Bird Lecture specific

Synapsid skull

Single low temporal fenestra

Gives rise to mammals

Diapsid skull

Temporal fenestra and antorbital fenestra

Gives rise to reptiles and birds

Reptiles & Birds – Shared Traits skull features

antorbital fenestra

occipital condyles

Reptiles & Birds – Shared Traits middle ear

Single middle ear bone

Reptiles & Birds – Shared Traits Jaw

Lower jaw composed of several fused bones

Reptiles & Birds – Shared Traits integument

Integument: the stuff what keeps your outsides out and your insides in

“Outermost protective layer of an organism”

Reptiles & Birds – Shared Traits integument Keratin

Reptiles and birds: beta-keratin “sheets” for scales and feathers

Mammals: alpha-keratin “spirals” for hair and horns

Reptiles & Birds – Shared Traits blood cells

Mammalian RBC - enucleated

Reptile and bird RBC - nucleated

Reptiles & Birds – Shared Traits offspring

Ovipary, lays eggs

Reptiles: leathery shell

Birds: hard, mineralized shell

Reptiles & Birds – Shared Traits Overview

• Presence of antorbital fenestra

• Single occipital condyle

• Single middle ear bone

• Lower jaw composed of several fused bones

• Similarity in integument – scales and feathers

• Nucleated red blood cells

• Ovipary

Traits of birds - feather function

• Flight

• Insulation

• Social signaling

Traits of birds

Feathers

Traits of birds - mouth

No teeth, bills, weight reduction

Traits of birds - How do they walk?

Bipedalism and digitigrade feet (walks on toes)

Traits of birds - bones

fusion and reduction of bones of hands, head, pelvis

Traits of birds - bone structure

pneumatic bones

Traits of birds - breastbone

well-developed keel of breastbone

Traits of birds - wishbone

Furcula

Traits of birds - overview

• Feathers

• Lack of teeth; bills

• Bipedalism and digitigrade feet

• Fusion and reduction of bones of hands, head, pelvis

• Pneumatic bones

• Well-developed keel of breastbone

• Furcula (wishbone)

Other traits of note

• Small size (relatively speaking)

• Highly developed brains and sensory systems

• Large, energy-rich eggs

• Extensive parental care

• Highly social

Ancient wing from the lithographic stone

Archaeopteryx lithographica

Archaeopteryx lithographica - bird traits feathers

Fully feathered

Wing feathers were specialized into primaries and secondaries

Feathers were asymmetrical

Archaeopteryx lithographica - bird traits bones

Clavicles fused into furcula

Partly fused metatarsals (leg bones)

Archaeopteryx lithographica - bird traits structure

Had wings and tail

Bird-like forelimb

Archaeopteryx lithographica - reptile traits

Small braincase

Hand bones not fused; claws on wing

Pelvic bones not fused

Long bony tail

Small cartilaginous sternum (no keel)

Simple ribs (lack uncinate process)

Teeth

Thecodont hypothesis

Birds did not evolve from dinosaur ancestors, rather a separate unique bird ancestor

Theropod hypothesis

Birds evolved from dinosaurs and are directly related to them, overwhelming evidence supports this hypothesis

Deinonychus antirrhopus

Bipedal, terrestrial theropod dinosaur

Fused clavicles

Hollow bones

Semi-lunate carpal bone in wrist which allowed rotation

Uncinate processes

Birds (Archaeopteryx) and theropods – shared characteristics skeleton

Large orbits (eye sockets)

Flexible wrist (semi-lunar carpals)

Hollow bones

Fused clavicles

Birds (Archaeopteryx) and theropods – shared characteristics structure

Elongated arms and forelimbs

3-fingered clawed opposable grasping hands

4 toes per foot (3 main)

Bipedal digitigrade stance

Feather

Timeline

first feather discovered

Archaeopteryx discovered

Theropod hypothesis proposed

Thecodont hypothesis - Disproved

Theropod hypothesis confirmed

Sinosauropteryx

Sinosauropteryx - basic traits

Fuzzy, with colors

Protarchaeopteryx

Protarchaeopteryx - basic traits

Vaned feathers, primitive

More recent than Archae

Sinovenator

Sinovenator - basic traits

Vaned feathers, primitive

More recent than Archae

Epidexipteryx

Epidexipteryx

Ribbon tail

Caudipteryx

Caudipteryx

Vaned feathers, primitive

More recent than Archae

Microraptor

Microraptor

feathers on both forelimbs and hindlimbs

Temporal paradox

Archeaoptryx a far more bird looking dinosaur developed before more under bird-developed dinosaurs like, Sinovenator, Sinornis or the Microraptor

The origin of flight - Arboreal theory

trees down

Ancestors climbed in trees

Jumping among branches and then gliding

Wings and feathers improve gliding; leads to powered flight

The origin of flight - Cursorial theory

ground up

Ancestors were ground-dwelling runners

leap to catch prey

Wing-assisted incline running

Surviving the KT extinction - 4 lineages which made it

Paleognathae, the ratites

Galliformes, the upland game birds

Anseriformes, waterfowl

Neoaves

Deep History facts

KT boundary - 65 million years ago

Birds, reptiles, and mammals last shared a common ancestor ~325 MYA

The forces of flight

Lift

Gravity

Thrust

Drag

How do birds generate lift

1) Bernoulli’s Law

2) Newton’s 3rd law of motion

Bernoulli’s Law

Static pressure + dynamic pressure = constant

Air moves faster over the top of the wing, reducing static pressure above it. Relatively higher pressure below the wing creates an upward pressure difference, producing lift.

Airfoil

Airfoil: symmetric teardrop or asymmetrically shaped surface

• This shape influences how air flows around the wing.

Air on top travels faster

Faster air leads to reduced static pressure above

Higher pressure below the wing helps create lift

Lift from static pressure underneath

Angle of attack

1) The wing pushes air downward. As the bird moves forward, its angled wing redirects some of the airflow toward the ground.

2) Newton's Third Law kicks in. For every action, there is an equal and opposite reaction. The wing pushes air downward, and the air exerts an upward force on the wing.

3) The upward force produces lift! The upward force from the air helps the bird stay aloft.

Flight is a drag

Airstream flowing over the surface of a wing can become turbulent

Friction between the air and wing surface = DRAG

Profile drag

frictional resistance of wing/body passing through the air

Induced drag

caused by vortices at wing tips

Dealing with drag: Profile drag

Reduce surface area (like tucking wings)

Alula: helps to maintain laminar flow at low speed

Dealing with drag: caused by wingtip vortices

Reduce area of wing tip – narrow, pointed wings

Reduce area of wing tip – slots between feathers

Fly low enough to disrupt the vortices

Wing dimensions

Wing span – tip to tip

Wing area – total wing surface

Wing chord - width

Wing loading

he ratio of a bird's body mass to its total wing surface area

Aspect ratio

Low aspect ratio: wide, short wings for short, powerful flight

High aspect ratio: long, narrow wings for gliding, soaring fligh

Flight Style as a Function of Wing Loading & Aspect Ratio

Low wing loading: Less weight per wing area; easier to stay aloft.

High wing loading: More weight per wing area; favors fast flight.

Low aspect ratio: Short, broad wings; maneuvering and burst flight.

High aspect ratio: Long, narrow wings; efficient soaring and gliding.

Systematics

the study of diversity and relationships among organisms and their evolutionary history

Taxonomy

naming and classifying organisms

A product of systematics

Phylogeny

depiction of evolutionary tree/hypothesis of relatedness

Monophyletic

contains a common ancestor and all of its descendants

Paraphyletic

contains a common ancestor and only some of its descendants

Polyphyletic

contains unrelated organisms that do not share a recent common ancestor

Node

ancestor split point

Clade

complete group of descendants

Sister group

pair of closest relatives

Outgroup

distant baseline comparison

Old birds,” Archaeopteryx and dinosaur-like things

Subclass Archaeornithes

New birds

Subclass Neornithes

Toothed jaw,” all extinct; like Hesperornis

Superorder Odontognathae

“Ancient jaw,” the 5 orders of ratites

Superorder Paleognathae