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Sunday, June 20, 2021

Dinosaurs 101: The Shifting Image of Dinosaurs – Facts, History, and Evolution

Scientific discoveries reach the general public through schooling and news stories, though occasionally this kind of information gets filtered through the lens of pop culture. When it comes to dinosaurs, Steven Spielberg’s Jurassic Park is a prime example of this. Insights and ideas gleaned from science can inform new and creative plot elements or action set pieces, though the same is true of scientific distortions and misunderstandings. Rather than nitpicking elements of a single film, this article will briefly highlight the areas in which our understanding of dinosaurs has evolved over the past few decades.

Dinosaur Feathers and Flight

Dinosaurs were not only large, scaly reptiles. They came in a variety of shapes and sizes, and some even sported feathers. While at one time it was thought that feathers had originally been a mutation of scales, it is now largely agreed due to fossil analysis that feathers evolved from hair-like structures called barbs. Originally, these barbs resembled hairs, though over time they developed smaller, horizontal structures called barbules, which created the vein-like structures that lend feathers their aerodynamic properties.

You may have heard that birds are the only remaining dinosaurs, and while this may clash with the fearsome image of the Tyrannosaurus rex, they are cousins of a sort. Both belong to the theropoda clade, and if one looks they can begin to see the resemblances between the two. Three-toed limbs, hollow bones, and their general skeletal structures align quite well. Of course, the most obvious difference between the two is size. Current theories point to the natural selection advantages for the smaller theropods that became birds, among other reasons. Birds, or Aves, became their own distinct class of animals over millions of years of evolution. Changes in size, and the development of things like feathers, wishbones, beaks, and wings helped to distinguish them from their fellow theropods. Because all of this did not happen at one place or time, several bird-traits can be found in non-birds, such as with T. rex young that possessed downy feathers to help keep them warm or with the Dilong paradoxus, which retained its hair-like feathers into adulthood.

Dinosaur Coloration and Camouflage

When we picture dinosaurs we often color them in with drab earthy tones and muted greens. What coloration can be gleaned from fossils supports this, though dinosaurs were also red, white-striped, and multicolored for the purpose of camouflage. But how do scientists know this?

Much of the coloration of living creatures is a result of melanin. Melanin is produced by organelles called melanosomes. Melanosomes have a distinct shape that when viewed via an electron microscope can differentiate them from one another and other microscopic bodies. By comparing the shapes of fossilized melanosomes, scientists are able to determine the coloration of dinosaurs. However, melanosomes do not exist in bones, so only fossils containing soft tissues, hairs, or feathers have a chance at shedding light on what color a dinosaur was. Certain colors like blue and yellow come from sources other than melanosomes and melanin, so unfortunately scientists are unable to identify these colors yet, but another scientific breakthrough could expand our knowledge of the dinosaur palette.

Owen (CHRIS PRATT) meets the vicious T. rex in “Jurassic World: Fallen Kingdom.” When the island’s dormant volcano begins roaring to life, Owen and Claire (BRYCE DALLAS HOWARD) mount a campaign to rescue the remaining dinosaurs from this extinction-level event. Welcome to “Jurassic World: Fallen Kingdom.”

Dinosaur Reptiles: Cold-Blooded or Warm-Blooded?

Were dinosaurs cold-blooded like the reptiles of today or warm-blooded like most birds and mammals? The answer is neither actually. The terms cold-blooded and warm-blooded are not scientific designations, but common shorthand for whether or not animals are able to maintain their own body temperature, a process known as thermoregulation. Given that thermoregulation is often a complex process involving various physiological systems, physical properties, and behaviors, the simplistic binary of cold-blooded or warm-blooded has become outdated and fallen out of scientific usage. Here, we see another instance of popular knowledge lagging behind scientific understanding. Instead, scientists use the terms ectothermic for animals that cannot regulate their own body temperature and endothermic for those that can.

As for dinosaurs, new evidence suggests that they may have been mesotherms, a middle ground between ectotherms and endotherms. Mesothermic animals, like tuna and echidnas, take cues from both ectotherms and endotherms. They can rely on their metabolisms to produce enough body heat to keep them thermoregulated in certain situations and environments, though in extreme circumstances they more so resemble ectotherms in that their body temperature becomes subject to the heat (or lack thereof) of their surroundings. This mesothermic theory was postulated based on a study of bone growth rings of various dinosaurs. Using these measurements, the scientists extrapolated out the metabolic relationship between size and growth, and thus roughly estimated their metabolic rates. By comparing these figures with those of living animals, they were able to plot the objects of their study between extant ectotherms and endotherms. Being mesothermic would have allowed dinosaurs to move faster than some of their competitors, like crocodiles, but conserve more energy and thus allow them to eat less than similarly sized animals with faster metabolisms.

All of this goes to show that there is still a lot more to be discovered about dinosaurs, and that the more we find out the more our image of them will likely change.

Works Cited

“A Feathered Tyrant”. amnh.org, American Museum of Natural History, https://www.amnh.org/exhibitions/dinosaurs-ancient-fossils/liaoning-diorama/a-feathered-tyrant, Accessed Feb 4, 2021

Black, Riley. “The Colors of Dinosaurs Open a New Window to Study the Past”. smisonianmag.com, Smithsonian Magazine, May 21, 2019, https://www.smithsonianmag.com/science-nature/colors-dinosaurs-open-new-window-study-past-180972070/, Accessed Feb 4, 2021

Padian, Kevin. “Feathered dinosaur”. britannica.com, Brittanica, Apr 14, 2011, https://www.britannica.com/animal/feathered-dinosaur, Accessed Feb 4, 2021

Singer, Emily. “How Dinosaurs Shrank and Became Birds”. scientificmaerican.org, Scientific American, June 12, 2015, https://www.scientificamerican.com/article/how-dinosaurs-shrank-and-became-birds/, Accessed Feb 4, 2021

Witze, Alexandra. “Dinosaurs neither warm-blooded nor cold-blooded”. nautre.com, June 12 2014, https://www.nature.com/news/dinosaurs-neither-warm-blooded-nor-cold-blooded-1.15399, Accessed Feb 4, 2021

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Categories: Biology, ecology, evolution, History

Tagged as: cold-blooded, Dilong paradoxus, dinosaur, dinosaur 101, dinosaur evolution, dinosaur exhibit, dinosaur facts, dinosaur history, dinosaurs, dinosaurs 101, evolution, feathered dinosaur, History, Jurassic Park, reptile, reptiles, T-rex, Tyrannosaurus rex


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