The aves Flashcards
How many species of bird are there?
Approx. 10,000
The birds are one of the most diverse vertebrates clades, second only to the…?
Teleosts
Which group were the birds descended from?
Saurischian theropod dinosaurs.
What were the feathers of a) Alverezaurid and b) Caudipteryx like?
a) Filamentous proto-feathers
b) Had large feathery tail plumes
It was thought feathers first evolved for what purpose?
Thermoregulation or display, not flight.
What was microraptor?
A dromeosaur from China, was fully arboreal with true feathers.
Archaeopteryx was the intermediate between theropods and birds. What time period was it from?
Late Jurassic.
Archaeopteryx was the intermediate between theropods and birds. What were its a) theropod and b) bird-like features?
a) Long tail, teeth and claws
b) Forelimbs with feathers, beak-like structure
What was Vagavis?
A neornithine from the late Cretaceous. This is the group containing modern birds.
Birds originate from the late Cretaceous. When did they diversify?
The Cenozoic.
List 3 synapomorphies of theropods and birds.
- 3 digits
- Half-moon shaped carpal bone
- Furculae
a) Theropods and b) birds both have 3 digits, but different 3 digits. Which ones have they both retained?
a) Thumb, index and middle
b) Middle 3 digits
What is a ‘half-moon shaped carpal bone’?
Wrist bone: reduces drag and allows birds to move their wings in a ‘figure of 8’ motion.
Define the furculae.
Fused clavicles (collar bones), form the characteristic ‘wish-bone’.
What are the furculae used for in modern birds?
Flight muscle attachment.
List 10 synapomorphies of modern aves.
- Backwards-facing first toe
- 3 digits
- Elongated metatarsals
- Large, keeled sternum
- Keratinous beaks
- No true teeth
- Enlarged furculum
- Enlarged sacrum
- Pygosytle
- Short femur and longer lower-leg bones
Why do birds have a backwards-facing first toe?
To grip branches.
Describe the arrangement of the digits in the wing.
The first digit sticks up like a little spur. The second digit is the alula. The third digit is the main wing-bearing bone.
Define the alula.
A bone that prevents stalling at high angles of attack.
Why have birds lengthened their metatarsals?
Most species adopt a digigrade stance.
What is the sternum for?
Flight muscle attachment.
Why is the sacrum enlarged?
Provides stability when landing on hard surfaces if the pelvis is strongly joined to the thoracic skeleton.
Define the pygostyle.
Fused caudal vertebrae to support the tail feathers and flight muscles. Helps to control flight.
Why do birds have a short femur and elongated lower leg?
Allows more mobility in the knee region.
