From Grazing Triceratops to the Ferocious Tyrannosaurus rex
The Age of Dinosaurs
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When thinking about the prehistoric world, dinosaurs are the first group that comes to mind. Reigning for around 165 million years on Earth during the Mesozoic Era, dinosaurs were certainly one of the most successful groups of animals that have ever existed. Even with such diversity and dominance, they met an untimely, infamous end with the most famous of all extinctions.
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One Era, Three Periods
The Mesozoic Era lasted from 252 to 66 million years ago and is more commonly known as the Age of Reptiles or the Age of Dinosaurs. Mesozoic means "middle life," in reference to the fact that it is the second of three geologic eras throughout Earth's history, the first being the Paleozoic Era and third being the Cenozoic Era.
Scientists further divide the Mesozoic Era into three periods: the Triassic, Jurassic, and Cretaceous. With each period came drastic changes and renowned dinosaurs that are beloved to this day.
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The Triassic Period
The Triassic Period marked the beginning of the Mesozoic Era, occurring after the Permian-Triassic extinction, the largest mass extinction event in history. Known as the Great Dying, the Permian extinction resulted in about 90% to 96% of species going extinct.
Such a wipeout of existing life allowed for the emergence of new species. During this period, the first mammals, flying vertebrates (pterosaurs), and dinosaurs appeared. Though it may seem as if dinosaurs appeared right as the Triassic began, they actually came around 230 million years ago during the Middle Triassic, evolving from reptiles.
This period ended with the Triassic-Jurassic extinction, resulting in 76% of species disappearing. With so many species now gone, the surviving dinosaurs were then able to dominate.
The Jurassic Period
The Jurassic Period occurred after the devastating Triassic-Jurassic extinction, which allowed dinosaurs to flourish. A wet, humid climate facilitated the growth of lush conifer forests and an abundance of life.
Dinosaurs especially diversified into many shapes and sizes with several becoming enormous, such as the emergence of long-necked sauropods including Brachiosaurus and Diplodocus. Some of the most famous dinosaurs appeared during the Jurassic, including Allosaurus and Stegosaurus. Other groups like pterosaurs and mammals also persisted during this time, living alongside the dominant dinosaurs.
A minor mass extinction ended the Jurassic Period, but the cause still remains unknown. One possible explanation is the release of huge amounts of methane, a notable greenhouse gas, from beneath the Earth's surface. Several species went extinct during this extinction event, including most of the largest sauropods and stegosaurids (the group Stegosaurus belongs to).
A Walking Tank
This specimen comes from the Morrison Formation in Wyoming, dating back to the Late Jurassic. The small size, leaf-shaped appearance, and large denticles are characteristic of Ankylosaur teeth. However, due to the tooth being heavily worn with much enamel stripped away, it cannot be identified as either Gargoyleosaurus or Mymoorapelta.
Nonetheless, Gargoyleosaurus and Mymoorapelta were two of the earliest ankylosaurs that ever lived. Ankylosaurs first appeared during the Jurassic and are known for their body armor of bony osteoderms. A famous ankylosaur that appeared much later during the Late Cretaceous was Ankylosaurus with its tail and club.
With such a fierce appearance, it is somewhat ironic to think that small teeth like this specimen belonged to such a dinosaur. A body built close to the ground and these triangular teeth allowed for a herbivorous diet of cycads, ferns, and angiosperms (flowering plants).
Explore this tooth further by checking out the gallery with multiple other angles!