birds 1

Question 1

How did birds evolve

Answer 1

Descendants of the Theropoda (small carnivorous dinosaurs) - first suggested by Huxley (1860) but disputed as based on little evidence

Question 2

Features of birds

Answer 2

1) adapted to wide range of habitats
2) adaptive feeding mechanisms (beaks)
3) underwent sustained miniaturization from theropods to birds
4) most modern birds less then 100g
- bones became hollow
5) birds have paedomorphic dinosaur skulls

Question 3

Dinosaur features of birds

Answer 3

1) egg laying -> parental care
2) scales (feather = scales)
3) s-shaped neck
4) tridactyl foot + digitigrade posture
5) bipedal
6) fused sternum (same as theorpods)

Question 4

example of a transitional form between dinosaurs and birds

Answer 4

• Archaeopteryx = transitional form
  1) Reptilian features = thick bones, toothed jaw, no fusion of vertebrae
  2) Avian features = well developed feathers, 3 fingers , s-shaped neck

Question 5

Examples of bird/theropod in early cretaceous

Answer 5

E.G. Mononykus - specimen with strange forelimbs, could not fly , but otherwise similar to known birds

Question 6

example of birds in mid-late cretaceous

Answer 6

E.g. Enantiornithes (“opposite birds) - most diverse group in cretaceous

E.g. Enalionis - flightless seabirds of late cretaceous

Question 7

Birds summary

Answer 7

1) birds evolved from theropod dinosaurs
2) modern birds diverged about 150 MYA
3) growing fossil evidence for diverse cretaceous avians
4) extant birds carry many dinosaur features