lecture 18 Flashcards
The Bird-Dinosaur Connection
We already know that modern birds (aves) share several
traits with non-avian theropod dinosaurs:
-hollow bones ( limb bones
braced by struts)
-bipedal and walk on their toe bones
-furcula
-complicated & efficient air sac system
-feather integument & bowed ulna
-pennaceous feathers
-pubis pointing to the back
Modern birds have many great
adaptations for strong,
powered flight, including _____
Large chest muscles (pectorals)
and many fused bones (see slide 4)
Modern Birds Limb bones are _______
thin-walled
and pneumatic (small ducts in
the bones pass air through them
during respiration).
Ducts connect to air sacs and
the bird’s lungs.
The wing feathers of modern birds include the :
- primaries
- secondaries
- tertials
Confuciusornis: A transitional bird
Confuciusornis is an Early
Cretaceous bird from northern
China. It is a “missing link”
between archaic birds &
modern birds.
Archaeopteryx: An ancient bird
In 1860 a single fossil feather was
discovered in the Solnhofen
Limestone (150 Ma) Late Jurassic. At that
time the only known feathered
animals were birds.
A year later the first of nearly a
dozen skeletons was found. The
bird was named Archaeopteryx
(“ancient wing”).
Archaeopteryx & Modern Birds
The differences Archaeopteryx has:
-Teeth
-clawed digits (modern bird has carpometacarpus alula, no claws)
-Small sternum (modern bird has large keeled sternum
No fusing (modern bird has synsacrum & fused pelvis)
Long bony tail ( Modern bird pygostyle)
No fusing, enlarged hyperextended digit 2 ( Modern bird tarsometatarsus no sickle claw)
Comparison: Archaeopteryx & Non-Avian Paraves
Both have small serrated teeth, feathers, S-shaped neck, long bony tail, backward-facing pubis, 3 pedal digits (including retractable pedal digit 2 + hallux), Hollow bones, long clawed hands with 3 digits, furcula, and small bony sternum
