Amniota

Question 1

Synapomorphies

Answer 1

• Claws/nails at the end of digits
• No water-breathing larva
• No lateral line system
• 2 sacral vertebrae
• Internal fertilization via penis
• Astragalus from fusion of 3 or more of the previous tarsals

Question 2

Amniota egg

Answer 2

Extraembyronic membranes
- Amnion: mechanical protection. From meso/ectoderm.
- Allantois: waste removal and respiration. From meso/endoderm.
- Chorion: water absorption, respiration, and protection. From ecto/mesoderm.
- Yolk sac: energy supply, yolk absorption. From meso/endoderm.

Question 3

Non-Amniota egg

Answer 3

• Must stay moist
• No extraembryonic membranes - only jelly-like layers
• Vitelline membrane surrounds the embyro

Question 4

Skull Fenestration Patterns

Answer 4

Linked to the evolution of jaw-closing muscles.
Anapsid: no fenestrae, turtles
Synapsid: lower fenestra between the jugal, postorbital, squamosal, and quadratojugal, 3 subdivisions of the original muscle for “chewing” or movement of jaws in many ways, multiple directions of closing.
Diapsid: ancestral turtle and snakes. Lower fenestra (same as synapsid). Upper fenestra between postorbital and squamosal.

Question 5

Early vs Derived Synapsid

Answer 5

Early - many bones in lower jaw, small limbs, sprawled posture, long ribs causally, big and heavy pelvic and shoulder girdles
Derived - fewer bones in lower jaw, tucked limbs, lighter shoulder girdle related to running and diaphragm.

Question 6

Evolution of ankles

Answer 6

Basal tetrapod: 3 proximal tarsal bones are fused = astragalus
Derived synapsid: larger astragalus and calcaneus which overlap, calcaneal heel, and the ankle joint path is between the astragalus and tibia
Basal reptile: larger astragalus between tib/fib, under tib, smaller calcaneus and larger fib, ankle joint path between distal tarsals and astra/calc
Lepidosaura and basal turtle: fused astra/calc, hinge, same path as basal reptile
Basal archosaur: ankle joint path between astra and tarsals and between astra/calc then calc and fib
Basal crocodylomorph: peg and lock = weird sideways movement. Same ankle joints path as basal archosaur.
Avemetatarsalian: distal tarsals and metatarsals are fused, ankle joint path between fused astra/calc and fused tarsals/metatarsals

Question 7

Circulation

Answer 7

No cutaneous circulation, lose many arches

Question 8

Waterproof skin

Answer 8

Multi-layered keratinous epidermis and thick dermis

Question 9

Kidney drained by the ureter

Answer 9

Kidney: removal of waste/toxins by filtering blood
Loop of Henle: water/ion/salt regulation = concentration of urine
- Move water based on solute concentration
- More and more water is moved down the descending loop
- Ascending loop is Na+ and Cl- only
ADH makes the collecting duct more permeable to water = organism is more hydrated

Question 10

Costal Aspiration

Answer 10

Synapsid: tidal flow ventilation, diaphragm, axial muscles for negative pressure on inspiration, alveoli = used and new air in same place
Sauropsida: flow-through ventilation, faveoli = gas exchange surface always has fresh air
Locomotion - can conflict with ventilation i.e forcing air out or collapsing lung with diagonal gait