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 195 million years ago

Mean atmospheric O2
 130% of modern level

Mean atmospheric CO2
 7x pre-industrial level

Mean temperature
 3C above modern level

Mesozoic Earth - A six inch ammonite floating in an Early Jurassic sea; index fossils; Lytoceratina; invertebrates - Natural History Illustration Geologic Time Scale

 Era: Mesozoic
  Period: Jurassic
   Epoch: Early
    Age: Sinemurian


Early Jurassic ammonite

A mollusk of the subclass Ammonoidea in a Jurassic sea 195 million years ago. This specimen's planispiral shell is about six inches in diameter.

Ammonites were plentiful in the Earth's oceans for about 400 million years becoming extinct, along with the dinosaurs, about 66 million years ago during the Cretaceous–Paleogene (K–Pg) extinction event. While resembling modern shelled nautiloids, these once plentiful mollusks are more closely related to living octopuses, squid, and cuttlefish.



Copyright Walter B. Myers. All rights reserved.

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