User:Obrian.11/sandbox

Source 1
Sander, P. M., Christian, A., Clauss, M., Fechner, R., Gee, C. T., Griebeler, E. M., Gunga, H. C., Hummel, J. R., Mallison, H., Perry, S. F., Preuschoft, H., Rauhut, O. W. M., Remes, K., Tütken, T., Wings, O., Witzel, U. 2011 Biology of the sauropod dinosaurs: the evolution of gigantism. Biol Rev 86(1): 117–155. (doi: 10.1111/j.1469-185X.2010.00137.x)

This paper provides a large amount of background and forms an evolutionary cascade model to describe how and why the sauropods grew to such massive sizes.

Source 2
Yates, A.M., Bonnan, M.F., Neveling, J., Chinsamy, A., Blackbeard M.G. 2010 A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. Proc Biol Sci. 277(1682): 787–794. (doi: 10.1098/rspb.2009.1440)

Here the bipedal Aardonyx celestae is examined and shows how quadrupedalism developed in the sauropods.

Source 3
Stevens, K.A. 2013 The Articulation of Sauropod Necks: Methodology and Mythology. PLoS One. 8(10): e78572. (doi: 10.1371/journal.pone.0078572)

Stevens details the methods used while examining the remains of sauropods, and discusses how their necks would actually have been used for feeding.

Source 4
Taylor, M.P., Wedel, M.J. 2013 Why sauropods had long necks; and why giraffes have short necks. Peerj. 1: e36 (doi: 10.7717/peerj.36)

The author argues that sauropods were only able to evolve their long necks because of their other bodily features, such as a small head, pneumatic vertebrae, and quadrupedal stance.

Source 5
Benson, R.B.J., Campione, N.E., Carrano, M.T., Mannion, P.D., Sullivan, C., Upchurch, P., Evans, D.C. 2014 Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage. PLoS Biol. 12(5): e1001853. (doi: 10.1371/journal.pbio.1001853)

The researchers provide an explanation of the "Niche-filling Patterns of Dinosaur Body Size Evolution", and specifically the niche of bulk herbivory filled by the sauropods.

Editing the Sauropoda Page
Changes were made on the wikipedia page https://en.wikipedia.org/wiki/Sauropoda

This sentence was added to the main page:

"These air sacs reduced the overall weight of the massive necks that the sauropods had, and made it possible for the sauropods to get enough oxygen."

The following was added to the talk page:

"This section could be tied in with the other characteristics mentioned in the description section. For example, the importance of pneumatic vertebrae to reduce weight, a quadrupedal stance and long tails to enable such long necks, small heads at the end of the long necks, etc. The section could also include the niche of bulk herbivory filled by the sauropods (see third source below), and discuss the Aardonyx celestae, a believed bipedal ancestor. Some good sources might be:


 * 1) Yates, A.M., Bonnan, M.F., Neveling, J., Chinsamy, A., Blackbeard M.G. 2010 A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. Proc Biol Sci. 277(1682): 787–794. (doi: 10.1098/rspb.2009.1440)
 * 2) Taylor, M.P., Wedel, M.J. 2013 Why sauropods had long necks; and why giraffes have short necks. Peerj. 1: e36 (doi: 10.7717/peerj.36)
 * 3) Benson, R.B.J., Campione, N.E., Carrano, M.T., Mannion, P.D., Sullivan, C., Upchurch, P., Evans, D.C. 2014 Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage. PLoS Biol. 12(5): e1001853. (doi: 10.1371/journal.pbio.1001853)

Obrian.11 (talk) 20:22, 30 September 2014 (UTC)"

Paper Final Draft
Evolution of massive neck length in Sauropoda. The sauropods were a clade of dinosaurs that existed approximately from 210 to 66 million years ago. The massive vertebrates are well known for being the largest known terrestrial animals to ever walk the earth, with body masses well exceeding one hundred thousand pounds in multiple evolutionary lineages (Sander et al. 2011). Sauropods were quadrupedal herbivores with extremely long necks and tails, with some reaching horizontal lengths of over 130 feet. These creatures raise the interesting evolutionary question of how this gigantism came to be, and why no other terrestrial animals were able to come close to a comparable size. In particular, the evolution of the necks will be examined, along with the other necessary features of the dinosaurs which enabled the elongation. The most widely accepted current theory is that the massive body size evolution of the sauropods is due to the niche-filling model of adaptive radiation (Benson 2014). Adaptive radiation is essentially the result of a change in selective pressures, either from a new resource or new challenge to overcome, through which new niches arise. This leads to rapid evolution of multiple divergent strategies, and the emergence of many new, distinct species. Early dinosaurs show an extreme increase in body size evolution, culminating especially in the Triassic and Early Jurassic eras approximately 225-175 million years ago. The sauropods are believed to have filled the niche of bulk-herbivory, clearing and feeding on large areas of plants (Benson 2014). An important place to start examining the evolution of the clade sauropoda from the broader suborder sauropodamorpha is to look at the features of the close relatives. The rather recently discovered Aardonyx celestae has been determined to be the sister group of the two obligate quadrupedal sauropodamorphs (Melanorosaurus and Sauropoda). The limbs of A. celestae suggest that it was bipedal, but that it did show many of the characteristics associated with the adoption of a quadrupedal gait. The bones in the forelimbs began to take more weight bearing structures, as the ulna began to show many similarities to the femur and the digits appeared to be an intermediate between those found in bipeds and quadrupeds (Yates et al. 2010). In addition, A. celestae appears to have had no cheeks, which suggests the evolution of the sauropod bulk-herbivory niche (Benson 2014). This ancestor helps to diagnose the changes that were necessary before massive body size could be supported in a terrestrial animal. The long necks were not only heavy but they extended far from the body of the dinosaur, making it impossible for locomotion on just two legs to be reasonable. This does however raise the question of why sauropods were not able to simply keep their necks vertical in order to reach higher food sources, keeping all of their weight above their two hindlimbs. In order for their necks to have been held vertical, the dinosaurs would also have needed extremely high blood pressure so that oxygen could be supplied to the muscles and brain, and it becomes more and more costly as the angle the neck is held at approaches 90°. In order to generate this blood pressure, the animal’s heart would have to work harder and harder, expending more energy and raising the basal metabolic rate. Additionally, there would be diminishing returns to being able to graze at such a great height. Not only would there be a decrease in the density of foliage above a certain height, but because the neck remains the same length, the available feeding area can simplistically be thought of as a sphere extending from where the neck meets the body. By the nature of a sphere, most of the volume is in the middle, representing the space where the head is lifted very little, while at the top there is small change in available grazing area (Stevens 2013). It becomes much more efficient to take a few steps forward than to lift the head a few feet. One estimate holds that in order for a sauropod to lift its head into the trees, it would have to increase its metabolic rate by 175%, resulting in 49% of the animal’s energy being used just to circulate blood (Seymour 2009). Compared to the estimated 10% of small mammals and 18% of giraffes, it is appreciable that this would be difficult to overcome by the slightly enhanced area available for grazing. This suggests that it would be the most energetically feasible to have a near horizontal neck with a very wide feeding area and low blood pressure. Sauropod necks have been found at over 50 feet in length, a full six times longer than the world record giraffe (Taylor 2013). Enabling this were a number of essential physiological features. The dinosaurs’ overall large body size and quadrupedal stance provided a stable base to support the neck, and the head was evolved to be very small and light, losing the ability to orally process food. By reducing their heads to simple harvesting tools that got the plants into the body, the sauropods needed less power to lift their heads, and thus were able to develop necks with less dense muscle and connective tissue. This drastically reduced the overall mass of the neck, enabling further elongation. Sauropods also had a great number of adaptations in their skeletal structure. Many sauropods had as many as 19 cervical vertebrae, whereas almost all mammals are limited to only seven. Additionally, each vertebra was extremely long and had a number of empty spaces in them which would have been filled only with air. This air-sac system not only lightened the long necks, but effectively widened the trachea, helping the creatures to breathe in enough air. By evolving to have vertebrae consisting of 60% air, the sauropods were able to minimize the amount of dense, heavy bone without sacrificing the ability to take sufficiently large breaths to fuel the entire body with oxygen (Taylor 2013). By examining these vertebrae and their connections, it is also possible to determine that the sauropods in fact were not able to life their heads vertically, supporting the analysis of energy costs and benefits mentioned earlier. Computer modeled reconstructions of the skeletons made from the vertebrae suggest that the sauropod necks were capable of sweeping out large feeding areas without needing to move their bodies, but were unable to be retracted to a position above the shoulders for exploring the area or reaching higher (Stevens 2013). It is important to recognize that there are other proposed functions of the sauropods’ long necks. One such suggested purpose is that the long necks and tails also served essentially as radiators, to deal with the extreme amount of heat produced just from having such a large body mass. Considering that the metabolism would have been doing an immense amount of work, it would certainly have generated a large amount of heat as well, and elimination of this excess heat would have been essential for survival (Sander 2011). It has also been proposed that the long necks would have cooled the veins and arteries going to the brain, avoiding excessively heated blood from reaching the head. It was in fact found that the increase in metabolic rate resulting from the sauropods’ necks was slightly more than compensated for by the extra surface area from which heat could dissipate (Henderson 2013). While it is difficult to directly attribute cooling as a major function of the neck, it has not been rejected by the scientific community. When combined with the pneumatic vertebrae and air-sac systems, the neck could have been an effective heat loss structure. However, remains of sauropods have been found on all continents, and in a wide variety of climates. In dry environments, heat radiation from the neck would have prevented loss of water through evaporative cooling mechanisms and been favorable, but many actually believe there was a preference for wetland habitats because of an abundance of available fossils in these areas. The variation in the dinosaurs is ultimately much better explained by adaptation to different available food sources than by the nature of the environment in regards to temperature and available water basins (Henderson 2013). Debate over what kind of habitat the sauropods would have preferred is not new, but most have agreed that wetlands were ideal. More recent fossil finds do suggest that they may have thrived in dry areas as well, but research is still ongoing. When they were first discovered, it was believed that the sauropods would have been too large to have had their mass fully supported on land, and that they must be water-dwelling creatures. The first shift in perception was a study which showed that the sauropods could not have survived when fully immersed in water, as the pressure would have collapsed the airways of the animals (Kermack 1951). This led most to believe that the sauropods would have lived primarily with their lower bodies in the water with the rest of the dinosaur able to graze from this position due to the elongated neck. However, the theory that the dinosaurs would sink to the bottom of the water was not challenged until the more recent models representing the sauropods’ actual size and density. When taking into consideration modern insights into the pneumatic structure of the skeleton and the minimal soft tissue needed in the dinosaur’s body, a model was able to be created to determine whether the enormous creatures would float or sink. It was found that the sauropods would in fact float if fully immersed in water, making the point of water pressure collapsing their lungs irrelevant as they would not reach the bottom of the lake (Henderson 2004). It was also found that the sauropods would have been very unstable if unable to touch the bottom of the water, and would be in danger of tipping over. This suggests that sauropods would likely not have been able to swim, unlike large extant animals such as elephants. Sauropods could have successfully walked in water that was as deep as chest height, but not much deeper (Henderson 2004). While this may seem like a rather irrelevant detail in terms of the evolution behind the neck length of the sauropods, it is absolutely necessary to first understand the habitat that the animal was adapting in if trying to make light of the adaptations themselves. The discoveries about sauropod buoyancy are consistent with the association of sauropods and wetland environments, which would have been dense with vegetation and an ideal area for bulk-herbivory to develop. The variation in the necks of sauropods from different regions is best fit to the differences in flora available for grazing, rather than the present environmental conditions. This suggests that the long necks of the sauropods, along with numerous other adaptations including their size, quadrupedal stance, a small head with little ability to process the food directly, and air sac systems, were driven by the selective pressure to fill the bulk-herbivory niche. References Benson, R.B.J., Campione, N.E., Carrano, M.T., Mannion, P.D., Sullivan, C., Upchurch, P., Evans, D.C. 2014. Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage. PLoS Biol. 12(5): e1001853 Henderson, D.M. 2004. Tipsy Punters: sauropod dinosaur pneumaticity, buoyancy, and aquatic habits. Proc Biol Sci. 271(Suppl 4): S180-S183. Henderson, D.M. 2013. Sauropod Necks: Are They Really for Heat Loss? PLoS One 8(10): e77108 Kermack, K. A. 1951. A note on the habits of sauropods. Ann Mag Nat Hist. 4: 830–832 Sander, P. M., Christian, A., Clauss, M., Fechner, R., Gee, C. T., Griebeler, E. M., Gunga, H. C., Hummel, J. R., Mallison, H., Perry, et al. 2011. Biology of the sauropod dinosaurs: the evolution of gigantism. Biol Rev 86(1): 117–155 Seymour, R.S. 2009. Raising the sauropod neck: it costs more to get less. Biol Lett. 5(3): 317-319 Stevens, K.A. 2013. The Articulation of Sauropod Necks: Methodology and Mythology. PLoS One. 8(10): e78572 Taylor, M.P., Wedel, M.J. 2013. Why sauropods had long necks; and why giraffes have short necks. Peerj. 1: e36 Yates, A.M., Bonnan, M.F., Neveling, J., Chinsamy, A., Blackbeard M.G. 2010. A new transitional sauropodomorph dinosaur from the Early Jurassic of South Africa and the evolution of sauropod feeding and quadrupedalism. Proc Biol Sci. 277(1682): 787–794.

Addition to Wikipedia Page
Section 1.6: Necks was created on the Sauropoda page (https://en.wikipedia.org/wiki/Sauropoda#Necks).

Written as:

Sauropod necks have been found at over 50 feet in length, a full six times longer than the world record giraffe [23]. Enabling this were a number of essential physiological features. The dinosaurs’ overall large body size and quadrupedal stance provided a stable base to support the neck, and the head was evolved to be very small and light, losing the ability to orally process food. By reducing their heads to simple harvesting tools that got the plants into the body, the sauropods needed less power to lift their heads, and thus were able to develop necks with less dense muscle and connective tissue. This drastically reduced the overall mass of the neck, enabling further elongation.

Sauropods also had a great number of adaptations in their skeletal structure. Many sauropods had as many as 19 cervical vertebrae, whereas almost all mammals are limited to only seven. Additionally, each vertebra was extremely long and had a number of empty spaces in them which would have been filled only with air. This air-sac system not only lightened the long necks, but effectively widened the trachea, helping the creatures to breathe in enough air. By evolving to have vertebrae consisting of 60% air, the sauropods were able to minimize the amount of dense, heavy bone without sacrificing the ability to take sufficiently large breaths to fuel the entire body with oxygen [23]. Computer modeled reconstructions of the skeletons made from the vertebrae suggest that the sauropod necks were capable of sweeping out large feeding areas without needing to move their bodies, but were unable to be retracted to a position above the shoulders for exploring the area or reaching higher [24].

Another proposed functions of the sauropods’ long necks suggests that it served essentially as a radiator to deal with the extreme amount of heat produced from having such a large body mass. Considering that the metabolism would have been doing an immense amount of work, it would certainly have generated a large amount of heat as well, and elimination of this excess heat would have been essential for survival [25]. It has also been proposed that the long necks would have cooled the veins and arteries going to the brain, avoiding excessively heated blood from reaching the head. It was in fact found that the increase in metabolic rate resulting from the sauropods’ necks was slightly more than compensated for by the extra surface area from which heat could dissipate [26].