The dinosaurs that lived in the Cretaceous Period are classified as Ornithopods, Sauropods, and Theropods. Some dinosaurs were recognized as dinosaurs with 500 teeth because they have a lot of teeth in their mouth. These three groups of dinosaurs comprised the plant-eating dinosaurs. The earliest known dinosaur fossils were found in China. But Chinese historians did not recognize the bones as dinosaur bones, but called them “dragon bones.” A report by the Chinese scholar Zhang Qu, written during the Western Jin Dynasty, mentions the discovery of dragon bones in the Sichuan Province. During this time, the dinosaurs were thought to be giants killed in the Great Flood.
Ornithopods
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Dinosaurs are diverse reptiles that once roamed the earth. They belonged to the clade Dinosauria and appeared between 243 and 233 million years ago. Whether they had wings or were powered by muscles, there was something for everyone to enjoy. These animals were once very common and have long been extinct, but now they are back on the scene. The world is in danger of losing this iconic group.
The first dinosaurs to roam the earth had erect bodies and legs that were perpendicular to their bodies. This suited them to survive in diverse ecosystems. In addition, they walked with their hind legs in a towering position. This allowed them to consume less nutritionally dense foods. They may have even produced live young at one time. But these creatures weren’t quite as intelligent as you might think.
Sauropods
Until recently, many paleontologists interpreted sauropod tracks as coming from the Late Triassic in Thailand and South Africa. However, recent stratigraphic analyses have shown that these animals lived as far back as the Early Jurassic. These new findings support the existence of stump-footed quadrupedal sauropodomorphs. In addition, some trackways have been found that suggest the presence of a quadrupedal sauropod in the Early Jurassic.
Sauropods shared many characteristics. They shared a long, massive body, a large gut, and long, tapering tails. Their massive hip girdle, which included five sacral vertebrae, provided solid support for the torso. Their hollowed-out backbone reduced their weight but maintained structural strength. They were thought to spend most of their time in the water, but substantial evidence suggests that they were much better suited to life on land.
Theropods
There is considerable variety among theropods, and their poster varied widely within and between lineages. However, all known theropods were bipedal, with the upper leg parallel to the spine and a knee that generates forward movement. Modern birds resemble theropods in their behavior, holding the body in a balanced position. This allows the legs to flex and extend. Theropods were large, but their stances were different from modern birds.
Theropods were largely predatory, though there were some herbivorous species as well. Some were small-bodied and herbivorous, while others only ate plants and had small, beakless heads. Although most theropods were predators, there were also a variety of herbivorous theropods that ate plants or even fish. Some of these were toothless, which makes them difficult to classify.
Ornithopods were plant-eating dinosaurs
The Ornithopoda are plant-eating dinosaurs like nigersaurus of the Cretaceous period. They began as small bipedal creatures, although some evolved to be larger than Camptosaurus. By the middle of the Cretaceous period, ornithopods had grown to be over thirty feet long. Many Ornithopods were able to switch from two to four legs, making them versatile hunters. Later Ornithopods evolved to become hadrosaurs, which were mainly land-based animals with powerful arrangements of hundreds of stacked teeth.
Ornithopods were constantly evolving. Early in the Cretaceous, Lanzhousaurus and Lurdusaurus were the largest ornithopods, weighing between five and six tons. These were the largest Ornithopods until the development of plus-sized hadrosaurs in the late Cretaceous. During the Cretaceous, ornithopods remained a diverse group, with some dinosaurs being more diverse than others.
Pterosaurs were flying reptiles
In the Jurassic period, pterosaurs, the first vertebrates to fly, reigned supreme in the skies. Their long, flexible wings were strong enough to endure the stresses of flight. They lived for more than 160 million years, from the end of the Triassic period until the 20th century. Their extinction coincided with that of most dinosaurs, around 66 million years ago.
The wings of pterosaurs were made of very strong and flexible fibers. They were connected to the hands by extended fingers, which provided ample lift. Their wings were not just skin flaps, but a series of muscle fibers arranged in long, parallel rows. These muscle fibers assisted in maintaining the shape of their wings. This resulted in pterosaurs’ flight abilities, and it was also possible for them to fly and maneuver in the air.
Synapomorphies between dinosaurs and modern species
Many synapomorphies between dinosaurs and modern species have been noted. All dinosaurs shared certain anatomical features, including erect limbs, a medially directed femur, and a relatively straight femur. Other similarities include two pairs of holes in the temporal region of the skull and rearward-pointing elbows and knees in the hind limbs.
The earliest known birds appear in the fossil record in the Middle-Late Jurassic. These are the archaeopteryx, xiaotingia, and anchiornis. Most of these dinosaurs were very small, with limbs that were long and thin. They were also feathered, which is a difficult characteristic to observe in a fossil. However, many of these earliest birds are similar to modern birds, which makes distinguishing them from their closest dinosaur relatively difficult.
