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. The type and only species, is "Thalassiodracon" ("Plesiosaurus") "hawkinsi" (Owen, 1838). Discovery and naming. "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. "Thalassiodracon" lived in the Late Triassic (Rhaetian) to the Early Jurassic (Hettangian) of Europe (age range: 201.6 to 196.5  million years ago). It was named as "Plesiosaurus hawkinsi" in 1838 by Richard Owen and it was made the type species of the genus "Thalassiodracon" in 1996 by Storrs & Taylor. 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. 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. Description. 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. 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. A computed tomography of an exceptionally preserved skull, and examination of other specimens (Benson "et al.", 2011) yields new anatomical data. "Thalassiodracon" had a dorsomedian ridge on the premaxilla, a squamosal bulb, four premaxillary teeth, and a heterodont maxillary dentition. Classification. "Thalassiodracon" was originally placed in the genus "Plesiosaurus". It has been classified in a new genus "Thalassiodracon" many years later following an examination of a skull. This animal is considered one of the oldest representatives of the group of plesiosaurs, perhaps ancestral  to the superfamily of Pliosauroidea (short-necked plesiosaurs). The following cladogram follows an analysis by Ketchum & Benson, 2011.