Trilobites

Question 1

Trilobitmorphia

Answer 1

Cambrian to Permian
Calcitic exoskeleton - preserved very well
Marine
3 body regions + 3 lobes
Highly complex eyes
Free cheeks break off during molting
Tagmata = big body segments
Underside contained hypostome - mouthpart

Question 2

Trilobite Limbs

Answer 2

Limbs were softer and didn’t preserve as well
Biramous limbs - two branches, common in arthropods
Able to roll up in self defense

Question 3

Trilobite Eyes

Answer 3

Lenses made of calcite
Many forms - some had no eyes
Holochroal - large # of small lenses, wide range of vision
Schizochroal - small # of large lenses

Question 4

Trilobite Growth

Answer 4

Larval stage
Protapsid stage - glabella only
Meriapsid stage - glabella + pygidium
Holapsid stage - glabella + pygidium + thorax
After the Holapsid stage it will continue to grow, but no new segments

Question 5

Trilobite Ecology

Answer 5

Trace fossils preserve tracks- can see behavior
Prey for something - shell deformation
Wide spatial ranges - some were burrowers and confined to one area
Spiny gnathobases used to catch prey
Predators - gut remains shows us they ate soft bodied organisms

Question 6

Agnostida

Answer 6

NOT TRILOBITES
2 or 3 segments
Free swimming