BIOLOGY OF THE SAUROPOD DINOSAURS THE EVOLUTION OF GIGANTISM PDF

Sauropod dinosaurs are a group of herbivorous dinosaurs which exceeded all other terrestrial vertebrates in mean and maximal body size. Sauropod dinosaurs were also the most successful and long-lived herbivorous tetrapod clade, but no abiological factors such as global environmental parameters conducive to their gigantism can be identified. These facts justify major efforts by evolutionary biologists and paleontologists to understand sauropods as living animals and to explain their evolutionary success and uniquely gigantic body size. Contributions to this research program have come from many fields and can be synthesized into a biological evolutionary cascade model of sauropod dinosaur gigantism sauropod gigantism ECM. This review focuses on the sauropod gigantism ECM, providing an updated version based on the contributions to the PLoS ONE sauropod gigantism collection and on other very recent published evidence. Each cascade starts with observed or inferred basal traits that either may be plesiomorphic or derived at the level of Sauropoda.

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To browse Academia. Skip to main content. By using our site, you agree to our collection of information through the use of cookies. To learn more, view our Privacy Policy. Log In Sign Up. Biology of the sauropod dinosaurs: the evolution of gigantism. Oliver Wings. Marcus Clauss. Oliver Rauhut. Carole Gee. Martin Sander. Steven Perry.

Kristian Remes. Holger Preuschoft. Andreas Christian. Perry9 , Holger Preuschoft10 , Oliver W. Several evolutionary lineages among Sauropoda produced giants with body masses in excess of 50 metric tonnes by conservative estimates. With body mass increase driven by the selective advantages of large body size, animal lineages will increase in body size until they reach the limit determined by the interplay of bauplan, biology, and resource availability.

There is no evidence, however, that resource availability and global physicochemical parameters were different enough in the Mesozoic to have led to sauropod gigantism.

We review the biology of sauropod dinosaurs in detail and posit that sauropod gigantism was made possible by a specific combination of plesiomorphic characters phylogenetic heritage and evolutionary innovations at different levels which triggered a remarkable evolutionary cascade.

Of these key innovations, the most important probably was the very long neck, the most conspicuous feature of the sauropod bauplan. Compared to other herbivores, the long neck allowed more efficient food uptake than in other large herbivores by covering a much larger feeding envelope and making food accessible that was out of the reach of other herbivores.

Sauropods thus must have been able to take up more energy from their environment than other herbivores. The long neck, in turn, could only evolve because of the small head and the extensive pneumatization of the sauropod axial skeleton, lightening the neck. The small head was possible because food was ingested without mastication. Both mastication and a gastric mill would have limited food uptake rate. Scaling relationships between gastrointestinal tract size and basal metabolic rate BMR suggest that sauropods compensated for the lack of particle reduction with long retention times, even at high uptake rates.

Martin Sander and others The extensive pneumatization of the axial skeleton resulted from the evolution of an avian-style respiratory system, presumably at the base of Saurischia. An avian-style respiratory system would also have lowered the cost of breathing, reduced specific gravity, and may have been important in removing excess body heat. Another crucial innovation inherited from basal dinosaurs was a high BMR. This is required for fueling the high growth rate necessary for a multi-tonne animal to survive to reproductive maturity.

The retention of the plesiomorphic oviparous mode of reproduction appears to have been critical as well, allowing much faster population recovery than in megaherbivore mammals. Sauropods produced numerous but small offspring each season while land mammals show a negative correlation of reproductive output to body size. This permitted lower population densities in sauropods than in megaherbivore mammals but larger individuals. Our work on sauropod dinosaurs thus informs us about evolutionary limits to body size in other groups of herbivorous terrestrial tetrapods.

Ectothermic reptiles are strongly limited by their low BMR, remaining small. Mammals are limited by their extensive mastication and their vivipary, while ornithsichian dinosaurs were only limited by their extensive mastication, having greater average body sizes than mammals. Key words: Dinosauria, Sauropoda, gigantism, Mesozoic, long neck, phylogenetic heritage, evolutionary innovation.

Bauplan and biology of sauropod dinosaurs. Body size evolution in sauropodomorpha. Hypotheses explaining giant body size. More resources available through different boundary conditions. More resources available through evolutionary innovation. Fewer resources used. Faster population recovery and faster individual growth. Historical contingency. While some sauropods, as well as between the largest land mammals body size maxima and minima can be observed and studied and sauropods Figs 1, 2 , has recently been highlighted by directly in living organisms e.

These must be studied from the fossil record, e. Paul, , a; Henderson, , largest terrestrial animals ever, the sauropod dinosaurs ; Seebacher, These estimates place common Fig. Their uniquely gigantic body size commands spe- sauropods consistently in the 15—40 t category Table 1. Sauropod In addition, there are a number of very large sauropods, dinosaurs represent a hugely successful radiation of herbi- e.

Body mass is The largest representatives of all other dinosaur lineages, more relevant to most biological processes and thus is most despite being very big in general perception, rarely exceeded commonly used throughout this review.

Martin Sander and others also Table 1 , mainly due to different methods employed. Mass estimates are generally either based on some measure of volume that is then converted into body mass or on a biomechanical approach, e. Each method has different sources of error, and the main advantages and disadvantages of some of these methods have been intensively discussed in the literature Colbert, ; Lambert, ; Schmidt-Nielsen, , ; Anderson et al.

The largest representatives of different terrestrial One method for estimating body mass based on vertebrate clades, both extant and extinct. A Non-dinosaurian reconstructed body volume involves three-dimensional terrestrial vertebrates and birds: a the tortoise Geochelone photogrammetry of actual skeletons using a laser scanner gigantea, b the Komodo dragon Varanus komodoensis, c the Gunga et al.

Segment masses can also easily be obtained. Among animals, only whales grow to result is that the total mass of the animal is calculated a body mass larger than sauropods, but a direct comparison incorrectly.

A similar method is based on creating 3D skeletal between these two groups is not very meaningful because of mounts from digitized bones, and using these instead of laser- the fundamentally different constraints of the aquatic versus scanned mounts Mallison, , in press b.

This allows easy the terrestrial environment. Recent work by Wedel suggests that volume-based 2 Importance of body size estimates are generally too high because they are based on Body size is fundamentally linked to the bauplan, life history, a specific density in a living sauropod of 0.

In addition, body size evolution and probably had a specific density of about 0. Wedel accordingly because it has been realized that evolutionary innovation is suggested that volume-based mass estimates published before closely tied to body size changes in evolutionary lineages. Plotting SCC diameter of the Berlin specimen of Brachiosaurus 3 Methods of estimating body mass in dinosaurs recently assigned to a new genus, Giraffatitan, based on Any discussion of gigantism in sauropod dinosaurs requires numerous differences from the type species, B.

Compilation of body mass estimates for selected sauropods from the literature. The table lists those species for which reliable estimates are available because of abundant and complete fossil material and the largest valid sauropod species in bold which are known from less complete material.

It also intends to show the variation of estimates obtained by different methods Taxon Reference Mass kg Method of mass estimate Amargasaurus cazaui Seebacher polynomial volume Amphicoelias fragillimus Paul — method not given Anchisaurus sinensis Seebacher 84 polynomial volume Antarctosaurus giganteus Mazzetta et al. Erickson et al. Seebacher polynomial volume Brachiosaurus altithorax Paul method not given Brachiosaurus altithorax Seebacher polynomial volume Brachiosaurus altithorax Foster long bone circumference Brachiosaurus brancai Janensch method not given Brachiosaurus brancai Colbert scale model Brachiosaurus brancai Anderson et al.

Martin Sander and others Table 1. Colbert scale model Diplodocus sp. Anderson et al. Henderson 3-D mathematical slicing Diplodocus sp. Packard et al. Paul b scale model Haplocanthosaurus sp. Seebacher polynomial volume Janenschia sp. Seebacher polynomial volume Omeisaurus tianfunensis Christiansen scale model Omeisaurus tianfunensis Seebacher polynomial volume Omeisaurus tianfunensis Mazzetta et al. Seebacher polynomial volume Plateosaurus engelhardti Seebacher polynomial volume Plateosaurus engelhardti Gunga et al.

Seebacher polynomial volume Sauroposeidon proteles Wedel et al. Comparison of body masses of sauropod dinosaurs, theropod and ornithischian dinosaurs and mammals. The mass data for sauropods are found in Table 1, while those for the other dinosaurs are primarily from Seebacher with additional data from Christiansen and Anderson et al.

With the exception of the two largest forms they represent extant mammals only. Mammals show a strongly right-skewed distribution, theropods and ornithischians show intermediate masses, and sauropods show a strongly left-skewed distribution. Not that the y-axis is logarithmic. At 30—50 t, When adding the largest herbivorous and carnivorous the most recent volume-based estimates for this individual dinosaurs then known to their dataset Fig. The largest herbivores in the study all belonged to Sauropoda Sauroposeidon, Argentinosaurus, Paralititan and the 4 Unique body size of sauropods and theropods largest carnivores to Theropoda Tyrannosaurus, Giganotosaurus, Charcharodontosaurus.

Specifically, the theropods were an Dinosaurs have long been associated with extraordinary body astounding 12 times heavier than predicted by the size Dodson, , and estimates of maximal dinosaurian regression equations for extant ectotherms, and the difference body size have received more than passing attention.

If both of these dinosaur groups were in identifying the largest ever representative of a group tachymetabolic endotherms, as we will argue below, the gap Owen-Smith, , which sometimes led to exaggerated between prediction and observation is even larger.

In fact, claims of body mass for dinosaurs and fossil mammals the magnitude of the gap led Burness et al. However, only recently that dinosaurs must have been ectothermic.

As predicted has it been realized that two groups stand out among the from energy loss between trophic levels Burness et al. The study included top species on land which the later giants with a BM of kg evolved.

Martin Sander and others Table 2. Body mass of the largest species inhabiting a land mass - Increased demand for resources regressed against the size of the land mass in extant and Late - Increased extinction risk because of: Pleistocene terrestrial amniotes.

The species are grouped by - Longer generation time gives a slower rate of evolution, metabolism bradymetabolic ectothermy versus tachymetabolic reducing the ability to adapt endothermy and trophic level herbivores versus carnivores.

The largest species were ectothermic herbivores on - Lower fecundity through reduced number of offspring only three land masses, precluding regression analysis of this group.

Note that maximum body mass for a given land mass decreases with increasing metabolic rate and trophic level.

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Biology of the sauropod dinosaurs: the evolution of gigantism

All rights reserved. Why was Supersaurus so big? This impressive, foot-plus sauropod was one of the largest creatures to ever walk the Earth — far larger than any terrestrial animal alive today. What could account for such superlative size? Baseball player Jose Canseco offered his own hypothesis on Twitter a few days ago. Plenty of bloggers picked up on the armchair speculation, and science communication star Bill Nye even chimed in.

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Biology of the Sauropod Dinosaurs: The Evolution of Gigantism

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Skip to content. Skip to navigation. Sauropod dinosaurs like Brontosaurus where the largest animals to ever walk the land. Immediately recognizable not only by their sheer size but by their extremely long neck bearing a diminutive head, sauropods are some of the most iconic dinosaurs Fig.

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The herbivorous sauropod dinosaurs of the Jurassic and Cretaceous periods were the largest terrestrial animals ever, surpassing the largest herbivorous mammals by an order of magnitude in body mass. Several evolutionary lineages among Sauropoda produced giants with body masses in excess of 50 metric tonnes by conservative estimates. With body mass increase driven by the selective advantages of large body size, animal lineages will increase in body size until they reach the limit determined by the interplay of bauplan, biology, and resource availability. There is no evidence, however, that resource availability and global physicochemical parameters were different enough in the Mesozoic to have led to sauropod gigantism. We review the biology of sauropod dinosaurs in detail and posit that sauropod gigantism was made possible by a specific combination of plesiomorphic characters phylogenetic heritage and evolutionary innovations at different levels which triggered a remarkable evolutionary cascade. Of these key innovations, the most important probably was the very long neck, the most conspicuous feature of the sauropod bauplan. Compared to other herbivores, the long neck allowed more efficient food uptake than in other large herbivores by covering a much larger feeding envelope and making food accessible that was out of the reach of other herbivores.

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