Cretaceous Period

Leptocleidus

NOTE: This post was originally published on May 13, 2022. It was updated and re-uploaded on April 14, 2026. Leptocleidus was a genus of plesiosaur which lived in the oceans during the early Cretaceous Period about 135 to 125 million years… Read More ›

Lissodus

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

NOTE: This article was originally published on May 4, 2022. On December 30, 2025, it was updated and re-uploaded. Polyacrodus was a genus of prehistoric shark, composed of several species, with fossils found in North America, South America, Europe, Asia, and… Read More ›

Arthropterygius

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 ›