[GlennS]

I was originally just going to link to a Colugo, which I think are still pretty cool, and probably good evidence of what early stages of vertebrate flight looked like. Functionally they're not doing full flight like a bat, but their flight is still quite a bit better than a flying squirrel, a sugar glider, or one of the assorted other gliding mammals can do. You can see them flapping.

https://www.youtube.com/watch?v=SIgv8Qw--kk

Like the flying squirrel example given by another poster, they're not closely related to bats. Actually quite closely related to us though.

Bats: https://www.onezoom.org/life/@CHIROPTERA=574724 Colugos: https://www.onezoom.org/life/@DERMOPTERA=987673 Flying squirrels: https://www.onezoom.org/life/@Petinomys=43434 Sugar gliders: https://www.onezoom.org/life/@Petauridae=323245

But the bat transitional fossils is also an interesting question. And some Googling finds this, which you might enjoy: https://arstechnica.com/science/2008/02/earliest-bat-fossil-...

[onionisafruit]

In that Colugo video the speaker says “they actually built a show around this shot”. Any idea what show he’s talking about?

Also tiny cameras have come a long way since that video was made.

[GlennS]

I don't, sorry, just found it by Googling.