Complex sentence: The Indian plate and Eurasia collided between 40 and 60 million years ago according to four observations, one being the fact that there is no mammalian fossil record in India from around 50 million years ago.
Split into simpler sentences: The Indian plate and Eurasia collided between 40 and 60 million years ago according to four observations. One of them being, that there is no mammalian fossil record in India about 50 million years ago.