About Marine Reptiles
Many giant reptiles lived in Mesozoic oceans, but they were not dinosaurs. Ichthyosaurs, plesiosaurs, and mosasaurs belonged to different reptile lineages that returned to life in the water and evolved bodies suited to swimming and marine hunting.
Not Dinosaurs
Marine reptiles lived alongside dinosaurs but belonged to other reptile groups.
Learn MoreIchthyosaurs
Ichthyosaurs had streamlined bodies that looked somewhat like modern dolphins.
Learn MorePlesiosaurs
Plesiosaurs had four powerful flippers and came in several body shapes.
Learn MoreMosasaurs
Mosasaurs became major marine predators during the Late Cretaceous.
Learn MoreAir Breathers
Marine reptiles still needed to breathe air.
Learn MoreMarine Food Webs
Mesozoic seas contained complex food webs.
Learn MoreMarine Fossils
Ocean sediments can preserve remarkable skeletons.
Learn MoreEnd-Cretaceous Losses
Mosasaurs and plesiosaurs disappeared in the same mass extinction that ended the non-avian dinosaurs.
Learn MoreNot Dinosaurs
Dinosaurs were primarily land animals with a specific skeletal arrangement. Mosasaurs were relatives of lizards and snakes, while ichthyosaurs and plesiosaurs belonged to other extinct reptile branches.
Ichthyosaurs
They first appeared during the Triassic and became highly specialized swimmers. Their fish-like body shape evolved independently from dolphins, an example of convergent evolution.
Plesiosaurs
Some plesiosaurs had very long necks and small heads, while pliosaurs had shorter necks and massive skulls. They used all four flippers to move through the water in a style unlike most living marine animals.
Mosasaurs
They were large aquatic squamates related to the broader lizard and snake group. Fossils show streamlined bodies, strong tails, flippers, and jaws lined with conical teeth.
Air Breathers
Unlike fish, these reptiles had lungs and had to surface. Several groups gave birth to live young in the water, allowing them to spend their whole lives at sea.
Marine Food Webs
Marine reptiles shared oceans with fish, sharks, ammonites, belemnites, turtles, plankton, and many other organisms. Bite marks and stomach contents sometimes reveal predator-prey relationships.
Marine Fossils
Fine seafloor muds sometimes buried animals rapidly. Fossils from places that are dry land today can show that the region was once underwater because sea levels and continents changed over time.
End-Cretaceous Losses
Ocean food webs changed rapidly after the asteroid impact. Many plankton groups were affected, which disrupted food chains from the bottom upward.