From my lecture notes:
Related to terrestrial Permian anapsids
First turtles about Late Triassic
Diverse in Jurassic and Cretaceous
Up to 3 m long, 4 m flipper span
Also derived from terrestrial ancestors
Separate invasion of aquatic habitats to parasuchids (phytosaurs)
Got huge (15+ m, 18 tons)
Like dolphins with vertical tail
Known as fossils for over 200 years
Up to 15 m (Nevada, including mass stranding of 37 animals)
Mostly Jurassic, One survivor in Cretaceous
"Nothosaurs" -> Later ->
Plesiosaurs (to 12 m., most smaller)
(Early Jurassic -> Late Cretaceous)
Pliosaurs (to 12 m., like an ichthyosaur)
Big monitor lizards (to 10 m.)
1. What are the five main groups of aquatic reptiles that lived in the Mesozoic Era? What evidence is there that each of these groups reinvented the aquatic environment separately?
2. How are these reptiles similar to each other? How do they differ? (Be sure to also consider the last section on air breathing at sea.) How can one come to the conclusion that many of the similarities are due to convergent evolution, not due to common ancestry.
3. How does an ichthyosaur compare to a dolphin?
4. How does a plesiosaur compare with a pliosaur? Which of these (if any) is more closely related to a mososaur?
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