Santonian

The Santonian is an age in the geologic timescale or achronostratigraphic 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.

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, nannoplankton or forams is more detailed.

Paleontology

†Ankylosaurs

Birds

Cartilaginous Fish

†Ceratopsians

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

Crocodylomorphs

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

Mammals

†Ornithopods

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

†Plesiosaurs

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

†Pterosaurs

Pterosaurs of the Santonian
Taxa	Presence	Location	Description	Images
†Aralazhdarcho				Reconstruction of Bakonydraco
†Bakonydraco

†Sauropods

Squamates

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

†Theropods (non-avian)

†Non-avian theropods of the Santonian
Taxa	Presence	Location	Description	Images
Achillesaurus[3]				Portrait of Oviraptor Portrait of Saurornithoides
†Achillobator
†Alectrosaurus
†Apatornis[4],
†Aucasaurus[3]
†Oviraptor[3] Occurrence outside this stage
†Patagopteryx[3]
†Saurornithoides

Flora

• Magnoliopsida

Advanced dicotyledons

• • Droseraceae: †Palaeoaldrovanda

References

Notes

1. ^ Gradstein et al. (2004)
2. ^ "GeoWhen Database - Barremian". http://www.stratigraphy.org/geowhen/stages/Barremian.html. Retrieved 2007-12-02. "Version 1.1.0." 
3. ^ ^{a b c d e f g h} Only known from this stage
4. ^ ^{a b c d e} Dating uncertain

Literature

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

External links

• 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