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5. Structure and Function of the Sauropod Respiratory System

Nicole Klein Indiana University Press ePub

STEVEN F. PERRY, THOMAS BREUER, AND NADINE PAJOR

Because dinosaur lungs do not fossilize, reconstruction of the sauropod respiratory system must rely on indirect evidence. We combine extant phylogenetic bracketing and functional morphological approximation to draw conclusions on the structure and function of the sauropod respiratory system. The combination of these techniques leads to strong evidence for the presence of lungs that consisted of two parts: a gas exchange region that was attached to the ribs and vertebrae, and a sac-like region below the exchange region, close to the liver and intestine. This respiratory system is similar to the efficient lung–air sac system of birds. It is highly adaptable and could have served to supply oxygen, remove carbon dioxide, and help with temperature control.

Indirect evidence for the reconstruction of the respiratory system of extinct animals can come from the skeleton itself, mainly from the ribs and the rib cage. Most interesting here is the morphology of the uncinate processes, the course and density of Sharpey’s fibers within the ribs, and the heads of the ribs and their articulation to the vertebrae.

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15. Neck Posture in Sauropods

Nicole Klein Indiana University Press ePub

ANDREAS CHRISTIAN AND GORDON DZEMSKI

The neck posture in sauropod dinosaurs is a crucial feature that affects their biomechanics, physiology, ecology, and evolution. Yet neck posture and utilization in sauropods are still controversial topics. In this chapter, we use a biomechanical approach to reconstruct the habitual neck posture of sauropods. The analysis is based on a comparison of stresses on the intervertebral cartilage along the vertebral column of the neck. In previous studies on extant animals with long necks, this method has shown to yield reliable results. The habitual neck posture is shown to differ considerably among sauropods. At least in some sauropod species, the long sauropod neck was biomechanically capable of both feeding at great heights and sweeping over a large feeding area without moving much of the body. Differences in neck posture indicate that the feeding strategy varied among sauropods.

A long neck is a characteristic feature of almost all sauropod dinosaurs (McIntosh 1990; but see Rauhut et al. 2005). The necks of some sauropods, such as Brachiosaurus, Barosaurus, Diplodocus, and Mamenchisaurus, reach twice or even more the length of the trunk (e.g., Janensch 1950a, 1950b; Bonaparte 1986; McIntosh 1990). Neck posture is a crucial feature for understanding the ecology, physiology, biomechanics, and evolution of sauropods. Yet the neck posture continues to be a highly controversial subject (Figs. 15.1, 15.2). The long neck has been interpreted as either a means for high vertical browsing (e.g., Bakker 1987; Paul 1987, 1988) or for increasing the horizontal feeding range (e.g., Martin 1987). Taking a single species, Brachiosaurus brancai for example, the range of neck postures suggested extends from horizontal (Frey & Martin 1997; Berman & Rothschild 2005; Stevens & Parrish 2005a, 2005b), to forwardly inclined (Janensch 1950b; Christian & Dzemski 2007), to nearly vertical (Bakker 1987; Paul 1987, 1988; Christian & Heinrich 1998; Christian 2002) (Figs. 15.1, 15.2).

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6. Reconstructing Body Volume and Surface Area of Dinosaurs Using Laser Scanning and Photogrammetry

Nicole Klein Indiana University Press ePub

STEFAN STOINSKI, TIM SUTHAU, AND HANNS-CHRISTIAN GUNGA

Crucial baseline data in dinosaur paleobiology and for reconstructing dinosaurs as living animals are accurate measurements of one- to three-dimensional features such as length, surface area, and volume. Dinosaur skeletons mounted and on display in museums offer the opportunity to obtain such data and to create digital models of them. These models, in turn, serve as the basis for estimating physiological and other biological parameters. In this chapter, we provide an overview of data capture using laser scanning and photogrammetrical methods and describe the working steps from the captured point clouds of the skeleton to the final volume model. Because dinosaur skeletons are complex objects with irregular structures, laser scanning proved to be much more accurate for capturing their shape than previously used methods such as photogrammetry. The modeling of the body surface area and body volume with digital techniques is also more accurate than established methods that are based on scale models. Here, nonuniform rational B spline (NURBS) curves and CAD software are used to reconstruct the body surface and for surface area and volume calculations.

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13. Plateosaurus in 3D: How CAD Models and Kinetic–Dynamic Modeling Bring an Extinct Animal to Life

Nicole Klein Indiana University Press ePub

HEINRICH MALLISON

Cad (computer-aided design) software combined with biomechanical considerations can be used to create extremely accurate skeletal reconstructions of dinosaurs and other extinct vertebrates. CAE (computer-aided engineering) methods that are based on such accurate models give insight into the way dinosaurs moved and behaved, and they greatly ease the task of calculating physical properties (such as position of the center of mass) compared to traditional methods. On the basis of a high-resolution 3D model of Plateosaurus, I show that this animal was an agile obligate biped with strong grasping hands. The assessment of possible postures and ranges of motions of the 3D model was done with a CAD program, while the total mass, mass distribution, and the position of the center of mass of the model were assessed with CAE software.

Biomechanics deals with the function and structure of biological systems. This chapter will address certain aspects within this broad field of study, focusing on the mechanics of posture and motion of animals. The prosauropod dinosaur Plateosaurus will be used as a detailed example of how two different modern computer technologies can aid research on extinct animals. CAD (computer-aided design) programs can be applied to the study of large assemblies of objects, for example, bones in a skeletal mount of a dinosaur, without the bother of actually having to lift and support the many, and often heavy, elements. Digital bones, in contrast, have no weight and cannot break, and are easily combined into a virtual skeleton in a CAD program. A virtual skeleton of Plateosaurus is used to assess the posture and range of motion of this animal. Additional information on posture and on locomotion capabilities is derived from CAE (computer-aided engineering) modeling, using a CAD model of the living animal based on the virtual skeleton. The CAE modeling can be used to determine the position of the center of mass (COM) and its shift when the animal moves, as well as joint torques and many other important physical parameters. This approach to biomechanical modeling was termed kinetic–dynamic modeling by Mallison (2007) because it derives information on the kinetics—the movements of the modeled animal—from the dynamics—the forces that cause this movement—and vice versa.

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Appendix: Compilation of Published Body Mass Data for a Variety of Basal Sauropodomorphs and Sauropods

Nicole Klein Indiana University Press ePub

In the appendix, published body mass data for a variety of basal sauropodomorphs and sauropods have been compiled. Note the differing results for some taxa, mainly depending on the method used for body mass reconstruction. The different methods used (as described by the authors cited) are coded in the table as follows: 0, method not given; 1, von Bertalanffy equation; 2, 3D mathematical slicing; 3, polynomial technique and volume figures; 4, log transformed (base 10) database consisting of model-based body estimates and measurements of bone dimensions; 5, bone measuring, midshaft femora, and/or humeri circumference; 6, ontogenetic growth curves of dinosaur species, estimated from data on the scaling of maximum growth rates for reptiles and mammals; 7, scale model, water displacement, and volume of living animals scaled up from the model; 8, weighing scale models in air and water, recalculation using a slightly lower overall density (950 kg/m3); 9, 3D stereophotogrammetry, laser scanning of mounted skeletons; 10, estimating cubic meters; 11, considering pneumaticity, reduced neck and tail volume; 12, laser stereophotogrammetry, laser scanning, and 3D reconstruction methods; 13, plasticine scale models, following a skeletal restoration; 14, estimated by personal opinion; 15, ‘‘gathered data’’; 16, modern skeletal reconstructions, numerical estimates of centers of mass.

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