Avian Lineage

Question 1

Describe how mesotarsal ankles define avian-lineage archosaurs

Answer 1

• found widely in tetrapods in modern day
• large astragalus and small calcaneum - proximal tarsals
• also distal tarsals
• single hinge
• mesotarsal joint between sets of tarsals, tarsals distal to distal tarsals

Question 2

Describe tarsometatarsus in birds

Answer 2

• can see tibia and proximal tarsals & distal and metatarsals separate in juvenile
• fused into tibiotarsus and tarsometatarsus in adults

Question 3

Describe pterosaur hindlimbs

Answer 3

• more like birds than bats
• metatarsals fuse in birds, separate in bats

Question 4

What are the 3 vertebrate wing structures?

Answer 4

• pterosaur ‘patagium’: wing from digit 4 to hindlimb, digits 1-3 very short
• bat interdigital ‘patagia’: digits 2-5 have patagia between them and a patagia from digit 5 to leg
• bird feathered forelimb: feathers instead of patagia

Question 5

Describe the pterosaur eco-morphological diversity of skulls

Answer 5

• insectivore: short head, pin-like teeth, fenestration
• piscivore: spaced, intermeshed fangs
• filter feeder: ~1000 bristle-like teeth in up-curved jaw
• durophagous: tweezer-like jaw & crushing teeth, shellfish diet

Question 6

Describe the manu bones in avian-line archosaurs and bats

Answer 6

• most of wing structure is digits not arm,
• longest is phalanx