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Paleozoic and Mesozoic Seas

During the Paleozoic and Mesozoic, six marine transgressions and regressions caused sea level to rise over the continents, leaving evidence in rocks in the Grand Canyon and elsewhere.

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Squid Cream Cones

Squid Cream Cones

Credit: Wilson44691
Source: http://en.wikipedia.org/wiki/File:OrhtocerasNautiloid092313.jpg
License: CC BY-NC 3.0

Kind of like an ice cream cone, but holding a squid-like creature, Orthoceras ruled the Ordovician seas. Today its fossils are abundant and popular.

Amazing But True!

Credit: Nobu Tamura (http://spinops.blogspot.com)
Source: http://en.wikipedia.org/wiki/File:Orthoceras_BW.jpg
License: CC BY-NC 3.0

Digitally recreated image of an Orthocera [Figure2]

  • Orthoceras was a cephalopod like octopus, squid and nautilus today.
  • Their fossils are found worldwide.
  • Orthoceras fossils are most commonly found in limestone.
  • There are millions of these fossils around.

Show What You Know

With the link below, learn more about Orthoceras. Then answer the following questions.

  1. What was the Cambrian explosion?
  2. What did marine organisms evolve to become predators? What did they evolve for protection from predators?
  3. Why did Orthoceras rule the seas?
  4. How did Orthoceras get around?
  5. Why are there so many Orthoceras fossils in some locations?

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    Image Attributions

    1. [1]^ Credit: Wilson44691; Source: http://en.wikipedia.org/wiki/File:OrhtocerasNautiloid092313.jpg; License: CC BY-NC 3.0
    2. [2]^ Credit: Nobu Tamura (http://spinops.blogspot.com); Source: http://en.wikipedia.org/wiki/File:Orthoceras_BW.jpg; License: CC BY-NC 3.0

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