A Klingon as their species appeared circa 2266. No explanation
has been offered for this transformation, though it is known to have
affected particular individuals rather than changing from one generation to the next.
This is the Commander of the Klingon Cruiser Amar, destroyed in 2271 with
the loss of all hands by the entity later known as Vjer. At this point in history,
all Klingons had a near-identical bone ridge running across their heads.
A Klingon female, circa 2372. By the 2270's the
Klingons had adopted a distinctive uniform/armour,
variations on which are worn by virtually the entire species.