The middle Jurassic period, known as the Dogger epoch came about 176 to 161 million years ago and was divided in to the Aalenian age, the Bajocian age, the Bathonian age, and the Callovian age. The middle of the Jurassic period saw the beginning of the separation of Pangea in to Laurasia and Gondwana and the formation of the Atlantic Ocean.
The middle Jurassic period saw both growth and reduction in life; however, it was certainly not as dramatic of a change as that during the beginning of the Jurassic period. The reason for such explosive growth at the beginning of the Jurassic period was the extinction of so many species during the Triassic period. Marine life during the Dogger epoch saw some thinning of marine life as Icthyosaurs diversity reduced; however this reduced diversity was met with increased numbers of existing species. Also during this period Pliosaurs grew to mammoth proportions, matching killer whales in mass. It is during this time also that Plesiosaurs made their appearance even more known by multiplying in numbers and the Metriorhynchid crocodilians also stepped on to the scene. The Dogger epoch also saw the appearance of new terrestrial life including Cetiosaurs, Hypsilophodonts, Megalosaurs, and Brachiosaurs. As Cynodonts continued to grow during this time the Trithelodont Cynodonts saw the end of the line at the end of the epoch. In terms of mammals it is the middle of the Jurassic era that saw the evolution of what we consider “real” mammals.
The middle Jurassic period saw both growth and reduction in life; however, it was certainly not as dramatic of a change as that during the beginning of the Jurassic period. The reason for such explosive growth at the beginning of the Jurassic period was the extinction of so many species during the Triassic period. Marine life during the Dogger epoch saw some thinning of marine life as Icthyosaurs diversity reduced; however this reduced diversity was met with increased numbers of existing species. Also during this period Pliosaurs grew to mammoth proportions, matching killer whales in mass. It is during this time also that Plesiosaurs made their appearance even more known by multiplying in numbers and the Metriorhynchid crocodilians also stepped on to the scene. The Dogger epoch also saw the appearance of new terrestrial life including Cetiosaurs, Hypsilophodonts, Megalosaurs, and Brachiosaurs. As Cynodonts continued to grow during this time the Trithelodont Cynodonts saw the end of the line at the end of the epoch. In terms of mammals it is the middle of the Jurassic era that saw the evolution of what we consider “real” mammals.
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