Hastanectes valdensis, whose name means “the Hastings swimmer from the Weald”, was a prehistoric marine reptile which swam the seas around Europe during the early Cretaceous Period approximately 140 to 135 million years ago.
The first fossils of this creature were found in the late 1800s near the town of Hastings in southern England within rock strata belonging to the Wadhurst Clay Formation. In 1889, the British geologist Richard Lydekker classified them as a species of the plesiosaur Cimoliasaurus, which had been named by the American anatomist and paleontologist Joseph Leidy earlier in 1851. However, in 2012, it was reclassified as a new and separate genus and was re-named as Hastanectes.
Two specimens of Hastanectes valdensis are currently known: the holotype “NHMUK R609”, which consists of a right humerus and 62 vertebrae (it’s been suggested that these vertebrae might belong to two individuals), and “NHMUK R5264” which is composed of a majority of the axial column (including the atlas/axis complex), the proximal end of one ischium, and some limb bones. There might also be a third specimen consisting of isolated vertebrae, but so far these have not been classified yet.
The 2012 article which officially named Hastanectes identified it as a member of the plesiosaur family Pliosauridae. As far as its placement goes within the pliosaur family tree, Hastanectes was apparently a middling species, more advanced than the basal forms which came before but still not as advanced as more derived genera like Pliosaurus, Liopleurodon, and Megalneusaurus. One of Hastanectes’ closer relatives was the British pliosaur Peloneustes, which existed during the middle Jurassic Period about 165 MYA and measured between 10 to 15 feet long. Hastanectes likely measured the same size and had a similar appearance.
Hastanectes shared its marine environment with numerous fish species including at least three different species of hybodont sharks. It might have co-existed with another marine reptile – the 10 foot long leptocleidid plesiosaur Leptocleidus. Meanwhile on land roamed the 20-25 foot long theropod dinosaur Altispinax, the iguanodontid dinosaurs Barilium and Hypselospinus, the somewhat dubious spinosaurid theropod Suchosaurus, and several species of crocodylomorphs and mammals.
Below is a drawing of Hastanectes, made with No.2 and No.3 pencil on printer paper. The drawing measures 10 inches long, which might make it 1/12 scale. However, until a complete specimen is found, the size is just an estimate.
Hastanectes valdensis. © Jason R. Abdale (September 6, 2022).
Benson, Roger B. J.; Ketchum, Hilary F.; Naish, Darren; Turner, Langan E. (2012). “A new leptocleidid (Sauropterygia, Plesiosauria) from the Vectis Formation (early Barremian–early Aptian; Early Cretaceous) of the Isle of Wight and the evolution of Leptocleididae, a controversial clade”. Journal of Systematic Palaeontology, volume 11, issue 2 (2012). Pages 233-250.