Extinct giant turtle had horned shell of up to three meters
(PHYSorg.com Archaeology & Fossils)

Paleobiologists from the University of Zurich have discovered exceptional specimens in Venezuela and Colombia of an extinct giant freshwater turtle called Stupendemys. The carapace of this turtle, which is the largest ever known, measured between 2.4 to almost 3 meters. Moreover, the shell of male Stupendemys had horns-a rare feature in turtles.