Lecture 12 - 2.0

Question 1

What is a Sauropsida?

Answer 1

Lizard-like in appearence

Question 2

Sauropsids: Turtles (Main Characteristics) (2):

Answer 2

1. Hard shell and solid (anapsid) toothess skull (stable over time)
2. Ventral plastron and dorsal carapace made up of fused bony elements covered by keratin scutes

Question 3

Origin of the Turtle Body Plan (2 Major Components):

Answer 3

1. Shell: [vertebral + ribs] and dermal [keratinized osteoderms] bones
2. Position of scapula: inside of rib cage

Question 4

Two Hypotheses for Turtle Development:

Answer 4

1. Classic Transformationist View: Gradual transformation/modification of pre-existing features
2. Emergentist View: Rapid evolution vis changes in developmental regulation

Question 5

Sauropsids: Lepidosaurs (2 Main Groups):

Answer 5

1. Sphenodontids = tuatara (single extant species)
2. Squamates = Lizards and snakes

Question 6

Skull Adaptations in Squamates (5):

Answer 6

1. Loss of temporal bar(s) around fenestae
   - Lower absent in lizards
   - Upper and lower absent in snakes
2. ‘Opening’ of skull allowed for improved jaw mobility and the ability to swallow
3. Cranial kinesis (mobility) in lizards and snakes modified jaw mechanics
4. Transcranial Joints across the top of the skull
   - Snakes = front of orbit (single)
   - Lizards = rear of orbit and back of skull (double)
5. Ability of quadrate bone to rotate about dorsal connection with braincase

Question 7

Skull Adaptations in Squamates (Loss of Temporal bar(s) around fenestrae) (2):

Answer 7

1. Lower absent in lizards
2. Upper and lower absent in snakes

Question 8

Skull Adaptations in Squamates (Cranial Kinesis):

Answer 8

Mobility in lizards and snakes modified jaw mechanics

Question 9

Skull Adaptations in Squamates (Transcranial Joint(s) Across the Top of the Skull) (2):

Answer 9

1. Snakes = front of orbit (single)
2. Lizards = rear of orbit and back of skull (double)

Question 10

Cranial Kinesis: Lizards (2):

Answer 10

1. Opening jaws leads to snout tips up
2. Closing jaws leads to snout tips down
   - Equal perpendicular force of both jaws on food item
   - Less chance prey is lost

Question 11

Cranial Kinesis: Snakes (4):

Answer 11

1. Lower jaw is loosely hinged
2. Two sides of mandible can come apart as they are only connected by muscle and skin
3. Skull and upper jaws are moveable
4. Moveable quadrate bone links jaw and skull

Question 12

Crawling Locomotion: Life Without Limbs (Lateral Undulation) (2):

Answer 12

1. Moving waves push sideways against contact points
2. Generated a reaction force with a forward component (lateral components cancel out)