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10. Finite Element Analyses and Virtual Syntheses of Biological Structures and their Application to Sauropod Skulls

Nicole Klein Indiana University Press ePub

ULRICH WITZEL, JULIA MANNHARDT, RAINER GOESSLING, PASCAL DE MICHELI, AND HOLGER PREUSCHOFT

In morphology and paleontology, the analysis of bony structures began with the art of drawing and the technique of photography. The first analytical calculations were possible by using simplified models, and quantitative measurements of strains on bone surfaces provided important opportunities for interpreting bony structures in recent animals. The development of finite element structure analysis (FESA) was a decisive step in obtaining spatial information about strain and stress distribution in models of both extinct and extant creatures. However, the inductive approach of FESA does not provide precise explanations for the existence of bone tissue in a specific position of a given finite element model. In contrast to FESA, the deductive technique of finite element structure synthesis (FESS) was developed for deducing a biological structure from a few initial conditions and boundary conditions. This makes FESS ideal for discovering which morphological structures can be explained in terms of mechanics and which cannot. Three examples of the applications of FESS illustrate its power: the virtual synthesis of the skull of a Neanderthal (Homo neanderthalensis) and of the skulls of the sauropods Diplodocus and Camarasaurus. These studies demonstrate the utility of FESS for the virtual synthesis of bony structures to test assumptions and hypotheses regarding the relationship between function and structure. By obtaining a high degree of conformity between the virtual model and the real object, the method is satisfyingly validated.

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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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8. How to Get Big in the Mesozoic: The Evolution of the Sauropodomorph Body Plan

Nicole Klein Indiana University Press ePub

OLIVER W. M. RAUHUT, REGINA FECHNER, KRISTIAN REMES, AND KATRIN REIS

Sauropod (or, more correctly, eusauropod) dinosaurs are highly distinctive, not only in their overall body form, but also in respect to many details of their anatomy. In comparison with basal dinosaurs, typical sauropods are characterized by small skulls, elongate necks, massive bodies, and an obligatory quadrupedal stance with elongate forelimbs and straight limbs in general. Tracing the anatomical changes that led to this distinctive body plan through sauropodomorph evolution is problematic as a result of the incompleteness of many basal taxa and phylogenetic uncertainty at the base of the clade. The decrease in skull size in sauropodomorphs seems to be abrupt at the base of the clade, but it is even more pronounced toward sauropods. Major changes in the sauropod skull are a relative shortening and broadening of the snout and an enlargement and retraction of the nares. Although the ultimate causes for these evolutionary changes are certainly manifold, most if not all of them seem to be related to the ecological and biomechanical requirements of the transition from a carnivorous to an herbivorous lifestyle, in which the skull is mainly used as a cropping device. A relatively elongate neck seems to be ancestral for sauropodomorphs, but the neck is further elongated on the lineage toward sauropods, especially by incorporation of two additional vertebrae at the base of Sauropoda. The relatively simple structure of the cervical vertebrae in basal sauropodomorphs might be a secondary reduction relative to basal saurischians as a result of changes in neck biomechanics in connection with the reduction of the size of the skull. Thus, the more complicated structure of sauropod cervicals probably reflects changing biomechanical requirements in connection with an elongation of the neck and an increase in body size, as does the opisthocoelous structure of the cervical vertebral centra. Limb evolution in sauropodomorphs is dominated by adaptations toward increasing body size and thus graviportality, with the limbs getting straighter and the distal limb segments relatively shorter. Body size increase in sauropodomorphs seems to have been rapid but even-paced, with the ancestral body size of the clade being in the 0–10 kg category, and the ancestral body size for sauropods probably being in the 1,000–10,000 kg category.

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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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3. Dietary Options for the Sauropod Dinosaurs from an Integrated Botanical and Paleobotanical Perspective

Nicole Klein Indiana University Press ePub

CAROLE T. GEE

During the majority of the Mesozoic, from the Triassic to the mid Cretaceous, the food plants of the sauropod dinosaurs were virtually limited to ferns, fern allies, and gymnosperms because the diversification of the angiosperms, which include the broad-leaved trees and grasses of today, only began in the Late Cretaceous. In this chapter, the preferences of the sauropods for one or more of these Mesozoic plant groups are evaluated by means of a survey approach that integrates botanical and paleobotanical data. These data include the growth habits of the nearest living relatives of these plant groups, their habitat, the amount of biomass produced, and the ability to regrow shoots, branches, and leaves after injury through herbivory. The relative quantities of energy and essential nutrients yielded to herbivores with hindgut fermentation, the consumption of the various plant groups by modern herbivores, and the coeval occurrence of sauropods and individual plant groups in the fossil record are other major factors taken into consideration here. As a result of this extensive survey, it appears that Araucaria, Equisetum, the Cheirolepidiaceae (an extinct conifer family), and Ginkgo would have been most accessible, sustaining, and/or preferred sources of food for the sauropods. Moderately accessible, sustaining, and/or commonly encountered plants would have been other conifers such as the Podocarpaceae, Cupressaceae, and Pinaceae. Less commonly browsed by the sauropods, especially by large, fully grown individuals, would have been forest-dwelling ferns such as Angiopteris and Osmunda. The least frequently eaten plants were probably the cycads and bennettitaleans.

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