Palaeobiology Flashcards
Give an account of the taphonomy of an organism. What factors contribute to its preservation?
1. Biostratinomy - before final burial
* Organism dies
* Before burial, soft parts decompose (bacteria). Hard parts abraded/bioeroded
* Preservation: fast burial under sediment, escape TAZ
* More likely in sea (net accumulation of sed) benthic (less travel before burial)
* Sedimentary reworking - return to TAZ
* Too deep, caco3 dissolves (CCD)
* Exceptional preservation: fast anoxic, eg storm, peat bog
2. Diagenesis - after final burial
* Hard parts lithified with sed
* Aragonite not stable, recrystallise to calcite, replaced by pyrite, lost giving mould/cast
* Soft parts: permineralisation (minerals grow in structure before destruction)
* Coal/oil/gas: chemical fossils
What makes a good index fossil?
- Morphologically distinctive
- Easily preserved
- Abundant
- Geographically widespread
- Facies independent
- Short stratigraphic range
- Pelagic - less tied to local env
- Microfossil - small size less vulnerable, superabundant
What are the three types of fossil, and what do they show?
- Body fossils - intact remains of living organisms
- Trace fossils - records of organism behaviour
- Chemical fossils - geochemical signatures
What are five ways in which the ecological habit of an extinct organism is determined?
- Phylogenetic inference: similar organisms have similar lifestyles
- Functional morphology: form is related to function
- Recurrent fossil associations: reveals behaviour such as symbiosis/parasitism
- Trace fossils: provide a direct record of ancient behaviour
- Geochemical signatures: evidence of metabolic activity
Corals
* Taxonomy
* Location
* Mode of life
* Groups
* Fossil record
- Cnidaria
- Marine, warm shallow seas
- Sessile epifaunal benthic
- Suspension feeders
- Symbiosis with zooxanthellae
- Aragonitic (Triassic-now), calcitic (Ord-Perm)
- Morphological groups: rugose, tabulate, scleractinian
- Range: Ord-Perm (rugose and tabulate), Triassic-now (scleractinian)
Foraminifera
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
What is special about coccolithophores relative to other plankton?
They photosynthesise
What was the effect of the appearance of marine carbonate producers?
Created a major long-term carbon sink in sediment on the ocean floor
Nautiloids
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
Cephalopod molluscs
* Shell had chambers separated by septa, meet shell at straight/weakly curved suture
* Chambers joined by siphuncle through centre of septa
* Marine, nektonic
* Buoyancy control by adjusting liquid/gas content of chamber
* Jet propelled, carnivorous
* Aragonitic shells (unstable, erode)
* Straight or coiled
* Range: Ord-Perm (straight), Ord-now (coiled)
Ammonoids
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
Cephalopod molluscs
* Siphuncle joins chambers at the edge of each septum
* Sutures have different patterns depending on type
* Marine, nektonic
* Liquid/gas content buoyancy control
* Jet propelled
* Carnivorous
* Aragonitic
* Range: Dev-Perm (goniatite), Triassic (ceratite), Jur-Cret (ammonite)
Belemnites
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
Coleoid cephalopods
* Bullet-shaped cylinder
* Posterior pointed, anterior has cavity
* Radially oriented needles of calcite
* Skeleton of a squid
* Marine, nektonic
* Jet propelled, carnivorous
* Range: very common Jur-Cret, present since Carb
Trilobites
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
Arthropoda
* Segmented body: head, thorax and tail
* Marine, vagrant, epifaunal/semi-infaunal
* Tracks can be trace fossils
* Deposit (eat decomposing stuff) feeders or scavengers
* Moults
* Calcitic
* Range: very common Camb-Sil, gone by Perm
Graptolites
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
- Stick-like or branch, sometimes sawtooth
- Marine, pelagic, dendroids benthic
- Suspension feeders
- Organic skeleton, preserved as films
- Range: common Ord-Sil, present Camb-Carb
Bivalves
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
Molluscs
* Two hinged valves (L and R)
* Sometimes symmetric about shell join
* Usually marine, benthic
* Can be epi/infaunal, sessile/vagrant
* Suspension feeders
* Calcitic/aragonitic
* Range: present since Ord, increasing since Triassic
Brachiopods
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
Brachiopods
* Two shells (dorsal and ventral)
* Symmetrical about shell mid-line
* Marine
* Benthic, epifaunal, sessile
* Calcitic
* Range: very common Ord-Perm, common Triassic-Cret
Gastropods
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
Molluscs
* Coiled shell, may be planispiral
* Marine/non-marine/land
* Benthic, vagrant, epifaunal
* Carnivorous or deposit feeders
* Aragonitic
* Range: common Carb-Perm, increasingly common since Jur
Echinoids
* Taxonomy
* Location
* Mode of life
* Groups, if any
* Fossil record
Echinoderms
* Pentaradial symmetry
* Calcitic tests made of plates with external spines
* Marine, benthic, vagrant, epifaunal (irregular are infaunal)
* Varied feeding
* Range: very common since Jur
Labelled diagram of bivalve outer surface
Labelled diagram of bivalve inner surface
Labelled diagram of trilobite
Labelled diagram of echinoid
