Pterosaurs flew like jumbo jets

Sunday, January 26, 2014

Illustration of the pterosaur quadrupedal launch. Appeared in Popular Science, credited to Kevin Hand (3 March 2009). 

Rossella Lorenzi
Discovery News

Pterosaurs, the flying lizards of the dinosaur age, ruled prehistoric skies with aerodynamic tricks like those found in modern aircraft, according to a fossil study. 

Pterosaurs appear in the fossil record at the end of the Triassic period, 220 million years ago and were the first vertebrates to achieve true flapping flight.

Like their dinosaur cousins, the creatures were affected by the mass extinction at the end of the Cretaceous period 65 million years ago, leaving no descendants.

Pterosaurs had light, hollow bones, but had wingspans up to 9 metres and more.

Indeed, fossilised bones recently found in Mexico suggest these creatures could have had a wingspan of at least 18 metres, the size of a plane.

Scientists have long wondered how these prehistoric jumbo jets could fly.

Now Dr Matthew Wilkinson of the University of Cambridge and colleagues report in the current issue of the journal Proceedings of the Royal Society B: Biological Sciences that these flying reptiles could take off and make soft landings thanks to the animal's pteroid bone.

The pteroid bone's connected to the ...
The pteroid was a long, slender bone unique to pterosaurs, was bent at the wrist and supported a membranous forewing that acted as a large flap at the front of each wing.

Scientists have debated the function of this bone, particularly its position in the wing.

Fossil studies suggest that it pointed toward the body, and that the forewing was relatively narrow.

Other studies suggest it was directed forward during flight, resulting in a much broader forewing.

"It is not possible to resolve the debate about pteroid function using fossil evidence alone," the researchers write.

They tackled the problem a different way. Using wind tunnel tests of scale models of pterosaurs, the researchers compared the performances of each position of the pteroid bone.

"We discovered that lift is greatly increased if the pteroid bone pointed forwards in flight, not inwards as had been previously believed. This had the effect of expanding the skin-like forewing in front of the arm," says Wilkinson.

Just like plane flaps
The high lift would have been vital in allowing the largest pterosaurs to take off and land, in a similar way that flaps work on aircraft wings.

Large pterosaurs would have been able to take off simply by spreading their wings while facing a breeze. The leading edge flap would also have slowed landings, acting as an airbrake.

"It would have also served as a control surface during normal flights. For example, flexing one pteroid while extending the other would have increased lift on one wing, thereby initiating a roll," the researchers write.

According to UK dinosaur expert Darren Naish of the University of Portsmouth, the study "provides a new rigorous interpretation of pterosaur aerodynamics".

"This work solves several mysteries that have long existed, and shows that pterosaurs evolved novel solutions to the problems of active flight."

Dino model shows the glide path to flight

Microraptor was a two-footed dinosaur - theropod - and the first to have feathers on its arms, legs and tail (Source: Jason Brougham/University of Texas, Austin)


Scientists using a wind tunnel and a full-scale model have shed light on how feathery dinosaurs adapted to the skies, a new study reports.

A widening consensus among palaeontologists is that birds evolved from small, feathery dinos. But the question is how?

Researchers at the University of Southampton created an anatomically correct model of a five-winged dinosaur deemed to be a precursor of birds.

"Normally people build models without the feathers, but we've tried to include the feathers because they bend with the wind and so we've got a combination of effects going on there," says study co-author Colin Palmer.

Microraptor was a two-footed dinosaur - theropod - and the first to have feathers on its arms, legs and tail, providing it potentially with five surfaces with which to gain "lift" against the air.

"It was a small animal that was discovered 15 years ago in the north east of China, and supposed to have been one of the first to have flown. So understanding how it flew is really important to know how flight began 150 million years ago," says Jacques Van der Kindere who was also involved in the study.

Experiments in a wind tunnel, supported by flight simulations, showed that even though these wings were rudimentary compared to those of modern birds, it could still carry out slow glides from low heights.

"Using a wind tunnel allows us to measure lift - the amount of force it could produce vertically to keep it in the air - the drag - the resistance to motion, and those two together gives us an idea of the speed that the animal could fly at. It also gives us the ability to look at the stability," says Palmer.
From a height of about 30 metres, it could glide between 70 and 100 metres - a useful means of grabbing a prey or fleeing a predator.

Judged by this, microraptor probably climbed a bit, foraged for food on the ground and glided only on occasion, say the authors.

"Microraptor did not require a sophisticated 'modern' wing morphology to undertake effective glides," write the authors of the paper published in the journal Nature Communications.

"Symmetric feathers first evolved in dinosaurs for non-aerodynamic functions, later being adapted to form lifting surfaces."

A leading hypothesis in the origin of birds is that, after learning to glide, feathered dinosaurs underwent evolutionary pressures that led to a more sophisticated wing, able to flap efficiently and adapt its shape to winds.

Smaug Breathes Fire Like A Bloated Bombardier Beetle With Flinted Teeth

Sunday, January 5, 2014

January 2, 2014

What does a narcissistic flying reptile that loves the taste of crispy dwarves have in common with a beetle that shoots hot, caustic liquid from its butt? More than you think.

A few weeks ago, audiences were finally treated to the Cumberbatch-infused reptilian villain from J.R.R. Tolkien’s classic The Hobbit. Smaug (pronounced and interpreted as if you smashed together “smug” and “smog”) is a terrible dragon that long ago forced a population of dwarves from under a mountain. He laid claim to all their treasures. He burned all their homes. The titular character of the book is then tasked with helping a company of these displaced dwarves take back the mountain from the beast. It wouldn’t be easy—the most common descriptor of a dragon is “fire-breathing,” after all. But unlike other aspects of the book and now the film that are wholly magic, Smaug’s burning breath is actually one of the least magical, and can be wrangled into plausibility. Doing so involves looking inside a beetle’s butt, a Boy Scout’s satchel, and a bird’s throat.

Even though they don’t exist, dragons, like all other real organisms, have evolved over time. They weren’t always so huge. Dragons were once the size of cattle in popular depictions. And some of them didn’t have wings, or breathe fire. Today’s dragons are uniquely terrible lizards—massive, spiked, voracious, flame-spewing beasts. If even mythical beasts evolve, how would a real dragon evolve its most recognizable ability?

First, a dragon needs fuel.

This aspect of dragon fire is the easiest to imagine. In fact, you are probably producing dragon fuel as you read this sentence. Methane—a highly flammable gas that is produced naturally by bacteria in the gut—is constantly bubbling up in your stomach as microbes munch on your food. With a large stomach or even a separate organ to house this gas, a dragon could easily eat enough food to produce a large amount of methane.

If methane isn’t the fuel, another more exotic liquid might be. Take the bombardier beetle. This incredible insect evolved (yes, evolved) a way to harness the chaos of chemical reactions in a defense mechanism. When under threat, the beetle excretes two chemicals from two separate reservoirs that mix in a third, producing a very hot liquid and the gas needed to propel it into the face of some would-be predator.

When two liquids come together, react, and spontaneously combust, they are called “hypergolic.” The bombardier beetle isn’t the only organism that takes advantage of hypergolic chemicals; we use them in rocket fuel. (You can see a nice small-scale demonstration of a hypergolic reaction here.) A dragon could do the same. It wouldn’t be the first fiction animal to do so either. Who can forget (or maybe remember?) the giant, fire-spewing “tanker” bug from the ironically classic sci-fi movie Starship Troopers?

If a dragon convergently evolved chemicals that combust upon mixing, like the explosive bombardier beetle, the reaction it harnessed could result in fire…terrible, terrible, fire. But these chemicals aren’t cheap, biologically speaking. A dragon would have to make a large biological investment to produce them. That would at least be consistent with dragons’ voracious appetite for dwarves, men, and livestock—the winged beasts need to produce more rocket fuel.

The next step in fire breathing is the spark.

Before you see a dragon’s flame you see the teeth. Terrifying spears and stake knives that click and clamor inside gigantic mouths—giant flints. Some dragon lore speculates that dragons, like modern birds, ingested rocks and stones to aid in digestion. Over time, stories say, the minerals would coat dragon teeth. Or maybe the dragons could hold some minerals in their mouths. Either way, quickly biting down on these minerals could produce a spark. Like a Boy Scout’s trusty flint, clicking dragon teeth would provide the ignition for either a glut of methane gas or a gush of hypergolic liquids (if needed).

Another possible spark could come from more detailed physics. If dragon teeth had piezoelectric properties—where mechanical stress produces small jolts of electricity—a combination of methane exhalation and teeth grinding could light the fire. Or maybe the crushed stones and minerals could vaporize in the air ahead of the methane and combust, as metals do on helicopter rotors in the Kopp-Etchells Effect. Perhaps the dragons could expel the liquids or gases so quickly from their bellies that static ignition would occur. (When cleaning out supertankers, for example, all the flammable vapors first must be vented. The high-pressure water jets used in cleaning can generate sparks that ignite the gas.) Could a dragon evolve an organ that produces its own spark like a kaiju from Pacific Rim? Science has many sources of ignition to choose from, it’s just a matter of what the fiction allows.

Dragons are basically our pipe-dreams of what birds would be if they still looked liked ancient dinosaurs but followed evolution’s flight plan. Dragons’ similarities with birds (themselves in fact dinosaurs) could provide the last critical link to flame flinging. With multiple stomachs aiding digestion, birds—and by extension, dragons—could evolve a specialized sack for storing either methane or combustible chemicals. Birds also eat stones and rocks to break up tough material in these stomachs, so Smaug munching on minerals isn’t that far-fetched either.

There are still a few problems. Dragons are huge, undoubtedly heavy creatures that would likely rip their own wings to shreds when attempting to stay airborne. Also, holding both a large amount of methane or hypergolic chemical internally is explosively problematic. Breathing out fire is a problem in and of itself. A dragon would need specialized tissues in the mouth to deal with the incredible heat, and lungs large enough to force the flames a significant distance (unless it was a dragon from Skyrim, which specializes in powerful blasts of voice). I imagine that a more scientifically plausible dragon wouldn’t be the slender, monitor lizard-like monstrosity we see in the latest Hobbit film and more like a flightless, bloated flame-thrower.

What does this mean for The Hobbit, a universe already filled with magic? Nothing at all. The film has its own problems to deal with. Nonetheless, I found Smaug’s fire breath to be one of the least distressing suspensions of reality. Whether a “true” fire-breathing dragon is filled with flint, gas, or rocket fuel, one thing is for sure: Where there is Smaug, there is fire.

About the Author: Kyle Hill is a freelance science writer and communicator who specializes in finding the secret science in your favorite fandom. Follow on Twitter @Sci_Phile