Not in stone of course, but in crocodilians' genomes. ERV covers well. Question for evolution, as she puts it: if this virus was good enough at what it did to work its way into a genome, why does it apparently have no descendants today? Two possibilities come to mind: 1) its descendants are still around, but we haven't discovered it yet (remember Nannarrup hoffmani? A whole new genus of metazoans found 7 years ago in Central Park, New York?). 2) the chance of becoming an ERV do not correlate over time with fitness.
"...there is good and bad speculation, and this is not an unparalleled activity in science...Those scientists who have no taste for this sort of speculative enterprise will just have to stay in the trenches and do without it, while the rest of us risk embarrassing mistakes and have a lot of fun." - Dan Dennett