This blog brings you back to the movie Jurassic Park to explore the truly amazing world of dinosaurs. These animals were of all sizes and dominated the surface of this earth as its lords. Some measured only a few feet while some of them were the biggest animals to have ever existed on the earth. They ruled the land for over 170 million years but are still quite a mystery. What kind of creatures dinosaurs were, when they evolved and what the first dinosaurs looked like are all questions we are looking answers for.
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Features of Dinosaurs
They belong to a group of animals called Archosaurs which are today represented by crocodiles and birds. Earlier, Archosaurs also included all extinct dinosaurs, pterosaurs and other ancestors of crocodiles. Some of the features that define a dinosaur are the modifications to their hips and legs. Some of their vertebrae were modified into a special structure called the sacrum that enabled a much stronger connection between their backbone and hips. While reptiles have up to two modified vertebrae, a dinosaur has at least three sacrums.
Dinosaurs such as the Iguanodon and Megalosaurus had a sacrum of five modified vertebrae. These changes probably happened because the first dinosaurs were bipedal or walked on their hind legs. Being bipedal is another important feature for defining early dinosaurs.
The legs of crocodiles and lizards stick out at right angles from their body. In order to be bipedal, dinosaurs had to tuck their legs beneath their body. For this, dinosaurs underwent modifications of the backbone and hip connections, the tops of the thigh bones where the bones join the hip, as well as in the knees and ankles.
The First Dinosaurs
The earliest known dinosaur refers to an entire ecosystem of different species rather than a single kind of dinosaur. The Ischigualasto Formation in Argentina has dinosaur remains belonging to the Late Triassic Period, which have been dated to approximately 230 million years ago. These remains prove that the Earth was dominated by dinosaurs known as rhynchosaurs, along with animals called cynodonts. It also included several different early dinosaur species, such as small bipedal creatures called Eodromaeus and Eoraptor and larger creatures such as Herrerasaurus.
Several places in Brazil and Argentina claim to be the origin of the earliest definite dinosaurs. But these animals were already recognisable as dinosaurs, so there’s a good chance that dinosaurs had a longer evolutionary history that we are unaware of.
The closest relatives to dinosaurs, known as the silesaurids, have only been identified in the last two decades. They look like tall lizards with long legs and are medium-sized quadrupedal animals. There is a 10 to 15 million year gap, that is unaccounted for, between the common ancestor of silesaurids and dinosaurs from the first true dinosaurs. A 240 million-year-old partial fossil of Nyasasaurus parringtoni was discovered in Tanzania in the 1930s near Lake Nyasa, which may be the answer.
The fossil has a few vertebrae, which are luckily from close to the hip and show that three of them were sacral vertebrae, which is one of the defining features of dinosaurs. The Nyasasaurus appears to be from the same age as the earliest silesaurs which means it could be the earliest dinosaur, or the closest relative of dinosaurs discovered so far.
The evidence provided by the earliest true dinosaurs gives a fair idea of what the first dinosaur may have looked like. They were probably small, bipedal predators with small hands for grasping and a body length of a couple of metres. They were either carnivores or omnivores.
They were not present in large numbers 230 million years ago. It was only at the end of the Triassic extinction event that dinosaurs rose in numbers 201 million years ago. This event wiped out almost all the other archosaurs and was gradually filled with different types of dinosaurs in the world.
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Jurassic and Cretaceous Periods
During the Jurassic and Cretaceous periods, dinosaurs evolved into a variety of different creatures. The Jurassic Period was a time of biodiversity and the rise of iconic dinosaurs such as huge, long-necked sauropods like Brachiosaurus and Apatosaurus and powerful predators like Velociraptor and Allosaurus.
The Cretaceous Period is the last chapter of the dinosaurs and it saw the largest, powerful and carnivorous dinosaur, Tyrannosaurus rex. This period also saw the formidable Triceratops, which have a distinctive frill and horns.
Extinction of Dinosaurs
As for the causes of various disasters that in one way or another eliminated all kinds of dinosaurs in the world, there are quite a few theories. These are the impact hypothesis where it is thought that a meteor or comet struck, and volcanic activity which is thought to have contributed to the extinction of the dinosaurs. It was fitting to note that the end of dinosaurs was witnessed to be a major shift in the ecology of the earth and the beginning of the dominance of mammals.
The natural world and the main subject of prehistoric animals, dinosaurs in particular, have influenced the world in many aspects and their fossils still amaze those who study them. It has led to a deeper understanding of Earth’s history and the evolution of various forms of life. These mighty creatures ruled Earth at one point in time but still retain many of their secrets. For more information on the evolution and life of dinosaurs, log into the EuroSchool website.
