The 'freaky giraffoid Barosaurus' meme
Lately I've become quite fond of those really weird depictions of fossil animals that were utterly, utterly wrong, yet somehow managed to persist in the literature for decades. Last time round, we saw how the meme of the 'demonic Quetzalcoatlus' passed from artist to artist, and had its genesis in a single, speculative illustration.
Source: scienceblogs.com