There are several nations who at one time or another lived in Guyana, and subsequently disappeared without trace. The Iaos, for example, were evicted from Moruka by the Arawaks with Spanish assistance as early as 1596. Their contemporaries, the Shebayos, on the other hand, were most likely absorbed by the Arawaks.
More tragic is the case of the Paravianas, a Cariban nation which once lived in the upper Demerara, Essequibo and possibly,