design: Cris Ropero Montoya
permission to print photos: Emma Clute
Nearly 90 percent of life was wiped from the Earth 252 million years ago. After this extinction event, known colloquially as the Great Dying, the Earth was also depleted of many resources necessary to sustain the life that did survive. With such bad conditions, it would take the world a long time to recover, but when it did, there was a new group of reptiles getting ready to take over the world: the dinosaurs.
The Mesozoic Era or, the Age of the Dinosaurs, was over 180 million years long and spanned three geologic periods, each with distinct dinosaurs. The first period, the Triassic, saw many lesser-known dinosaurs like the Herrerasaurus and the Eoraptor who lived on the supercontinent of Pangea. This period was also when the world began to recover from the repercussions of the mass extinction, according to Britannica.
The most well-known period, the Jurassic, followed. It is during this time that Pangea began to break apart, resulting in large amounts of flooding that led to widespread shallow bodies of water. There was also a rise of powerful carnivores, like the Allosaurus, that weren’t as prevalent before, according to the Natural History Museum.
While the Jurassic period is the most recognizable by name, the Cretacous period had the most well-known dinosaurs. It is during this time that the Tyrannosaurus Rex, Triceratops and Velociraptor lived, according to the NHM. Land also continued to drift apart during this time, leading to an increase in the diversity of dinosaurs and in the landmasses that would eventually become the continents we know today.
One thing that can be hard for people to wrap their heads around is the size of the dinosaurs. For example, the Patagotitan could reach 120 feet in length–about three-and-a-half times the length of the average telephone pole, according to National Geographic. This is especially long, but it is not a significant outlier, as many dinosaurs grew to sizes unfathomable by today’s standards.
One factor that could explain their size is the way they reproduce. Unlike mammals, reptiles don’t need to carry babies, so they don’t have the size limit that pregnancy puts on other animals. Another theory is that the higher level of oxygen at the time allowed them to grow larger than creatures can today, according to the Independent.
Their size allowed them to dominate the planet, but it also came with a big appetite, according to the New York Times. Some of the biggest herbivores ate over 1,000 pounds of food a day, which ended up being very disadvantageous during the time that followed.
65 million years ago, a meteorite hit the Earth during a time of heavy volcanic activity, creating a significant amount of noxious gas in the air, according to PBS. After this, the gigantic dinosaurs that required the most food were some of the first to go. All other non-avian dinosaurs would go on to die out with them, making way for mammals to increase in size and eventually dominate the Earth.
