Many transposable element (TE) families show surprisingly high levels of similarity between distantly related species. How can we explain such observations? One possibility is frequent horizontal transfers of TEs, which is often at least partly based on our intuition that TE sequences between such distantly related species “should not be that similar”. However, do we really know how similar the TE sequences should be? In this study, based on careful comparative genomic analyses, we reconstructed the evolutionary history of a particular TE family in plants called the Au SINE. Our results suggest that the Au SINE originated >150 million years ago (mya) in the common ancestor of all angiosperms, and retained ∼80% nucleotide similarity between many plant species that diverged >100 mya, probably because maintaining their sequences was important for their survival. Thus, even if TE sequences between certain species may seem “too similar”, a simple model of vertical transmission without any horizontal transfers may sometimes provide a sufficient explanation.