Olmec hieroglyphs

From the longer Wikipedia page 
Olmec hieroglyphs (alternatively Olmec glyphs, Olmec writing, or Olmec script) designate a possible system of writing or proto-writing developed within the Olmec culture. The Olmecs were the earliest known major Mesoamerican civilization, flourishing during the formative period (1500 BCE to 400 BCE) in the tropical lowlands of the modern-day Mexican states of Veracruz and Tabasco. The subsequent Epi-Olmec culture (300 BCE to 250 CE), was a successor culture to the Olmec and featured a full-fledged writing system, the Isthmian (or Epi-Olmec) script.
The existence of a writing system in Middle and Late Olmec periods has been a matter of long-standing debate. Direct evidence includes the appearance of individual (potential) glyphs as well as the singleton Cascajal Block that bears a potential text. Indirect evidence includes similarities in calender and writing systems between subsequent Mesoamerican cultures, for which the Olmecs are sometimes considered a mother culture.
See also Cascajal Block
Category:Undeciphered inscriptions