Bajocian
From Wikipedia, the free encyclopedia
In the geologic timescale, the Bajocian is an age of the Middle Jurassic epoch of the Jurassic period of the Mesozoic era of the Phanerozoic eon. It lasted from approximately 171.6 Ma to around 167.7 Ma (million years ago). The Bajocian age succeeds the Aalenian age and precedes the Bathonian age, all in the same epoch.
The stage takes its name from the town of Bayeux, in the region of Normandy in France.
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[edit] Vertebrate Fauna
[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.
- The most plesiomorphic known metriorhynchid.
[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.
- Alfeldites
- Metrolytoceras
- Nannolytoceras
[edit] Genera Originating in Aalenian Strata
- Asthenoceras
- Bradfordia
- Euaptetoceras
- Eudmetoceras Image:1212amma.jpgA fossil ammonite of the order ammonitida
- Euhoploceras
- Fontannesia
- Graphoceras
- Haplopleuroceras
- Hyperlioceras
- Padragosiceras
- Praestrigites
- Reynesella
- Sonninia
- Spinammatoceras
- Trilobiticeras
- Tugurites
[edit] Originating in Lower Bajocian Strata
The following is a list of ammonite genera whose fossils are geochronologically found first in lower Bajocian strata. These genera may survive into later portions of the Bajocian stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included.
- Apsorroceras
- Asphinctites
- Cadomoceras
- Chondroceras
- Darellia
- Docidoceras
- Dorsetensia
- Duashnoceras
- Emileia
- Fissilobiceras
- Frogdenites Image:Douvilleiceras Hoplites.jpgLife restorations of two different ammonite genera.
- Guhsania
- Hebetoxyites
- Kumatostephanus
- Labyrinthoceras
- Leptosphinctes
- Lissoceras
- Newmarracarroceras
- Normannites
- Oecotraustes
- Oppelia
- Otoites
- Phaulostephanus
- Poecilomorphus
- Praebigotites
- Protoecotrausites
- Pseudotoites
- Shirbuirnia
- Skirroceras
- Skolekostephanus
- Sphaeroceras
- Stemmatoceras
- Strigoceras
- Stegoxyites
- Subcollina
- Teloceras
- Toxamblyites
- Toxolioceras
- Witchellia
- Zemistephanus
- Zurcheria
[edit] Originating in Upper Bajocian Strata
The following is a list of ammonite genera whose fossils are geochronologically found first in upper Bajocian strata. These genera may survive into later portions of the Bajocian stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included.
- Bigotites
- Caumontisphinctes
- Cleistosphinctes
- Dimorphinites
- Diplesioceras
- Durotrigensia
- Eocephalites
- Ermoceras
- Hlawiceras
- Kosmermoceras
- Lupherites
- Magharina
- Megasphaeroceras
- Orthogarantiana
- Parastrenoceras
- Praeparkinsonia
- Prorsisphinctes
- Pseudogarantiana
- Sohlites
- Spiroceras
- Strenoceras
- Telermoceras
- Thamboceras
- Trimarginia
- Vermisphinctes
- Cranocephalites
- Okribites
- Parkinsonia
- Synonymous with a modern plant genus.
- Garantiana
- Epistrenoceras
- Procerites
- Siemiradzkia
- Cadomites
- Oecoptychius
- Oxycerites
[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.
- Produvalia
[edit] Genera Originating in Aalenian Strata
- Holcobelus
- Sachsibelus
[edit] Originating in Lower Bajocian Strata
The following is a list of belemnite genera whose fossils are geochronologically found first in lower Bajocian strata. These genera may survive into later portions of the Bajocian stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included.
- Hibolites
[edit] Originating in Upper Bajocian Strata
The following is a list of belemnite genera whose fossils are geochronologically found first in upper Bajocian strata. These genera may survive into later portions of the Bajocian stage, or even into later geological stages. This list should not be thought of in terms of the lifespan of the genera included.
- Belemnitina
[edit] Nautiloids
Nautiloids are a group of marine mollusks in the subclass Nautiloidea, which all possess an external shell, the best-known example being the modern nautiluses. They flourished during the early Paleozoic era and subsequently developed an extraordinary diversity of shell shapes and forms. Some 2,500 species of fossil nautiloids are known, but only a handful of species survive to the present day.
- Ophionautilus
- Somalinautilus
| Jurassic period | ||
|---|---|---|
| Lower/Early Jurassic | Middle Jurassic | Upper/Late Jurassic |
| Hettangian | Sinemurian Pliensbachian | Toarcian | Aalenian | Bajocian Bathonian | Callovian | Oxfordian | Kimmeridgian Tithonian |
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