ichthyopterygia

Ichthyopterygia is an extinct clade of marine reptiles that includes the ichthyosaurs, a successful group that dominated open-ocean ecosystems from the Early Triassic to the Late Cretaceous, roughly 250 to 90 million years ago. They are among the earliest major radiations of amniotes adapted to life in the sea and left a rich fossil record worldwide.

Anatomically, ichthyopterygians exhibit strong adaptations for aquatic life. They typically had streamlined, fish-like bodies, broad heads with elongated snouts, and paddle-like limbs that supported powerful swimming. Their tails often ended in a crescent-shaped fluke, and many species possessed a dorsal fin and oversized eyes, the latter indicating adaptation to low-light or deep-water environments. Their teeth varied with diet, ranging from sharp, conical teeth to robust, crushing types.

Ecology and life history were diverse. Ichthyopterygians were active predators feeding on fish and cephalopods. In many species, embryos or undeveloped young are found within the mother, indicating viviparity (live birth) and efficient reproduction in the marine environment. They occupied a range of marine habitats and achieved global distribution, with fossils from Europe, North America, Asia, and other regions.

Taxonomically, Ichthyopterygia is sometimes treated as the broader grouping containing ichthyosaurs and their stem relatives, while some classifications place the crown group within Ichthyosauria. Despite varying schemes, the clade is central to discussions of Triassic–Cretaceous marine reptile evolution and the recovery of marine ecosystems after the Permian extinction.