Petralona skull

The Petralona skull is the skull of a hominid found in Petralona Cave, about 35 km south-east of Thessaloniki city on the Chalkidiki peninsula, Greece. According to Aris Poulianos, head of the excavation team since 1965, it was found by a villager,  Christos Sariannidis, in 1960. It was sticking to the cave wall in a small cavern of the cave, called "Layer 10" by Poulianos, about 30 cm above ground, held by sinter. Its lower jaw is missing and it was "encrusted by brown calcite soon after the death of the individual".

Dating
Poulianos (1981) estimated the age of the skull at around 700,000 years. He announced that "the date was based on analyses of the cave's stratigraphy and the accumulated sediments".

Poulianos concluded that the skull represented a previously unknown hominin genus, unrelated to Homo erectus, and even outside of Homo, introducing the genus name Archanthropus, and the trinomial Archanthropus europaeus petraloniensis for the Petralona skull itself. Independent paleanthropologists have tended to classify the skull as either Homo erectus, Homo heidelbergensis or Homo neanderthalensis.

Poulianos's claims have been a continuing cause of controversy since, his conclusions being in conflict with mainstream models of the speciation of genus Homo and its early dispersal.

In 1981, the age of the Petralona skull deduced by Poulianos was investigated and the protocol published in the journal Nature. The scientists involved used electron spin resonance measurements of the calcite encrustation and of bone fragments, and dated the age of the skull to between 240,000 and 160,000 years old.

Poulianos dates the fossil stratigraphically, claiming an age of the relevant layer of about 670,000 years old, also based on electron spin resonance measurements. Other researchers point out that contextual animal fossils "found with it are known elsewhere from approximately 350,000 years ago". In 1987, researchers announced that the cranium cannot be older than 620,000 years, based on palaeomagnetic and mineral magnetic studies of the cave's sediments.

Layer 10
In 1992 an international team published its results of a uranium-series dating analysis of the small cavern, called "The Mausoleum", where the skull was allegedly found and the sediments, named "Layer 10" by Poulianos. The results confirm earlier findings "that the whole of layer 10 represents a long time span, from about 160 ka to more than 350 ka". The minimum age refers to the brown calcite layer, which covered and cemented the hominid skull to the wall. The fossil encrustation is insufficient to date it by alpha-spectrometric, uranium-series methods, yet its minimum age was concluded to be also 160.000 years.

Today, most academics who have analyzed the Petralona remains classify the hominid as Homo erectus. However, the Archanthropus of Petralona has also been classified as a Homo heidelbergensis, Neanderthal (Homo sapiens neanderthalensis) and as an early generic class of Homo sapiens. A. Poulianos, on the other hand, believes that the Petralona cranium is derived from an independent class of hominids unrelated to Homo erectus.

Runnels and van Andel summarise the situation as follows: "The only known hominid fossil in Greece that may be relevant is the Petralona hominid, found by chance in 1960 in a deep cavern in the Chalkidiki. Controversy surrounds the interpretation of this cranium, and it has been variously classified as Homo erectus, as a classic Neanderthal (Homo neanderthalensis), and as an early representative of Homo sapiens in a generalized sense. The consensus among today's paleoanthropologists [is centered around the idea] that the cranium belongs to an archaic hominid distinguished from Homo erectus and both the classic Neanderthals and anatomically modern humans. Whatever the final classification may be, the cranium has been provisionally dated to ca. 200–400 thousand years old and it is thus possible that the Petralona hominid is a representative of the lineage responsible for the Thessalian Lower Paleolithic sites."

The fossils have been preserved at the Geology School of the Aristotle University of Thessaloniki since 1960.