Turtles are exceptionally successful as a species. They are part of the Testudine group of reptiles, including tortoises and terrapins, found on every continent apart from Antarctica, which have evolved to live on land and in both salt and fresh water.
They share common ancestry with dinosaurs — having first appeared around million years ago — and show remarkable resilience considering their fellow creatures are being wiped out. Turtles also survived one mass extinction at the end of the Tri-assic period that left an evolutionary space for dinosaurs to evolve, as well as the one at the end of the Cretaceous era that then wiped out the dinosaurs.
Those shells are clearly very tough, because immediately after that catastrophe, turtles began to diversify, hugely. There is some debate as to whether turtles count as archosaurs or whether they are more closely related to snakes and lizards.
But we don't have that many informative transitional fossils. The evolutionary link between dinosaurs and birds is well established, even within the not-always-scientifically-accurate world of Jurassic Park. A more recent discovery is that one particular dinosaur — the T.
As there was no other dinosaur collagen to work with, they cross-referenced the Tyrannosaur collagen with modern day animals, including humans, mice and salmon. The closest match was found in chickens and ostriches — two species that have surprisingly little in common, genetically speaking — with alligators coming in third.
They have populated our nightmares for so long and taken a central role in our phobic mythologies. There is, as the Beatles might put it, something in the way they move. The snake is another species that evolved to how we know it today by getting rid of key assets — most notably legs, and several bones in the skull that prevented total mobility.
For the same reason, snakes either predominantly favour the right lung over the left, or get by with just the one. Sleep tight! So, the next time you find yourself watching Chris Pratt trying to do his Velociraptor-whisperer act in Jurassic World, consider how much more realistic it might be to have him face down three angry emus, or a crocodile with a grudge. We are walking with dinosaurs all the time and we should continue to be both grate-ful and amazed that this continues to be the case.
The cassowary's crest , 2. Cassowary call, 3. 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! Crabs first emerged in the Jurassic period about — million years ago , but they flourished in the Cretaceous period , just before dinosaurs went extinct. One of the most interesting species of crab alive during this time was the Megaxantho Zogue , which was found in Mexico.
Larger than the crabs of today, it was the first crab to evolve a claw that was specially developed to break the shells of prey.
This was an important evolutionary step, and one that many crabs still have today! Like dinosaurs? Check out these dinosaurs that called Canada home and Canada's best fossil hunting locations! New research suggests that bird ancestors shrank fast, indicating that the diminutive size was an important and advantageous trait, quite possibly an essential component in bird evolution. Like other bird features, diminishing body size likely began long before the birds themselves evolved.
A study published in Science last year found that the miniaturization process began much earlier than scientists had expected. Some coelurosaurs started shrinking as far back as million years ago—50 million years before archaeopteryx emerged. At that time, most other dinosaur lineages were growing larger.
That shrinkage sped up once bird ancestors grew wings and began experimenting with gliding flight. The rapid miniaturization suggests that smaller birds must have had a strong advantage over larger ones.
Benton speculates that the advantage of being pint-size might have emerged as bird ancestors moved to trees, a useful source of food and shelter. But whatever the reasons may be, small stature was likely a useful precursor to flight. Though larger animals can glide, true flight powered by beating wings requires a certain ratio of wing size to weight. Birds needed to become smaller before they could ever take to the air for more than a short glide.
Since alligators descend from a common ancestor with dinosaurs, they can provide a useful evolutionary comparison to birds. Despite their appearance, birds are more closely related to alligators than lizards are. Fossilized skulls of baby dinosaurs show the same pattern—they resemble adult birds. With those two observations in mind, Abzhanov had an idea.
Perhaps birds evolved from dinosaurs by arresting their pattern of development early on in life. They tracked how the skull shape changed as dinosaurs morphed into birds. Over time, they discovered, the face collapsed and the eyes, brain and beak grew. This process, known as paedomorphosis, is an efficient evolutionary route. 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. A telling example comes from fossils of Oviraptor —a theropod unearthed in Mongolia that lived around 75 million years ago—squatting over egg-filled nests. Oviraptors tucked their legs into the center of the clutch and hugged the periphery with their long forelimbs—a posture bearing an uncanny resemblance to brooding birds keeping their eggs warm.
Dinosaurs related to Oviraptor were covered with pennaceous feathers, suggesting that Oviraptor was as well. Feathers did, of course, eventually become an instrument of flight. Some paleontologists envision a scenario in which dinosaurs used feathers to help them occupy trees for the first time.
Maybe feathers helped them scramble up tree trunks," Carrano says. Baby birds of primarily ground-dwelling species like turkeys use their wings in this way. Feathers may have become increasingly aerodynamic over millions of years, eventually allowing dinosaurs to glide from tree to tree. Individuals able to perform such a feat might have been able to reach new food sources or better escape predators—and pass the trait on to subsequent generations. One of the most beguiling specimens to emerge from Liaoning's shale beds is Microraptor , which Xu discovered in The bantamweight beast was a foot or two long and tipped the scales at a mere two pounds.
Microraptor , from the Dromaeosaur family, was not an ancestor of birds, but it was also unlike any previously discovered feathered dinosaur. Xu calls it a "four-winged" dinosaur because it had long, pennaceous feathers on its arms and legs. Because of its fused breastbone and asymmetrical feathers, says Xu, Microraptor surely could glide from tree to tree, and it may even have been better at flying under its own power than Archaeopteryx was.
Last year, Xu discovered another species of four-winged dinosaur, also at Liaoning. Besides showing that four-winged flight was not a fluke, the new species, Anchiornis huxleyi , named in honor of Thomas Henry Huxley, is the earliest known feathered dinosaur. It came from Jurassic lakebed deposits million to million years old. The find eliminated the final objection to the evolutionary link between birds and dinosaurs. For years, skeptics had raised the so-called temporal paradox: there were no feathered dinosaurs older than Archaeopteryx , so birds could not have arisen from dinosaurs.
Now that argument was blown away: Anchiornis is millions of years older than Archaeopteryx. Four-winged dinosaurs were ultimately a dead branch on the tree of life; they disappear from the fossil record around 80 million years ago.
Their demise left only one dinosaur lineage capable of flight: birds. Just when did dinosaurs evolve into birds? Hard to say. Aside from minor differences in the shape of neck vertebrae and the relative length of the arms, early birds and their Maniraptoran kin, such as Velociraptor , look very much alike.
You would call it a feathered dinosaur," says Carrano. It's still called the first bird, but more for historic reasons than because it is the oldest or best embodiment of birdlike traits.
On the other hand, Confuciusornis , which possessed the first beak and earliest pygostyle, or fused tail vertebrae that supported feathers, truly looks like a bird. Since the last of the non-avian dinosaurs died out 65 million years ago during the mass extinction that closed the curtain on the Cretaceous period, birds have evolved other characteristics that set them apart from dinosaurs.
Modern birds have higher metabolisms than even the most agile Velociraptor ever had. Teeth disappeared at some point in birds' evolutionary history.
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