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Dinosaur sculptures outside the Crystal Forest Museum Gift Shop. Photo by Erik Washam.

Even though some roadside dinosaur parks may be going extinct, there are still plenty of funky dinosaur sculptures standing on the side of highways and in front of gift shops. These two, photographed by Smithsonian staffer Erik Washam, stand outside of the Crystal Forest Museum Gift Shop in Holbrook, Arizona. They look a little worn down, but that adds a little something to their appeal.

Have you stumbled across a dinosaur in an unexpected place? If you have, and have a photo of the encounter, send it to us via dinosaursightings@gmail.com!

A restoration of Styracosaurus. From Wikipedia.

As a group, dinosaurs were certainly well-ornamented animals. Horns, spikes, crests, plates, sails, clubs and other strange structures marked the bodies of many dinosaurs, but figuring out why these dinosaurs had these structures in the first place has often been difficult to figure out. Numerous hypotheses for different structures have been proposed over the years. Were the horns of Triceratops used for defense, one-on-one combat between members of the species, or as a way to identify members of a group? Were the plates along the back of Stegosaurus just for display, or did they play some role in regulating body temperature? Were the crests of some hadrosaurs used as snorkels, or did they allow the dinosaurs to make low calls which resonated across the landscape?

Some of these ideas—such as the snorkeling hadrosaurs—have been abandoned over the years, but in many cases the strange features of dinosaurs remain mysterious. More than that, the reason such features might have evolved in the first place is often unclear, and as paleontologists Kevin Padian and Jack Horner point out in a new review of these structures published in the Journal of Zoology, no hypothesis can be taken as a default explanation for why a certain kind of structure evolved. Instead, the paleontologists propose, a new approach must me taken—one that explicitly views dinosaurs within their evolutionary context.

Figuring out the function and origin of a particular structure is a complicated process. Something like the horns of a Styracosaurus may have been used for both defense and social displays, for example, but even if the functions of the horns can be identified it does not mean that horns originally evolved for these reasons. Instead horns may have evolved due to one kind of evolutionary pressure and been co-opted for another at a different time, so there can be a disparity between why a structure evolved and what it ends up being used for. This is why understanding the evolutionary history of a particular lineage of dinosaurs is so important.

After looking at groups of dinosaurs famous for having strange structures—such as ankylosaurs and the horned dinosaurs—Horner and Padian identified only weak trends. The latest ankylosaurs were better armored than the earliest ankylosaurs, for example, but the patterns of armor varied so widely among the later forms that it seems as if display may have been more important than defense. If defense were the sole factor in determining the pattern of ankylosaur armor then it might be expected that different species would show very similar arrangements that were optimized for protection against predators, but the variation suggests that defense was not the sole factor shaping ankylosaur armor. Similarly, even though some horned dinosaurs almost certainly did lock horns in combat, there is no sign that horns evolved for this purpose—the dinosaurs’ ability to joust with each other was the consequence of having horns evolved for another reason.

What Padian and Horner propose is that species recognition might have played a more important role in the evolution of strange structures than has otherwise been appreciated. Strange structures may have begun to evolve to allow members of a species to identify each other, particularly potential mates, and only later been co-opted for other uses. If this is correct, they predict, then the pattern of evolutionary change should not have a straightforward direction. If the armor of ankylosaurs had evolved solely for defense, for example, we would expect to see a straightforward evolutionary trajectory in which the protective function of the armor gets better and better over time with little variation. If species recognition was more important, however, the pattern would increasingly vary as it would only be important for species to differ from one another. Additionally, this hypothesis would be strengthened if several closely-related species were living in the same place at the same time and their structures showed divergence into new forms, making it easier to tell species apart.

According to Padian and Horner, the overall evolutionary pictures of many groups of dinosaurs is consistent with their hypothesis, but the paper focuses on proposing a new way of looking at the fossil record rather than providing flat answers. The reexamination of old material and the discovery of new fossils will be essential to testing their ideas, especially as more specimens of rare dinosaur species are uncovered. (Relatively few dinosaur species are well-represented enough to look at these patterns, especially among theropod dinosaurs.) Furthermore, it is still worthwhile to try to determine the function of structures in particular dinosaur species. If the mysteries of these structures can be unlocked and then viewed in the context of the dinosaur evolutionary tree then it may become possible to gain insight into how those structures originated and changed over time. This is not something that can be accomplished in a year or even a decade, but as we learn more about each dinosaur species we can gain a greater appreciation for the patterns which marked their evolution.

Padian, K., & Horner, J. (2010). The evolution of ‘bizarre structures’ in dinosaurs: biomechanics, sexual selection, social selection or species recognition? Journal of Zoology DOI: 10.1111/j.1469-7998.2010.00719.x

The 1912 AMNH crew on the scow Mary Jane. From the Dinosaur Hunting by Boat in 2010 blog.

Between 1910 and 1916, during the second great dinosaur “bone rush” in North America, the famous fossil hunters Barnum Brown and Charles Sternberg engaged in a bit of friendly competition along the Red Deer River in Alberta, Canada. The areas along the banks, often inaccessible by land, were rich in Cretaceous fossils, and both expeditions used large, flat boats called scows as floating bases of operation from which to collect specimens along the waterway. A century later, paleontologist Darren Tanke and colleagues are going to recreate this journey, right down to the clothes and toilets used by the 20th century crews.

Preparations for the 2010 expedition have been underway for quite some time. The Dinosaur Hunting by Boat in 2010 blog has updates and photos stretching back through last year showing the step-by-step construction of the boat. The scow they have created, based on the boat Brown’s crew used called the Mary Jane, is nearly finished, and the crew will soon set off on their journey along the river. As the paleontologists stop and retrace the ground once prospected by earlier crews they hope to clear up some mysteries about where particular fossils came from, information essential to fully understanding some of the famous specimens the Brown and Sternberg crews collected.

If all goes as planned, the crew should reach Canada’s Dinosaur Provincial Park around the beginning of August, and there will be public and private events to celebrate the trip. As they go along, however, the scientists hope to provide semi-regular updates about their progress and special events on their blog. While some paleontologists would prefer to hold on to the few comforts they can take into the field (one field scientist I mentioned the scow trip to scoffed and said he wouldn’t go out into the field without his air-conditioned truck), I think the recreation of the scow expeditions is exciting, and I look forward to hearing about its progress as it winds down the Red Deer River.

A restoration of Mosasaurus. From Wikipedia.

During the 1970s a major debate erupted among paleontologists. On the basis of new evidence, from the anatomy of the recently-discovered dinosaur Deinonychus to the microscopic bone structure of dinosaurs, paleontologists such as John Ostrom and Bob Bakker proposed that dinosaurs may have been endotherms—animals able to internally regulate their own body temperature. The work generated waves of support and criticism and ultimately gave birth to the image of fast, dynamic dinosaurs that we know today. While things are not as vociferous as they used to be, paleontologists are still investigating what kind of metabolisms dinosaurs had, how they regulated their body temperatures, and other aspects of their physiology. Similar questions have been asked about many of the creatures that lived alongside the dinosaurs, as well, and a new study published last week in Science suggests that some of the great vertebrates that lived in the sea may also have had unique metabolisms which allowed them to carry out active lifestyles.

During the time of the dinosaurs there were various types of marine reptiles, but among the most successful were the ichthyosaurs, the plesiosaurs and the mosasaurs. As with dinosaurs, it was previously suggested that some of these marine reptiles might have been able to maintain high, constant body temperatures (meaning they were both endotherms and homeotherms), but a team of paleontologists led by Aurélien Bernard and Christophe Lécuyer has found another way to approach the same hypotheses.

To investigate what kind of metabolisms these animals had, the scientists sampled the oxygen isotopes contained inside the teeth of the marine reptiles and compared them to oxygen isotopes taken from fish that lived at the same time. Previous studies have determined that the values of these oxygen isotopes can serve as signals of body temperature and the makeup of the water taken in by the animal’s body during the time its teeth were being developed, and so they provided scientists with a way to investigate the metabolism of these animals. Furthermore, since the body temperatures of most fish are dictated by the surrounding water, their body temperatures would provide a proxy for the temperature of the sea in each place marine reptile samples were taken. By looking at the correspondence between the body temperatures of the fish and the marine reptiles, the scientists could see whether the marine reptiles had body temperatures dictated by the surrounding environment or whether they had some other metabolic mechanism.

What the scientists found was that the body temperatures of ichthyosaurs and plesiosaurs did not appear to be tied to the seawater temperature around them—they maintained their body temperature of about 95° Fahrenheit (35° Celsius) and as high as 102° F (39° C). This is within the range of living whales. The body temperatures of mosasaurs, on the other hand, did appear to be influenced by the surrounding water. They could maintain body temperatures above that of the surrounding seawater, like some sharks can, but their body temperatures still dipped as water temperature fell.

Based upon the evolutionary history of the three types of marine reptiles—each having a different origin—the results of the study suggest that homeothermy evolved among marine reptiles at least twice and the ability to maintain a body temperature above that of the surrounding seawater evolved three times. But what could account for the difference between plesiosaurs/ichthyosaurs and the mosasaurs? As the scientists behind the study hypothesize, it may be a matter of feeding habits. Ichthyosaurs were pursuit predators which relied on speed to catch food, and plesiosaurs were probably long-distance ocean cruisers—both lifestyles would have required high metabolic rates and hence body temperatures maintained above that of the seawater. Mosasaurs, by constrast, were probably ambush predators who lay in wait for prey and then struck quickly. They would not have to engage in the same kind of sustained activity, and so it makes sense that they did not have the same kind of high, constant metabolism.

Unfortunately there are no living plesiosaurus, ichthyosaurs, or mosasaurs for us to examine, but the study of these oxygen isotopes allows scientists to test ideas about the biology of these animals. Through a bit of geochemistry paleontologists can gain insight into the physiology of long-extinct animals, and I look forward to seeing how the results of this new study will be reassessed and investigated as further research is carried out.

Bernard, A., Lecuyer, C., Vincent, P., Amiot, R., Bardet, N., Buffetaut, E., Cuny, G., Fourel, F., Martineau, F., Mazin, J., & Prieur, A. (2010). Regulation of Body Temperature by Some Mesozoic Marine Reptiles Science, 328 (5984), 1379-1382 DOI: 10.1126/science.1187443

The sign for Ohio's Prehistoric Forest. From Flickr user erikadotnet.

After entertaining guests for over half a century, Ohio’s “Prehistoric Forest” will soon be closing. The roadside attraction—filled with fiberglass dinosaurs and other miscellaneous tourist-trap draws—has had a successful run, but at the end of this year the owners of the park will be putting the dinosaurs into storage so that the owners can enjoy their retirement. This is sad news for many local people who brought their families to the park year after year, but, then again, there is no shortage of roadside dinosaurs. Even as old parks close, new ones—such as Virginia’s Dinosaur Kingdom—will open up to entertain fans of dinosaur kitsch.

Have you visited Prehistoric Forest or seen other roadside dinosaurs? If you have, send your photos to us via dinosaursightings@gmail.com!