Chosen Extinct Reptile & Research

I have chosen to create a Tylosaurus which is an extinct marine reptile from the Cretaceous period.

Fig 1. Tylosaurus  

Tylosaurus was a large marine reptile that lived 89-65 million years ago during the Cretaceous period and is a member of the Mosasaur group. It was a vicious predator that grew to an average size of 15 meters and preyed on everything including sharks, plesiosaurs, pliosaurs, large fish and they even resorted to cannibalism. Inside the upper jaw is a second row of teeth which could move up and down independently from the skull. These secondary teeth shown in Fig 2 are thought to be used to help clamp onto struggling prey and prevent it from swimming out of the Tylosaurus' mouth.

Fig 2. Inner Teeth

Not only does it have these extra teeth, Tylosaurus had and extra hinge in the lower jaw to allow it to open more wider much similar to a snake does today. They are also thought to be ancestors of  modern snakes, as quoted from www.nature.com. 'Mosasaurs share a common ancestor with snakes, but their evolution took another path. They had a long streamlined body, a deep tail and paddle-shaped limbs. Their strong, snout-like jaws were lined with sharp teeth for gripping their prey. But the lower jaw of the mosasaur resembles that of a snake far more than that of a lizard. It has a loose joint between the front and back halves of the lower jaw, which immediately makes it able to stretch round a larger object than the jaw of a lizard of the same size.' (www.nature.com, 1999)

Tylosaurus was one of the biggest of the mosasaur family and discoveries of skin impressions shown in Fig 3 show that it had scales like that of a snake, explained from the book The World Encyclopedia of Dinosaurs & Prehistoric Creatures. 'One of the biggest and the last of the mosasaurs was Tylosaurus. It was so big that it preyed on other sea reptiles including smaller mosasaurs like Clidastes. Plotosaurus, another mosasaur of a similar size, from California, USA, has been found with impressions of skin, indicating that it was covered in scales, like a snake.' (Dixon, 2011:284)

Fig 3. Tylosaurus Fossil Skin Impression

Skeleton of Tylosaurus

Tylosaurus Skull

Notes about the features of Tylosaurs from watching Mega Beasts: T-rex Of The Deep

• Sonar pits along the upper jaw.
• Very good hearing under water.
• Possibly a forked tongue like monitor lizards and snakes, also used in the same way to track potential prey.
• Flat rudder tail 
• Ambush predator
• Highly aggressive
• Territorial
• Murdered its own kind, not for food but for other reasons, deep scar marks and broken necks found on specimens.

List of Illustrations

Figure 1. MMVII Night, inc, Tylosaurus [Render] At: http://animals.nationalgeographic.co.uk/animals/prehistoric/tylosaurus.html (Accessed on: 10.02.12)

Figure 2. Willderbeast's photostream, Inner Teeth [Photograph] At: http://www.flickr.com/photos/willdebeast/5288881332/ (Accessed on: 10.02.12)

Figure 3. Lawrence, Da Lee, Tylosaurus Fossil Skin Impression [Photograph] At: http://www.oceansofkansas.com/Snow1878.html (Accessed on: 10.02.12)

Figure 4. Loozrboy, Skeleton of Tylosaurus [Photograph] At: http://en.wikipedia.org/wiki/File:Tylosaurus_Bruce.jpg (Accessed on: 10.02.12)

Figure 5. Williston, Skeleton of Tylosaurus [Drawing] At: http://www.oceansofkansas.com/about-mo.html (Accessed on: 10.02.12)

Figure 6. Ghedoghedo, Tylosaurus Skull [Photograph] At: http://it.wikipedia.org/wiki/File:Tylosaurus_proriger_skull.JPG (Accessed on: 10.02.12)

Bibliography

Website

Lawrence, Eleanor (1999) Open Wide http://www.nature.com/news/1999/990812/full/news990812-11.html (Accessed on: 10.02.12)

Video

Mega Beasts: T-rex Of The Deep (2009) Directed by: Geoffrey Sharp [TV Series] USA: Discovery Channel

Book

Dixon, Dougal (2011) The World Encyclopedia of Dinosaurs & Prehistoric Creatures. (2nd Ed.) Leicestershire: Lorenz Books