Sporting an elaborate headdress and shield, the Palenque king named Kan Bahlam, or Snake Jaguar, is depicted on one of the tomb walls.
Eight other figures are depicted as well, "each probably a different royal ancestor of the tomb occupant," said Stuart.
"The imagery of nine ancestors seems to have been a theme repeated in other Palenque royal tombs, such as Pakal's own huge one in the Temple of the Inscriptions."
The region's most famous king, Pakal, came to power in A.D. 615 at age 12 and ruled until he was in his 80s. He turned Palenque into a thriving, world-class city. Because Pakal built over much of what existed before him, little is known about the time prior to his ascension to power.
If this tomb predates the famous king, as INAH and Stuart suspect, its contents could offer clues about life in pre-Pakal times.
It's unclear yet what might be found inside, but it's "cool enough," said Stuart, that there's now "firm archaeological evidence of a Palenque ruler from the years before Pakal's reign."
(Read about the rise and fall of the Maya in National Geographic magazine.)