Aplacophora, Monoplacophora, Polyplacophora, Scaphopoda

Question 1

ocellii

Answer 1

Chiton eyes

Question 2

aesthetes

Answer 2

Chiton light sensing structures

Question 3

special feature of chiton radula

Answer 3

coated in biomineralized iron oxide

Question 4

mantle groove

Answer 4

infold between foot and mantle (ctenidia are here in chitons)

Question 5

scaphopoda: atypical features

Answer 5

no ctenidia, no heart, no eyes

Question 6

scaphopoda: molluscan features

Answer 6

shell, foot, tentacles, mantle

Question 7

Aplacophora (molluscan features)

Answer 7

Radula (most), ctenidia (only Caudo.), foot (most)

Question 8

Monoplacophora: serially repeated structures

Answer 8

ctenidia (5 pairs), muscles (8 pairs), kidneys (5 pairs), gonads (2 pairs)

Question 9

Arguments for segmented molluscan ancestor

Answer 9

1. molecular data says yes (but contaminated!)
2. segmented Aplacophora fossil (probably annelid)
3. NEW molecular data suggests ceph- and mono- have segmented ancestor
4. repeated structures in mono- and poly-