Evolution of Bats

The early Eocene fossil microchiropteran Icaronycteris, from the Green River Formation

Bats are mammals that have their forelimbs specially adapted for flight as wings, and this is unique. Bats are the only mammals that have the ability for true and sustained flight. They are even capable of more dexterity in the air than birds as they have their flight with elongated digits covered by a fragile member. Bats vary from about six inches to well over five feet in wingspan. 

Bats form the second biggest order in the mammal family, second to the rodents. Most bats feed on insects, while others depend on fruits or nectar. Several species depend on blood, and these are the vampire bats. Most bats are active at night, and they are found in various parts of the globe, with the notable exception of the coldest regions. 

Bats Evolution

Owing to the fragile nature of the skeletons of bats, there are few good fossils, and scientists have surmised that just a little above 10% of bats that have lived can be found in fossilized forms. The study of these fossils shows that the oldest ones available are similar to bats that lived around 32 million years ago. It is also interesting to know that the bat fossils dated back to approximately 50 million years ago were the very first mammalian fossils whose particular and correct coloration has been known. 

In the past, bats were classified in the superorder called Archonta. In this group were others like the colugos, treeshrews, and primates. Recent evidence in genetics now reclassifies bats as in the same superorder as the pangolins, cetaceans, even and odd-toed ungulates. 

There is still a lot of controversy and discussion regarding the phylogenetic links between various bats. The conventional classifications into Microchiroptera and Megachiroptera showed that these bats had had their evolution independently over time but from a common ancestor that was already able to fly. The theory in place noticed the variations between the megabats and microbats and agreed that flight passed through evolution just once in the mammals. Evidence from molecular biology studies also points to the fact that bats constitute a monophyletic or natural group. 

More evidence from genetics shows that the megabats must have originated during the early Eocene epoch, alongside the four main lines of the microbats. There has also been a proposal for two new suborders. These are the Yinpterochiroptera, which has the Pteropodidae, also known as the megabat family, alongside the Yangochiroptera, which has other bat families. 

All the bat families under discussion here make use of laryngeal echolocation, and this study provided a conclusion to the DNA basis in research done in 2005. Another study done in 2013 on the phylogenomic aspects also gave more credence to the pair of suborders proposed. 

A hypothesis had been put forward earlier in the 1980s, and it was based on morphological evidence, which concluded that the Megachiroptera had the evolution of flight differently from the Microchiroptera. It was called the flying primate hypothesis. It clarified that when the adaptations to flight were detached, the megabats were connected to the primates due to similarities in the anatomy that were not shared with the microbats. 

An example in this regard will be the brains of the megabats with their sophisticated properties. Even though the latest studies in genetics give good credence to the monophyly of bats and the discussion on this continues. 

A significant discovery was made in 2003 with the early fossil bat from the Onychonycteris finneyi dated back to 52 million years ago. It showed the evolution of flight before the coming of echolocation features. 

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