I have found this fossil tooth, could it be pliosaur ? Or maybe theropod? Lenght: 10 mm, striated, circular cross-section

Site: Brno-Hády (limestone quarry), Moravia, Czech republic, central Europa

Age: Jurassic, oxford

The site is a good source of fossil shark teeth, but this tooth I am wondering about has absolutely different structure and does not have as strong luster as shark teeth have. 

An example of shark tooth fossil from Brno-Hády site:

See my shark-tooth photos here.
Most likely plesiosaur. That fluted structure is indicative of marine reptile teeth. My first guess was mosasaur but their are a lot of plesiosaurs from that formation so I would go with that. It is obviously a shed tooth which makes it harder. shark teeth flare out at the base becasue they attach differently than marine reptile teeth, sharks need more surface area for a strong connection.  Hopefully a marine reptile person can give you a tighter identification, I mostly work on dinosaurs.