STL Science Center

STL Science Center

22 December 2018

Celebrating Lyme Regis

©Dmitry Bogdanov
The holotype of Temnodontosaurus platyodon (originally Ichthyosaurus platyodon) is approximately 6.1 m (20 ft) long and was discovered in 1821. Although the name means "cutting tooth lizard" the fossil is best known for two radically different reasons. The first is that the orbits and the 25 cm diameter sclerotic rings indicate that the eyes were approximately 20 cm (8 in) in diameter, making these the second largest known eyes in any animal. Prior to a 2008 dissection of a rare Colossal Squid (Mesonychoteuthis hamiltoni) which has eyes approximately 27 cm (11 in) in diameter Temnodontosaurus had the largest known eyes. The second most important reason that Temnodontosaurus is well remembered is because this large ichthyosaur was one of the first fossils found by Joseph and Mary Anning in 1811; it was initially described as a crocodile. Joseph outlived Mary by a few years, but Mary was the true force in the family fossil collecting business despite being largely deleted from the literature of the time by the geologists to whom she sold her fossils. Anning also led geologists (including Buckland, Agassiz, Owen, and Conybeare among others) on expeditions, taught them how to collect fossils from Lyme Regis, and trained their field assistants and wives how to collect fossils. Temnodontosaurus may be well known for being discovered by the Annings, having large eyes, and being one of the first known ichthyosaurs, but it is not the best known of Anning's discoveries; that distinction belongs to (depending on who one asks) either her 1823 discovery of Plesiosaurus, or her 1828 discovery of what later became known as Dimorphodon. During this week we will talk a little about Temnodontosaurus and Mary Anning both every day. The reason for that, for those interested, is that many of Anning's discoveries were made or published during December and her life was actually strangely influenced by the month. Additionally, it was recently announced (14 December) that a movie based on part of her life, titled "Ammonite" will begin production in March 2019. Anning and December seem intertwined and Temnodontosaurus was her first big find. It all goes together for a fitting end to the year.

Also, I just realized this is blog post #2500. Hooray!

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