Do horses sleep standing up?

Megan has been sitting up in her crib lately after I put her down for a nap. Up until the last few days, she just lays there and goes to sleep once I put her down, but since she's figured out that she can sit up (and pull herself up) in the crib, she does it!

Today was no different. I put her in the crib and she sat right up. I left the room for a while and heard her babbling to herself. About 20 minutes later, I peek into the room. Megan is still sitting up, eyes closed, head bobbing, etc. Too funny! She's asleep and still sitting up!

(Darn, I should have gotten a picture!)