While excavating for a subway extension under the streets of Mexico City a few years ago, a dog skull was discovered. Archaeologists have confirmed that the skull has holes that were used to display it on a ritual skull rack.

While excavating for a subway extension under the streets of Mexico City a few years ago, a dog skull was discovered.

Archaeologists have confirmed that the skull has holes that were used to display it on a ritual skull rack.

The Aztecs were only known to do this with human remains, so the dog skull is of unique interest to researchers who say it is the first to be found along with a display rack.

Found buried alongside it were three human skulls, two male and one female, all with similar holes.

They have all been dated to between the years of 1350 and 1521 according to data from Mexico’s National Institute of Anthropology and History.

Archaeologist Maria de Jesus Sanchez, who worked on the study is quoted as saying: “We know that during the conquest some horse skulls were placed on this type of structure, but not dogs. Perhaps there are dogs associated with these altars in other sites and we don't know it.”

Another expert noted that the female skull was unusual because the display racks were usually used for war trophies, and women rarely engaged in combat or were taken as trophies.