Avian - Evolution and Skeletal Structure 0.0 / 5 ? OtherAnimal ManagementOtherOther Created by: Becky_BerryCreated on: 18-01-21 09:46 Evolution birds evolved from therapod dinosaurs had solid bones had sharp teeth were all bipedal it is thought they evolved via the Archaeopteryx reptilian teeth forelimbs had a wing-like structure would have been covered in feathers found imprints of fossilised feathers probably could fly they were not strong fliers they still lacked a toothless beak a keeled sternum no claws on their wings a pygostyle Chicken no teeth some bones fused together hollow bone structure 1 of 4 Evolution Early Reptiles splayed hand, similar to a mammal quadrupedal Early Archosaur crocodiles hands splayed more Early Dinosaur would have had a long claw raptor-like dinosaur evolved swivel in the thumb so they can move the thumb foot bones reduced bipedal Archaeopteryx thinner bones separate digits Modern bird fused digits can support force of flying for long period of time 3rd digit occasionally sticks out (known as a spur) modern birds still have spurs (e.g., yellow-wattled lapwing) 2 of 4 Adaptations for Flight bones lightened and strengthened compared to a similar sized mammal or reptile only exception is bats have eliminated some structures and modified others feathered wing evolved feathers before flight, therapod dinosaurs had feathers original evolution for the feather was for warmth therapod dinosaurs were likely to have been endothermic mass reduction wrist bones reduced to two, limited movement of wrists hollow bones and supported by internal struts lost reptilian tail, fused tail bones (pygostyle) support tail feathers no teeth skull and bill strong and light Strengthened skeletons ribs have rear-facing uncinate processes that overlap and strengthen the walls of the thorax bones of the wrist and pelvis fused 3 of 4 Adaptations for Flight enlarged sternum or breastbone with keel keel (carina) attaches to the large flight muscles e.g., pectoralis and supracoracioideus fused hand bones support and manoeuvre primary flight feathers clavicles are fused to form the furcula furcula flexes during flight and spreads and contracts with each wingbeat the flexing may enhance gas exchange by assisting movement of air through air sacs in therapod dinosaurs before flight thought to have helped with breathing/respiration 4 of 4
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