vertebrae; more may have been present but were later lost to erosion or after excavation. Only Albertonectes had more neck vertebrae, 75, and the two are the only plesiosaurs with a count higher than 70; more than 60 vertebrae is very derived (or "advanced") for plesiosaurs. The atlas and axis bone complex, consisting of the first two neck vertebrae and articulated with the back of the skull, was long, low, and horizontally rectangular in side-view. The centra, or "bodies", of these vertebrae were co-ossified in the holotype specimen, which indicates it was an adult. The neural arches of these vertebrae were very thin and rather high, which gave the neural canal (the opening through the middle of the vertebrae) a triangular outline when seen from the back. The lower part of the neural canal was narrow towards the back by the axis, where it was half the breadth of the centrum. It became broader towards the front, where it was almost the same breadth as the centrum of the atlas. The neural arches were also more robust there than in the axis, and the neural canal was higher. The neural spine was low and directed upwards and back. The centra of the atlas and axis were of equal length, and had a quadratic shape in side view. The surface (or facet) where the axis articulated with the next vertebra had an oval outline, and an excavation for the neural canal in the middle of its upper edge. A distinct keel ran along the lower middle of the atlas and axis vertebrae. Most of the neck vertebrae were compressed sideways, especially at the middle of the neck. A crest (also termed ridge or keel) ran longitudinally along the side of the neck vertebrae (a feature typical of elasmosaurids), visible from the third to the fifty-fifth vertebrae, at the hind part of the neck. This crest was positioned at the middle of the centrum in the front vertebrae, and at the upper half of the centrum from the 19th vertebra and onwards. The crest would have served to anchor the musculature of the neck. The centra differed in shape depending on the position of the vertebrae in the neck; that of the third vertebra was about as long as it was broad, but the centra became longer than broad from the fourth vertebra and onwards. The centra became more elongated at the