Wow ...I dont know exactly what they are...but the markings...especially the Thumbnail indentation one...is very much like Mississippian in origin ....You need to post this in Native American forum also ...Atlantis or someone there would probally be able to ID
Very nice shards. I cannot tell you the exact origin (state), but can tell you that they appear eastern. I have an extensive potttery collection and reference library and will look to see what I can find.