Complex sentence: The fossil record of roots--or rather, infilled voids where roots rotted after death--spans back to the late Silurian, but their identification is difficult, because casts and molds of roots are so similar in appearance to animal burrows.
Split into simpler sentences: The fossil record of roots--or rather, infilled voids where roots rotted after death--spans back to the late Silurian. Their identification is difficult, because casts and molds of roots are so similar in appearance to animal burrows.