| System (period) | Series (epoch) | Stage (age) | Lower boundary, Ma | |
|---|---|---|---|---|
| Paleogene | Paleocene | Danian | 66,0 | |
| Cretaceous | Upper (Late) | Maastrichtian |  72.1±0.2
| |
| Campanian | 83.6±0.2
| |||
| Santonian | 86.3±0.5
| |||
| Coniacian | 89.8±0.3
| |||
| Turonian | 93.9
| |||
| Cenomanian | 100.5
| |||
| Lower (Early) | Albian | ~113.0
| ||
| Aptian | ~121.4 | |||
| Barremian | 125.77* | |||
| Hauterivian | ~132.6
| |||
| Valanginian | ~139.8 | |||
| Berriasian | ~145.0 | |||
| Jurassic | Upper | Tithonian | older | |
| Subdivisions and "golden spikes" according to IUGS as of September 2023[1] *A golden spike is seen in chart but not ratified yet. | ||||
The Santonian is a fourth stage of the Upper Cretaceous series, corresponding to the Santonian age of the Late Cretaceous epoch. It lasted from approximately 86.3 Ma to around 83.6 Ma (million years ago). It is preceded by the Coniacian and is followed by the Campanian.
Definition[]
The GSSP of the Santonian stage was ratified in 2013. The lower boundary is fixed in the "Cantera de Margas" quarry, Olazagutia, Spain, and related to the first appearance of the inoceramid species Platyceramus undulatoplicatus.[2]
Santonian life[]
The seas were home to a great variety of ammonites of various shapes and sizes. Santonian genera include Pseudoschloenbachia, Scaphites, Glyptoxoceras, Boehmoceras and Baculites. Cartilaginous fishes including chimaeriforms (Edaphodon) and sharks (Pseudocorax, Squalicorax, Cretoxyrhina) are known from the Santonian sediments. Bony fishes of the time include pachycormiforms (Protosphyraena), ichthyodectiforms (Saurocephalus, Saurodon, Xiphactinus), aulopiforms (Enchodus, Stratodus), tselfatiiforms (Moorevillia, Bananogmius, Pentanogmius) and other groups. Various turtles (Bothremys, Ctenochelys) and long-necked elasmosaurids (Elasmosaurus) fell prey to predatory mosasaurs such as Tylosaurus and Platecarpus. Pterosaurs like Pteranodon soared over the seas and hunted for fish.
Fresh waters were home to numerous amphibians (Eoscapherpeton, Bakonybatrachus, Hungarobatrachus), turtles (Kallokibotion, Foxemys, Shachemys) and relatives of crocodiles, such as Shamosuchus and Kansajsuchus. Among dinosaurs, ornithopods (Kritosaurus, Eotrachodon, Bactrosaurus, Jaxartosaurus) were the most numerous. Ceratopsians like Ajkaceratops and Graciliceratops gradually spread across the northern continents. Plant-eating ankylosaurs like Hungarosaurus defended themselves from predators with armor and spikes, and some, as Talarurus, had a bony thickening on the tail with which they could deliver strong blows. Pachycephalosaurs like Amtocephale could defend themselves by hitting predators with their heads with thickened bony outgrowths. Sauropods like Erketu became rare in Northern Hemisphere. Bonitasaura, a small sauropod, was found in the Upper Santonian of Río Negro, Argentina. Theropods gave rise to unusual omnivorous therizinosaurs (Enigmosaurus, Segnosaurus) and ornithomimids (Archaeornithomimus). Dromaeosaurids like Kansaignathus hunted small animals.
References[]
- ↑ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. https://stratigraphy.org/chart#latest-version.
- ↑ "GSSP Table - Mesozoic Era". https://timescalefoundation.org/gssp/index.php?parentid=35.