ENORMOUS SPREAD. “The phylogeny of ERV lineages in vertebrates indicates that they have undergone more than 1000 HT events at the host family level, thus the number of HTs is likely to be extremely high at the species-level across vertebrate diversity.” (ERV= Endogenous retroviruses); (HT = horizontal gene transfer).
https://www.sciencedirect.com/science/article/pii/S0959437X17301685