ichthyosauriërs

Ichthyosauriërs, commonly called ichthyosaurs, are an extinct order of marine reptiles that inhabited the world’s oceans from the Early Triassic epoch about 250 million years ago to the Late Cretaceous around 90 million years ago. They arose after the end-Permian extinction and rapidly diversified into forms adapted to open-ocean life, with fossils found on every major paleocontinent.

Their bodies were highly streamlined and fish-like, built for fast swimming. The forelimbs were transformed into paddle-like flippers, and the hind limbs were reduced or incorporated into the body wall. Many species had a crescent-shaped tail fin oriented horizontally, a dorsal fin in some lineages, and an elongated snout with conical teeth for catching prey. Eye size varied considerably, with several genera possessing exceptionally large eyes, suggesting enhanced vision in dim offshore waters.

Ichthyosauriërs were primarily marine predators. Their teeth and jaw shapes indicate diets ranging from soft-bodied cephalopods to fast-swimming fish. Most species were viviparous, giving birth to live young at sea; fossil evidence includes embryos preserved within adults, illustrating their aquatic reproductive strategy.

Fossil records show an early radiation in the Triassic, with later lineages such as ichthyosaurids and ophthalmosaurids. They achieved a near-global distribution, with significant finds in Europe, North America, Asia, and Australia. Their decline in the Late Cretaceous coincides with the rise of mosasaurs and other marine reptiles, marking the end of their long, successful marine career. The group remains important for studying secondary aquatic adaptation and convergent evolution with other marine predators.