Alien-like skulls found
It is believed that they were deliberately deformed by a common practice in Central America in the past, whereby children's skulls would be warped as they grew.
The find in the small village of Onavas, Mexico, does mean that the strange tradition was practiced much further north than initially known, however.
The cemetery in the Mexican state of Sonora itself was found by local residents in 1999 as they were building an irrigation canal through the area.
Sonora is just south of the Arizona and New Mexico borders.
The cemetery site contained the remains of about 25 human bodies, and it now is suggested that 13 of the 25 had deformed, almost alien-like skulls.
The 13 warped skulls were described as elongated and pointy at the back; five of them also had mutilated teeth, filed or ground down into various shapes.
Of the 25 bodies, 17 were children aged 5 months-16 years.
No remains had any signs of disease that could've caused the deaths, leading some to speculate that the attempted skull deformations had been the cause.
The high number of children found there also suggest that the cranial deformation caused by excessive force being applied to the skull could be a cause.