Pneumatic structures in the cervical vertebrae of the Late Jurassic Tendaguru sauropods Brachiosaurus brancai and Dicraeosaurus

Abstract

Pneumatic vertebrae of Brachiosaurus and Dicraeosaurus 65 ABSTRACT The presacral vertebrae of sauropod dinosaurs were surrounded and invaded by a complex system of pneumatic diverticula, which originated most probably from cervical air sacs connected with the respiratory apparatus. Cervical vertebrae of Brachiosaurus brancai and Dicraeosaurus sp., two sauropods from the Late Jurassic (?Oxfordian-Kimmerigian-Tithonian) eastern African locality Tendaguru, were examined with computed tomography to visualize internal pneumatic structures. With this method, comparative reconstructions of pneumatic diverticula in the neck of these sauropods were done that help to understand the biomechanical role of vertebral pneumaticity in sauropods. Internal pneumatic structures in Brachiosaurus brancai are semicamellate with few large camerae in the vertebral centrum, surrounded by pneumatic camellae. Dicraeosaurus exhibits a procamerate pneumatization pattern with few deep fossae penetrating to a broad median strut in the vertebra, but no internal pneumaticity was found. The semicamellate pneumatization pattern of Brachiosaurus brancai corresponds with another Late Jurassic Brachiosaurus specimen, whereas in Cretaceous brachiosaurid taxa like Sauroposeidon, the complexity of internal pneumatization increases to form a fully camellate pneumatization pattern. In Dicraeosaurus, internal pneumatization has most likely secondarily been reduced.Brachiosaurus and Dicraeosaurus possess a similar distribution of main external pneumatic diverticula, with Brachiosaurus having much more subdivided diverticula. Due to the weight reduction achieved by these pneumatic diverticula, the neck of Brachiosaurus was up to 25 per cent lighter than without pneumatic structures, whereas that of Dicraeosaurus was only 6 per cent lighter. Pneumatization of the cervical vertebrae therefore can play an important role in lightening some sauropods. ZUSAMMENFASSUNGDie Präsacralwirbel sauropoder Dinosaurier waren von einem komplexen System pneumatischer Diverticula umgeben und ausgehöhlt. Die pneumatischen Diverticula entstammten wahrscheinlich einem paarigen cervicalen Luftsack, der mit dem Atemapparat verbunden war. Zur Darstellung der internen pneumatischen Strukturen wurden Halswirbel von Brachiosaurus brancai und Dicraeosaurus sp. der spätjurassischen (?Oxfordium-Kimmeridgium-Tithonium) Fundstelle Tendaguru aus dem östlichen Afrika mit Computertomographie untersucht. Die daraus resultierenden vergleichenden Rekonstruktionen der pneumatischen Diverticula im Halsbereich dieser Sauropoden-Taxa dienen dazu, die biomechanische Bedeutung pneumatischer Strukturen in den Wirbeln von Sauropoden besser zu verstehen. Interne pneumatische Strukturen bei Brachiosaurus brancai sind semicamellat mit wenigen großen Camerae in den Wirbelkörpern, welche von Camellae umgeben sind. Dicraeosarus zeigt hingegen ein procamerates Pneumatisierungsmuster ohne interne Pneumatisierung, bei dem wenige tiefe pneumatische Fossae bis zu einem breiten medianen Septum im Wirbel vordringen. ...

A new multi-faceted framework for deciphering diplodocid ontogeny

“…MOR 790 8-10-96-204, the lateral margins of the condyle have continued to thin and taper. The bulk of the condyle is composed of large camerae (larger rounded cavities with a regular pattern) as observed in other sauropod condyles (Wedel, 2003;Schwarz and Fritsch, 2006;Schwarz et al, 2007a). The posterior portion of the cotyle also seems to possess camerae (Figure 6).…”

Mechanical implications of pneumatic neck vertebrae in sauropod dinosaurs

“…This demonstrates that the position of the pneumatic spaces is consistent with the distribution of main stresses within the vertebrae. The absence of higher loads within the vertebral body and neural arch allows thin and even perforate internal and median bony septa within the vertebrae (see Wedel et al (2000) and Schwarz & Fritsch (2006) for CT images).…”

Evidence for bird‐like air sacs in saurischian dinosaurs

“…The cervical vertebrae of almost all sauropods and theropods have invasive pneumatic features (Britt, '97;Wedel et al, 2000;Wedel, 2003a,b;O'Connor and Claessens, 2005;O'Connor, 2006;Schwarz and Fritsch, 2006;Schwarz et al, 2007). Furthermore, putative PSP in basal sauropodomorphs and theropods is confined to cervical vertebrae that are not adjacent to the lungs, so the pneumatic diverticula that pneumatized the neck must have originated from another source.…”

“…Postcranial skeletal pneumaticity (PSP) is also present in most saurischian dinosaurs and pterosaurs and was recognized in these animals from very early discoveries (Owen, 1857;Seeley, 1870). After a century of infrequent study (Janensch,'47), PSP in fossil archosaurs has received increasing attention in the past decade and a half (Britt, '97;Britt et al, '98;Christiansen and Bonde, 2000;Wedel et al, 2000;Bonde and Christiansen, 2003;Wedel, 2003aWedel, ,b, 2005Wedel, , 2006Wedel, , 2007O'Connor and Claessens, 2005;O'Connor, 2006;Schwarz and Fritsch, 2006;Schwarz et al, 2007;Sereno et al, 2008).…”