definition of a bird - Answers anything alive today with feathers, are warm blooded with hollow bones
4 toes
paper thin skin
aerodynamic with compact skeleton (short bony tail and small head)
3 fingers
keels for flighted and none for flightless
toothless
how fossils are dated - Answers based on stratigraphy (studying how deeply a fossil is buried in the rock
strata) and radioisotope dating
reasons for the lack of bird fossils - Answers many eaten
small bones didn't survive
only ones we have are from volcanic stone or sandstone where bird gently covered by silt or ash until
fossilized
most found are aquatic birds (loons, gulls, petrels, cranes, etc)
Archaeopteryx - Answers first fossil animal with feathers
discovered in Barvaria in 1861
had reptilian teeth
tail heavy
couldn't fly
most basal bird in avian lineage
the fact that cladistics are not static, relationships change as new fossils are found - Answers they
change as fossils of new species are found and their morphology info is entered into data sets
-individual cladograms can vary, depending on the morphology data utilized to make them; up to
scientists' judgement
characteristics of theropod dinosaurs - Answers bipedal
carnivorous
, many had feathers
laid eggs in nest
ornithurines give rise to modern birds arising in the last 5 million years - Answers had superior flight
capability than basal avian species because of several anatomical changes. elongated coracoid bones
and strengthened rib cage to provide skeletal strength for physical stress of flight and large keeled
sternum to support flight muscles
anatomical differences between prehistoric birds and the birds of today - Answers no present birds have
teeth, birds of today are better adapted for flight, past birds had claws on wings
controversies and unanswered questions related to birds evolving from theropod
dinosaurs - Answers theropod digit morphology data and current embryo developmental data;
theropods had well-formed I-II-III with vestigial 4th and 5th digits but as theropod lineage evolves to
Archaeopteryx, only I-II-III remained
the evolutionary advantages (functions) for the development of feathers - Answers insulation,
camouflage, social signaling, anti-predator defense mechanism (central tail feathers)
arboreal versus cursorial origin of flight - Answers Arboreal: birds lived in trees or climbed trees and
started flying by gliding down from branch to branch or tree to tree. As feathers became more
structured and stronger, flapping flight would evolve during the gliding until birds had the flight muscles
to sustain airborne flight.
Cursorial: basal bird species ran along the ground with their forearms outstretched for balance as they
pursued prey or ran from predators. Forearms covered with feathers would've increased lift and as
these feathers grew longer and stronger, more lift would've been generated until animal was off the
ground. Full flight would've eventually evolved. This hypothesis strengthened by fact that theropod
ancestors of birds were terrestrial, long legged, bipedal and lightweight.
arboreal - Answers leaping from trees
cursorial - Answers taking flight by running or taxiing
the fact that current phylogenetic relationships between birds are based both on
structural(morphological) similarity and molecular genetic data and are constantly
evolving. - Answers no agreement among phylogeneticists as to the number of bird orders; Kingdom,
Phylum, Class, Order, Family, Genus, Species
convergent evolution - Answers Process by which unrelated organisms independently evolve similarities
when adapting to similar environments
taxonomy neornithes - Answers modern birds