Neck biomechanics indicate that giant Transylvanian azhdarchid pterosaurs were short-necked arch predators

Abstract

Azhdarchid pterosaurs include the largest animals to ever take to the skies with some species exceeding 10 metres in wingspan and 220 kg in mass. Associated skeletons show that azhdarchids were long-necked, long-jawed predators that combined a wing planform suited for soaring with limb adaptations indicative of quadrupedal terrestrial foraging. The postcranial proportions of the group have been regarded as uniform overall, irrespective of their overall size, notwithstanding suggestions that minor variation may have been present. Here, we discuss a recently discovered giant azhdarchid neck vertebra referable to Hatzegopteryx from the Maastrichtian Sebeş Formation of the Transylvanian Basin, Romania, which shows how some azhdarchids departed markedly from conventional views on their proportions. This vertebra, which we consider a cervical VII, is 240 mm long as preserved and almost as wide. Among azhdarchid cervicals, it is remarkable for the thickness of its cortex (4–6 mm along its ventral wall) and robust proportions. By comparing its dimensions to other giant azhdarchid cervicals and to the more completely known necks of smaller taxa, we argue that Hatzegopteryx had a proportionally short, stocky neck highly resistant to torsion and compression. This specimen is one of several hinting at greater disparity within Azhdarchidae than previously considered, but is the first to demonstrate such proportional differences within giant taxa. On the assumption that other aspects of Hatzegopteryx functional anatomy were similar to those of other azhdarchids, and with reference to the absence of large terrestrial predators in the Maastrichtian of Transylvania, we suggest that this pterosaur played a dominant predatory role among the unusual palaeofauna of ancient Haţeg.

The first pterosaur pelvic material from the Dinosaur Park Formation (Campanian) and implications for azhdarchid locomotion

“…Recent studies Naish 2008, 2015;Naish and Witton 2017) have suggested that azhdarchids were pterosaurs adapted for increased terrestrial locomotion. They envision azhdarchids as "terrestrial stalkers", using their tall frame and long neck to ambush unsuspecting prey.…”

Cryodrakon boreas, gen. et sp. nov., a Late Cretaceous Canadian azhdarchid pterosaur

“…Currie and Russell, 1982;Currie and Jacobsen, 1995;Godfrey and Currie, 2005), all remains are here identified as belonging to azhdarchid pterosaurs. Despite varying degrees of completeness, all cervical vertebrae show some or all of the characteristic features of members of the clade: a low centrum, greatly reduced 'bifid' neural spine (that is, one that has separate anterior and posterior components with a space in between), and dorsoventrally flattened zygopophyses, pneumatic foramina lateral to the neural canal, greatly elongated mid cervicals (e.g., Kellner, 2003;Naish and Witton, 2017;Vidovic and Martill, 2017). Wellnhofer (1970) suggested that the cervical vertebrae of azhdarchids elongate during ontogeny (i.e.…”

“…This is especially the case for issues such as lengthwidth ratios, which are commonly used in azhdarchid descriptions. Azhdarchids are well known for elongate middle cervicals although recently animals with proportionally short and robust vertebrae have been described (Vremir et al, 2015;Naish and Witton, 2017), further complicating the issues of length-width ratios. However, recent papers (Averianov, 2010;Naish and Witton, 2017) have suggested characteristics that can help identify isolated azhdarchid cervicals and are followed here.…”

Does postcranial palaeoneurology provide insight into pterosaur behaviour and lifestyle? New data from the azhdarchoid Vectidraco and the ornithocheirids Coloborhynchus and Anhanguera

“…; Lockley & Rainforth ; Mazin et al . ), demonstrates that many of these animals were also adept terrestrial locomotors, and that members of some groups may even have foraged and fed extensively on the ground (Witton & Naish , ; Naish & Witton ). Members of Azhdarchoidea in particular (the toothless, Cretaceous clade that includes the typically gigantic, long‐jawed azhdarchids, the short‐faced tapejarids, and the intermediate chaoyangopterids and thalassodromids) appear to be well adapted for terrestrial behaviour; notably the azhdarchids with their long hindlimbs and compact feet (Witton & Naish , ; Witton ).…”