Mechanical implications of pneumatic neck vertebrae in sauropod dinosaurs

Schwarz, Daniela; Meyer, Christian A.; Frey, Eberhard; Manz-Steiner, Hans-Rudolf; Schumacher, Ralf

doi:10.1098/rspb.2009.1275

Cited by 21 publications

(15 citation statements)

References 28 publications

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“…The neck ‘locks up’ and those vertebrae effectively becomes a rigid body protecting the intervertebral joint. Zygapophyseal bracing is also noted to be assist in stabilizing the neck against torsion and lateral tilting [83]. Osteological bracing may also prevent excessive mediolaterally flexion in some extant vertebrates (e.g., in the base of the neck in giraffes, Figures 11b, 12, and rhinos, pers.…”

Section: Methodsmentioning

confidence: 99%

The Articulation of Sauropod Necks: Methodology and Mythology

Stevens

2013

PLoS ONE

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Sauropods are often imagined to have held their heads high atop necks that ascended in a sweeping curve that was formed either intrinsically because of the shape of their vertebrae, or behaviorally by lifting the head, or both. Their necks are also popularly depicted in life with poses suggesting avian flexibility. The grounds for such interpretations are examined in terms of vertebral osteology, inferences about missing soft tissues, intervertebral flexibility, and behavior. Osteologically, the pronounced opisthocoely and conformal central and zygapophyseal articular surfaces strongly constrain the reconstruction of the cervical vertebral column. The sauropod cervico-dorsal vertebral column is essentially straight, in contrast to the curvature exhibited in those extant vertebrates that naturally hold their heads above rising necks. Regarding flexibility, extant vertebrates with homologous articular geometries preserve a degree of zygapophyseal overlap at the limits of deflection, a constraint that is further restricted by soft tissues. Sauropod necks, if similarly constrained, were capable of sweeping out large feeding surfaces, yet much less capable of retracting the head to explore the enclosed volume in an avian manner. Behaviorally, modern vertebrates generally assume characteristic neck postures which are close to the intrinsic curvature of the undeflected neck. With the exception of some vertebrates that can retract their heads to balance above their shoulders at rest (e.g., felids, lagomorphs, and some ratites), the undeflected neck generally predicts the default head height at rest and during locomotion.

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Section: Methodsmentioning

confidence: 99%

The Articulation of Sauropod Necks: Methodology and Mythology

Stevens

2013

PLoS ONE

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“…Sauropod pneumaticity is extensive (Britt, 1993); Wedel (2005) estimated that derived sauropod vertebrae comprised 60% air by volume, comparable to the situation in avian limb bones. Due to their large body size, most hypotheses of the function of sauropod pneumaticity focus on skeletal lightening as an adaptation related to mass reduction (Cope, 1877; Janensch, 1947; Britt, 1993; Schwarz, Frey & Meyer, 2007 a ), particularly of the extremely long neck (Wedel, 2003 b ; Sander et al , 2010; Schwarz et al , 2010). It has also been suggested that pneumatic diverticula could provide a lightweight mechanism for support and stabilisation of an extremely long neck, though this remains strictly hypothetical (Akersten & Trost, 2004; Schwarz et al , 2007 a ; Schwarz & Frey, 2010).…”

Section: Postcranial Skeletal Pneumaticity In Extinct Non‐theropomentioning

confidence: 99%

Air‐filled postcranial bones in theropod dinosaurs: physiological implications and the ‘reptile’–bird transition

et al. 2011

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Pneumatic (air-filled) postcranial bones are unique to birds among extant tetrapods. Unambiguous skeletal correlates of postcranial pneumaticity first appeared in the Late Triassic (approximately 210 million years ago), when they evolved independently in several groups of bird-line archosaurs (ornithodirans). These include the theropod dinosaurs (of which birds are extant representatives), the pterosaurs, and sauropodomorph dinosaurs. Postulated functions of skeletal pneumatisation include weight reduction in large-bodied or flying taxa, and density reduction resulting in energetic savings during foraging and locomotion. However, the influence of these hypotheses on the early evolution of pneumaticity has not been studied in detail previously. We review recent work on the significance of pneumaticity for understanding the biology of extinct ornithodirans, and present detailed new data on the proportion of the skeleton that was pneumatised in 131 non-avian theropods and Archaeopteryx. This includes all taxa known from significant postcranial remains. Pneumaticity of the cervical and anterior dorsal vertebrae occurred early in theropod evolution. This 'common pattern' was conserved on the line leading to birds, and is likely present in Archaeopteryx. Increases in skeletal pneumaticity occurred independently in as many as 12 lineages, highlighting a remarkably high number of parallel acquisitions of a bird-like feature among non-avian theropods. Using a quantitative comparative framework, we show that evolutionary increases in skeletal pneumaticity are significantly concentrated in lineages with large body size, suggesting that mass reduction in response to gravitational constraints at large body sizes influenced the early evolution of pneumaticity. However, the body size threshold for extensive pneumatisation is lower in theropod lineages more closely related to birds (maniraptorans). Thus, relaxation of the relationship between body size and pneumatisation preceded the origin of birds and cannot be explained as an adaptation for flight. We hypothesise that skeletal density modulation in small, non-volant, maniraptorans resulted in energetic savings as part of a multi-system response to increased metabolic demands. Acquisition of extensive postcranial pneumaticity in small-bodied maniraptorans may indicate avian-like high-performance endothermy.

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“…For example, many sauropod dinosaurs exhibit evidence of extensive pneumaticity of the axial skeleton that would have resulted in decreased bone mass. This has been interpreted as a mechanism allowing for the large body size attained by members of the clade (Sander et al, ; Wedel, ; Schwarz‐Wings et al, ).…”

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confidence: 99%

Postcranial Pneumaticity and Bone Structure in Two Clades of Neognath Birds

Gutzwiller

O’Connor

2013

The Anatomical Record

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Most living birds exhibit some degree of postcranial skeletal pneumaticity, aeration of the postcranial skeleton by pulmonary air sacs and/or directly from the lungs. The extent of pneumaticity varies greatly, ranging from taxa that are completely apneumatic to those with air filling most of the postcranial skeleton. This study examined the influence of skeletal pneumatization on bone structural parameters in a sample of two size-and foraging-style diverse (e.g., subsurface diving vs. soaring specialists) clades of neognath birds (charadriiforms and pelecaniforms). Cortical bone thickness and trabecular bone volume fraction were assessed in one cervical and one thoracic vertebra in each of three pelecaniform and four charadriiform species. Results for pelecaniforms indicate that specialized subsurface dive foragers (e.g., the apneumatic anhinga) have thicker cortical bone and a higher trabecular bone volume fraction than their non-diving clademates. Conversely, the large-bodied, extremely pneumatic brown pelican (Pelecanus occidentalis) exhibits thinner cortical bone and a lower trabecular bone volume fraction. Such patterns in bone structural parameters are here interpreted to pertain to decreased buoyancy in birds specialized in subsurface dive foraging and decreased skeletal density (at the whole bone level) in birds of larger body size. The potential to differentially pneumatize the postcranial skeleton and alter bone structure may have played a role in relaxing constraints on body size evolution and/or habitat exploitation during the course of avian evolution. Notably, similar patterns were not observed within the equally diverse charadriiforms, suggesting that the relationship between pneumaticity and bone structure is variable among different clades of neognath birds. Anat Rec, 296:867-876,

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Mechanical implications of pneumatic neck vertebrae in sauropod dinosaurs

Cited by 21 publications

References 28 publications

The Articulation of Sauropod Necks: Methodology and Mythology

The Articulation of Sauropod Necks: Methodology and Mythology

Air‐filled postcranial bones in theropod dinosaurs: physiological implications and the ‘reptile’–bird transition

Postcranial Pneumaticity and Bone Structure in Two Clades of Neognath Birds

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