Ch 16 Turtles

Question 1

sister group of turtles

Answer 1

archosaurs (crocs, dinos, birds)

Question 2

turtle shell composition

Answer 2

2 separate pieces, evolved independently,
carapace and plastron,
mainly endochondral bone, some dermal bones on outside,

Question 3

carapace

Answer 3

upper shell made primarily of ribs and vertebrae, enclosing girdles

Question 4

plastron

Answer 4

lower shell made primarily from shoulder girdle bones (endochondral) and gastralia (dermal)

Question 5

gastralia

Answer 5

ventral dermal bones in sauropsids

Question 6

eunatosaurus

Answer 6

early primitive turtle ancestor,
Late Permian,

Question 7

derived characteristics (synapomorphies) of eunatosaurus

Answer 7

• wide and flat ribs, similar to primitive carapace
• number, size, and structure of vertebrae nearly identical to some turtles
• no intercostal muscles, like turtles

Question 8

primitive characteristic (plesiomorphy) of eunatosaurus

Answer 8

had teeth and diapsid skull, unlike modern turtles

Question 9

pappochelys

Answer 9

middle triassic (mesozoic era),
- discovered in 2015
- broad ribs
- partial plastron created by broadening of gastralia bones
- sternum lost
- diapsid (primitive)
- had teeth (primitive)
- long tail (primitive)

Question 10

odontochelys

Answer 10

late Triassic (Mesozoic Era),
- fully developed plastron, expansion and ossification of gastralia (derived)
- only partial carapace, broadened ribs and distinct vertebrae
- anapsid skull (derived)
- had teeth (primitive)

Question 11

proganochelys

Answer 11

late triassic (mesozoic era),
- earliest known turtle species with fully formed shell (derived)
- long tail
- lacked full neck retraction, unlike modern turtles
- anapsid
- lacked teeth (derived)

Question 12

turtle synapomorphies

Answer 12

1. shell: 2 sections of bony skeleton and covering, body axis is not flexible,
   affects locomotion and respiration
2. limb girdles deep to ribs,
   unique among vertebrates,
   ribs grow out laterally to enclose girdles
3. no teeth (keratin beak only)

Question 13

modern turtle characteristics (not synapomorphies)