Trilobites Flashcards
What are the 4 types of Trilobite
Calymene
Agnostus
Deiphon
Trinucleus
What is the phylum and class for Trilobites
Phylum - Arthropoda
Class - Trilobita
When did Trilobites evolve and become extinct
Evolved - Cambrian
Extinct - End of permian period
What is their exoskeleton made out of
Chitin
What does the exoskeleton act as
An anchorage for muscles
a suit of armour
What are the jointed legs and antennae known as
Appedages
What were the appendages used for
Moving
Feeding
What is a pleuron
Segment adjoining the axis
Each pleuron had a pair of what
Jointed legs
What did the legs have attached to them
Gills
What is the cephalon
The head
What role did the antennae have
Feeding
Sensory role
What is the cephalon made up of
Eyes
Facial structures
Free cheeks
Glabella
How would you describe the eyes and what did they consist of
Compound eyes
Many small lenses made of calcite
What may be attached to the glabella at the genal area
Spines for protection or spread the organisms mass
What is the thorax made up of
Thoracic segments
What does each thoracic segment possess
A pair of appendages and gills in life
What does each thoracic segment consist of
Two pleurae
A segment from the axis
What may each pleuron have
Spines extending from them
The thorax is made up of many what and making it what
Individual plates articulated together
Making it very flexible
Some trilobites were so flexible they could what
Enroll
What is the pygidium
Tail
What is the pygidium composed of
Several segments fused together
What is the process called by which a Trilobite sheds its skin
Ecdysis
How did ecdysis occur
The exoskeleton fractured along the lines of weakness such as the facial structures. This separated the fixed cheek from the free cheek along the surface of the eye. The animal could then free its self then go on a period of rapid growth before the new exoskeleton was completely formed
What is adaptive radiaion
Its when Trilobites evolved to be a variety of different shapes and sizes probably as a response to the environment they lived in and the selection pressures in the environment
What is an example of a bethonic trilobite
Calymene
How big is the Trilobite Calymene
They are large
What do they show little of (Calymene)
Streamlining
What type of eyes do they have (Calymene)
Complex compound eyes
What did they have a lot of and what ability did it give them (Calymene)
Lot of pleura
The ability to enrol
mode of life for Calymene
Benthonic
Epifaunal
Living on the substrate
Active hunters
Probable function for many pleura (Calymene)
Many pairs of legs for walking
Supports many gills for respiration
Can enrol for protection
Probable function for present-shaped compound eyes set high on the cheeks (Calymene)
Ability to see forward, backwards and sideways
Complex eyes may mean the animal was a hunter or scavenger
probable function for large and not streamline (Calymene)
Animal did not swim so no need to be small, light and streamline
What is an example of a pelagic trilobite
Agnostus
How big is the trilobite Agnostus
These are small and probably light trilobites
What did they lack (Agnostus)
Eyes
What did they have few of and what does this mean (Agnostus)
Pleura
Therefore few gills and legs
Where are they found (Agnostus)
They are widespread geographicaly
What type of sediments are they found in and what energy environment (Agnostus)
Shales
Low-energy deep waters
What is their mode of life (Agnostus)
Pelagic
Planktonic
Possible that their lack of eyes means a benthonic lifestyle in deep, cold water on ocean floor with no or minimal light
Probable function for no eyes or very small eyes (Agnostus)
Blind or nearly blind which means the animal did not hunt and its food source was filtered from the sea water or organic rich sediment
Probable function of inflated or large glabella and large pygidium (Agnostus)
Maybe filled with fat or gas
Seen as possible flotation device
Probable function for very small size (Agnostus)
Small to possibly stay afloat in water column
Probable function of few pleura (Agnostus)
Few legs which may be used as paddles or to steer animal
Limited flexibility and movement restricted
What is an example of a Nektonic trilobite
Deiphon
How big is the trilobite Deiphon
Small
What do they show (Deiphon)
Streamlining and have complex compound eyes on stalks
What is their mode of life (Deiphon)
Planktonic
living in water column and nektonic
Actively swimming possibly active hunters
Probable function for eyes on stalks (Deiphon)
Ability to see forwards, sideways, backwards and underneath
Complex eyes may mean the animal is an active hunter of scavenger
Probable function for inflated or large glabella (Deiphon)
May be filled with fat or gas which could be a possible flotation device
Probable function for very small size (Deiphon)
Small to stay afloat in water column
Probable function for numerous separated pleura, with spines (Deiphon)
Had many legs for swimming
The spines and separated pleura increased surface area to aid buoyancy
What is an example of a Burrowing trilobite
Trinucleus
What do these types of trilobites lack (Trinucleus)
Eyes
How was their cephalon modified (Trinucleus)
Shovel shaped with pits running along its margins
What is their mode of life (Trinucleus)
Benthonic
Living on substrate as epifaunal or infernal organisms
May have dug shallow borrows for protection or feed on organic rich sediment
Lived at a 200M depth
Probable function of no eyes (Trinucleus)
Unlikely to hunt
Fed on organic rich sediment
Probable function of wide cephalic fringe (Trinucleus)
Maybe to spread was on soft substrate
Or as a digging tool
Extended genal spines (Trinucleus)
To spread mass
As a defence weapon
Pitted cephalic fringe (Trinucleus)
Pits may have housed sensory hairs in life
These may have been able to detect the movement of prey and water currents on the sea floor or temperatures or chemicals
