MEXICO CITY.- More than 500 Prehispanic lithic objects and ceramic fragments were discovered in different points of the border between San Luis Potosi and Guanajuato. Among artifacts, arrowheads elaborated by Prehispanic nomadic groups outstand. With an antiquity range that goes from 1000 BC to 1800 DC, artifacts were found in 37 different sites distributed in 5 areas that correspond, according to historical sources to those occupied in the 16th century by Guachichil and Guamar tribes, part of the cultural region known as Great Chichimeca. Archaeologist Ruben Manzanilla, from the National Institute of Anthropology and History (INAH), informed that between localized items are lithic tools such as scrappers, knives and projectiles, elaborated mainly with rhyolite of different colors and qualities. Other material found was flint, basalt, quartz and obsidian. A rock painting with the representation of a heron made with mineral red