Fossil Morphology



Invertebrate with segmented body and CHITIN exoskeleton; 3 segments are cephalon, thorax and pygidium. Could live in HIGH energy 
The THORAX is made of individual plates articulated together = can enroll for protection, v flexible

ECDYSIS - moulting; exoskeleton is shed by fractures along lines of weakness (FACIAL SUTURE) seperating the FIXED and FREE CHEEKS. (vulnerable to predation)


  • Many pleura (legs or gills) 
  • Crescent compound eyes (scavenger/hunter)       
  • Large (didn't swim; TRACE FOSSILS)                


  • Eyes on stalks (360+ downview)
  • Gas/fat filled glabella (flotation aid)
  • V small (float)
  • Seperated pleura (increase SA)
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  • No eyes (filter feeder)                                          
  • Gas/fat filled glabella and large pygidium (float)
  • V small (float)                                                    
  • Few pleura (few legs)    


  • No eyes (buried)
  • Wide cephalic fringe (shovel/SA)
  • Extended genal spines (SA/defence)
  • Pitted fringe (house sensory hairs)
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POLYP - soft bodied organism secretes CaCO3 skeleton with outer ectoderm and inner endoderm and nematoblasts (stinging cells).
Solitary = 1 polyp and single skeleton. Compound = many polyps in fused corallites.

Mode of Life...

  • Sessile, benthonic, marine
  • Zooxanthelle algae have symbiotic relationship - they photosynthesise producing oxygen, water and sugars while corals produce CO2, phosphate and nitrates as waste.
  • Polyp has tentacles which extend to feed; extract zooplankton using stinging cells/mucus.

Conditions for growth:

  • Tropical, shallow and clear waters so algae can photosynthesise
  • Clean water free from sediment particles - clogs polyp!
  • High energy/wave action to incorporate oxygen in the water and circulate nutrients by upwelling
  • Fully marine (30-40 parts per thousand) and warm (23-27C)
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2 uneven CaCO3 valves showing BILATERAL symmetry. Pedicle protrudes to attach itself to the sea floor. The shell is secreted by the soft tissue of the mantle (inside shell)

Mode of Life:

  • Benthonic, sessile, marine, epifaunal
  • Filter feeders using fluid filled lophophore - it's covered in cilia to generate currents - bring in fresh water and remove waste, the filaments trap food particles + pass to groove.

OPEN = CONTRACT DIDUCTOR MUSCLE to feed and let in fresh water.

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Turbulent water

  • Large pedicle opening - support pedicle for attachment
  • Strongly ribbed - strengthens shell
  • Zig-zag commissure - reduce sediment entering
  • Thick/heavy shells - stability to prevent rolling

Quiet water

  • Median fold - seperate inhalent/exhalent currents
  • Wings - large SA to prevent sinking
  • Smooth - no need to be robust
  • No pedicle opening - not attached

Soft muddy substrate

  • Flat valves - large SA to prevent sinking
  • Margin turned up - shell above sediment 
  • Spines - protection, stability, attachment, SA
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REGULAR - 5-fold symmetry, hemispherical test, high energy env (rocky shores)

Interlocking calcite plates - Ambulacra (pore pairs + tube feet) and Interambulacra (larger, tubercles + spines)

Apical System... (centre of aboral surface)
5 genital plates; largest is the madreporite - peforated with tiny holes so water can enter.
On top so waste, eggs and sperm are removed by the current.

Mouth... (centre of oral surface)
Large peristome to support heavy jaws (5 = Aristotle's lantern) Perignanthic girdle = LIP
Scrape algae off substrate or scavenge on organic matter.

SPINES - muscle contraction allows spine to move; DEFENCE and MOVEMENT by rotation.

TUBE FEET - attachment, movement and exchange surface for respiration
Water from madreporite is passed to the tube feet.

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IRREGULAR: heart shaped, bilateral symmetry, anus moved towards edge of the test, infaunal.

Petaloid Ambulacra
Don't extend from top to mouth; have pore pairs for tube feet to DIG BURROWS + STABILISE
Anterior groove marks the heart shape - lined with cilia to direct currents to pass food.

Sub Anal Fasciole
Cilia take waste particles and direct them to the sanitary tube; tube feet on the posterior keep burrow clean.

Underside; lacks jaws and perignanthic girdle =FILTER FEEDER
Lobrum directs currents to prevent sediment entering the mouth. 

SPINES - dig burrows; wedge shaped to move easily through sediment
TUBE FEET - extend from petaloid ambulacra out of the burrow to allow gas exchange

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2 equal sized calcareous valves with a plane of symmetry along the hinge line. 
EPIFAUNAL (sessile)

  • Feed using inhalent and exhalent siphons; particles removed by gills = FILTER FEEDER
  • Valves open (ligament) and close (adductor muscle) to bring in water

Mytilus - bysally attached in the high energy, littoral zone. (strong protein threads)
- Streamlined, elongate, thin shells for protection against currents + strong to prevent breakage 
- Large muscles to close and stop drying out and dessication
- Periostraum layer from protection from acid rain/water

Ostrea - cemented in high energy environments
- Strong thick shells to withstand currents
- Monomyrian to stay closed in high energy
- Uneven shells; large is cemented and other is lid to close exactly

Gryphaea - freelying in low energy environments
- Strong thick shells to withstand currents; curved so feeding edge is above sediment
- Large rounded valve to increase SA, prevent sinking + lid-like valve for stability 
- Monomyrian to stay closed

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  • Extend siphons out of the burrow for feeding and respiration
  • Move using muscular foot to burrow into sediment

Cytherea - shallow burrower in littoral zone
- Shallow pallial sinus shows short retractable siphons
- Large muscles scars to stay completely closed for protection from dessication
- Strong growth lines to move and grip sediment in burrow, streamlined to move easily

Solen - deep burrower in littoral zone
- Large pallial sinus shows large siphons - gape means retractable foot and siphons
- Small adductor muscle scars; no need to open/close
- Elongate to move up and down the burrow

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- Ears to direct water currents away from shell; longer hinge line increases stability
- Tiny eyes among sensory tentacles to sense shadows or movement of predator
- One flat, one curved valve = hyrdofoil effect
- Ribbed corregated thin valves means strong but lightweight
- Monomyarian to repeatedly close valves while the ligament opens them - swim!

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Body enclosed in a CaCO3 shell to form a vertically coiled unchambered spiral (helical/spiral). Has recognisable head and tentacles to sense surroundings, crawls using muscular foot, gut twists 180 to fit in shell, when threatenned the whole body retracts.

DEXTRAL = aperture on right hand side
SINISTRAL = aperture on left hand side

Mode of Life:

  • Large siphonal canal to seperate inhalent and exhalent currents
  • Thin shells if low energy, thick shells if high energy

Turitella - burrowing in high energy environment
- High spire (to anchor), tapered shell with small apical angle
- Filter feeder

- Short siphon extends upwards and forwards to take in clean water for respiration
- Carnivorous - rasp-like tongue  on soft tissue of prey (+ Natica uses acid and drills into prey)

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When it dies it falls through the water column and is aligned by currents - Palaeocurrent analysis of death assemblage

Mode of life:

  • Predator
  • Nektonic
    Swims vertically by gas in the chambers being adjusted which controlled by the siphuncle
    Swims horizontally by tentacles and jet propulsion (water is forced out in a rapid stream in the opposite direction, propelling the belemnite forward).
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5 calcerous plates which show 5 fold symmetry - upon death the organic matter decays and the skeleton falls apart. (the degree of disarticulation depeds on energy)

Mode of Life:

  • Sessile or nektonic
  • Found in all water depths
  • Shallow marine reefs - found in bioclastic limestone 
    (Same conditions for growth as corals)
  • FILTER FEED using tube feet on brachia
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Used to correlate rocks and are preserved in ocean floor sediments (CHALK/CHERT)

Important Features...

  • Small size
  • Abundant
  • Short life span - rapid evolution
  • V. environmentally sensitive


- 10-200 microns in diameter
- Sporopollenin composition
- Controlled by latitude
- Found on land or in shallow water

SPORE = moss/ferns (Ord-present)
POLLEN = seed bearing plant (Dev-present)

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Ostracod (Cambrian - Present) - indicates salinity, limited dating use
- <2mm in length, benthonic
- CaCO3; 2 valves, hinge with teeth/sockets, adductor muscle

Conodonts (Precambrian - P-T) - dating, env, correlation                               
- 200um to 5mm
- calcium phosphate teeth in pairs                          - 

Radiolaria (Precambrian - Present) - stratigraphy, palaeoenv                           
- 30um to 2mm; marine + planktonic                                                      
- silica skeleton (preserved below CCD)

Foraminifera (Cambrian - Present) - stratigraphy for oil or evolutionary change
- simple single celled with protective test
- 1um to 110mm, benthonic or planktonic

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