Flight was first achieved by the insects (invertebrates), but in the Triassic Period, pterosaurs became the first flying vertebrates. The word "pterosaur" means "wing lizard." Pterosaurs dominated the skies throughout the Mesozoic Era, but were eventually replaced by birds.
Sharovipteryx (formerly known as Podopteryx) was a small archosaur (the ancestor of dinosaurs and birds) that lived north of the Himalayan Mountains during the Triassic Period. It was not actually a true Pterosaur, but an early, gliding reptile. Sharovipteryx lived in trees, and had a membrane of skin joining its ankle to part way down its tail, and a second, smaller membrane that joined its elbows to its knees. Sharovipteryx is thought to have used these membranes to allow it to parachute out of trees to catch prey.
The true pterosaurs supported their membraneous wings with an elongated fourth metacarpal (finger). Bats support their wings by elongating all of their fingers, and having the membrane stretched between the fingers. The scientific name for the bats is the "chiroptera", which means "wing hand."
All of the early pterosaurs had teeth, and long, bony tails, similar to Archaeopteryx. Both Archaeopteryx and the pterosaurs inherited their teeth from their carnivorous archosaur ancestors. Teeth are heavy and dense, and both the pterosaurs and our modern birds lost them in order to become lighter for flight.
The long, bony tail would have also added extra weight, but it acted as a stabilizer, and would correct any tendency of the pterosaur to pitch forward during flight. However, this stabilizer had another disadvantage in that it kept the stalling speed, at which an animal can no longer remain airborne, high. Also, it made manoeuvring difficult, because it is difficult to twist and turn in the air with a stiff projection in the rear. Later pterosaurs lost the tail, and had to use muscular adjustments to correct the tendency to pitch forward with out the stabilizing weight of the tail. We see an increase in brain size with the loss of the tail, the larger brain would provide improved muscular co-ordination and balance; there was also a substantial increase in the size of the pterosaurs' eyes.
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