 Concentrating on tombs, he dug at five sites between Siquirres and Guapiles, and published a series of C- 14 dates ranging from 1440 to 1470 CE, and arranged much of the pottery excavated in an approximate chronological sequence.In the Sierra de Ameca between Ahualulco de Mercado and Ameca, Jalisco, a large number of stone spheres, many of which are almost perfectly spherical, can be found.Their generally spherical shape led people to suspect they were manmade stone balls, called petrospheres, created by an unknown culture.