[1] Fossil seeds have been found in Russia, and the predicted paleoregion of the species stretched across Eurasia.

[2] It is theorized that one factor leading to the species' extinction is a global cooling at the end of the Eocene that removed much of its habitat.

[7] One possible origin of the genus name Hypericum is that it is derived from the Greek words hyper (above) and eikon (picture), in reference to the tradition of hanging the plant over religious icons in the home.

[8] The specific epithet antiquum derives from the Latin word antiquus which means "archaic" or "old".

[9] Hypericum antiquum was first described in 2005 in volume 4 of the Russian series Iskopaemye Tsvetkovye Rastenija Rossii I Sopredel'nykh Gosudarstv (Fossil Flowering Plants of Russia and Adjacent States) by G.A.