Rodent biostratigraphy of the Eocene-Oligocene transitional strata of the Isle of Wight

Abstract

The Paleogene deposits of the Isle of Wight in the Hampshire Basin have yielded mammalian remains at various levels. The lowest level is situated near the base of the Lower Headon Beds, while the highest level is situated in the Lower Hamstead Beds. The rodent species belonging to the families Pseudosciuridae, Theridomyidae, Cricetidae, Castoridae and Paramyidae are described in detail. One of these, the theridomyid species Isoptychus headonensis, is new. The pseudosciurid species Paradelomys quercyi is subdivided into two subspecies, P. quercyi quercyi and P. quercyi vectisensis n. subsp. The taxonomic value of the genera Paradelomys and Isoptychus is reassessed. A biozonation is inferred from the sequence of rodent associations. The following zones are recognized from below upwards: Isoptychus headonensis Zone, Paradelomys quercyi vectisensis Zone, Paradelomys quercyi quercyi-Suevosciurus palustris Zone, Paradelomys quercyi quercyi-Suevosciurus fraasi Zone, Eetropomys exiguus Zone and Eucricetodon atavus Zone. The Headonian is proposed as a new stage in the chronostratigraphic scale of continental deposits. Correlation of the Headonian with the Priabonian and Lower Tongrian of the marine chronostratigraphic stage succession is suggested.