It’s the Kingdom of the calcite skull.

A horned hominid skull might sound like something out of Greek mythology, but it actually could be a separate species of human ancestor that lived alongside Neanderthals, according to a groundbreaking study in the Journal of Human Evolution.

“This fossil has a key position in European human evolution,” the researchers wrote.

Originally discovered attached to a wall in Petralona Cave in northern Greece in 1960, the unicorn-esque noggin’s age place our family tree have eluded researchers — until now, Livescience reported.

However, researchers were able to estimate that the calcite (a mineral form of calcium carbonate often found in caves) jutting from the cranium was at least 277,000 years old.

While yet unclear how long the fossil was in the cave, amassing the skull stalagmite, they were reportedly able to narrow the window down from the previous range of between 170,000 and 700,000 years old.

These findings align with previous research indicating that the individual lived during the Pleistocene epoch in Europe alongside Neanderthals, but was part of the Homo heidelbergensis group, which is distinct from both H. sapiens and Neanderthals.

This group lived between 300,000 and 600,000 years ago, evolving in Africa, with some populations migrating to Europe 500,000 years ago.

In fact, the European population of Homo heidelbergensis — which potentially hunted large game and wore their hides in colder climates — reportedly evolved into neanderthals while the African iterations were our predecessors.

”The new age estimate supports the persistence and coexistence of this population alongside the evolving Neanderthal lineage in the later Middle Pleistocene of Europe,” study author Chris Stringer, a paleoanthropologist at the Natural History Museum in London, told Live Science.

Judging from fossil’s size and robustness, Stringer estimated that the individual was male, hence the moniker “Petralona man.” He also identified it as a young adult based on the moderate amount of wear and tear on the teeth.

Despite poor records of the skull, the team was able to pinpoint the age using a novel method uranium series dating. Calcite contains a small amount of uranium, which decays into another radioactive element called thorium over a certain time period.

By analyzing the ratio of uranium to thorium, researchers were able to pinpoint the approximate age of the skull as well as determine that the calcite spread quite rapidly in the cavern.

As it didn’t take long for the skull to acquire its initial layer of calcite — which reportedly fastened it to the wall, per the study — the skull was determined to be around 300,000 years old.

These findings rang similar to a the Kabwe skull found in Africa in 2019, which dated back to around 299,000 and is therefore also identified as a H. heidelbergensis specimen.

This marks a major milestone in the ongoing efforts to identify said specimen, which, due to the difficulty of interpreting early results, had been previously assigned to a variety of different species, including Homo erectus, Homo neanderthalensis, or ‘archaic Homo sapiens.'”

“This topic has been debated since its discovery more than 60 years ago, highlighting the difficulties in applying physical dating methods to prehistoric samples,” the team wrote.

However, more research is needed to definitively determine that the skull was a Homo heidelbergensis.