Callovian
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The Callovian is a stage on the geologic time scale occurring 164.7 ± 4.0 Ma to 161.2 ± 4.0 Ma (million years ago). It is the last stage of the Middle Jurassic.
The stage takes its name from an old spelling of Kellaways Bridge, 3 km north-east of Chippenham in Wiltshire in England.
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[edit] Geography
During the Callovian, Europe was an island chain.
[edit] Vertebrate Fauna
[edit] Dinosaurs
- A four foot long bipedal herbivore that was built for speed. It was discovered in one of China's many Callovian deposits.
- A moderately large (17-23 feet long) predatory dinosaur that was closely related to Megalosaurus.
- A Kyrgistani sauropod genus that resembled Rhoetosaurus.
- Ferganasaurus verzilini
- An 11-13 foot predator from China whose discovery was assisted by the petroleum industry.
- Gasosaurus constructus
[edit] Pliosaurs
The Pliosaurs ("Fin Lizards") were marine reptiles from the Jurassic and Cretaceous Periods. This group was characterised by having a short neck and an elongated head, in contrast to the long-necked plesiosaurs. They were more crocodile-shaped. However, the four-paddle swimming action, using the large flipper-like limbs was shared with plesiosaurs and they were possibly better adapted to deeper waters. They were carnivorous and their long and powerful jaws carried many sharp, conical teeth. Their prey may have included fish, ichthyosaurs and other plesiosaurs.
[edit] Sphenosuchians
- Junggarsuchus
- The sphenosuchian Junggarsuchus was a small, ~1 meter long, Chinese predator.
[edit] Thalattosuchians
Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution.
- An opportunistic carnivore that fed on fish, belemnites and other marine animals and possible carrion. Metriorhynchus grew to an average adult length of 3 meters (9.6 feet), although some individuals may have reached lengths rivaling those of large nile crocodiles.
[edit] Invertebrate Fauna
[edit] Ammonitida
Members of the order ammonitda are known as Ammonitic ammonites. They are distinguished primarily by their suture lines. In ammonitic suture patterns, the lobes and saddles are much subdivided (fluted) and subdivisions are usually rounded instead of saw-toothed. Ammonoids of this type are the most important species from a biostratigraphical point of view. This suture type is characteristic of Jurassic and Cretaceous ammonoids but extends back all the way to the Permian.
[edit] Surviving From the Bajocian
The following ammonite genera first appear in the fossil record during the Bajocian stage of the Jurassic Period and survive into the Callovian.
- Cadomites
- Oecoptychius
- Oecotraustes
- Oxycerites
- Somalinautilus
[edit] Belemnites
Belemnites (or belemnoids) are an extinct group of marine cephalopod, very similar in many ways to the modern squid and closely related to the modern cuttlefish. Like them, the belemnites possessed an ink sac, but, unlike the squid, they possessed ten arms of roughly equal length and no tentacles.
[edit] Genera Surviving From the Bajocian
The following genera of Belemnites first appear in Bajocian rocks, but survived to this article's eponymous stage.
- Produvalia
[edit] Octopuses
The octopus is a cephalopod of the order Octopoda. Octopuses are characterized by their eight arms (not tentacles), usually bearing suction cups. These arms are a type of muscular hydrostat. Unlike most other cephalopods, the majority of octopuses — those in the suborder most commonly known, Incirrina — have almost entirely soft bodies with no internal skeleton. They have neither a protective outer shell like the nautilus, nor any vestige of an internal shell or bones, like cuttlefish or squids. A beak, similar in shape to a parrot's beak, is the only hard part of their body.
- Proteroctopus
[edit] Squid
Squid are a large, diverse group of marine cephalopods. Like all cephalopods, squid are distinguished by having a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms and two tentacles arranged in pairs.
- Rhomboteuthis Image:Vampylarge.JPGPyritized fossil of Vampyronassa rhodanica from Voulte-sur-Rhône, France.
- A squid species discovered in France.
[edit] Vampyromorphida
Vampyromorphida is an order of cephalopods comprising one extant species (Vampyroteuthis infernalis) and several extinct taxa.
- Vampyronassa
| Jurassic period | ||
|---|---|---|
| Lower/Early Jurassic | Middle Jurassic | Upper/Late Jurassic |
| Hettangian | Sinemurian Pliensbachian | Toarcian | Aalenian | Bajocian Bathonian | Callovian | Oxfordian | Kimmeridgian Tithonian |
de:Callovium fr:Callovien nl:Callovien pl:Kelowej pt:Calloviano sh:Callovij uk:Келовейський ярус
