Triassic Ichthyosaur Fossil from Falong Formation

The name Ichthyosaur means "fish-lizard", and is an apt descriptor for these sea-going reptiles that predated the earliest dinosaurs by some 20 million years, appearing some 250 million years ago (mya). Ichthyosaurs disappeared some 90 mya, about 25 million years before the dinosaurs became extinct. During the early Triassic, ichthyosaurs evolved from as-yet unidentified land reptiles that moved back into the water, in a development parallel to that of modern-day dolphins and whales.

The earliest Ichthyosaurs are known from Lower Triassic strata of North America and Asia. While the first Ichthyosaurs looked much like a lizard with fins, they rapidly evolved a more fish-like form which was a remarkable parallel to the modern-day dolphin. They were unable to return to land to lay eggs, so theydeveloped the ability to give birth to live young. Several examples of mother Ichthyosaurs are known, particularly from the Jurassic Posidonia shale of Holzmaden, Germany. They preceded the dinosaurs into extinction during the Cenomanian Stage of the Cretaceous about 90 million years ago, presumably because of their inability to compete with the Pliosaurs as the top predator of their day.

This spectacular specimen is preserved in the ventral state in a remarkable 3-D manner as the photos show. It is remarkably complete, with the bones in a wonderful state of articulation. The dark-gray to black marly mudstone was capable of preserving the finest details of various marine reptiles and the well-known crinoid Traumatocrinus. The deposits are thought to have formed at depths in excess of 500 meters in an anoxic environment.