Shark fins

Was driving along today and spotted a 14 plate with a shark fin, mines a 64 plate with no shark fin, and some have twin shark fins.

So why are they fitted?
When were they changed to twin fins?

Are they model specific? - I was following a Evoque with round exhausts, which I thought indicated a Pure or Pure-tech (same as mine), the rectangular indicating a Dynamic or Prestige.

Shark fins are used on the non pano-roof early cars, dual fins were 2016 on, and to do with the In-Control system.

Prestige has round exhausts like the Pure. Square exhausts are on Dynamic and Autobiography.

Cheers Gents