Trilobites (Chapter 14)

Question 1

Edicarian Trilobitomorphs

Answer 1

explain diversity a& drastic radiation of trilobites at beginning of Cambrian
shelly organisms existed before explosion, in microscopic size

Question 2

Trilobites

Answer 2

strictly marine
mobile swimmers & floaters
majority crawlers (epifaunal)
handful dug down (infaunal)
various growth stages, each can look radically different
  (earlier stages - microscopic & may be inarticulate)
roll up - defense or feeding position
sizes for each species varies 
Cambrian - calcium phosphate shell

Question 3

Trilobite lobes

Answer 3

axial - center lobe - protects digestive system

pleural lob - 2 side lobes on each side of axial - cover appendages

Question 4

Cephalon

Answer 4

region of head
fused segments
eyes, cheeks, facial sutures, & glabella

Question 5

Trilobite eye

Answer 5

highly complex with random or organized lenses

Question 6

glabella

Answer 6

smooth part b/w & above eye

Question 7

cephalic suture

Answer 7

separates inner fixed & outer freed cheeks
may inarticulate after death
sometimes useful in classification

Question 8

pygidium

Answer 8

terminal part of body - tail of trilobite

Question 9

thorax

Answer 9

middle section of body - holds abdomen & appendages (legs)

Question 10

Cambrian Trilobites

Answer 10

same segments in each body part
usually smaller
ex: Hypagnostus parvifrons

Question 11

Middle Paleozoic Trilobites

Answer 11

better locked spines & sockets around skeleton

ex: Pharops plana

Question 12

Upper Paleozoic Trilobites

Answer 12

usually fewer possible species
trilobites began to die out in diversity
ex: Ameura sangomonensis