Tag Archives: University of Portsmouth

Four-legged snake is missing link between lizards and serpents

An “absolutely exquisite” fossil of a juvenile snake with limbs has been discovered by paleontologists, forgotten in a museum. The fossil dates back from the early Cretaceous, 110 million years ago, and is the oldest evidence of a definitive snake.

Snakes are elongated, legless, carnivorous reptiles that evolved in the late Cretaceous; the earliest evidence (before this) of a snake was 94 million years old, but the fossil record of snakes is relatively poor because snake skeletons are typically small and fragile making fossilization uncommon. Based on comparative anatomy, there is consensus that snakes descended from lizards, and these legged snakes further strengthen this theory.

Dr Dave Martill from the University of Portsmouth who conducted the study, says this fossil can show how and why snakes lost their limbs.

“It is generally accepted that snakes evolved from lizards at some point in the distant past. What scientists don’t know yet is when they evolved, why they evolved, and what type of lizard they evolved from. This fossil answers some very important questions, for example it now seems clear to us that snakes evolved from burrowing lizards, not from marine lizards.”

The first observation that they made is that the limbs show adaptation for burrowing, not swimming, which indicates that snakes evolved on land, not in water, as was proposed by some scientists.

“This is the most primitive fossil snake known, and it’s pretty clearly not aquatic,” said Dr Nick Longrich from the University of Bath, one of the study’s authors.

Researchers were actually surprised by how clear the features of the fossil are – they were expecting something more ambiguous, more “in between”. Instead, he saw “a lot of very advanced snake features” including its hooked teeth, flexible jaw and spine – and even snake-like scales.

Furthermore, the fossil also reveals that the ancient snake had ingested a vertebrate – a clearly snake behaviour.

“And there’s the gut contents – it’s swallowed another vertebrate. It was preying on other animals, which is a snake feature. It was pretty unambiguously a snake. It’s just got little arms and little legs.”

The snake, named Tetrapodophis amplectus by the team, measured just 20 cm from head to tail, though it likely grew much bigger than that in adulthood. The head was about the size of a fingernail and the limbs were actually very little, but still useful.

“They’re actually very highly specialised – they have very long, skinny fingers and toes, with little claws on the end. What we think [these animals] are doing is they’ve stopped using them for walking and they’re using them for grasping their prey.”

The fossil had a history as strange as the snake itself. It was simply acquired by a private collector, where it languished for decades before a museum in Solnhofen, Germany, acquired and exhibited it with the label “unknown fossil”. It was actually when Dr David Martill, another of the paper’s authors, took his students out for a field trip that the fossil was rediscovered and properly appreciated.

“All of a sudden my jaw absolutely dropped, when I saw this little fossil like a piece of string,” said Dr Martill, from the University of Portsmouth. He immediately asked for permission to study the fossil more closely. “The fossil was part of a larger exhibition of fossils from the Cretaceous period. It was clear that no-one had appreciated its importance, but when I saw it I knew it was an incredibly significant specimen.”

Journal Reference:

  1. Dave Martill et al. A four-legged snake from the Early Cretaceous of Gondwana. Science, July 2015 DOI: 10.1126/science.aac5672

 

Limpet Teeth May Be World’s Strongest Material

According to a new study, limpet teeth may be the strongest material known to man, stronger than spider silk or kevlar. The potential applications for use are virtually endless, especially as the strength isn’t affected by the material’s size.

Surprising news: limpet teeth may be the world’s strongest material. Image via I Love Shelling.

“Limpet” is a common name given to aquatic snails with shells broadly conical in shape. It’s not necessarily a scientific term, and it’s used out of convenience to describe any gastropod whose shell has no obvious coiling. Researchers from the University of Portsmouth have discovered that limpets have incredibly strong teeth – they may actually be the strongest material in the world.

Professor Asa Barber from the University’s School of Engineering led the study. He said:

“Nature is a wonderful source of inspiration for structures that have excellent mechanical properties. All the things we observe around us, such as trees, the shells of sea creatures and the limpet teeth studied in this work, have evolved to be effective at what they do. Until now we thought that spider silk was the strongest biological material because of its super-strength and potential applications in everything from bullet-proof vests to computer electronics but now we have discovered that limpet teeth exhibit a strength that is potentially higher.”

Limpets need the high-strength teeth to cling on to rock surfaces and remove algae for feed when the tide is in. For this study, researchers used atomic force microscopy to test the strength of the teeth. Atomic force microscopy is a very high-resolution type of scanning probe microscopy, with a resolution on the order of fractions of a nanometer, much higher than optic microscopy.

They found that the teeth contain a mineral called goethite – an iron bearing hydroxide mineral. Goethite isn’t particularly strong, but goethite fibers are laced through a protein base in much the same way as carbon fibres can be used to strengthen plastic. The mineral forms as the limpet grows, but the strength of the teeth didn’t seem impacted by the limpets’ age.

A scanning electron microscope image of limpet teeth. Image credits: Portsmouth University.

“Limpets need high strength teeth to rasp over rock surfaces and remove algae for feeding when the tide is in. We discovered that the fibres of goethite are just the right size to make up a resilient composite structure. This discovery means that the fibrous structures found in limpet teeth could be mimicked and used in high-performance engineering applications such as Formula 1 racing cars, the hulls of boats and aircraft structures. Engineers are always interested in making these structures stronger to improve their performance or lighter so they use less material.”

Indeed, the applications for such a strong material are basically endless – strong materials are needed in most industries, from computer electronics to the car and plane industries, strong materials are a godsend. But what makes it even more spectacular and more applicable to industry is the fact that the material’s strength is not dependent on its size – in other words, you can scale it up or make it as tiny as you want.

“Generally a big structure has lots of flaws and can break more easily than a smaller structure, which has fewer flaws and is stronger. The problem is that most structures have to be fairly big so they’re weaker than we would like. Limpet teeth break this rule as their strength is the same no matter what the size.”

The tooth fragments were milled into a microscopic dog-bone shape and glued to a lever for testing.

The material the team tested in the lab was approximately 100 times thinner than a human hair. For future studies, they will have to apply more tests under more sizes and see what factors can further amplify (or threaten) the material’s strength. So far, the shape seems to be very important.

“The testing methods were important as we needed to break the limpet tooth. The whole tooth is slightly less than a millimetre long but is curved, so the strength is dependent on both the shape of the tooth and the material. We wanted to understand the material strength only so we had to cut out a smaller volume of material out of the curved tooth structure.”

It will be quite a while before we actually start seeing practical applications for limpet teeth, but the fact that scientists found such a strong material in an unexpected place is definitely thrilling and opens new perspectives.

The research was published today in the Royal Society journal Interface.

dark matter

Study shows Dark Energy is erasing Dark Matter

A newly published study has revealed that dark matter is being swallowed up by dark energy, offering valuable data not only about the nature and structure of these mysterious entities, but also about the future of the Universe.

Dark Matter and Dark Energy

dark matter

Artistic representation of dark matter. Image credits: tchaikovsky2, Deviant Art

In case you’re wondering, dark matter and dark energy are not Star Trek concepts – they’re real forms of energy and matter; at least that’s what most astrophysicists claim. Dark matter is a kind of matter hypothesized in astronomy and cosmology to account for gravitational effects that appear to be the result of invisible mass. The problem with it is that it cannot be directly seen with telescopes, and it neither emits nor absorbs light or other electromagnetic radiation at any significant level. It is believed that it does not react with light in any way; the only reason we know about it is that we see its effects. Basically, astronomers have consistently observed something causing a gravitational attraction, so therefore there has to be some matter with mass causing the attraction. They coined the term dark matter, and we still don’t really know what it’s made of.

Meanwhile, dark energy is a hypothetical form of energy which permeates all of space and tends to accelerate the expansion of the universe. Basically, ever since the 1990s, observations have revealed that the Universe is expanding at an accelerating rate. This baffled researchers; ok, it’s clear  that it expands, but why is it expanding faster? If anything, it should expand slower, due to all the gravitational attraction. Well, dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate. The evidence for dark energy is indirect, just like with dark matter. Dark energy is thought to be very homogeneous, not very dense and have a negative pressure (acting repulsively) in order to explain the observed acceleration of the expansion of the universe.

Image via Discover Magazine.

According to modern measurements, on a mass–energy equivalence basis, the observable universe contains 26.8% dark matter, 68.3% dark energy (for a total of 95.1%) and 4.9% ordinary matter. So everything we know (humans and animals, planets, stars and galaxies) amounts for some 5% of the known Universe – the rest, the huge 95% is made out of dark energy and dark matter – something we still don’t know much about. Naturally, physicists and astronomers are trying to figure out how the two react with ordinary matter and with themselves.

Energy eats matter

Researchers in Portsmouth and Rome have made a stunning discovery, showing that dark matter is being slowly erased, swallowed up by dark energy. Professor David Wands, Director of Portsmouth’s Institute of Cosmology and Gravitation and one of the research member said:

“This study is about the fundamental properties of space-time. On a cosmic scale, this is about our Universe and its fate. If the dark energy is growing and dark matter is evaporating we will end up with a big, empty, boring Universe with almost nothing in it. Dark matter provides a framework for structures to grow in the Universe. The galaxies we see are built on that scaffolding and what we are seeing here, in these findings, suggests that dark matter is evaporating, slowing that growth of structure.”

Interestingly enough, there is no proposed mechanism to how or why this happens. What this type of study shows is that the Standard Model is no longer sufficient to explain all the interactions taking place at a cosmological scale. In other words, we’re missing something pretty important.

Research students Valentina Salvatelli and Najla Said from the University of Rome worked in Portsmouth with Dr Marco Bruni and Professor Wands, and with Professor Alessandro Melchiorri in Rome examined data from several surveys to reach this conclusion. Professor Wands said:

“Valentina and Najla spent several months here over the summer looking at the consequences of the latest observations. Much more data is available now than was available in 1998 and it appears that the standard model is no longer sufficient to describe all of the data. We think we’ve found a better model of dark energy.”

The Universe is expanding at an accelerated rate, something which we are still struggling to understand. Image via Wiki Commons.

The models seem to support these claims; the fact that the Universe is accelerating, but at a slower pace than expected (following 90s observations) also seems to support their hypothesis.

“Since the late 1990s astronomers have been convinced that something is causing the expansion of our Universe to accelerate. The simplest explanation was that empty space – the vacuum – had an energy density that was a cosmological constant. However there is growing evidence that this simple model cannot explain the full range of astronomical data researchers now have access to; in particular the growth of cosmic structure, galaxies and clusters of galaxies, seems to be slower than expected.”

The community still hasn’t had a coherent reaction, but initial reviews seem to be positive. Professor Dragan Huterer, of the University of Michigan feels that other researchers should take not of these findings, and include them in future models and theories.

“The paper does look very interesting. Any time there is a new development in the dark energy sector we need to take notice since so little is understood about it. I would not say, however, that I am surprised at the results, that they come out different than in the simplest model with no interactions. We’ve known for some months now that there is some problem in all data fitting perfectly to the standard simplest model.”

To me, the fact that we can do so much, and yet know so little about 95% of the Universe we live in is stunning. There’s still so much to learn, and so much we have yet to understand. It’s a great time to be a scientist!

Journal Reference: Valentina Salvatelli, et al., “Indications of a Late-Time Interaction in the Dark Sector,” Physical Review Letters, 113, 181301, 30 October 2014; doi:10.1103/PhysRevLett.113.181301