It also may have answered my question about bat limitations, as it mentioned that almost all bats lack protection from the sun, and would quickly sunburn if exposed to direct sunlight for an extended period of time, hence one reason for their nocturnal habits (Or a result of them). That right there would put pressure on them to remain small enough to be able to find cover during the day.

I guess they were more a “what do we know about why we know what we know” kind of questions I was asking, which are always good to ask from time to time.

First of all, you asked how we know fossil bats had echolocation. The answer is that there are bony ears parts that are found on all bats with echolocation and it is these that provide the evidence in fossils that a bat demonstrated this ability. Interestingly enough, there was a long standing debate about which bats developed first, flight or echolocation. Recent research seems to answer that question and shows that bats developed flight before the ability to echo-locate. This was determined by studying the extremely well preserved fossils of a specimen from the species called Onychonycteris finneyi, one of the most primitive forms of Chiroptera, which could fly but did not have echo-location. How did they know this? Because of the absence of those bony parts of the ear needed for echo-location.

Second, you asked if there is some physical size limit imposed on bats. Well, one thing that I can say is that their size would not be limited for the same reasons insect size is. Insects or other arthropods have a limited size due to several factors that are not a problem for mammals. First, their particular methods of breathing become inefficient at larger sizes. Second, and an even bigger challenge, is the fact that they have exoskeletons. Muscle strength is a basically factor of the muscle’s cross-section, or width. So as the exoskeleton grows in three dimensions, the muscles only grow in two. Simply, the exoskeleton gets heavy faster than the muscle strength to support it can keep up. Aquatic arthropods can get larger because the water helps support them. Mammals don’t have that problem, so in my opinion the things keeping the sizes of bats where they are don’t have to do with physiological limits so much as it has to do with their niche, adaptations, availability of food resources, amount of competition from other animals, metabolism, predation, and the like. These are all factors than can contribute to how large or small a species of animal evolves to be.

Anyway, I hope that is helpful!

Another thought- If another mass extinction were to strike the Earth, and most bird species go extinct, might bats (Providing they DO survive) grow to much more massive size as they expand into the now empty niches vacated by the birds? Or does scientific consensus contend that they are small due to some biological limitation, such as the spiricles of insects not being scalable to large sizes?

There is also a report of a “Flying Cat” from Punch Mehali, India. Killed in 1868 and exhibited at a meeting of the Bombay Asiatic Society, it was about 18 inches in length and purportedly feline. It was almost certainly a bat, but as its discoverer was quite certain that it was not a Flying Fox bat, it could possibly represent a new, undiscovered species.

Kittenz- I suppose it is possible there could be a carnivorous flying fox type bat out there, but it would be unusual since this hasn’t been seen before in any of the known large species of bats. It would be a pretty remarkable discovery!

All of the Megachiroptera that we know about are herbivores! Wouldn’t a big carnivorous flying fox-type bat be something, though!

Actually I believe that they very well might exist. I think of Ivan T. Sanderson’s ahool and of the tribe which he said had a word that meant specifically “hacked by an ahool”. The description of the ahool sounds like it could be an enormous bat - as tall as a toddler. Even the Mothman - many of the descriptions of the Mothman sound like they could be describing a giant bat (though I personally think a giant owl would be more likely, especially since the largest bats are found in tropical or subtropical regions).

There’s a lot of tropical rainforest that is still relatively unexplored. That giant carnivorous bat just may be out there!