0012-9402/06/010065-14 Eclogae geol. Helv. 99 (2006) 65–78 DOI 10.1007/s00015-006-1177-x Birkhäuser Verlag, Basel, 2006 Pneumatic structures in the cervical vertebrae of the Late Jurassic Tendaguru sauropods Brachiosaurus brancai and Dicraeosaurus DANIELA SCHWARZ1 & GUIDO FRITSCH2 Key words: Sauropoda, Brachiosaurus, Dicraeosaurus, vertebral pneumaticity, cervical vertebrae, computed tomography ABSTRACT ZUSAMMENFASSUNG The presacral vertebrae of sauropod dinosaurs were surrounded and invaded Die Präsacralwirbel sauropoder Dinosaurier waren von einem komplexen Sys- by a complex system of pneumatic diverticula, which originated most probably tem pneumatischer Diverticula umgeben und ausgehöhlt. Die pneumatischen from cervical air sacs connected with the respiratory apparatus. Cervical verte- Diverticula entstammten wahrscheinlich einem paarigen cervicalen Luftsack, brae of Brachiosaurus brancai and Dicraeosaurus sp., two sauropods from the der mit dem Atemapparat verbunden war. Zur Darstellung der internen pneu- Late Jurassic (?Oxfordian-Kimmerigian-Tithonian) eastern African locality matischen Strukturen wurden Halswirbel von Brachiosaurus brancai und Di- Tendaguru, were examined with computed tomography to visualize internal craeosaurus sp. der spätjurassischen (?Oxfordium-Kimmeridgium-Tithonium) pneumatic structures. With this method, comparative reconstructions of pneu- Fundstelle Tendaguru aus dem östlichen Afrika mit Computertomographie matic diverticula in the neck of these sauropods were done that help to under- untersucht. Die daraus resultierenden vergleichenden Rekonstruktionen der stand the biomechanical role of vertebral pneumaticity in sauropods. Internal pneumatischen Diverticula im Halsbereich dieser Sauropoden-Taxa dienen pneumatic structures in Brachiosaurus brancai are semicamellate with few dazu, die biomechanische Bedeutung pneumatischer Strukturen in den Wir- large camerae in the vertebral centrum, surrounded by pneumatic camellae. beln von Sauropoden besser zu verstehen. Interne pneumatische Strukturen Dicraeosaurus exhibits a procamerate pneumatization pattern with few deep bei Brachiosaurus brancai sind semicamellat mit wenigen großen Camerae in fossae penetrating to a broad median strut in the vertebra, but no internal den Wirbelkörpern, welche von Camellae umgeben sind. Dicraeosarus zeigt pneumaticity was found. The semicamellate pneumatization pattern of hingegen ein procamerates Pneumatisierungsmuster ohne interne Pneumati- Brachiosaurus brancai corresponds with another Late Jurassic Brachiosaurus sierung, bei dem wenige tiefe pneumatische Fossae bis zu einem breiten medi- specimen, whereas in Cretaceous brachiosaurid taxa like Sauroposeidon, the anen Septum im Wirbel vordringen. Das semicamellate Pneumatisierungs- complexity of internal pneumatization increases to form a fully camellate muster von Brachiosaurus brancai enspricht dem anderer spätjurassischer Bra- pneumatization pattern. In Dicraeosaurus, internal pneumatization has most chiosaurus-Arten, während kretazische Brachiosauriden wie Sauroposeidon likely secondarily been reduced. ein komplexeres, vollständig camellates Pneumatisierungmuster besitzen. Bei Brachiosaurus and Dicraeosaurus possess a similar distribution of main Dicraeosaurus wurde die interne Pneumatisierung höchstwahrscheinlich se- external pneumatic diverticula, with Brachiosaurus having much more sub- kundär reduziert. divided diverticula. Due to the weight reduction achieved by these pneumatic Für Brachiosaurus und Dicraeosaurus kann eine ähnliche Verteilung der diverticula, the neck of Brachiosaurus was up to 25 per cent lighter than with- hauptsächlichen externen pneumatischen Diverticula rekonstruiert werden, out pneumatic structures, whereas that of Dicraeosaurus was only 6 per cent welche bei Brachiosaurus jedoch viel stärker unterteilt waren als bei Dicraeo- lighter. Pneumatization of the cervical vertebrae therefore can play an impor- saurus. Aufgrund der Gewichtsreduzierung durch die pneumatischen Diverti- tant role in lightening some sauropods. cula war der Hals von Brachiosaurus wahrscheinlich bis zu 25 % leichter als ohne pneumatische Strukturen, derjenige von Dicraeosaurus hingegen nur ca. 6 % leichter. Die Pneumatisierung der Halswirbel kann demnach eine bedeutende Rolle für die Gewichtsreduzierung bei verschiedenen Sauropoden spielen. 1. Introduction most sauropods are hollowed out by a complex system of cavi- Sauropod dinosaurs are the largest land vertebrates that ever ties, which in analogy to extant birds, is interpreted to be the existed. One of the most remarkable features of these gigantic osteological correlate to a system of pneumatic diverticula herbivores is the long neck, reaching more than 10 metres in (Seeley 1870; Janensch 1947; Britt 1993; Wedel 2003a). In sauropods such as Brachiosaurus. The presacral vertebrae of birds, pneumatic diverticula in the neck originate from cervical 1 Naturhistorisches Museum Basel, Augustinergasse 2, CH-4001 Basel, Switzerland. E-mail: [email protected] 2 Klinik und Poliklinik für Kleine Haustiere, Fachbereich Veterinärmedizin, Freie Universitiät Berlin, Oertzenweg 19b, 14163 Berlin, Germany. E-mail: [email protected] Pneumatic vertebrae of Brachiosaurus and Dicraeosaurus 65 for fos lsp fos pr fos ipo for for fos ipr fos idi for nc for crped for for fos ca pl fos parap fos cr pl A B fos lsp fos psp fos ipo for caped fos psp for nc for fos ipo for crped for caped for nc for nc C fos cr pl fos ca pl D E F fos parap fos lsp fos ipo fos lsp fos idi fos ipo fos lc fos idi fos pl G H fos pl Fig. 1. External pneumatic structures in the cervical vertebrae of Brachiosaurus brancai and Dicraeosaurus hansemanni from Tendaguru. 4th cervical of Bra- chiosaurus brancai A) Photograph (left) and schematic drawing with external pneumatic structures (right) in right lateral view, B) cranial view, C) caudal view. 7th cervical vertebra of Brachiosaurus brancai D) left lateral view with close-up to lateral surface of the neural arch showing the subdivided laterospinal fossa, E) cra- nial view, F) neural arch in caudal view showing the postspinal fossa. G) right lateral view of 8th cervical vertebra of Dicraeosaurus hansemanni as displayed on the mounted skeleton in the HMN with photograph (left) and schematic drawing with pneumatic structures (right). H) 5th cervical vertebra of Dicraeosaurus hanse- manni in left lateral view. Abbreviations: for, foramen; for caped, caudal peduncular foramen; for crped, cranial peduncular foramen; for nc, neural foramen; fos cau pl, caudal pleurocoelous fossa; fos cr pl, cranial pleurocoelous fossa; fos idi, infradiapophyseal fossa; fos ipo, infrapostzygapophyseal fossa; fos ipr, in- fraprezygapophyseal fossa; fos lsp, laterospinal fossa; fos parap, parapophyseal fossa; fos psp, postspinal fossa. Scale bar: 10 cm. air-sacs in the cranial thorax region and are part of the respira- umn (Wedel 2003a). Several ideas and hypotheses about the tory apparatus (Müller 1908; Duncker 1971). In sauropods, functions of postcranial pneumaticity in sauropods, such as similar cervical air-sacs can be reconstructed, from which di- weight-saving or cooling device or as a part of the respiratory verticula emerged to pneumatize the presacral vertebral col- apparatus have been proposed (Janensch 1947; Britt 1993; 66 D. Schwarz & G. Fritsch A B C D fos psp J I H G F E D C B nc nc cl E F G H I J cm cl cl cm for nc Fig. 2. Transverse sections through axis of Brachiosaurus brancai (HMN SI 70) with computed tomography. A) Photograph (left) and schematic drawing (right) of the vertebra in right lateral view with levels of transverse cross-sections as displayed in B-J. Abbreviations as in Fig. 1 and: cl, camella; cm, camera; nc, neural canal. Scale bar: 5 cm. Perry & Reuter 1999; Wedel 2003a), but none of them dealt so ution of internal and external pneumatic structures in the cer- far with the biomechanical role of pneumaticity in sauropods. vical vertebrae of Brachiosaurus brancai and Dicraeosaurus Therefore, finding reasonable explanations for the presence from the Late Jurassic (?Oxfordian-Kimmeridgian-Tithonian) and possible biological role of pneumatic diverticula in Tendaguru beds of Tanzania (Aberhan et al. 2002) are de- sauropods is still problematic and the main purpose of a SNF scribed in detail, leading to a reconstruction of the distribu- (Swiss National Foundation) project in the Natural History tion of pneumatic diverticula in the neck of these taxa. Pneu- Museum of Basel (Switzerland). In this project, sauropod ver- matic structures in both taxa were described for the first time tebrae were studied with computed tomography to make com- by Janensch (1929a; 1947; 1950b), but exclusively in German parative reconstructions of the distribution of pneumatic diver- and only on the basis of broken remains or thin sections ticula in sauropods. With the help of these reconstructions it through single vertebrae. Our goal herein is to use computed will be possible to devise models for the construction of the tomography to provide a new exhaustive description of these extremely long sauropod necks and to explain the presence of structures and make them available for a broader range of sci- pneumaticity in the sauropod axial skeleton. entists. The internal pneumatic structures in the neck of sauropods Brachiosaurus is one of the largest sauropods and phyloge- have been studied and described extensively (Janensch 1947; netically represents a basal titanosauriform (Upchurch 1998; Britt 1993; Wedel et