Ichthyosaur is a generic term for an extinct group of aquatic reptiles. There were over 100 distinct types of Ichthyosaur. The most closely resemble porpoises and distant relatives of lizards and snakes (lepidosaurs)
Ichthyosaur fossil remains span almost the entire Mesozoic Era (251 million to 65.5 million years ago). However, they were most common during the Triassic and Jurassic periods (251 million to 145.5 million years ago) about 25 million years before the dinosaurs became extinct. Ichthyosaur fossils have been found on every continent except Africa and Antarctica.
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