The earliest known moss fossil is from the early Carboniferous period, about 320 million years ago. Mosses are not well-represented in the fossil record because their soft tissue is not well preserved. An examination of extant species indicates that bryophytes are a polyphyletic group. They appear to have evolved from more than one ancestral line.
Most botanists believe that mosses evolved from aquatic ancestors but there is debate about their evolutionary ancestry. It is commonly accepted by most botanists that mosses evolved from a simpler filamentous green alga. Although bryophytes appear intermediate in complexity between algae and vascular plants, they are unlikely to be an evolutionary "missing link" between these two groups.
Science EncyclopediaScience & Philosophy: Molecular distillation to My station and its duties:Moss - Bryophyte Characteristics, Moss Characteristics, Life Cycle, Habitat And Ecology, Evolution, Importance To Humans