Cretaceous Period

Leptocleidus

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Leptocleidus was a genus of plesiosaur which lived in the oceans during the early Cretaceous Period about 135 to 125 million years ago. It measured just 10 feet long, which is quite small for a plesiosaur. Three species of Leptocleidus… Read More ›

Lissodus

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Lissodus was a prehistoric shark which lived from the early Triassic to the middle Cretaceous Period, about 250 to 110 million years ago, give or take. Named in 1835, it was a member of a group of sharks called the… Read More ›

Polyacrodus

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Polyacrodus was a genus of prehistoric shark, composed of several species, with fossils found in North America, South America, Europe, Asia, and Africa. The name Polyacrodus means “tooth with many bumps”, and it was officially named by the German paleontologist… Read More ›

Arthropterygius

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Arthropterygius, “jointed fin”, was a genus of ichthyosaur which lived in the Arctic Ocean during the Jurassic/Cretaceous transition period about 150 to 140 million years ago. Fossils of it have been found in Canada, Scandinavia, and Russia, and bones which… Read More ›

Semionotus

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Semionotus was a genus of prehistoric fish which lived throughout the world during much of the Mesozoic Era. It was named by the famous Swiss ichthyologist and paleontologist Louis Agassiz in 1843 (type species: Semionotus bergeri). Semionotus first appeared during… Read More ›