| System (period) | Series | Stage (age) | Lower boundary, Ma | |
|---|---|---|---|---|
| Quaternary | Pleistocene | Gelasian | 2.58 | |
| Neogene | Pliocene | Piacenzian |  3.600
| |
| Zanclean | 5.333
| |||
| Miocene | Messinian | 7.246
| ||
| Tortonian | 11.63
| |||
| Serravallian | 13.82
| |||
| Langhian | 15.98
| |||
| Burdigalian | 20.44 | |||
| Aquitanian | 23.03
| |||
| Paleogene | Oligocene | Chattian | older | |
| Subdivisions and "golden spikes" according to IUGS as of September 2023[1] | ||||
The Tortonian is a fifth stage of the Miocene series, corresponding to the Tortonian age of the Miocene epoch. It lasted from approximately 11.63 Ma to around 7.246 Ma (million years ago). It is preceded by the Serravallian and is followed by the Messinian. The last choristoderes are known from this stage.
It was named after the Italian city of Tortona by Karl Mayer-Eymar in 1858.
Definition[]
The GSSP of the Tortonian stage was ratified in 2003. The lower boundary is fixed on Monte dei Corvi Beach, near Ancona, Italy, and related to mid-point of sapropel layer of basic cycle 76. The last common occurrence of the calcareous nanofossil Discoaster kugleri is used for correlation.[2]
Tortonian life[]
A reconstructed skull of Livyatan melvillei
Life flourished both in the seas and on land. The most numerous group of vertebrates were fish, but mammals surpassed everyone in the diversity of ecological niches they occupied. Remarkable fauna of this age have been found in Pisco Formation of Peru. Two apex predators, the shark Otodus megalodon and the physeteroid whale Livyatan melvillei existed simultaneously in the same location. Megalodon reached more than 12 m in length and was one of the largest fish of all time, while Livyatan, with a length of 13 to 17 m, was slightly inferior to the modern sperm whale. Other animals from the same formation include bony (Sardinops) and cartilaginous fishes (Carcharhinus, Galeocerdo, Carcharodon), turtles, crocodiles, suliform birds (Sula, Phalacrocorax), cetaceans (Messapicetus, Brachydelphis) and seals.
Mammals have spread throughout almost the entire planet. Cetaceans (Lophocetus, Mixocetus), sirenians (Metaxytherium), desmostylians (Desmostylus, Paleoparadoxia) and odobenids (Imagotaria) inhabited the seas. Land species migrated from continent to continent, although endemic fauna remained in some areas.
Africa[]
A skull of Mixocetus
Propotamochoerus skull
A diverse mammal fauna similar to that of today lived in continental Africa. Fossil finds include rodents (Vulcanisciurus, Afrocricetodon, Thryonomys, Paraulacodus), proboscideans (Deinotherium, Choerolophodon, Tetralophodon), orycteropodids (Orycteropus) and primates (Microcolobus). Land artiodactyls reached large numbers. Various pigs (Propotamochoerus, Nyanzachoerus), hippopotamids (Kenyapotamus), tragulids (Dorcatherium), giraffids (Palaeotragus) and bovids (Gazella) are known from the Tortonian sediments. Perissodactyls were represented by rhinocerotids (Chilotheridium, Diceros, Brachypotherium, Kenyatherium), horses (Hipparion) and chalicotheriids. All these animals were hunted by carnivorans, including the large, hyena-like Percrocuta. Many crocodiles lived in rivers and lakes, including Euthecodon.
Eurasia[]
Lazarussuchus, the last known choristodere, existed in Germany during Tortonian alongside numerous turtles, birds and mammals.
Numerous proboscideans (Deinotherium, Tetralophodon, Mammut, Zygolophodon), pigs (Hyotherium, Listriodon, Parachleuastochoerus), bovids (Miotragocerus), giraffids (Helladotherium), rhinocerotids (Dihoplus, Aceratherium, Chilotherium, Hoploaceratherium), horses (Anchitherium, Hipparion, Sinohippus), chalicotheriids (Chalicotherium, Ancylotherium), hyaenids (Ictitherium, Lycaena, Thalassictis), cats (Machairodus, Paramachaerodus, Leptofelis, Pseudaelurus) and mustelids (Martes, Trocharion, Eomellivora) have been found in the Tortonian strata of Europe. A similar fauna existed in Asia, where, in addition to numerous ungulates, hominids lived, such as Khoratpithecus from Myanmar or Sivapithecus from China. Some species of mammals have survived to this day. Among them was the beaver (Castor fiber), which already lived in the northern latitudes. Eurasian rodents of the time also include Muscardinus, Myoglis, Glirulus, Anomalomys, Keramidomys and others.
North America[]
A diverse fauna also lived in North America. Herbivores, in addition to the peccaries and deer that are typical today, were also represented by rhinocerotids (Aphelops, Teleoceras), horses (Neohipparion, Nannippus, Cormohipparion), proboscideans (Amebelodon, Mammut matthewi) and camelids (Aepycamelus, Hemiauchenia). Enhydritherium, a marine otter, and Huracan, a bear, have been discovered in the Tortonian of Polk County, Florida, USA.
South America[]
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A skeleton of Hapalops
Notiomastodon skeletal reconstruction compared to a human
The endemic fauna existed at that time in South America. Animals that lived on the Tortonian sea coast were found in Entre Rios, Argentina. Fossils include litopterns (Proterotherium, Scalabrinitherium), notoungulates (Haplodontherium), sparassodonts (Notictis, Stylocynus), cetaceans (Pontistes, Balaena) and other mammalian groups. Some animals that appeared outside of South America already lived on its territory at that time. Phugatherium was a rodent from the family Hydrochoeridae, which also includes modern capybaras. Dinomyids, giant rodents with a head size of up to half a meter and more lived at that time in Brazil. Scleromys, Ferigolomys, Potamarchus, Gyriabrus, Eumegamys and Simplimus lived alongside such andemic mammals as ground sloths (Hapalops, Pliomorphus, Protomegalonyx, Mionothropus), glyptodontids (Plohophorus, Paraglyptodon) and astrapotherians (Xenastrapotherium). Proboscideans (Notiomastodon) and primates (Stirtonia, Solimoea, Acrecebus) also lived in South America.
Australia[]
Australia, an isolated continent, was dominated by marsupials. Among them, diprotodontians were the most diverse. Various members, including vombatids (Warendja), palorchestids (Palorchestes), diprotodontids (Neohelos), burramyids (Burramys) and thylacoleonids (Wakaleo) have been found in the lacistrine sediments in Queensland. Non-diprotodontian carnivorous Ganbulanyi and Mayigriphus are known from the same strata. Non-marsupial Tortonian mammals were represented by bats, such as still existing Macroderma.
Antarctica[]
Spheniscus, a modern penguin genus, existed in Antarctica during this age. Its fossils have been found in Fisher Bench Formation.
References[]
- ↑ "Latest version of international chronostratigraphic chart". International Commission on Stratigraphy. https://stratigraphy.org/chart#latest-version.
- ↑ "GSSP Table - Cenozoic Era". https://timescalefoundation.org/gssp/index.php?parentid=2.