Are there modern descendants of dinosaurs

Living about 80 million years ago, the Archelon was over four metres long and was almost five metres wide from flipper to flipper. A grown man could easily fit inside its shell. Today, the leatherback sea turtle is its closest living relative. Sharks have been around a long, long time.

The earliest sharks first emerged around million years ago, with modern sharks first appearing around million years ago. In fact, the largest predator of all time was a shark called a Megalodon. It lived just after the dinosaurs, 23 million years ago, and only went extinct 2.

It could reach lengths of up to 20 metres and could weigh up to metric tonnes! However, what remains clear is that dinosaurs might have gained the upper hand by the time the Jurassic period started. The path of dinosaur evolution gets into sharper focus immediately if you shift your attention towards the Triassic Period and look at dinosaur species in South America and we may find some clues in determining the closest living things to dinosaurs. During this period, the first dinosaurs slowly evolved into the tyrannosaurs, the raptors, and the sauropods we know today.

The best candidate to suit the label of the first real dinosaur must be the Eoraptor. The Eoraptor was a South American, two-legged, and nimble meat-eater that is related to the Coelophysis that emerged much later in North America. The Eoraptors survived by consuming the smaller archosaurs, mammals, and crocodiles. Additionally, it might have only hunted during the night. The next crucial evolutionary event that followed the appearance of the Eoraptor might have been the split between the ornithischian dinosaurs bird-like species , and the Saurischian dinosaurs lizard-like species.

The ornithischian dinosaurs may have been the direct descendant of all herbivorous dinosaurs. Herbivorous dinosaurs include the ornithopods, ceratopsians, and the hadrosaurs. Meanwhile, the Saurichians split into two distinct families: the prosauropods and the theropods.

The prosauropods are the bipedal, slender, and herbivorous dinosaurs. These types of dinosaurs may have eventually evolved into titanosaurs and sauropods. Theropods are the carnivorous dinosaurs , such as the raptors and the T-Rex. The dinosaurian evolution continued to form its course even after these dominant dinosaur species were formed.

However, according to recent paleontological research, the speed of dinosaur adaptation drastically slowed down during the Cretaceous period. During this period, dinosaurs were locked into existing species, and their rates of diversification and speciation slowed down considerably.

It is because, among other things, they hatched from eggs, they existed in the Mesozoic Era — the age of reptiles. However, there are more in-depth scientific data that aims at accurately classifying dinosaurs in light of both modern and traditional methods of classification.

The ideal solution to this seemingly straightforward classification problem relies mainly on pre-determined taxonomy standards. Traditional taxonomy dictates that animals must be grouped in light of their common characteristics.

Arguably, most dinosaur species did not have all features found in the modern-day reptiles. However, scientists still considered them to hold enough reptilian characteristics to be considered as such.

This system is called phylogenetics. In this case, scientists would have to go many centuries back to find out which organism had the first reptile-like characteristics. This organism would then be considered to be the common ancestor for this group of animals.

Consequently, scientists will classify all its descendants in one group. Therefore, to accurately apply the modern system of classification, we must have a look at dinosaur evolution. Amphibians gained the capability to lay eggs more than three hundred million years ago. Additionally, they developed a tough skin; this reduced their chances of drying out whenever they moved on land.

With this evolutionary leap, amphibians gained the ability to survive on land as well as on water. Scientists consider these amphibians to be the earliest reptiles. Soon afterward, the first reptiles split into other branches, like snakes and lizards, archosaurs, turtles, and the swimming reptiles.

Therefore, in light of the phylogenetic method of classification, dinosaurs should be considered to be direct descendants of reptilian amphibians that had migrated from water bodies. This insight has prompted paleontologists to revise their view of other non-avian dinosaurs, such as the notorious meat eater Velociraptor and even some members of the tyrannosaur group.

They, too, were probably adorned with feathers. The abundance of feathered fossils has allowed paleontologists to examine a fundamental question: Why did feathers evolve? Today, it's clear that feathers perform many functions: they help birds retain body heat, repel water and attract a mate.

And of course they aid flight—but not always, as ostriches and penguins, which have feathers but do not fly, demonstrate. Many feathered dinosaurs did not have wings or were too heavy, relative to the length of their feathered limbs, to fly. Deciphering how feathers morphed over the ages from spindly fibers to delicate instruments of flight would shed light on the transition of dinosaurs to birds, and how natural selection forged this complex trait. He has discovered 40 dinosaur species—more than any other living scientist—from all over China.

Xu envisions feather evolution as an incremental process. Feathers in their most primitive form were single filaments, resembling quills, that jutted from reptilian skin.

These simple structures go way back; even pterodactyls had filaments of sorts. Xu suggests that feather evolution may have gotten started in a common ancestor of pterodactyls and dinosaurs—nearly million years ago, or some 95 million years before Archaeopteryx.

After the emergence of single filaments came multiple filaments joined at the base. Next to appear in the fossil record were paired barbs shooting off a central shaft. Eventually, dense rows of interlocking barbs formed a flat surface: the basic blueprint of the so-called pennaceous feathers of modern birds. All these feather types have been found in fossil impressions of theropods, the dinosaur suborder that includes Tyrannosaurus rex as well as birds and other Maniraptorans. Filaments are found elsewhere in the dinosaur family tree as well, in species far removed from theropods, such as Psittacosaurus , a parrot-faced herbivore that arose around million years ago.

It had sparse single filaments along its tail. It's not clear why filaments appear in some dinosaur lineages but not in others. Or filaments may have evolved independently at different times.

As Sues points out, "It seems that, genetically, it's not a great trick to make a scale into a filament. Originally, single filaments may well have been for display, the dinosaur equivalent of a peacock's iridescent plumage. Vivid evidence for that theory appeared when scientists unveiled the true colors of million-year-old feathers.

Bird feathers and reptile scales contain melanosomes—tiny sacs holding varieties of the pigment melanin. Many paleontologists suspected that dinosaur feathers also contained melanosomes. In Mike Benton's laboratory at the University of Bristol, IVPP's Zhang Fucheng spent more than a year searching for melanosomes in photographs of bird and dinosaur fossils taken with an electron microscope.

Zhang's diligence paid off in when he pinpointed melanosomes in Confuciusornis that contained eumelanin, which gives feathers a gray or black tinge, and pheomelanin, which gives them a chestnut to reddish-brown color.

The animal's feathers had patches of white, black and orange-brown coloring. Sinosauropteryx was even more stunning. Zhang found that the filaments running down its back and tail must have made the dinosaur look like an orange-and-white-striped barber pole.

Such a vibrant pattern suggests that "feathers first arose as agents for color display," Benton says. Early feathers could have served other purposes. Hollow filaments may have dissipated heat, much as the frills of some modern lizards do today. Other paleontologists speculate feathers first evolved to retain heat. These all descended from a common ancestor shared by Triceratops and modern birds. So for a dinosaur to re-evolve in the future, it would have to come from a bird.

Modern birds evolved from a small group of theropods. However, since so much time has passed, this link is limited. The more generations that pass between an ancestor and their descendant, the more different their genes will be. Think of how much a bird would need to change to look like Tyrannosaurus rex or Triceratops. A lot. Dinosaurs had long tails with bones all along them.