TINY pinkie, rat or squirrel?

[Cesta]

My daughter was walking home from swim practice today and found a tiny pink animal in the gutter. She brought it home and I have it on heat, with rehydration fluid ready to go. I'm worried about two things:
1) I've cared for a pinkie but not one this small. My guess is 2-3 days old. The umbilical stump is still there. This is a little scary for me. I usually get them at 3-4 weeks.k
2) Is this even a squirrel?
It is literally so small I can't tell-- but one main thing makes me wonder. It's ears are open, which I've never heard of or seen in a baby squirrel.

Are there any other signs that can help me differentiate from a newborn squirrel and a newborn rat?
Any hints on special care for pinkies?

[kendradfw]

Can you post a photo? Ive had a rat that had babies before and may be able to help.

[Chickenlegs]

Are your baby's nails black? Squirrels' are.

[Cesta]

Can you post a photo? Ive had a rat that had babies before and may be able to help.

I have some fantastic pictures, but I don't know how to get them from my phone to you! Thanks, tho....

[Cesta]

Are your baby's nails black? Squirrels' are.

Yes, or at least dark brown. I read online that dark nailed babies are squirrels and white nailed babies are rats, but I don't really trust the internet!

I will treat him like a squirrel and see how he turns out!!

PS-- tips on caring for such a tiny little guy?