What are other "sightings" of prehistoric/mythological creatures?

You know how people say they've seen Big Foot, the Yeti, Lochness Monster, and the Mighty Thunderbird. Are there any more of those? I don't exactly believe in the first three but I believe there could be a giant bird we haven't found yet. But what others are there that I'm missing that could be prehistoric beings or what have people claimed to have seen that is related to mythology?