Cretaceous Marine Life
Many of the marine species that existed during the Jurassic era continued to live during the Cretaceous period also. Different varieties of sharks and bony fishes were found in plenty during this era. |
One of the notable marine species that evolved during the Cretaceous years was the Mosasaurs, a type of lizard, about 14 meters long! Crocodiles and the dangerous plesiosaurs also existed, but were not as common as Mosasaurs. Ichthyosaurs species that were dominating the Jurassic and Triassic periods were extinct during the early years of the Cretaceous period.
In addition to the reptiles, rudistid clams which were pretty gigantic, reaching up to a length of one metre, dominated the tropical oceans. These were the reminiscent of the coral varieties that ended up forming large reefs in the shallow waters. Besides, baculites, a species with a straight shell, also existed.
Similarly, Inoceramid clams were found in the warmer seas that had a shallow depth. They were able to flourish in areas that had very little oxygen! Another variety that diversified into amazing sizes and shapes were the ammonite cephalopods that formed coils of about two metres in length. Some resembled the shape of a hook.
The Cretaceous period is notable for bio-erosion, a phenomenon in which scrapings and borings in rocks, shells and hard grounds were formed. Plankton evolution was also at its high during the cretaceous period. A new group of marine organisms called Diatoms originated during the early years of this era. They were photosynthesizing in nature. Foraminifera and coccoliths outnumbered the diatoms. Starfishes were also known to flourish during this period.
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