Unlike what may have been thought previous to 1824, mammals were no new creation. At their most primordial form, they have existed since a little over 200 million years ago following the end of the Permian period and into the Triassic. For mammals, it was through essential physiological changes that allowed them to survive each new natural disaster that had ended the existence of many other species.
Fossils found in Fleming Fjord in Greenland shed some light on which and when traditional mammalian traits existed. The fossils showed that the small rodent-like creatures had fur, better chewing ability, and also a shift in tooth development from continual tooth growth cycle to only having one set of adult teeth after losing baby teeth. These traits combined with many others allowed mammals to survive natural disasters such as the end of the Triassic period when the splitting of Pangaea caused volcanoes to to erupt and poison the environment. When events like these occur, killing most of the world’s population, the animals that survive have an automatic advantage for the next period with ample resources. With these new resources, the original mammal populations experienced adaptive radiation and had a burst of evolution. Following the large evolution burst, fossils in China have shown just how varietal mammals had become as they developed in their ecological niches.
Mammal species continued to grow at a fast pace as resources were abundant and evolutionary changes allowed them to take advantage of even more resources. A pivotal change in mammal history was the involvement of angiosperm plants which provided food for mammals all over the world, but mainly only helped the populations which had developed tribosphenic molars, which was just another innovation for chewing. All of these new changes came at a great time as survival ability would be essential to survive the Cretaceous. The catastrophes that so infamously killed the dinosaurs is in reality what has allowed for the modern mammal to develop. Though not all mammalian species survived the period, research shows that the ones that did, the earliest placentals were the species that most closely relates to us today as young are given birth to when they are relatively well-developed.
Many people do not know the many aspects of the rise of mammals. For many it is mystery how and when the earliest mammals existed and how populations were able to to develop into mammalian species today. This article provided a lot of insight for myself and helped me better understand the traits that play the most pivotal role in survival. Though I had learned before that the death of the dinosaurs was what helped the rise of mammals, it was only what allowed them to become the main planetary “players”. It was the advantageous traits that allowed them to survive to that period in the first place and continue developing species that exist today.