Ichthyosaurs are the most specialized marine reptiles. Its characteristics: fish-eating, fish-like body shape (they are reptiles that breathe air). In fact, they do resemble mackerel and tuna, and the extreme fluid shape allows these extant fish to swim at speeds of up to 40 kilometers per hour.
Unlike its contemporaries, ichthyosaurs did not swim on paddle-like flippers, but developed a fish-shaped tail that relied on lateral movements to provide propulsion, similar to the tail function of modern sharks and tuna. Ichthyosaurs are well adapted to the marine environment, no longer need to go ashore to lay eggs like turtles and plesiosaurs, but instead give birth to pups directly in the sea. The most high-profile ichthyosaur fossils document the process by which adult female ichthyosaurs are giving birth to their pups, a process that has been preserved forever.
Ichthyosaurs live in a similar environment to modern dolphins, they are diverse, and they have survived for 100 million years. These marine creatures roamed the oceans of the early Triassic period, peaked in species during the Jurassic Period, and then declined until they became extinct in the middle of the Cretaceous Period. Their extinction may be related to the emergence of the advanced shark, which by this time had evolved into modern forms and were the main carnivores in the late Mesozoic oceans.
The origin of ichthyosaurs is unknown, but the only thing that can be determined is that they came from a group of terrestrial reptiles, not from a known marine reptile.
Name: Ichthyosaur (marine reptile)
Age: Early Jurassic to Early Cretaceous
Locations: Europe (England and Germany), Greenland and North America (Alberta, Canada)
Size: up to 2 meters
Ichthyosaurs are the most familiar prehistoric animals, and their fossils are figuratively preserved near the Hozmadon Shale in southern Germany. These rocks were deposited in shallow waters during the early Jurassic period, and hundreds of complete ichthyosaur skeletons have been found in these rocks, some of which are still connected to each other. The small bones of the pups have been found in several adult ichthyosaurs, and some specimens have preserved the circumstances in which the pups were born from the adult ichthyosaurs (the tail is first out, similar to modern whales), which fully indicates that these marine animals can give birth directly to the young in the ocean.
Many specimens are surrounded by a thin layer of charcoal, clearly showing the shape of the body when the flesh and blood on the bone were still alive. From these fossils can be seen the body structure of the ichthyosaur: the towering dorsal fin on the back; Half-moon-shaped caudal fin (caudal lateral fin), the lower lobe formed by the downward curvature of the vertebrae; Short hydrofoil-shaped flattened tarsal joints that surround the slender toes of the limbs; A pair of forelimbs is longer than the hindlimbs.
The nostrils of the ichthyosaur are located at the back of the snout, near the eyes, so it needs to stick out of the water to breathe. The ichthyosaur has larger ear bones and may transmit perceived fluctuations of water to the inner ear to determine the direction of the prey, but the main organ for locating the prey is the eye, which is large and very sensitive.
The rocks also preserve the feces of these marine reptiles, known as fecal fossils, which indicate that ichthyosaurs feed on fish while preying on small numbers of cephalopods. The fossil pigment cells of Ichthyosaurus have also been preserved, and their analysis reveals that the smooth thick skin of Ichthyosaurus is reddish brown.