Fossils and Evolution By Lauren Raynault 1/7/09 Science, Mr. Civita

WHAT IS A TRANSITIONAL FOSSIL?

TRANSITIONAL FOSSIL - Fossilized remains that illustrate an evolutionary transition - Evolutionary bridge between two groups - These fossils are the strongest evidence of Darwin’s theory of evolution Example: Dinosaur to Bird ?

WHAT IS AN ARCHAEOPTERYX?

ARCHAEOPTERYX (ancient wing) Some Facts: - A dinosaur - Dates back to 150 million years ago - An example of a transitional fossil because it is believed to be an intermediate between dinosaur and bird. - The archaeopteryx is closer to coelurosaurian (Suh-Loor-Oh-Saur) theropods, Velociraptor is an example.

ARCHAEOPTERYX (image)

ARCHAEOPTERYX (ancient wing)- Characteristics: The Archaeopteryx shows characteristics from both dinosaur and bird ArchaeopteryxDinosaur √ Teeth √ Claws (on wings) √ Breastbones √ Belly ribs √ Long bony tails ArchaeopteryxBirds √ Feathers √ Wings √ Wishbone √ Reduced fingers √ Light built body √ Hollow bones

ARCHAEOPTERYX (ancient wing) Some More Facts: - The first found fossil was a feather found in Jurassic limestone in southern Germany (1860) - Complete skeleton found (1862) - There have only been eight specimen found and the feather Why do you think there have only been a few specimen found? Bird fossils are more difficult to find because their bones are hallow and fragile.

ARCHAEOPTERYX Fossil

OTHER EXAMPLES OF TRANSITIONAL FOSSILS

Tiktaalik Some Facts: - Transitional fossil from fish to land animals, or in other words, tetra pod to fish (fishapod) million years old. - Fossil found in Canadian artic (2004) TiktaalikFish √ Fins √ Gills √ Scales TiktaalikLand Animal (Tetrapod) √ Flat body √ Eyes on the top of skull (like a crocodile) √ A functional neck (which fish lack) √ Ribs (support body and aid breathing)

Acanthostega Some Facts: - Transitional fossil from fish to land animals -400 million years old -Devonian period Land AnimalAcanthostegaFish Lungs √ Internal Gills “Tiny fingers” √ Paddle-like limbs Bony legs arms and digits √ Fish-like tail

Acanthostega model Acanthostega skeleton model Acanthostega finger model

Acanthostega Do you think these changes happened in the water or on land? It is believed that the changes happened in water. The purpose of these changes was to help navigate through swampy wetlands, not to move onto land, but later proved to be a survival advantage on land. Water

ARE TRANSITIONAL FOSSILS THE ONLY WAY TO SHOW EVOLUTION? NO!

Non-transitional fossil evolution: An example: Horses - There are Fossils that have been found of early horses. - These can be compared with fossils of horses up until today. Does anyone know what some early horses were like? One early horse from 60 million years ago, was called Hyracotheriun This horse was small and dog-like and lived in forests.

Early Horses and Present-day Horse