Trilobites Flashcards Preview

Geology F795 > Trilobites > Flashcards

Flashcards in Trilobites Deck (16):
1

Phylum and class?

Arthropoda
Trilobita

2

Exoskeleton?

Chitin

3

Three main body parts

Cephalon, thorax, pygidium

4

How does it breathe?

Gills attached, underneath pleuron with appendages

5

Describe morphology of cephalon

Several structures, compound eyes, facial sutures, free cheek, fixed cheek and glabella. Spines may be attached at genal angle, for defence or to spread mass

6

Describe morphology of the thorax

Made up of thoracic segments, each has pair of appendages and gills, two pleurae and segment from axis. Many articulated plates which may enable it to enroll

7

Describe morphology of the pygidium

Several segment fused together

8

What is ecdysis?

Exoskeleton cannot grow so is shed. Fractured along lines of weakness like facial sutures, separated fixed cheek from free cheek, animal wriggles out, period of rapid growth before new skeleton forms

9

When did trilobites live?

Cambrian to Permian-died at end Permian extinction, peaked in Ordivician

10

Example of epifaunal trilobite

Calymene

11

What morphological features did Calymene posses?

Many pleura, to support many legs and gills, flexible so could enroll
Compound eye, ability to see 360 degrees, so safe from predation, may be active hunter
Large and not streamlined, didn't need to swim or float, walked on sea floor

12

Name a pelagic trilobite

Agnostus

13

What morphological features did Agnostus possess?

No eyes, did not need to hunt for food as filter feeder
Very small and light, so could easily float in water column
Inflated glabella, filled with gas for buoyancy
Few pliers, didn't swim, limited flexibility

14

Name a nektonic trilobite

Dephion

15

What are the morphological features of Dephion?

Eyes on stalks, could see all around it
Inflated glabella for flotation
Very small size, light to stay afloat
Numerous separated pleura with spines, could be used to paddle, increase surface area for buoyancy

16

Name a burrowing, infaunal trilobite

No eyes, unlikely to hunt, couldn't see in sediment
Wide cephalic fringe, spread mass on soft sediment
Extended genal spines, defence and to spread mass
Pitted cephalic fringe, sensory hairs