Thunnosauria

Thunnosauria is a clade of marine reptiles that includes the ichthyosaurs and their relatives. The name Thunnosauria is derived from the Greek words "thunnos," meaning "tuna," and "sauros," meaning "lizard," reflecting the group's affinity for tuna-like swimming. This clade first appeared during the Late Triassic period and thrived throughout the Mesozoic era, eventually going extinct at the end of the Cretaceous period.

Ichthyosaurs are the most well-known members of Thunnosauria, characterized by their streamlined bodies, flippers, and a single dorsal fin. They were highly adapted for aquatic life, with features such as a streamlined body, powerful flippers, and a single dorsal fin. Ichthyosaurs ranged in size from small, dolphin-like forms to large, whale-sized species.

The relationships within Thunnosauria are complex, with various groups of ichthyosaurs and their relatives, such as the plesiosaurs and the pliosaurids, all belonging to this clade. The exact evolutionary relationships between these groups are still a subject of ongoing research and debate among paleontologists.

Thunnosauria went extinct at the end of the Cretaceous period, likely due to a combination of factors including climate change, competition with other marine reptiles, and the impact of the asteroid that caused the Cretaceous-Paleogene extinction event. Despite their extinction, ichthyosaurs have left a significant fossil record, providing valuable insights into the evolution of marine reptiles and the history of the oceans during the Mesozoic era.