Birds and feathers are synonymous now, but what prompted their evolution?
Photograph: Rodrigo Buendia/AFP/Getty Images
by Dr Dave Hone
A common creationist canard is the supposedly unanswerable “what use is half a wing?”.
Apparently there to confound biologists, what it generally does is demonstrate the ignorance of the asker with respect to evolutionary theory. However, the actual broader question that is inferred – what use is a feather to a non-flying bird? – is both relevant and interesting.
The earliest filamentous feathers appeared in dinosaurs well before birds ever did, and were present in plenty of species that had no hope of taking to the air (though I for one would love to see a flying tyrannosaur).
So then, what might their original function have been, and what prompted them to be maintained, grow larger and change over time?
The exact answer is sadly unknown. It is likely a number of factors in concert, or different ones having greater importance over others at various times, and piecing those fragments together is very tricky.
However, there are some strong leads and ideas, and for some feather types in some groups the answer is rather convincing.
To deal with the central issue though, there are in fact various things that feathers may offer animals aside from flight alone.
A quick look at living birds reveals plenty of possibilities, and almost all of them may be applied to various (or even all) dinosaurs that preceded true, powered flight.
There really are quite a few, so I’ll try to be brief, but it shows just how many selective pressures may have acted on feathers and led to their spread and development across the various dinosaurs that had them.
It was Professor Phil Manning who discovered the first known Tyrannosaur footprint in the Hell Creek formation in Montana.
He’d seen it on the last day of an expedition in 2006 but did not have the time to investigate further, so he returned the following year and began to search for it all over again.
It is rather unremarkable to look at and unless you knew what you were looking at you wouldn’t notice it.
Rather thinner than one would expect a foot to be, the toes only just joined to the main foot and it is raised in profile rather than indented.
And it is much darker than the rock around it.
It measures around 29 inches long and similarly wide and was formed when a T-Rex walked in the clay of a flood plain, compressing it enough that it became tougher than the rock surrounding it and so it survived, just, when the rock around it eroded.
As well as the footprint itself being the right size and shape for a T-Rex, the other compelling evidence that this is genuinely from a T-Rex is that it was discovered right where it is known T-Rex died, and therefore lived.
One that was claimed to have been found in Mexico was disputed and dismissed as there was no sign anywhere near it that T-Rex was ever there.
Now one has been found, others will come to light but considering the timescale it is astounding that even one survives.
A hadrosaur Skeleton, Field Museum (Credit: Lisa Andres)
by Paul Rodgers.
Dinosaurs would be walking the Earth today if it weren’t for a “colossal” piece of bad luck.
Had the asteroid that brought their reign to an end struck at “a more convenient time” they could well have survived the cataclysm, according to new research.
And that in turn would mean no humans.
“If dinosaurs didn’t go extinct, then mammals would have never had their opportunity to blossom.
So if it wasn’t for that asteroid, then humans probably wouldn’t be here. It’s as simple as that,” said Dr Stephen Brusatte, a palaeontologist at Edinburgh University’s school of geosciences.
“Not only did a giant asteroid strike, but it happened at the worst possible time, when their ecosystems were vulnerable,” said Dr Brusatte, a co-discoverer of the Pinnochio rex tyrannosaur (Qianzhousaurus sinensis) announced in May.
“It was a perfect storm of events, when dinosaurs were at their most vulnerable.”
A triceratops at the American Museum of Natural History (Credit: Wikipedia)
The arrival of the Chicxulub bolide (comet or giant meteorite) 66 million years ago, in what is now Mexico’s Yucatan Peninsula, left a crater 20km deep and 180km in diameter and caused a global catastrophe including firestorms, tsunamis, and earthquakes.
The 10km wide rock released enough dust, ash, and aerosols into the air to create a global “impact winter” that lasted for a decade.
The Cretaceous-Paleogene extinction event (formerly known as the Cretaceous-Tertiary) is thought to have killed three quarters of the earth’s species.
At particular risk were large creatures – the dinosaurs – that depended on equally large food intake.
Only those dinosaurs that could fly survived, eventually evolving into today’s birds.
The stegosaurus is one of the more well-known dinosaurs out there, appearing in more forms of media than almost any of its lizardy brethren with the exception of the T-Rex and possible that dinosaur with wings on its legs.
Interestingly, it’s also one of the dumbest.
We say this not because we have anything against the stegosaurus, because that couldn’t be further from the truth, we love the stegosaurus because how could we not love a dinosaur with an in-built Mohawk?
No, the reason we’re saying that the stegosaurus is probably one of the dumbest dinosaurs to have existed is because it literally had one of the smallest brains we’re aware of.
As noted here, the stegosaurus had a brain no bigger than a lime, although this is bigger than people initially thought, since it used to be believed that the stegosaurus’ brain was no bigger than a walnut, it still means that the dinosaur had statistically, the smallest brain of any dinosaur we’re currently aware of.
We should make it clear that this isn’t necessarily a bad thing, a stegosaurus didn’t need to contemplate philosophy or do long division in its head because it’s life was, overall, pretty good.
However, in the early days of palaeontology, people examining the skulls of stegosaurus remains couldn’t accept that a creature of such immense size and girth could survive with such a tiny brain, so it was theorised that the creature must have had a second brain, in its arse.
The actual reasoning behind the theory isn’t as stupid as that, but it is is painfully close.
To explain, palaeontologists back in the day noticed that the stegosaurus had a weird cavity in the booty area of its spine.
This cavity was larger than the cranial cavity that housed the dinosaur’s brain so it was simply assumed that it must have contained a second brain of some sort.
That was literally it.
This theory persisted for decades because what else could that cavity be for? As it so happens, no one really knows what the cavity is for.
But we’re getting ahead of ourselves, the important thing to remember here is that at one point in time, it was literally believed that stegosaurus’ had a second brain in it’s arse.
Changyuraptor, a 125 million year old four winged dinosaur with record breaking tail feathers from China. Image Credit: Stephanie Abramowicz
Contributor: John Pickrell is the editor of Australian Geographic.
IN THE EARLY stages of evolving flight, feathered dinosaurs tried an interesting experiment: they developed four wings.
These small dinosaurs – such as Microraptor, Anchiornis and Xiaotingia – had large flight feathers on their hind limbs as well as their fore limbs, and they had long bony tails, similarly replete with large feathers.
It appears that many early birds, such as Archaeopteryx, may also have had long feathers on their hind limbs.
It was only later that birds developed the characteristically bald legs that (most) birds have today, and became aerodynamically stable on two wings and a much-reduced tail.
Microraptor was the first of the four-winged dinosaurs to be discovered, in 2003, and it was tiny for a dinosaur: approximately 1kg in weight and similar to a crow or a raven in size.
Miniaturisation, experts thought, was an essential step in developing flight.
But now a totally new four-winged dinosaur has been discovered, and it was much larger.
Changyuraptor yangi – described in the journal Nature Communications – would have been around 4kg in weight and about the size of a turkey.
It also has a really unusual feature: an incredibly long tail with 30cm feathers that trailed out behind the body.
These tail feathers were around 30 per cent of the length of the skeleton, making them the longest known feathers of any (non-bird) dinosaur.
The study suggests that it displayed a camouflage effect known as counter-shading. Illustration: Julius Csotonyi/Courtesy of the Royal Tyrrell Museum of Palaeontology.
It was built like a tank, covered in armour, and weighed about the same as a caravan – but this beefy dinosaur was still at risk of being gobbled up by predators, scientists have discovered.
Thought to have lived about 110m years ago, the giant herbivore is believed to be a type of heavily armoured dinosaur known as a nodosaur and would have reached up to 5.5 metres in length.
On show at the Royal Tyrrell Museum of Paleontology in Alberta, Canada, its fossilised remains have stunned researchers, who have hailed it as the best-preserved armoured dinosaur in the world.
Not only are its bones preserved, but the fossil also boasts the creature’s armour, stomach contents and even a thin film of organic material, thought to be remains of pigments from the skin and horns.