19 Chapters
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4. The Diet of Sauropod Dinosaurs: Implications of Carbon Isotope Analysis on Teeth, Bones, and Plants

Nicole Klein Indiana University Press ePub

THOMAS TÜTKEN

Sauropods were megaherbivores that fed predominantly on nonangiosperm vegetation such as gymnosperms, sphenophytes, and pteridophytes. In this chapter, the potential of carbon isotope (δ13C) analysis in skeletal apatite for inferring the diet and niche partitioning of sauropods was tested. The carbon isotope composition of food plants is transferred with a metabolic offset to higher trophic levels along the food chain, which suggests that differences in isotopic composition of sauropod food plants can be used to infer sauropod feeding behavior. For this purpose, the δ13C values of sauropod bones and teeth, primarily from the Late Jurassic Morrison Formation, USA, and the Tendaguru Beds, Tanzania, East Africa, were analyzed, as were the leaves of extant and fossil potential sauropod food plants such as Araucaria, cycads, ferns, horsetails, and ginkgo. The metabolic carbon isotope fractionation between diet and enamel apatite estimated for sauropods is 16‰. By means of this fractionation, a diet based only on terrestria C3 plants can be reconstructed for sauropods. Therefore, sauropods did not ingest significant amounts of plants with high, C4 plant-like δ13C values such as marine algae or C4 plants. However, plants that used crassulacean acid metabolism for biosynthesis and possibly freshwater aquatic plants may have contributed to the diet of sauropods. A more detailed discrimination of exactly which type of food plants was consumed by sauropods based on apatite δ13C values alone is difficult because taxon-specific differences between C3 plants are small and not well constrained. Mean enamel δ13C values of sympatric sauropods differ by approximately 3‰, which may indicate a certain niche partitioning. Differences in mean δ13C values for the living representatives of potential sauropod food plants suggest that a differentiation between low-browsing taxa feeding on ferns or horsetails with lower δ13C values and high-browsing taxa feeding on conifers with higher δ13C values might be possible.

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18. Skeletal Reconstruction of Brachiosaurus brancai in the Museum für Naturkunde, Berlin: Summarizing 70 Years of Sauropod Research

Nicole Klein Indiana University Press ePub

KRISTIAN REMES, DAVID M. UNWIN, NICOLE KLEIN, WOLF-DIETER HEINRICH, AND OLIVER HAMPE

The skeletal reconstruction of Brachiosaurus brancai displayed in the Museum für Naturkunde, Berlin, is the largest mounted dinosaur skeleton in the world that incorporates original fossil material. Found during the course of the German Tendaguru expedition from 1909 to 1913, a composite skeleton of B. brancai was first mounted in 1938, and although it was demounted and remounted several times, it remained unchanged until the renovation of the Berlin dinosaur exhibition hall in 2005–2007. Here we describe the scientific progress, technical solutions, and specific decisions that led to the new mount, which has been on display since 2007. The new mount differs in a number of points from the old mount, including improved models of the presacral vertebrae and head, the posture of the neck, the shape of the torso, the orientation of the pectoral girdle and forelimbs, and the posture of the tail. Overall, the Brachiosaurus skeleton now looks livelier, evoking the impression of an active, relatively agile animal and symbolizing developments in our understanding of sauropods since the first mounting of the skeleton.

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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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2. Sauropod Feeding and Digestive Physiology

Nicole Klein Indiana University Press ePub

JÜRGEN HUMMEL AND MARCUS CLAUSS

Sauropod dinosaurs dominated the large herbivore niche in many Mesozoic ecosystems. On the basis of evidence from extant herbivores, significant symbiotic gut microbe activity can safely be inferred for these animals. A hindgut fermentation chamber as in horses or elephants appears more likely than a foregut system. Sauropods are unusual in several herbivore-relevant features such as their large foraging range (due to a long neck), apparent lack of food comminution (which is highly untypical for large extant herbivores), and their extremely high body weights (which is likely linked to several key features of herbivore foraging and digestion). On the basis of regressions on extant herbivores, their gut capacity can be safely assumed to have been highly comprehensive in relation to energy requirements. This can, but need not necessarily, imply extremely long food retention times. Besides these animal features, the spectrum of food plants available for sauropods in sufficient quantity (sphenophytes, pteridophytes, and gymnosperms) was completely different from that of extant herbivores (mostly angiosperms), which has some potential implications for the respective harvesters of these plants. Gymnosperms have a tendency to facilitate rather large cropping sizes (measured in kilograms of dry matter per bite) and therefore large intakes. In vitro digestibility of several living representatives of potential sauropod food plants was estimated to be better than expected, and at least comparable to the level of extant browse. Although sauropods are different from extant large herbivores in several aspects, they must be considered one of the greatest success stories in the long history of large animal herbivory.

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16. The Life Cycle of Sauropod Dinosaurs

Nicole Klein Indiana University Press ePub

EVA MARIA GRIEBELER AND JAN WERNER

Because sauropod dinosaurs are extinct, it might seem impossible to fully reconstruct their life cycles. Nevertheless, information on reproduction, reproductive behavior, growth in body size, and sexual maturity can be indirectly derived from the fossil record. In addition, we can also use living, phylogenetically related taxa as models for these extinct animals in order to support and expand our knowledge on sauropod life cycles. Predictions from life history theory on the relationship between reproductive traits and body size as well as the analyses of life cycle characteristics of extant reptiles, birds, and mammals are also appropriate. In the present chapter, we utilize this complex approach for the reconstruction of sauropod life cycles. We summarize the information on eggs, clutches, nests, hatching, adolescence, and growth in body size that has been derived from the fossil record. In addition, we try to fill the gaps in our knowledge concerning the reproductive behavior, the total reproductive output of animals, and the mortality during the life cycle using information from extant phylogenetic brackets or predictions of life history theory. Finally, we discuss hypotheses explaining gigantism of sauropods based on their life cycles.

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