Remains
The actual organism can be preserved
What are the three processes in which actual remains can be preserved?
Refrigeration, Dehydration (mummification), Peat bog
What are three examples of hard parts?
Hair, Teeth, Scales
For the hard part to be preserved, what neds to happen?
The minerals that make it up have to be changed into a more stable mineral
What are the two replacement methods for hard parts?
Petrification and Carbonisation
What are the three types of petrification?
Silicification, Calcification, Pyritisation
What is the first method of petrification?
The remains of the organism are dissolved away by percolating waters, then the space is filled in by minerals precipitated from solution by subsequent percolating waters
What is the second method of petrification?
Spaces within the organic structure are impregnated with minerals precipitated from solution by percolating waters, molecule by molecule
What happens during carbonisation
Common method of preserving plants as compaction squeezes out hydrogen etc. to leave carbon
Define Mould
The cavity left after the remains of an organism are dissolved
Define Cast
The result of the mould being filled with mineral matter or sediment. Can be internal or external
How does a mould and cast form?
Shell is dissolved by acidic water percolating through sediments to leave a mould. Infilling a mould by percolating waters with minerals in solution
Define Trace Fossil
Evidence of life
What are three types of trace fossils?
Tracks and trails, Burrows, Coprolites
Define Transported Fossil
Organisms may have been transported from the environment where they were living into a different environment for deposition
Define Derived Fossil
A fossil may have become weathered and eroded out of the rock that it was fossilised in and transported to a younger depositional area
Define Life Assemblage
Some organisms are preserved in their life positions
Define Death Assemblage
The remains have been moved after death but before deposition
What are three differences between life and death assemblage?
Death has fragmented shells but life has whole, Death has been moved but life hasn’t, Death has been sorted by size but life has a range of sizes
What are three purposes of fossils?
To determine the relative age of the rock, To determine the paleoenvironment conditions at the time of deposition, To study the process of evolution
What are six factors making the fossil record incomplete?
Rarity of organism, Predation of organism, Bacterial decay of organism, Scavenging of organism, Weathering and erosion of fossil, Metamorphism
What are four factors making the fossil record biased?
Organisms with hard parts, Rarity of organism, Energy level of depositional environment, Marine environment
Define Terrestrial
On land
Define Marine
In sea water
Define Non-Marine
In freshwater
Define Pelagic
Organism lives in water column in the surface layers
Define Benthonic
Organism lives freely on or in the sediment of the sea floor
Define Planktonic
Floats in water column to wherever the current takes it
Define Nektonic
Actively swims in the water column
Define Infaunal
Organism lives in the sediment, in a burrow
Define Epifaunal
Organism lives on the sediment substrate
Define Sessile
Organism does not move around on the sediment substrate
Define Vagrant
Organism moves around on the sea floor
Define Bivalve
A marine or freshwater mollusc with a shell consisting of two hinged valves connected by a ligament e.g. clam
Define Adductor Muscle
The muscle allowing bivalves and brachiopods to open and close
Define Gape
Where the two valves of a bivalve don’t meet
Define Hinge Line
Where the two valves of a bivalve shell meet
Define Muscle Scars
Marking on the interior of a bivalve shell showing where the adductor muscles were
Define Pallial Line
Mark on the interior of a bivalve showing where the soft parts were
Define Pallial Sinus
Indention on the pallial line showing the position of the siphons
Define Teeth and Sockets
Hold the valves of a bivalve together
Define Umbo
The most prominent part of a shell where the valves grow from
Where is symmetry found in a bivalve?
Between the two valves
What do the adductor muscles do to close a bivalve shell?
Contract
What do the adductor muscles do to open a bivalve shell?
Relax
Define Brachiopod
A marine animal with one valve larger than the other
Where is symmetry found in a brachiopod?
Within one valve
Define Brachial Valve
The smaller valve of a brachiopod
Define Pedicle Valve
The larger valve of a brachiopod
Define Diductor Muscles
Muscles in a brachiopod which contract to open the shell and relax to close it
Define Foramen
A rounded, slit-like opening in the pedicle valve of a brachiopod
What happens to the muscles in a brachiopod to make it open?
Adductor muscles relax, Diductor muscles contract
What happens to the muscles in a brachiopod to make it close?
Adductor muscles contract, Diductor muscles relax
Define Cephalopod
Generally have a planispiral or flat coiled shell, though some have evolved and lost their shells
Define Evolute
Can see inner whorls of a cephalopod
Define Involute
Can’t see inner whorls of a cephalopod
Define Keel
The outside edge of a shell of a cephalopod
Define Suture Line
Rigid joint between two chambers shown by frilly line on the outside of a cephalopod
What are the three types of cephalopod?
Ammonite, Ceriatite, Goniatite
Which of the three types of cephalopod is the youngest?
Ammonite
What happens to the shape of the suture line as the cephalopods get younger?
Becomes more frilly
Define Trilobite
A pelagic and benthonic marine creature which was alive in the Palaeozoic
Define Cephalon
The head of a trilobite containing the glabella and eyes
What are trilobite eyes made of?
Calcite
Define Genal Angle/Spine
An angle/spine from the cephalon of a trilobite
Define Glabella
The middle portion of the cephalon of a trilobite
Define Pygidium
The tail section of a trilobite where the thoracic segments are fused together
Define Thoracic Segments
Segments of a trilobites thorax showing how many paris of legs it had
Define Thorax
The middle section of a trilobite
What are the three ways trilobites found their food?
Benthonic crawlers, Burrowers, Swimmers/floaters
Define Graptolite
Extinct marine organisms that were pelagic and planktonic
Define Stipe
The whole stalk or stem of a graptolite
Define Theca(e)
Tubular or cup-like structure housing a zooid
What are three ways graptolites have changed over time?
Thecae shape has become more complex, Earlier organisms had more stipes, Attitude of stipe gone from pendant to scandent
What part of a coral is fossilised?
The hard parts
Define Colonial Coral
Coral with more than one septum close together
Define Septa
Radiating plates inside the corallite wall
Define Solitary Organism
Coral with a single polyp
Define Zone Fossil
Unique organisms that are used to characterise a particular horizon and therefore are able to date a sequence of rocks
What are six criteria a good zone fossil fulfils?
Wide distribution, Abundant, Rapid evolution, Facies independent, Good preservation, Easy identification
