An ode to the world’s meanest dinosaurs | Science
Dinosaurs are worshiped for their size, ferocity, and strangeness; nothing sparks the imagination more than the reverie of strange ancient creatures traversing lush ancient landscapes millions of years ago. Some of the larger ones, such as Patagotitan– stretched over 100 feet long and weighed over 70 tons. The jaws of the dreaded Tyrannosaurus could crush bones. The armored Stegosaurus sported a flashy array of three-foot-long plates and spikes at the end of his tail. But, despite the striking appearance of our favorites, not all dinosaurs were fierce, giant, highly decorated, or even so weird.
It wasn’t necessarily the most showy dinosaurs that made the Mesozoic world go round. Credit goes to the average dinosaurs, the seemingly mundane herbivores that were essential to the ancient ecosystems that lived 66 to 251 million years ago. These kinds of dinosaurs are often given nicknames like “Cretaceous cows”, but this nickname belies their history. Average dinosaurs – both in terms of size and appearance – were essential parts of ancient dinosaur communities. Carnivores must eat, after all. By getting a clearer picture of what the average dinosaur looked like, the best paleontologists can understand the nature of the ancient ecosystems where these dinosaurs roamed.
The very first dinosaurs, as far as science can tell, evolved around 243 million years ago. Even compared to other animals from the same Triassic environment, they were not very large. One of the candidates for the first dinosaur, Nyasasaurus, was about the size of a German Shepherd, and was a skinny omnivore that likely fed on leaves and beetles. “By exploring the evolutionary models of body size, we found that the ancestral body size of all dinosaurs was actually quite small, varying between 14 and 24 kilograms,” says the paleontologist from the University of New Brunswick. England Nicolas Campione.
But dinosaurs weren’t pipsqueaks for long. Shortly after their appearance, the dinosaurs began to divide into different groups. There were the sauropodmorphs, or ancestors and relatives of dinosaurs like the long neck, long tail Apatosaurus. So, too, roamed theropods, which were related to carnivores like the bipedal, with sharp claws Allosaurus, and the early ornithischians who paved the way for the evolution of horned, armored, and duck-billed dinosaurs. Around 225 million years ago, in the Upper Triassic, some even got quite big. “At the end of the Triassic and certainly the beginning of the Jurassic,” Campione says, “ornithischians, sauropods, and non-avian theropods would explore most of the body size ranges they would have for the rest of the Mesozoic.” The smaller dinosaurs were about the size of a pigeon, while the larger one stretched out longer than a blue whale.
Throughout the Jurassic and Cretaceous Periods between 66 and 200 million years ago, dinosaurs of all shapes and sizes continued to evolve
. The size range of dinosaurs from tiny to titanic is a testament to their evolutionary success and ecological significance. “Body size is a known predictor of ecology and likely reflects the range of ecological roles that non-avian dinosaurs played during the Mesozoic,” says Campione. Dinosaurs filled their ancient ecosystems so much that they suppressed the evolution of mammals. “It is only after the extinction of non-avian dinosaurs that mammals will finally be able to explore other ecologies,” says Campione.
However, among all these awesome dinosaur species, what was the average size of a dinosaur? According to Campione, from a dataset of 584 dinosaurs, most non-avian dinosaurs had a mass of around 7,700 pounds. It’s a pretty big animal, somewhere between rhinos and modern day elephants. But this was not uncommon in the Mesozoic. Most non-avian dinosaurs were around this size, Campione notes, exemplified by the duck-billed dinosaurs that were common in the Late Cretaceous.
A duck-billed hadrosaur like Edmontosaurus is a perfectly medium sized beast; most dinosaurs were around this size, with the largest and smallest being relatively rare. And that’s important in describing how the Mesozoic was different from our present day.
We live in a megafaunal lull, when large animals are scarce. Knowing that the average dinosaur was roughly the size of an elephant indicates that plant life must have been incredibly productive to support such creatures, and perhaps dinosaurs were better protected from predators when they reached a certain point. cut. Dinosaur Growth Studies reported that hadrosaurs gain weight rapidly as a defense against carnivores, so an adult hadrosaur represents the height threshold when the potential lunch has become too inconvenient.
But the average also has another meaning, less quantitative. Many famous dinosaurs were adorned with horns, had impressive teeth, or stood out because they looked weird. The dinosaurs probably developed these characteristics to impress each other, so we’re in awe of ourselves. With that in mind, which dinosaurs were just plain boring? Ornithopods
This group of herbivorous dinosaurs includes some favorites such as the crested hadrosaur Parasaurolophus, but also small beaked herbivores like Dryosaurus. What unites these dinosaurs is that they all have three toed feet, were able to walk on two legs, and had both beaks and teeth to help them process a lot of plant food, the smallest measuring about five feet long and the largest extending to 50 feet long. Often times, they are seen as the prey of the charismatic and toothy predators of their time. “These dinosaurs definitely don’t care about being boring or, in the case of Dryosaurusbeing dry, ”says Central Michigan University paleontologist Karen Poole. Most of the time, these dinosaurs are moved to the side in museum halls while the most ornate and spooky dinosaurs take center stage.
Simple as many of them may seem, ornithopods were no less important. “If we had to draw an analogy with modern herbivore groups,” says Poole, “ornithopods would look like horses and donkeys.” And just like horses and donkeys, what makes some ornithopods special is that they are plentiful.
While rarity often gets a lot of attention in news reports, paleontologists can learn relatively little from a single specimen. To understand growth, variation, pathology, and many other aspects of paleobiology, researchers need a larger sample size. The fossil record contains only a fraction of all the creatures that have ever lived, so a large collection of bipedal pimple dinosaurs Iguanodon, for example, can allow scientists to examine questions that singletons cannot answer – species known only from a single specimen. Studying large samples of the ornithopod Maiasaura—Another common dinosaur and a relative of Edmonotsaurus– experts were able to determine that these dinosaurs suffered terrible death rates in their first year of life. It was difficult to be a baby dinosaur, these fossils indicate, and reaching adulthood required a very difficult first year.
In fact, Poole notes, ornithopods offer a tantalizing puzzle for paleontologists. Where other groups of dinosaurs are demarcated on the basis of showy features like horns and ridges, ornithopods are sometimes grouped together due to their lack of telltale ornaments. But as paleontologists have begun to take a closer look at the anatomy of these animals, notes Poole, “we are finding that ornithopods may not all form a group.” Some might be more closely related to horned dinosaurs, for example, while others are closer to armored dinosaurs, with hidden connections popping up thanks to an ongoing study. By sorting out these connections, paleontologists can sort the number of times certain characteristics have evolved – like beaks adapted to pinch plants – and update who is related to whom in the dinosaur family tree.
If paleontologists focused only on the most superlative and bizarre species, the resulting picture of the Mesozoic world would be distorted. The emphasis would be on rare, terrifying and anatomical values. But the least popular and most common species are those where learning occurs. It was the dinosaurs that altered ecosystems based on the plants they ate and even where they walked, trampling certain areas and allowing others to grow. They were often the food our favorite carnivores relied on. And these dinosaurs were often so abundant that they were more useful for paleontologists who want to know how dinosaurs varied, how they developed, and other basic facts about what dinosaurs looked like.
Just as a modern forest cannot be understood without deer, squirrels, and other common animals, understanding the Mesozoic requires an appreciation of the most ordinary dinosaurs.