Weresharks are in the lore.
No there really wasn't though.
Rumored to not exist. While they are mentioned and speculated to exist, we don't know for sure. But they might exist within Elder Scrolls fantasy. Werebears are confirmed to exist(Infernal City, Hircine's Realm). Werevultures(Lycanthropic Legends of Skyrim), Wereboars and werewolves.
And that's your opinion. But to some people, there were more important things than slaying dragons.