Carrying a meis (Shabbos 93b)

The Mishna says that the shiur for hotzaa for a meis is a kezayis because that's the amount that is metamei b'ohel. Earlier though on daf 90a the mishna said that the shiur for mekak sefarim is a kol shehu because you need to bury it. Don't you need to bury a meis also? Tosafos Yom Tov has two answers:
1. You don't need to bury less than a kezayis of a meis. (I don't think that we pasken that way)
2. It's not so common to have less than a kezayis of a meis therefore the shiur is for the common ramification which is a kezayis for tuma.