The answer is: a headdress.
The Olmec colossal heads are massive figures of basalt stone representing heads of what is believed were important characters of Olmec civilization. The heads were created, at least, as far back as 900 BCE. All of them have distinct features, such as flat noses and a complexion that is similar to that of current inhabitants of certain parts of Mexico, like Veracruz and Tabasco. One distinct feature is that each head has a characteristic and singular headdress.