Formation specimen TMM 42489-2), and gracile forms with elongate rostra

and Volasertib Zhejiangopterus (McGowen et al., 2002). It has been speculated that azhdarchids could be roughly grouped into `robust' and `gracile' types according to these variations (Witton, 2013). It surely seems proper to consider types like Hatzegopteryx `robust' and others--e.g., Quetzalcoatlus and Zhejiangopterus--`gracile', but some taxa show `mixed' anatomies (e.g., Montanazhdarcho has proportionally stocky wing bones, but elongate neck bones (McGowen et al., 2002)), suggesting these categories must be regarded loose. Azhdarchid body plans may have been rather much more varied than imagined previously. Our assessment of vertebral mechanics in Hatzegopteryx and Arambourgiania suggests that azhdarchid necks had drastically diverse functional capabilities. We presume that cranial and cervical disparity reflects distinct foraging habits and prey preferences, with robust azhdarchids tackling fairly bigger prey than their gracile counterparts. The stout,Naish and Witton (2017), PeerJ, DOI 10.7717/peerj.20/Figure eight Azhdarchid disparity in cranial and limb anatomy. Abbreviations: automobile, carpals; cer, cervical vertebrae; cor, coracoid; fem, femur; hum, humerus; mcIV, metacarpal IV; pt, pteroid; rad, radius; tib, tibia; ul, ulna; wpI, wing phalanx I. Scale bars represent one hundred mm, except for any (10 mm).thick-walled cervicals of Hatzegopteryx, as well as its commonly reinforced bones and wide jaws (Buffetaut, Grigorescu Csiki, 2002; Buffetaut, Grigorescu Csiki, 2003), look far better suited to tackling larger, extra powerful prey, or for working with greater force and violence when obtaining food, than azhdarchid species with thin-walled bones, long, gracile necks and narrow skulls. Undescribed fossils most likely referable to Hatzegopteryx (including extra skull and limb elements that can not be described here) show that robust construction was constant across its body. The high resistance to bending stresses and indications of big cervical muscle tissues in Hatzegopteryx are consistent with this notion, as will be the inverse findings for Arambourgiania. Contemporary studies on azhdarchid foraging behaviour recommend that they had been terrestriallyforaging generalists (Witton Naish, 2008; Witton Naish, 2015; Carroll, Poust Varricchio, 2013; Witton, in press). What little is recognized of giant azhdarchid anatomy is equivalent sufficient to that in the smaller, better identified azhdarchids to assume that in addition they foraged terrest.Formation specimen TMM 42489-2), and gracile types with elongate rostra and slender jaws (Quetzalcoatlus sp.; Zhejiangopterus; Alanqa). Some azhdarchids also seem to possess comparatively slender rostra, as indicated by the concave dorsal skull margin of Azhdarcho (Fig. 8A, Averianov, 2010). A third category concerns the wing skeletons: we note that the comparatively abbreviated metacarpal IV and proximal wing phalanx from the diminutive azhdarchid Montanazhdarcho minor contrasts markedly with the elongate distal forelimb elements of Quetzalcoatlus sp. and Zhejiangopterus (McGowen et al., 2002). It has been speculated that azhdarchids could be roughly grouped into `robust' and `gracile' forms based on these differences (Witton, 2013). It undoubtedly appears suitable to think about forms like Hatzegopteryx `robust' and others--e.g., Quetzalcoatlus and Zhejiangopterus--`gracile', but some taxa show `mixed' anatomies (e.g., Montanazhdarcho has proportionally stocky wing bones, but elongate neck bones (McGowen et al., 2002)), suggesting these categories must be viewed as loose. Azhdarchid physique plans may have been rather additional varied than imagined previously. Our assessment of vertebral mechanics in Hatzegopteryx and Arambourgiania suggests that azhdarchid necks had drastically diverse functional capabilities. We presume that cranial and cervical disparity reflects distinct foraging habits and prey preferences, with robust azhdarchids tackling comparatively bigger prey than their gracile counterparts.