Thalassiodracon
Thalassiodracon (tha-LAS-ee-o-DRAY-kon) is an extinct genus of plesiosauroid from the Pliosauridae that was alive during the Late Triassic-Early Jurassic (Rhaetian-Hettangian) and is known exclusively from the Lower Lias of England.[1] The type and only species, is Thalassiodracon (Plesiosaurus) hawkinsi (Owen, 1838).[2][3]
Thalassiodracon hawkinsi is known from a number of complete skeletons (Holotype: BMNH 2018) found by the fossil collector Thomas Hawkins in Somerset, England during the early 1830s, before 1835.[3][4][5] Thalassiodracon lived in the Late Triassic (Rhaetian) to the Early Jurassic (Hettangian) of Europe (age range: 201.6 to 196.5 million years ago).[3] It was named as Plesiosaurus hawkinsi in 1838 by Richard Owen[2] and it was made the type species of the genus Thalassiodracon in 1996 by Storrs & Taylor.[1]
A replica of the holotype specimen, replica catalogued as LDUCZ-X227, has been in the collection of the Grant Museum of Zoology and Comparative Anatomy in London, England since 1890 aafter being catalogued by Ray Lankester, and it is a cast of a specimen created in 1862 by Henry Augustus Ward.[6] The original fossil, catalogued as BMNH 2018 and also found by Hawkins in the 1830s, can be seen on display at the Natural History Museum, also in London, England.
The genus name Thalassiodracon means "sea dragon", while the species name hawkinsi honours its discoverer.
This marine reptile measured 1.5–2 m. (5-6.5 ft) had a relatively long neck but the small skull was proportionally larger than Plesiosaurus, being 1/10 of the total body length.
The neck of Thalassiodracon, however, was slightly shorter than that of subsequent Plesiosaurs.[6] The cervical vertebrae were between 27 and 31, while those of Plesiosaurus were 35 - 37. Moreover, the skull was unusually short and equipped with long teeth. The orbits were very large, with sclerotic rings. Like all plesiosaurs, this animal had legs like paddles for swimming in the sea.
