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Hands

- Semilunate wristbone shifted to the lateral side. Homeotic shift.

- Bones in the hands fused together

- Alula evolved to allow for stable flight at low speeds

Shoulder/Chest

- Sternum lengthens. More space for muscles to attach.

- Evolution of flapping flight stroke. Appearance of the musculoskeletal configuration of the m. supracoracoideus (SC)

- These traits developed around 115 million years ago

What about after Archaeopteryx?

Arm and Shoulder

- In Theropods, forelimb (ulna,radius,humerus) lengthened over the course of evolution

- Advantageous when it came to grabbing prey

- Long forelimbs made it easy for wings to evolve

- Scapula (shoulder blade) and Coracoid became longer and narrower. Better movement

- Clavicles fused to form wishbone. Muscle anchor point

- All these changes = strengthened skeleton

What evolutions contributed to flight?

Here's the wrist of the information

- Many of these characteristics were already present in pre-avian Theropods

- Hands became three-fingered

- Wristbone became half-moon shaped

- Clavicles fused into a wishbone

- Forelimbs become longer, although there are exceptions

Hands Solo

- Ancestors of Theropods had 5-fingered hands

- Lost digits IV and V to form 3-fingered hands

- Basal Theropods had a flat wristbone. (carpus) Overlapped metacarpus.

- Soon became crescent in shape (semilunate)

- Flexibility increased; flexing sideways became possible.

- Advantageous for catching prey.

- More flexible wrist = more efficient flight stroke

-Evolution of Characteristics Necessary for Flight

- Refinement of those characteristics

Is it a bird? Is it a plane? No, it's Archaeopteryx!

- Discovered 1861 (soon after Darwin's Species)

- Widely accepted as the first known avialan

- Transitional fossil between Theropods and Birds

- Lived in Late Jurassic; 150 million years ago

- Feathered

- Could not fly well.

- Lacked a m. supracoracoideus (SC) muscle.

- But how did we get here?

Evolution of Avian Wings and Flight

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