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Large extinct sea reptiles known as ichthyosaurs. Ichthyosaurs are members of the Ichthyosauria or Ichthyopterygia (‘fish flippers,’ a word coined by Sir Richard Owen in 1840, but now more commonly used to the Ichthyosauria’s parent group).

Ichthyosaurs flourished for most of the Mesozoic era; according to fossil evidence, they initially emerged approximately 250 million years ago (Ma), and at least one species lived until the Late Cretaceous, about 90 million years ago. Ichthyosaurs evolved from an unidentified group of land reptiles that returned to the sea during the Early Triassic epoch, in a process similar to how the mammalian land-dwelling ancestors of modern-day dolphins and whales returned to the sea millions of years later, which they gradually came to resem

ble in a case of convergent evolution. Ichthyosaurs were abundant in the Late Triassic and Early Jurassic periods, until they were replaced as the top aquatic predators by another marine reptilian group, the Plesiosauria, in the later Jurassic and Early Cretaceous periods, though previous views of ichthyosaur decline during this period were probably exaggerated. Ichthyosaurs became extinct during the Cenomanian-Turonian boundary as a result of environmental instability caused by climatic upheavals in the early Late Cretaceous.

When the first complete ichthyosaur bones were discovered in England in the early 1800s, science became aware of their existence. The order Ichthyosauria was established in 1834. Many well-preserved ichthyosaur fossils, including soft-tissue remnants, were unearthed in Germany later that century. There has been a renewed interest in the group since the late twentieth century, resulting in a rise in the number of identified ichthyosaurs from all continents, with over fifty genuine taxa being recognized.

The length of several Ichthyosaur species ranged from 1 to 16 meters (3 to 52 feet). Ichthyosaurs looked like a cross between current fish and dolphins. Their limbs had been completely converted into flippers, with a high number of digits and phalanges on occasion. A dorsal fin was present in at least some species. Their heads were pointed, and their jaws typically had conical teeth to aid in the capture of smaller prey. Larger, bladed teeth were seen in some species, allowing them to attack huge animals. The eyes were enormous, which was presumably advantageous for deep dives. The neck was short, and the trunk of later species was rigid. There was also a more vertical tail fin on them, which was employed for a forceful propelling stroke. The simple disc-like vertebrae of the vertebral column persisted into the lower lobe of the tail fin. Ichthyosaurs were warm-blooded, air-breathing creatures that gave birth to live offspring. They may have been insulated by a coating of blubber.

Edward Lhuyd of Wales provided the earliest known pictures of ichthyosaur bones, vertebrae, and limb parts in his Lithophylacii Brittannici Ichnographia in 1699. They seemed to Lhuyd to be fish remnants. Johann Jakob Scheuchzer, a Swiss biologist, published two ichthyosaur vertebrae in 1708, presuming they belonged to a man perished in the Universal Deluge. An ichthyosaur jaw with teeth was discovered near Bath in 1766. The Society for Promoting Natural History presented this item in 1783 as crocodilian skin. In John Walcott’s Descriptions and Figures of Petrifications, published in 1779, ichthyosaur bones were shown. The extent of British fossil collections significantly grew at the end of the eighteenth century. Naturalists Ashton Lever and John Hunter’s collections were purchased in their whole by museums, and it was later discovered that they contained hundreds of ichthyosaur bones and teeth. The bones were usually identified as those of fish, dolphins, or crocodiles, and the teeth as those of sea lions.

Due to the increased demand from collectors, commercial digging activities became more aggressive. This led in the finding of more complete bones in the early nineteenth century. Edward Donovan discovered a four-metre-long (13-foot) ichthyosaur specimen with a jaw, vertebrae, ribs, and a shoulder girdle in St Donats in 1804. It was thought to be a massive lizard. In October 1805, a newspaper story announced the discovery of two further bones, one by Jacob Wilkinson at Weston and the other by Reverend Peter Hawker in the same settlement. Joseph Hawker, the latter’s relative, described the final specimen in 1807. As a result, geologists dubbed this specimen ‘Hawker’s Crocodile.’ An ichthyosaur jaw was discovered in Stratford-upon-Avon in 1810, and it was merged with plesiosaur bones to create a more complete specimen, indicating that the distinctive character of ichthyosaurs was still unknown, pending the discovery of considerably better specimens.

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