Kawtcho, a mythical devil of the Alakaluf (also known as Kawesqar) canoe people of the southwestern coast of Chile, by the Pacific Ocean's mouth of the Strait of Magellan, was drawn by these people in their rock art.
Several paintings were discovered in a cave at the Madre de Dios Island, among which was one described as "an anthropomorphic horned figure which could correspond to the Alakaluf god Kawtcho".  or "a horned anthropomorphic figure could correspond to Kawtcho, the Kawesqar [Alakaluf]divinity". 
The image shown above, is painted with reddish colors and shows a horned being.
Could be a depiction of the stranged horned beings mentioned by Fitz Roy during his surveying expedition in that region in the early 1800s?
Perhaps it is Kawtcho, the mythical man-eating monster of the Alakaluf.
The "horns" are new for me, yet it was described as having its head covered with stiff hairs that resembled spikes (horn-like bristles?).
 Ultima Patagonia 2006 Rapport scientifique Expedition franco-chilienne et internationale a Madre de Dios (Magallanes, Chili). Expédition nationale 2006
de la Féderation Française de Speleologie. Association Centre Terre - www.centre-terre.fr. pp. 89+. Image is Fig. 20.
Mairie Richard, Bernard Tourte, Stephane Jaillet, Joel Despain, Benjamin Lans, Franck Brehier, Luc-Henri Fage, Laurent Morel, et al., (2009). Geomorphic and archaeological feautes of coastal caves in Madre de Dios Archipielago (Patagonia, Chile)Proceedings of 15th International Congress of Speleology, Kerrville, Texas, USA, 19-26 july 2009. Symposium on Karst Islands.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia2011 International Year of Forests Copyright 2009-2011 by Austin Whittall ©