Bats popped out of the evolutionary woodwork about 55 million years ago.  They first appear as a radically new yet fully developed form, which was not in any way significantly different from modern bats.  Their debut in the fossil record is sudden, complete, and lacks intermediaries.  In 55 million years, they have changed little. 

     Among the earliest bats is a 54.6 million year-old bat from Queensland Australia, which is similar to another early bat named Palaeochiropteryx.[1]  Other early bat fossils include Icaronycteris[2] and Onychonycteris.[3]  

     Modern bats are similar to these most primitive bats in all their most vital characteristics, including the same diamond-shaped skull, the same square rib cage followed by a sizeable and very distinct lumbar region, narrow bones in the limbs, the distance from shoulder to elbow is roughly two thirds the distance from elbow to wrist – and most obviously, the third, fourth, and fifth digits in the forelimb are long and narrow to support the wing.  It is this character, the length of the digits, which is most striking about the skeleton of bats, for it appears fully developed in the most primitive bats, with no link between it and the short fingers of its supposed insectivore ancestors.  The best explanation for this is that bats must have evolved very rapidly – so rapidly that intermediary forms did not last long enough to stand a good chance at being preserved. 

     Yet Nature presented Onychonycteris as an intermediary, because it differed both from modern bats and from its contemporaries in having claws on all its fingers, rib and vertebral fusion, a shorter wingspan, and lack of echolocation ability.  However, there are some modern bats that do not echolocate, and some still have claws on more than one finger, so not all these characters necessarily make Onychonycteris a missing link.  Rather, they make it a different sort of bat.  In other respects Onychonycteris was similar to both modern bats and to its advanced contemporaries.  It had long narrow fingers, flapping flight, as well as a similar skull shape, pelvis, hind limbs, rib cage, scapula, clavicle, and sternum.[4] 

     Onychonycteris was a contemporary with the more advanced bats Icaronycteris and Palaeochiropteryx, and it is actually predated by the bat from Queensland Australia.  As with the small-limbed snakes and feathered raptors, it occurs too late in the fossil record to be a direct ancestor to the earliest bats.  Therefore, it cannot constitute evidence for a gradual transition from terrestrial insectivore to bat-like forms.  Nevertheless, its primitive characters, such as shorter wingspan and claws on all fingers, can plausibly be interpreted as intermediary features.  Hence, although this fossil indicates that a transition did indeed happen, it does not support that such a transition was necessarily gradual.  Rather, the fact that it was contemporary with advanced modern-like bats supports the theory that bat evolution happened rapidly.  That is to say, when the intermediaries do not predate the fully developed forms, then evolutionary transitions most likely took place over periods of time that were so brief that missing link fossils were not preserved.

     If the distinctive characters of bats evolved by means of natural selection, such evolution must have occurred gradually, over a multitude of generations, as natura non facit saltum mandates.  If this were the case, then we should see a gradual change from insectivores to bats in the fossil record.  Instead, we find a sudden appearance of fully-formed advanced bats, without intermediaries before them.  Some would take this as evidence against evolutionary theory, and assert that God created the bats from scratch.  But this cannot be supported by the data, for the bats did not persist as immutable species each after its own kind.  Rather, the bat lineage has subsequently diversified into more than 200 genera.[5]  This must mean that species have been morphing into other species.  This has happened gradually, as natural selection has caused bats to adapt to a multitude of different ecological niches, which are well represented in the fossil record. 

          The evolution of bats follows the same pattern seen time and time again in the fossil record:  Sudden emergence of a new body plan followed by an adaptive radiation.  That is, evolutionary advancements involving gross morphological changes occur suddenly; however, what is gradual is the manner in which the species possessing those advancements adapt to fill every environmental niche permitted by the advancement.