Trilobites

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Phylum
Arthropoda
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When were trilobites alive?
Cambrian- end of Permian period
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Class
Trilobita
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Skeleton
Hard exoskeleton, made of chitin
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Function of the skeleton
Anchorage for muscle, provides protection and support, made up of 3 layers- a waxy outer layer and two further layers of chitin and protein, may have sensory hairs to detect chemicals or changes in environment
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What are the appendages?
Jointed legd and antennae
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Function of appendages
Appendages on thorax used for moving and feeding
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Where were the jointed legs attached to?
Pleuron
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Function of jointed legs
Walking or swimming, also had gills attached to them for respiration
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Name a place in which the appendages were fully preserved
Burgess shale
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Describe trilobite eyes
Compound eyes made of calcite lenses and allowed wide angled vision
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What is a facial suture?
A line of weakness where the exoskeleton breaks first during ecdysis
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What is the librigena?
'free cheek' part of cephalon which breaks away from the skeleton during ecdysis
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What is the genal angle
Part of the cephalon which may have spines attached to it
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What is the glabella?
Part of the cephalon which is formed by the presence of the stomach, which is inside the head
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What is the a pleuron?
Segment adjoining the axis
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What is the a thoracic segment?
1 thoracic segment is made of three articulating plates
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What is ecdysis?
Where the trilobite shed its exoskeleton at various times in its life
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Where would the skeleton fracture?
Along the suture lines
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What happens after ecdysis?
A period of rapid growth, before the new exoskeleton was formed
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Define isopygous
Where the cephalon and pygidium are of similar sizes
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Define macropygous
Where the pygidium is larger than the cephalon
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Define micropygous
Where the pygidium is much smaller than the cephalon
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What does benthonic mean?
Living on the bottom of the sea or a river, maybe in the sediment or on top of it
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What does epifaunal mean?
Living on top of the sediment
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What does infaunal mean?
Living in the sediment, maybe a burrower
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What does planktonic mean?
Flaotin in the water column, usually in open ocean
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What does pelagic mean?
Living in the water column
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Name a benthonic trilobite and its mode of life
Calymene. benthonic epifaunal
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Name and describe 3 morphological features of Calymene/benthonic trilobite
1. Many pleura= Supports gills for respirations and legs for walking, flexible thorax=enrollment. 2. crescent shaped eyes= 360 vision, hunter or scavenger 3. large & not streamlines= no need to be small, it walked- no need for streamlining
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Name a planktonic trilobite
Agnostus
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Name and describe 3 morphological features of a Agnostus/planktonic trilobite
1. No eyes= animal did not hunt, food source was in sediment. 2. Inflated glabella= possibly filled with fat or gas to aid buoyancy in water column. 3. Very small= stay afloat. 4. Few pleura= limited felxibility
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Name a nektonic trilobite and its mode of life
Deiphon. Pelagic
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Name and describe 3 morphological features of Deiphon/nektonic trilobite
1. Eyes on stalks= 360 vision, could see underneath animal, hunter or scavenger. 2. Inflated glabella= buoyancy device in water column. 3. Small in size= stay afloat. 4. Separated pleura= many legs for swimming, increased s.a. to aid buyoncy
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Name a burrowing trilobite and its mode of life
Trinucleus. Benthonic epifaunal or infaunal
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Name and describe 3 morphological features of Trinucleus/burrowing trilobite
1. No eyes= unlikely to hunt but get its food source from organic-rich sediment. 2. Wide cephalic fringe= spread its mass on soft substrate or as a digging tool. 3. extended fenal spines=spread its mass, defence4. Pitted cephalic fringe=sensory hairs
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Other cards in this set

Card 2

Front

Cambrian- end of Permian period

Back

When were trilobites alive?

Card 3

Front

Trilobita

Back

Preview of the back of card 3

Card 4

Front

Hard exoskeleton, made of chitin

Back

Preview of the back of card 4

Card 5

Front

Anchorage for muscle, provides protection and support, made up of 3 layers- a waxy outer layer and two further layers of chitin and protein, may have sensory hairs to detect chemicals or changes in environment

Back

Preview of the back of card 5
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