Santonian

Template:Cretaceous 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 85.8 ± 0.7 mya (million years ago) and 83.5 ± 0.7 mya. The Santonian is preceded by the Coniacian and is followed by the Campanian.^[1]

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 (the base of the Campanian stage) is marked by the extinction of the crinoid Marsupites testudinarius.^[2] In 2009, a GSSP (official reference profile) for both base and top had not yet been appointed.

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, nannoplankton or forams is more detailed.

Ankylosaurs of the Santonian
Taxa	Presence	Location	Description	Images
Hungarosaurus^[3]
Pinacosaurus
Tsagantegia

Cartilaginous Fish of the Santonian
Taxa	Presence	Location	Description	Images
†Hexanchus microdon
†Notidanodon
†Notidanoides^[4]

Ceratopsians of the Santonian
Taxa	Presence	Location	Description	Images
Craspedodon				Graciliceratops Reconstruction of Udanoceratops
Graciliceratops
Udanoceratops^[4]

Crocodylomorphs of the Santonian
Taxa	Presence	Location	Description	Images
†Notosuchus				Reconstruction of Notosuchus, a relative of the crocodiles
†Shamosuchus

Mammals of the Santonian
Taxa	Presence	Location	Description	Images
Paracimexomys †Paracimexomys magister^[3]

Ornithopods of the Santonian
Taxa	Presence	Location	Description	Images
†Arstanosaurus				Claosaurus Gryposaurus Reconstruction of Nipponosaurus, a duck-billed dinosaur
†Claosaurus^[3]
†Gryposaurus
†Nipponosaurus

Plesiosauria of the Santonian
Taxa	Presence	Location	Description	Images
†Dolichorhynchops	Dolichorhynchops osborni from Coniacian to Campanian	Fort Hays Limestone, Kansas, USA

Sauropods of the Santonian
Taxa	Presence	Location	Description	Images
†Quaesitosaurus

Squamates of the Santonian
Taxa	Presence	Location	Description	Images
†Eonatator				Reconstruction of Tylosaurus, a mosasaur
Madtsoia †Madtsoia madagascariensis^[4]
†Tylosaurus

†Non-avian theropods of the Santonian
Taxa	Presence	Location	Description	Images
†Achillesaurus^[3]
†Achillobator
†Alectrosaurus
†Aucasaurus^[3]

^ Gradstein et al. (2004)
^ "GeoWhen Database - Barremian". Archived from the original on 2007-10-22. Retrieved 2007-12-02. Version 1.1.0.
^ ^a ^b ^c ^d ^e ^f ^g Only known from this stage
^ ^a ^b ^c ^d ^e Dating uncertain

Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.

GeoWhen Database - Santonian
Late Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS
Stratigraphic chart of the Late Cretaceous, at the website of Norges Network of offshore records of geology and stratigraphy