| System (period) | Series (epoch) | Stage (age) | Lower boundary, Ma | |
|---|---|---|---|---|
| Jurassic | Lower | Hettangian | 201.4±0.2 | |
| Triassic | Upper (Late) | Rhaetian | ~208.5 | |
| Norian | ~227 | |||
| Carnian |  ~237
| |||
| Middle | Ladinian | ~242
| ||
| Anisian | 247.2 | |||
| Lower (Early) | Olenekian | 251.2 | ||
| Induan | 251.902±0.024
| |||
| Permian | Lopingian | Changhsingian | older | |
| Subdivisions and "golden spikes" according to IUGS as of September 2023[1] | ||||
The Ladinian is a second stage of the Middle Triassic series, corresponding to the Ladinian age of the Middle Triassic epoch. It lasted from approximately 242 Ma to around 237 Ma (million years ago). It is preceded by the Anisian age of the Middlte Triassic and is followed by the Carnian age of the Late Triassic.
It includes Fassanian and Longobardian substages. The Ladinian is coeval with the Falangian Chinese regional stage.
Definition[]
The GSSP of the Ladinian stage was ratified in 2005. The lower boundary is fixed in the Buchenstein Beds in Province of Brescia, Northern Italy, and related to the first appearance of the ammonite species Eoprotrachyceras curionii. This species also defines the base of the E. curionii zone, and the first appearance of the conodont Budurovignathus praehungaricus can be seen in the uppermost Anisian strata.[2]
Ladinian life[]
The shell of Protrachyceras
Various gastropods (Naticopsis, Dicosmos, Delphinulopsis) and bivalves (Mysidioptera, Leptochondria, Prospondylus) lived on coral reefs. Ammonites like Trachyceras, Protrachyceras, Celtites and Lecanites predominated among cephalopods. Hybodontiform fishes like Acrodus have adapted to chewing hard shells. This was a time when the seas were inhabited by a wide variety of marine reptiles. Thalattosaurs (Xinpusaurus), ichthyosaurs (Guizhouichthyosaurus, Mikadocephalus), nothosaurs (Nothosaurus, Ceresiosaurus, Simosaurus) and placodonts (Cyamodus, Placodus) inhabited the warm shallow waters off the eastern coasts of Pangaea. Many of them ate fish, although some placodonts also adapted to eating animals with hard shells and carapaces. Some reptiles like Tanystropheus and Macrocnemus have also been found in marine sediments, but, due to their limbs, typical for terrestrial animals, they likely were semiaquatic.
Fresh water bodies were still inhabited by numerous dipnoan fishes (Ceratodus) and temnospondyls, from small Gerrothorax to large Cyclotosaurus and Mastodonsaurus. Phytosaurs like Diandongosuchus had already appeared and were beginning to compete with them. Being reptiles, phytosaurs were better adapted to the droughts and high temperatures of the time. Moreover, unlike amphibians, they laid their eggs on the shore.
Chalishevia
Plants of the groups Voltziopsida (Voltzia) and Polypodiopsida (Schizoneura) grew on land, and rhynchosaurid reptiles like Brasinorhynchus fed on them. Numerous archosauromorph reptiles were the dominant group among terrestrial vertebrates. From small Chanaresuchus to large Chalishevia, they occupied a variety of ecological niches. Chalishevia, as other erythrosuchids, had a large head compared to its body, which made these animals probably not very fast. Over time, they were replaced by more mobile and long-legged reptiles like Energosuchus and large Luperosuchus, both related to modern crocodiles. Small Lagerpeton was probably an ancestor of pterosaurs, while Lagosuchus and Lewisuchus are closely related to dinosaurs. It can be assumed that true pterosaurs and dinosaurs already existed in the Ladinian, but fossils that can be confidently attributed to them have not yet been discovered.
Another group of land vertebrates, Synapsida, was represented mainly by huge plant-eating dicynodonts like tusk-bearing Dinodontosaurus, and smaller cynodonts like herbivorous Massetognathus and carnivorous Chiniquodon. Cynodonts are the most successful group of synapsids since they include later evolved mammals. The Ladinian was probably the last age when therocephalians were still living on our planet. A skull of Microgomphodon was found in the Anisian-Ladinian terrestrial shale of the Omingonde Formation in Namibia.
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.