Santonian


The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 86.3 ± 0.7 mya and 83.6 ± 0.7 mya. The Santonian is preceded by the Coniacian and is followed by the Campanian.

Stratigraphic definition

The Santonian stage was established by French geologist Henri Coquand in 1857. It is named after the city of Saintes in the region of Saintonge, where the original type locality is located.
The base of the Santonian stage is defined by the appearance of the inoceramid bivalve Cladoceramus undulatoplicatus. Its top is marked by the extinction of the crinoid Marsupites testudinarius. In 2009, a GSSP for both base and top had not yet been appointed.

Subdivision

The Santonian is sometimes subdivided into Lower, Middle and Upper substages. In the Tethys domain the Santonian is coeval with a single ammonite biozone: that of Placenticeras polyopsis. Biostratigraphy based on inoceramids, nanoplankton or forams is more detailed.

Paleontology

†Ankylosaurs

Birds (avian theropods)

Cartilaginous Fish

†Ceratopsians

Crocodylomorphs

Mammals

†Ornithopods

†Plesiosaurs

†Pterosaurs

†Sauropods

Squamates

†Theropods (non-avian)

Flora