this surface is less than thick. Although the neural spine of the vertebra is not completely preserved, the width of the preserved portion suggests that it was relatively tall and robust relative to those of other pterosaurs. Other aspects of the vertebra converge upon the seventh neck vertebra of the smaller Azhdarcho most closely: the articulating sockets (cotyles) are much shallower than the neural arches, and are four times as wide as they are tall; a process on the bottom of the vertebrae, known as a hypapophysis, is present; the processes at the front of the vertebrae, the prezygapophyses, are splayed; and the vertebra has a tapered "waist" in the middle of the centrum. Although initially identified as a third neck vertebra, these traits supports the identification of the vertebra as coming from the rear of the neck, more specifically as being the seventh vertebra. Size The size of Hatzegopteryx was initially estimated by comparing the humerus fragment with that of Quetzalcoatlus northropi, which has a -long humerus. Observing that the Hatzegopteryx fragment presented less than half of the original bone, Buffetaut et al. established that it could possibly have been "slightly longer" than that of Quetzalcoatlus. The wingspan of the latter had been estimated at in 1981; earlier estimates had strongly exceeded this at . They concluded that an estimate of a wing span for Hatzegopteryx was conservative, "provided that its humerus was longer than that of Q. northropi". In 2010, Mark Witton and Michael Habib concluded that Hatzegopteryx was probably no larger than Q. northropi in wingspan; the initial conclusions did not account for distortion of the bone. The latter is generally estimated at in length. It has been suggested, on the basis of the wide and robust neck vertebra referred to Hatzegopteryx, that the entire vertebral column of the animal was similarly expanded, increasing its overall size. However, this is likely not true, since the neck vertebrae of large pterodactyloids generally tend to be wider and larger than the rest of the vertebrae. Although estimates of pterosaur size based on vertebrae alone are not particularly reliable, the size of this vertebra is consistent with an animal that measured in wingspan. Classification Similarities between the humerus of Hatzegopteryx and Quetzalcoatlus northropi have been noted; both have a long, smooth deltopectoral crest, and a thickened humeral head. These were initially the basis of the taxon's referral to the clade