Trying to decipher the evolution of flight in Bats.
[sciencythoughts.blogspot.com]
Powered flight has evolved in four Animal groups independently, Insects, Pterosaurs, Birds, and Bats, potentially with more than one origin of flight in each of these groups. The first group to develop the ability was the Insects, during the mid-Devonian period. It is likely that this ability originated in controlled aerial descent by the wingless Archaeognathans (basal Insects), which is also observed in some extant Ant taxa (Formicidae). Due to a gap in the fossil record, intermediate stages between this controlled aerial descent and winged flight are unknown, but around 400 million years ago, we see the first known winged Insect, Rhyniognatha hirsti. The small body mass of Insects may have allowed them to take advantage of gusts of wind to become airborne, much like lift-enhanced seed dispersal in some Plants, but Vertebrates cannot afford this advantage. It was not until around 228 million years ago that the first winged Vertebrate occurs in the fossil record, the basal Pterosaur, Preondactylus. Unlike Insects, whose wings are formed by cuticle membranes, Pterosaur wings were formed by skin membranes known as patagia extending from highly derived forelimbs, along with patagia which extended towards the neck, and between the hindlimbs. Much of the characteristic anatomy of pterosaurs is present in their sister group, the Protosauria, and it is likely that proto-Pterosaurs possessed a wing precursor in the form of an actinopatagium; a membrane extending from digit IV to the body wall. This membrane is believed to have been used for display purposes prior to being recruited as flight apparatus, meaning that the wings of pterosaurs would have originated at the distal end of the limb and developed proximally later. Pterosaurs are not the only Animals believed to have had wing precursors used for display rather than aerial movement. The early pre-Bird Avian Dinosaurs are likely to have possessed feathered forelimbs that may have had display functions, given evidence of high melanosome diversity in the preserved feathers of these Animals that suggests elaborately coloured wings. From there, Animals such as Archaeopteryx emerged around 150 million years ago, with full-feathered wings potentially capable of primitive flapping flight. The Insects, Pterosaurs, and Birds ruled the skies until the Cretaceous–Palaeogene extinction event around 66 million years ago, when the Pterosaurs and non-Avian Dinosaurs became extinct, and Mammals entered their age of dominance.