Language Isthmian Writing
Isthmian script (From Wikipedia)
The Isthmian script is a very early Mesoamerican writing system in use in the area of the Isthmus of Tehuantepec from perhaps 500 BCE to 500 CE, although there is disagreement on these dates.
Epi-Olmec Writing (PDF Document)
Epi-Olmec Hieroglyphic Writing and Text