Docstoc

BirdEvolution

Document Sample
BirdEvolution Powered By Docstoc
					Where did they come from?
Archaeopteryx lithographica
Archaeopteryx
        •Fossils known only from the
        Solnhofen lithographic limestone
        quarry in Bavaria
        •first discovered in 1861
        •the perfect ‘missing link’ between
        reptiles and birds
        • (Origin of Species - 1859)
        •only other specimens found in
        1857, 1877, 1951, 1974 (birds don’t
        fossilize well . . .why?)
        •the most important and valuable
        fossil known
What was Solnhofen like then?
Solnhofen Quarry now
                A feather!




•probably for thermoregulation rather than flight
   Archaeopteryx
•dates to the Jurassic, ~160
mybp
•slightly larger than a pigeon
•did more gliding rather than
flying
•clawed ‘fingers’ for climbing
•solid reptilian bones
•had feathers and a furcula
•probably not on the mainline
of bird evolution
                     Diatryma
• ~60 mybp
• large carnivore
• 7 ft. tall and flightless
• probably ran down
  mammals and reptiles
• found in New Jersey
  (as well as elsewhere)
                Phororhacos
• ~30 mybp
• about as tall as a man
• lived in South
  America, probably
  before the before large
  predatory mammals
  lived there
   Aepyornis
•Elephant bird
•weighed ~1000 pounds
•2 gallon eggs
What is the ancestral line?
       Dinosaurs?

       Crocodiles?
  Recent research developments:
• 1984 finding of a new ‘oldest bird fossil’ from
  Texas, Protoavis
• ~75 my older than Archaeopteryx
• more birdlike, more advanced
• perhaps more on the evolutionary mainstream of
  birds
• gives stronger evidence to dinosaur lineage
• and there’s more . . .
                    Feathered Dinosaurs Found!
   Two species of dinosaur have recently been found in northeast China which possess
feathers (Qiang et al. 1998).
   Protoarchaeopteryx robusta and Caudipteryx zoui show remiges, rectrices and
plumulaceous feather impressions.
   Further, they are not birds, lacking a reverted (backwards facing) big toe (see number 2
below) and a quadrratojugal squamosal contact, having a quadrojugal joined to the quatrate
by a ligament and a reduced or absent process of the ishium. These and other characters
group Protoarchaeopteryx and Caudipteryx with maniraptoran coelurosaurs rather than
birds.
   This fossil of Caudipteryx reveals an animal with the features of a theropod dinosaur, but
with feathers over its body, which supports the idea of birds arising from dinosaurs.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:7
posted:10/13/2012
language:English
pages:13