Cetiosaurus

Cetiosaurus (/ˌsiːtioʊˈsɔːrəs, ˌsiːʃi-) meaning 'whale lizard', from the Greek keteios meaning 'sea monster' (later, 'whale') and sauros meaning 'lizard', is a genus of herbivorous sauropod dinosaur from the Middle Jurassic Period, living about 171 to 165 million years ago during the Bajocian and Bathonian ages in what is now Britain and probably France.

Cetiosaurus was named in 1842, making it the first sauropod from which bones were described and is the most complete sauropod found in England. It was so named because its describer, Sir Richard Owen, supposed it was a marine creature, initially an extremely large crocodile, and did not recognise it for a land-dwelling dinosaur. Cetiosaurus was a quadrupedal, long-necked, small-headed herbivore. It had a shorter tail and neck than most sauropods. The forelimbs, on the other hand, were relatively long. It is estimated to have been about 16 metres (52 ft) long and to have weighed roughly 11 tonnes (12 short tons).

Discovery and species

Cetiosaurus is the first sauropod dinosaur to be discovered and named, and it is the best-known sauropod from England. Many species have been linked to Cetiosaurus over the years, belonging to different groups of sauropod dinosaurs. The genus worked as a typical "wastebasket taxon," meaning many different fossils were grouped under this name.

The first fossils of Cetiosaurus, including vertebrae and limb bones, were found near Chipping Norton, Oxfordshire, in the early 1800s. They were first thought to belong to a whale or crocodile. In 1841, biologist and paleontologist Sir Richard Owen named these fossils as Cetiosaurus. Owen did not recognize them as dinosaurs at first and thought they were from a giant sea-dwelling reptile. He named two species in 1842: Cetiosaurus hypoolithicus and Cetiosaurus epioolithicus. These names described whether the fossils were found below or above certain rock layers.

In 1868, workers near Bletchingdon found a sauropod right femur. Professor John Phillips later uncovered three skeletons and more bones at the site. In 1871, he named two species from these finds: Cetiosaurus oxoniensis and Cetiosaurus glymptonensis. In 1968, a new C. oxoniensis specimen called the "Rutland Dinosaur" was discovered. It is the most complete sauropod fossil found in the United Kingdom. This fossil was displayed in the Leicester Museum & Art Gallery starting in 1985.

The naming of Cetiosaurus species has been complex. Traditionally, C. medius was thought to be the main species, but later studies showed it was not clearly defined. In 2014, scientists officially changed the main species to C. oxoniensis, which is the best-known and most complete species from the Middle Jurassic period.

Valid Species

The only widely accepted species of Cetiosaurus is:

• Cetiosaurus oxoniensis Phillips, 1871: type species of Cetiosaurus

Doubtful species

These species are not well-defined or are not considered part of Cetiosaurus:

• Cetiosaurus hypoolithicus Owen, 1841: not a valid name
• Cetiosaurus epioolithicus Owen, 1841: not a valid name
• Cetiosaurus brachyurus Owen, 1842: not clearly defined
• Cetiosaurus longus Owen, 1842: not clearly defined
• Cetiosaurus medius Owen, 1842: not clearly defined
• Cetiosaurus giganteus Owen vide Huxley, 1870: not a valid name
• Cetiosaurus philippsi Sauvage, 1880

Misassigned and reclassified species

These species were once thought to be Cetiosaurus but are now placed in other genera:

• Cetiosaurus brevis Owen, 1842: now Pelorosaurus conybearei
• Cetiosaurus glymptonensis Phillips, 1871: now Cetiosauriscus glymptonensis
• Cetiosaurus rigauxi Sauvage, 1874: a pliosaurid, not a sauropod
• Cetiosaurus humerocristatus Hulke, 1874: now Duriatitan humerocristatus
• Cetiosaurus leedsi (Hulke, 1887) Woodward, 1905: not clearly defined
• Cetiosaurus rugulosus (Owen, 1845) Steel, 1970: now Cardiodon
• Cetiosaurus mogrebiensis de Lapparent, 1955: not a Cetiosaurus

Description

Cetiosaurus, including the species C. oxoniensis, is known from fairly complete fossils. These fossils include three skeletons found by a person named Phillips. One skeleton is from a larger animal and was selected as the main example of the species. Another set of bones comes from a smaller individual, and the third skeleton is from a young animal.

Cetiosaurus was a long-necked, four-legged dinosaur. In 2010, an expert estimated it to be about 16 meters (52 feet) long and to weigh around 11 tonnes (12 short tons). Its neck was fairly long but not longer than its body. The tail was much longer, with at least forty tail bones. Unlike some later sauropods, Cetiosaurus had solid back bones without much air space. Its forearm was as long as its upper arm, making its front legs the same length as its back legs. The bone in its thigh was about six feet long.

Classification and phylogeny

Sir Richard Owen, who first described Cetiosaurus, wasn’t sure what kind of animal it was. He knew it was a reptile but thought it might live in the water, like a large crocodile. It wasn’t until later that scientists began to understand it was a land animal and a type of dinosaur.

Over time, scientists placed Cetiosaurus in different groups. Some put it in a group called Cetiosauridae, but today we know there are many more simple sauropods than Cetiosaurus. Modern studies still aren’t sure exactly where Cetiosaurus fits among other sauropods. Some think it belongs with dinosaurs like Barapasaurus, Patagosaurus, or Chebsaurus, while others think it sits near the base of larger sauropod groups.

Ecology

During the Middle Jurassic period, Europe was made up of many islands surrounded by shallow seas. Cetiosaurus lived on an island called the London–Brabant Massif, which included parts of southern Britain and nearby areas of northern France, the Netherlands, Belgium, and western Germany. This island was about the size of Cuba.

Other dinosaurs that lived around the same time as Cetiosaurus in Britain included large meat-eating dinosaurs like Megalosaurus, Magnosaurus, and Duriavenator, as well as smaller dinosaurs such as Proceratosaurus.

Cetiosaurus lived in areas with floodplains and open woodlands. It likely ate plants from both low and medium heights, thanks to its long neck. The climate on the island was sometimes dry, and the plants there included different types of conifers, ferns, and other ancient plants.