How big was Ichthyosaurs?

Ichthyosaurs measured around 8 feet (2.4 metres) in length and weighed around 163 to 168 kilograms (360 to 370 pounds). Although Ichthyosaurs looked like dolphins, however they were very different.

Ichthyosaurs had fin-like limbs, which were possibly used for stabilisation and direction control underwater, rather than propulsion. Ichthyosaurs speed through the water came from its large shark-like tail.

The tail was bi-lobed, with the lower lobe being supported by the caudal vertebral column, which was ‘kinked’ ventrally to follow the contours of the ventral lobe. Ichthyosaurs had a porpoise-like head and a long, toothed snout, which gave Ichthyosaurs its Dolphin like appearance.

Built for speed

As already mentioned, Ichthyosaurs were very strong swimmers fully adapted to life in the seas. They were better adapted than any other reptiles, although they still needed to go to the surface periodically to breathe air.

Built for speed, some Ichthyosaurs appear also to have been deep divers. It has been estimated that Ichthyosaurs could swim at speeds up to 25 miles per hour (40 kilometres per hour).

Due to the various sizes of Ichthyosaurs and as they were one of the most successful marine reptiles ever, it is believed that Ichthyosaurs likely had a wide range of prey. One distinctive feature of Ichthyosaurs were their large eyes, protected within a bony ring, suggested that they may have hunted at night.

Evolution of Ichthyosaurs

During the middle Triassic Period, Ichthyosaurs evolved from unidentified land reptiles that moved back into the water, in a development parallel to that of modern-day dolphins and whales. They were particularly abundant in the Jurassic Period, until they were replaced as the top aquatic predators by plesiosaurs in the Cretaceous Period

When did Ichthyosaurs live and Die?

Ichthyosaurs were still common in the middle of the Jurassic period, but at this point Ichthyosaurs had now decreased in diversity. All remaining species of Ichthyosaurs all belonged to the single clade called Ophthalmosauria.

Ichthyosaurs seemed to decrease further in diversity in the Cretaceous Period. By this time only a single genus is known which was called Platypterygius, and although it had a worldwide distribution of this species existed, there was little diversity species-wise.

This last Ichthyosaur genus fell victim to the mid-Cretaceous or Cenomanian-Turonian extinction event. Ichthyosaur weren’t the only marine reptile to go extinct in this event, even the giant Pliosaurs could not escape. However, it’s important to note that less hydrodynamically efficient animals like Mosasaurs and long-necked Plesiosaurs flourished.