Pneumatization of an immature azhdarchoid pterosaur

Elgin, Ross A.; Hone, David W. E.

doi:10.1016/j.cretres.2013.06.006

Cited by 16 publications

(18 citation statements)

References 33 publications

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“…Differing from what was observed in the notarium, the free dorsal vertebrae of pterosaurs presented pneumatic foramina on the margins of the bases of the transverse processes, which were already reported in the Pteranodontoidea [9, 11, 19, 29] and the Azhdarchoidea [35, 47, 48], being similar both in form and number to the taxa analyzed here. Pneumatic foramina in similar position were observed in all analyzed Neornithes, and can be explained from a biomechanical point of view, because these are areas where their presence does not compromise the physical integrity of the vertebra [3].…”

Section: Discussioncontrasting

confidence: 55%

Comparative analysis of the vertebral pneumatization in pterosaurs (Reptilia: Pterosauria) and extant birds (Avialae: Neornithes)

2019

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Birds and pterosaurs have pneumatic bones, a feature likely related to their flight capabilities but whose evolution and origin is still poorly understood. Pneumatic foramina are present on the external surface of the bone and are reliable indicators of post-cranial skeletal pneumatization present in Pterosauria, Eusauropoda, and Neotheropoda. Here, we carried out a qualitative analysis of the position, size and number of pneumatic foramina of the cervical and thoracic/dorsal vertebrae of pterosaurs and birds, as they have the potential to challenge hypotheses about the emergence and evolution of the respiratory trait in these groups. We also discussed differences between pneumatic and vascular foramina for identification purposes. Besides phylogenetic representativeness, the pterosaur taxonomic sampling considered the preservation of specimens and, for birds, their life habit, as this relates to the level of pneumatization. Pneumatic foramina on the lateral faces of the centrum of the mid-cervical vertebrae of pterosaurs and birds differ in position and size, and those adjacent to the neural canal additionally differ in number. The avian posterior cervical vertebrae show a higher number of pneumatic foramina in comparison to their mid-cervicals, while the opposite is true for pterosaurs, suggesting differences in the cervical air sac of these clades. Pneumatic foramina were found at the base of the transverse processes of the notarial vertebrae of birds, while they were absent from some of the pterosaurs analyzed here, revealing the presence of a pneumatic hiatus in the vertebral column that might be explained due to the distance of this structure to the cervical air sac. These findings indicate that, although the overall skeletal pneumatization of pterosaurs and birds present deep homologies, some pneumatic features occurred convergently because variation in the number of pneumatic foramina along the vertebral column is related to the position of the air sacs in pterosaurs and birds and/or the habit of each species. There is an evident reduction of the pneumatic foramina in birds that have aquatic foraging and an increase in the ones which perform static soaring. Although we did not find any external anatomical difference between pneumatic and vascular foramina, we observed that vascular foramina occur at specific sites and thus identification on the basis of location is reliable.

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Section: Discussioncontrasting

confidence: 55%

Comparative analysis of the vertebral pneumatization in pterosaurs (Reptilia: Pterosauria) and extant birds (Avialae: Neornithes)

2019

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“…While a few studies have calculated metrics such as trabecular density and cortical thickness from a region or volume of interest for variably pneumatized birds (Fajardo et al, 2007; Gutzwiller et al, 2013), most efforts to quantify pneumaticity have used a measure called air space proportion (ASP), which is the ratio of air to total (i.e. air+bone) volume calculated from one or more CT image slices or from broken bone surfaces (Elgin and Hone, 2013; Fanti et al, 2013; Martin and Palmer, 2014; Taylor and Wedel, 2013; Wedel, 2005; Zurriaguz and Cerda, 2017). To assess holistic variation in extent of pneumaticity between vertebrae, I used a three‐dimensional implementation of ASP, measured as the ratio of the volume of air space to the total volume of the vertebra (Figure 1); this is akin to the bone volume:total volume measurement often used in studies of trabecular bone, reformulated to emphasize air space occupation.…”

Section: Methodsmentioning

confidence: 99%

Vertebral pneumaticity is correlated with serial variation in vertebral shape in storks

Moore

2020

Journal of Anatomy

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Birds and their ornithodiran ancestors are unique among vertebrates in exhibiting air‐filled sinuses in their postcranial bones, a phenomenon called postcranial skeletal pneumaticity. The factors that account for serial and interspecific variation in postcranial skeletal pneumaticity are poorly understood, although body size, ecology, and bone biomechanics have all been implicated as influencing the extent to which pneumatizing epithelia invade the skeleton and induce bone resorption. Here, I use high‐resolution computed‐tomography to holistically quantify vertebral pneumaticity in members of the neognath family Ciconiidae (storks), with pneumaticity measured as the relative volume of internal air space. These data are used to describe serial variation in extent of pneumaticity and to assess whether and how pneumaticity varies with the size and shape of a vertebra. Pneumaticity increases dramatically from the middle of the neck onwards, contrary to previous predictions that cervical pneumaticity should decrease toward the thorax to maintain structural integrity as the mass and bending moments of the neck increase. Although the largest vertebrae sampled are also the most pneumatic, vertebral size cannot on its own account for serial or interspecific variation in extent of pneumaticity. Vertebral shape, as quantified by three‐dimensional geometric morphometrics, is found to be significantly correlated with extent of pneumaticity, with elongate vertebrae being less pneumatic than craniocaudally short and dorsoventrally tall vertebrae. Considered together, the results of this study are consistent with the hypothesis that shape‐ and position‐specific biomechanics influence the amount of bone loss that can be safely tolerated. These results have potentially important implications for the evolution of vertebral morphology in birds and their extinct relatives.

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“…Unlike most pterosaur groups, azhdarchids are known primarily from terrestrial settings (Witton and Naish, 2008) and, despite their likely capacity to cross oceanic distances in flight (Habib, 2010), they are broadly considered to be terrestrially capable animals that were adapted for, and lived in, inland environments. This preference for inland environments, coupled with the thin-walled and highly pneumatic bones typical of these derived pterosaurs (Elgin and Hone, 2013), has likely contributed to their limited fossil record. Despite their large size and a distribution across North and South America, Asia, Africa and Europe (Witton, 2013), few taxa are known from more than fragmentary remains and the majority of taxonomic work has focused on rostral morphology, cervical vertebrae, and humeri.…”

Section: Introductionmentioning

confidence: 99%

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

Hone

Habib

Therrien

2019

Journal of Vertebrate Paleontology

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Azhdarchid pterosaurs have been known from the Upper Campanian deposits of Alberta, Canada since 1972. Originally represented by only very fragmentary remains tentatively assigned to the genus Quetzalcoatlus, additional material uncovered over the years has revealed that the taxonomic identity of the Alberta pterosaur material is at odds with this in the light of the growing understanding of azhdarchid diversity. Here we describe previously undocumented pterosaur remains from Alberta and reassess previously studied material. The specimens collected from the Dinosaur Park Formation can be assigned to a new genus and species Cryodrakon boreas gen. et sp. nov. The largest elements referable to this taxon suggests that this genus reached sizes comparable to other giant azhdarchids.

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Pneumatization of an immature azhdarchoid pterosaur

Cited by 16 publications

References 33 publications

Comparative analysis of the vertebral pneumatization in pterosaurs (Reptilia: Pterosauria) and extant birds (Avialae: Neornithes)

Comparative analysis of the vertebral pneumatization in pterosaurs (Reptilia: Pterosauria) and extant birds (Avialae: Neornithes)

Vertebral pneumaticity is correlated with serial variation in vertebral shape in storks

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

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