cats

Probably a domestic longhair. Maine Coons have really distinctive heavy snouts, they're dramatically huge, like the size of a bobcat, and they've got this dense 3 layer coat that forms a lion-like mane.

If it's just some little dude that wandered up out of the world in the top 50th percentile of fluffiness, what you've got there is a domestic longhair. Probably introduce him to brushing while he's young because mats aren't fun, otherwise same operator's manual as a shorthair. Obligate carnivore diet, scatching post and sandbox, gentle scritches behind the ears, lots of naps, sunny windowsill for basking.