Archaeological research has determined that the site of the present ruin of the temple of Apollo was in continuous use since the archaic period, the existing temple is the last of four on the site and designated Apollo IV. Pausanias records that this last sanctuary was dedicated to Apollo Epikourios (helper or succourer) by the Phigalians in thanks for delivery from the plague of 429 BC. The architecture of the temple is one of the most strikingly unusual examples of the period, departing significantly from the norms of Doric and Ionic practice and including what is perhaps the first use of the Corinthian order and the first temple to have a continuous frieze around the interior of the naos. From the style of the frieze it belongs to the High Classical period, probably carved around 400 BC. Nothing is known of its authorship: despite an ascription of the metopes to Paionios (since refuted), the frieze cannot be associated with any sculptor, workshop or school. Instead Cooper identifies the artists of the frieze on morellian evidence as a group of three anonymous masters.