| System (period) | Series (epoch) | Stage (age) | Lower boundary, Ma | |
|---|---|---|---|---|
| Cretaceous | Lower | Berriasian | ~145 | |
| Jurassic | Upper (Late) | Tithonian | 149.2±0.7 | |
| Kimmeridgian |  154.8±0.8
| |||
| Oxfordian | 161.5±1.0 | |||
| Middle | Callovian | 165.3±1.1 | ||
| Bathonian | 168.2±1.2
| |||
| Bajocian | 170.9±0.8
| |||
| Aalenian | 174.7±0.8
| |||
| Lower (Early) | Toarcian | 184.2±0.3
| ||
| Pliensbachian | 192.9±0.3
| |||
| Sinemurian | 199.5±0.3
| |||
| Hettangian | 201.4±0.2
| |||
| Triassic | Upper | Rhaetian | older | |
| Subdivisions and "golden spikes" according to IUGS as of September 2023[1] | ||||
The Bajocian is a second stage of the Middle Jurassic series, corresponding to the Bajocian age of the Middle Jurassic epoch. It lasted from approximately 170.9 Ma to around 168.2 Ma (million years ago). It is preceded by the Aalenian and is followed by the Bathonian.
Definition[]
The GSSP of the Bajocian stage was ratified in 2008. The lower boundary is fixed in Ravin du Bès, Bas-Auran area, France, and related to the first appearance of the ammonite Gonolkites convergens. This species also related to the base of Zigzagiceras zigzag Zone.[2]
Bajocian life[]
The seas were inhabited by numerous cephalopods. The rostra of belemnites, which in appearance and lifestyle resembled squids, are well preserved in the fossil state. Cylindroteuthis (Belemnitidae) and Paramegateuthis (Megateuthididae) are known from the Bajocian deposits of Yuryung-Tumus Peninsula, Russia. Along with belemnites lived ammonites that had a twisted shell. Cartilaginous fish reached enormous diversity. Various synechodontiforms and hybodontiforms are known from the Bajocian strata of Moselle, France. Ichthyosaurs like Mollesaurus, Stenopterygius and Chacaicosaurus hunted cephalopods and small fish. Rhomaleosaurids like Maresaurus also ate mainly small animals. The dominant marine predators were pliosaurids such as Lorrainosaurus.
Turtles like Xinjiangchelys lived in rivers and lakes. Dinosaurs were widespread on land. Sauropods have almost completely replaced their non-sauropod relatives. The last indeterminate plateosaurids and massospondylids are known from the Bajocian of Liangshuijing, China. Long-necked mamenchisaurids like Analong and Chuanjiesaurus grazed near water bodies, and theropods like Shidaisaurus hunted them. Several theropods like Magnosaurus lived along the sea coasts and ate what the sea washed ashore. The australian Ozraptor and South American Eoabelisaurus that lived at this age are probably the oldest abelisauroids.
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.