Category: Palaeontology

Fossil insect hid by carrying a basket of trash

By Ed Yong | December 10, 2012 2:00 pm

If you travelled back to Spain, during the Cretaceous period, you might see an insect so bizarre that you’d think you were hallucinating. That’s certainly what Ricardo Pérez-de la Fuente thought when he found the creature entombed in amber in 2008.

The fossilised insect of the larva of a lacewing. Around 1,200 species of lacewings still exist, and their larvae are voracious predators of aphids and other small bugs. They also attach bits of garbage to tangled bristles jutting from their backs, including plant fibres, bits of bark and leaf, algae and moss, snail shells, and even the corpses of their victims. Dressed as walking trash, the larvae camouflage themselves from predators like wasps or cannibalistic lacewings. And even if they are found, the coats of detritus act as physical shields.

We now know that this strategy is an ancient one, because the lacewing in De la Fuente’s amber nugget—which is 110 million years old—also used it. It’s barely a centimetre long, and has the same long legs, sickle-shaped jaws, and trash-carrying structures of modern lacewing larvae. But it took camouflage to even more elaborate extremes. Rather than simple bristles, it had a few dozen extremely long tubes, longer even than the larva’s own body. Each one has smaller trumpet-shaped fibres branching off from it, forming a large basket for carrying trash.

De la Fuente called it Hallucinochrysa diogenesi, a name that is both evocative and cheekily descriptive. The first part comes from the Latin “hallucinatus” and references “the bizarreness of the insect”. The second comes from Diogenes the Greek philosopher, whose name is associated with a disorder where people compulsively hoard trash.

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Fossilised microbe found in 200 million year old Leech cocoon

By Ed Yong | December 4, 2012 8:00 am

If you want to preserve your body so that scientists will dig it up millions of years from now, there are a few standard ways of doing it. You could get buried in sediment, so your bones and other hard tissues turn into stony fossils. You could get trapped in the sap of a tree, which will eventually entomb your body in gorgeous amber. Or if that’s a bit too flashy, try snuggling up in the cocoon of a leech.

Leeches and earthworms secrete cocoons of mucus and lay their eggs inside. After a few days, the mucus hardens into a hard protective capsule that’s remarkably resistant to changes in temperature and chemical attacks. These cocoons fossilise very well, and palaeontologists have found many made by prehistoric leeches, dating right back to the Triassic period when dinosaurs first appeared.

To Benjamin Bomfleur from the University of Kansas, these cocoons are a goldmine of information into the past. In one specimen, 200 million years old, he has found the remains of a microscopic soft-bodied creature that would normally be impossible to fossilise. In the leech’s cocoon, it found a way into the present.

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CATEGORIZED UNDER: Palaeontology

‘Bird mimic’ dinosaur hints that wings evolved for show not flight

By Ed Yong | October 25, 2012 2:00 pm

In 1890, the fossil-hunter Othniel Charles Marsh described a new species of dinosaur from Colorado. He only had a foot and part of a hand to go on, but they were so bird-like that Marsh called the beast Ornithomimus – the bird mimic. As the rest of Ornithomimus’ skeleton was later discovered, Marsh’s description seemed more and more apt. It ran on two legs, and had a beaked, toothless mouth. Despite the long tail and grasping arms, it vaguely resembled an ostrich, and it lent its name to an entire family – the ornithomimids—which are colloquially known as “ostrich dinosaurs”.

Now, the bird mimic has become even more bird-like. By analysing two new specimens, and poring over an old famous one, Darla Zelenitsky from the University of Calgary has found evidence that Ornithomimus had feathers. And not just simple filaments, but wings – fans of long feathers splaying from the arms of adults. (More technically, it had “pennibrachia” – a word for wing-like arms that couldn’t be used to glide or fly.)

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At the bottom of a Japanese lake, the key to more accurate carbon-dating

By Ed Yong | October 19, 2012 9:00 am

Carbon-dating is a widely used technique that allows us to gauge the age of archaeological samples from up to 60,000 years ago. But it’s not a straightforward method.

It relies on a radioactive version of carbon called carbon-14, which is formed in the atmosphere and is taken up by plants (and whatever eats the plants). Once these die, the carbon-14 in their bodies decays away at a steady, predictable rate. By measuring it, we can calculate how old an ancient sample is.

But there’s a catch. The levels of carbon-14 in the atmosphere vary from year to year, so scientists need some way of assessing these fluctuations to correct their estimates. They need long-running timetables, where each year in the past several millennia can be “read”, but where true levels of atmospheric carbon-14 can be measured.

And now, in the bottom of a Japanese lake, scientists have found the best such timetable yet. As I write in The Scientist:

The sediment of a Japanese lake has preserved a time capsule of radioactive carbon, dating back to 52,800 years ago. By providing a more precise record of this element in the atmosphere, the new data will make the process of carbon-dating more accurate, refining estimates by hundreds of years.

The data will allow archaeologists to better gauge the age of their samples and estimate the timing of important events such as the extinction of Neanderthals or the spread of modern humans through Europe.

“It’s like getting a higher-resolution telescope,” said Christopher Bronk Ramsey from the University of Oxford, who led the study. “We can look [with] more detail at things [such as] the exact relation between human activity and changes in climate.”

Head over there for more.

Image by Christopher Bronk Ramsey

Thousands of dinosaur skeletons, but just two dozen complete tails

By Ed Yong | September 3, 2012 11:37 am

Look up any dinosaur, and chances are you will soon come across an estimate for how long it was. And chances are that estimate is wrong. That’s because, as Dave Hone from University College Dublin points out, our knowledge of dinosaur tails is woefully inadequate.

After searching through papers, museum collections, photos, and the minds of his colleagues, Hone found that among the thousands of dinosaur specimens that have been found, there are “barely two dozen complete tails”. These range from animals like Spinosaurus, where virtually no tail fragments have been found, to others where skeletons are missing an unknown number of vertebrae from the tips. Even in complete skeletons, Hone’s research showed that closely related species, and even individuals, can vary greatly in the length and number of bones in their tails.

This matters since tails are factored into estimates of the animals’ lengths, and lengths are often used to estimate mass. As I wrote in my Nature piece on Hone’s work, “If tails are telling tall tales, other important measures could be inaccurate.” Head over there for the rest of the story.

Image by Ballista

Mystery of the flatfish head solved *cough* four years ago *cough*

By Ed Yong | June 26, 2012 2:16 pm

Amphistium_reconstruction_p.jpg

Oh excuse me. I appear to have a cough.

There’s anew press release out about a fossil flatfish called Heteronectes, which is oddly half-committed. In modern flatfishes, like flounders or plaices, one eye moves across the other side of the body, allowing the animal to lie on its side. In this fossil species, the eye only made it halfway around. It’s a beautiful animal.

It was also discovered and described four years ago in a Nature paper, by the same authors. I wrote about it then. That fact is completely missing from the new release, which talks about “a new fossil discovery” described in a new study in the Journal of Vertebrate Palaeontology. Writer The person named on the press release (but apparently didn’t write it) Cody Mooneyhan ignored my email pointing this out.

It’s a shame. All it would take to cross the line from misleading to accurate would be a brief acknowledgement of the initial description and then some detail about what the new paper actually entails. As far as I’m aware, it’s a more detailed description of the same specimen, and some discussion about its relationship to other fish. Or maybe what’s new is that they’re writing about it for the second time, which they clearly couldn’t do the first time round :-/

You may not care. After all, a very beautiful fossil gets another shot at the limelight and we can all agree that this is a good thing. The science itself is accurate, even if the timeline is fudged. But I’m a stickler about this. I really don’t think that science is in such a desperate state that we need to wilfully hide information in order to make things more appealing. It’s just cheap, and frankly, I think it takes us journalists for fools. Andy Farke also pointed out on Twitter that the Journal of Vertebrate Palaeontology selects just one paper per issue to be laid before the Gods of Media. Some other paper could have used the slot more effectively.

CATEGORIZED UNDER: Palaeontology

Will we ever clone a mammoth?

By Ed Yong | June 6, 2012 9:00 am

Here’s the eighth piece from my BBC column

Tens of thousands of years ago, woolly mammoths roamed the northern hemisphere. These giant beasts may now be extinct, but some of their bodies still remain in the frozen Arctic wilderness. Several dozen such carcasses have now been found, and some are in extremely good condition. Scientists have used these remains to discover much about how the mammoth lived and died, and even to sequence most of its genome. But can they also bring the animal back from the dead? Will the woolly mammoth walk again?

Akira Iritani certainly seems to think so. The 84-year-old reproductive biologist has been trying to clone a mammoth for at least a decade, with a team of Japanese and Russian scientists. They have tried to use tissues from several frozen Siberian specimens including, most recently, a well-preserved thighbone. Last year, Iritani told reporters, “I think we have a reasonable chance of success and a healthy mammoth could be born in four or five years.”

A few months ago, a second team led by Korean scientist Hwang Woo Suk also expressed interest in cloning a mammoth. While Iritani comes with impressive credentials, Hwang’s resume is less reassuring. He is perhaps best known for faking experiments in which he claimed to have cloned the first human embryo and produced stem cells from it. The fact that he has confessed to buying mammoth samples from the Russian mafia does not help to instil confidence.

Regardless of their pedigree, both teams have their work cut out. Any attempt to resurrect the mammoth faces an elephantine gauntlet of challenges, including the DNA-shattering effects of frost and time, and the rather unhelpful reproductive tract of the eventual surrogate parent—the elephant.

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How to weigh dinosaurs with lasers

By Ed Yong | June 5, 2012 7:00 pm

The camera adds 10 tonnes…

The largest mounted dinosaur skeleton in the world towers over visitors in the central hall of Berlin’s Museum of Natural History. It belongs to Giraffatitan, an animal formerly known as Brachiosaurus (the big one from the opening act of Jurassic Park). From the bones, we can tell how long and tall Giraffatitan was, but how much did it weigh?

The dinosaur’s flesh has long decayed, but Bill Sellers from the University of Manchester has developed a new way of reconstructing its physique and estimating its weight. By laser-scanning the skeleton, and wrapping skin around its virtual bones, he calculated that this particular Giraffatitan weighs in at a hefty 23,200 kilograms, or 23.2 tonnes. And no matter what the university’s press office would like you to believe (more on this later), that’s virtually identical to the best current estimates.

There are two typical approaches for estimating the weight of fossil animals. You can compare the lengths of certain bones with those of known animals, assume that its mass scales accordingly. This is the predictive regression approach, and it can be unreliable. Skeletal features can vary greatly and they may not relate to weight in the same way between different animal groups. The alternative is the volumetric approach: you draw an outline of its body, estimate how much volume it took up, and multiply that with its predicted density. It’s better, but drawing the outline is both subjective and laborious.

Sellers has devised a third option. He scans an entire skeleton and his software automatically stretches a virtual skin over the outline as tightly as possible. This estimates the volume of the animal, albeit of an emaciated unrealistic individual.

When Sellers tested this technique with 14 mammal skeletons, from a wild boar to an African elephant, he found that it underestimated the weight of all the species. You’d expect that – after all, the virtual reconstruction doesn’t include any muscles or organs. The point is that the technique consistently underestimated the animals’ weight by around 21 per cent. You can just take the former, multiply it by 1.21 and get the latter.

The relationship between the predicted and actual weight is remarkable in its reliability. Sellers thinks that this is because most of the missing volume in the virtual models is from the limbs muscles, which make up a fairly fixed proportions of a mammal’s mass, regardless of its size.

Sellers then applied his method to Berlin’s famous Giraffatitan and got a value of 23.2 tonnes. Obviously, it’s not clear if a technique that was calibrated against large mammals would apply to dinosaurs, or other groups like reptiles or birds. Sellers acknowledges this, and plans to test his technique in a wider range of animal groups.

There are other potential issues. Mike Taylor from the University of Bristol and SV-POW has estimated the weight of Giraffatitan before, and thinks that around 70 per cent of its volume comes from the torso. And reconstructing the torso is very difficult for large dinosaurs, because the ribs are often poorly preserved or distorted. Taylor also says that using a single density value isn’t that appropriate for brachiosaurs. “The very long neck likely had a density no more than half that of the legs,” he says.

For the moment, it’s encouraging that the new estimate is very close to previous ones. You might not get that from the press release (and probably most of the resulting coverage). It leads with “Dinosaurs lighter than previously thought”, and follows with “Previous estimates of this Brachiosaur’s [sic] weight have varied, with estimates as high as 80 tonnes, but the Manchester team’s calculations – published in the journal Biology Letters – reduced that figure to just 23 tonnes.”

While it is true that the weight of Giraffatitan and Brachiosaurus have varied wildly over the years, the most recent estimates have been nowhere near the cherry-picked 80-tonne figure. Indeed, in 2009, Taylor concluded that Giraffatitan weighed 23,377 kilograms, or 23.3 tonnes. Sellers’ new estimate shaves off a mere 177 kg from that figure – around 2 humans from a dinosaur that weighed as much as 300.

Taylor used the volumetric method to get his result. If his result was exactly the same as the new figure, one might question whether Sellers’ method adds anything new. It does, however, have several benefits. “It requires no irreproducible judgements on the part of the person using it, and it’s ground-truthed on solid data from extant animals,” says Taylor. It’s also automated. If it truly works for dinosaurs, we can weigh these extinct beasts as quickly as the laser-scanner can be wheeled around a museum. Even with the caveats, Taylor says “It’s an important new method which I expect to see widely adopted.”

Reference: Sellers, Hepworth-Bell, Falkingham, Bates, Brassey, Egerton & Manning. 2012. Minimum convex hull mass estimations of complete mounted skeletons. Biology Letters http://dx.doi.org/10.1098/rsbl.2012.0263

Image from Berlin Natural History Museum postcard

HT Matthew Cobb for the story tip

More on sauropods

CATEGORIZED UNDER: Dinosaurs, Palaeontology

Virtual resurrection shows that early four-legged animal couldn’t walk very well

By Ed Yong | May 23, 2012 2:00 pm

In a small office north of London, Stephanie Pierce from the Royal Veterinary College is watching a movement that hasn’t been seen for 360 million years. On her computer, she has resurrected the long-extinct Ichthyostega – one of the earliest four-legged animals to creep about on land. By recreating this iconic beast as a virtual skeleton, Pierce has shown that while it looked like a giant salamander, it couldn’t possibly have walked like one. It had some of the planet’s earliest bony legs, but they weren’t very good at taking steps.

Ichthyostega hails from the Devonian period, a time in Earth’s history when swimming transformed into walking. Fish invaded the land and evolved into the first tetrapods—four-limbed animals that include amphibians, reptiles, birds and mammals.  Muscular fins used for steering and balance evolved into legs for walking.

Since its discovery over 50 years ago, Ichthyostega has been an icon of this pivotal transition. Some 300 specimens have been found but many are incomplete, flattened or distorted. Pierce’s new model provides the best look yet at the animal’s skeleton. “It makes Ichthyostega a bit more tangible,” she says. “It’s not just a fossil laying in a rock now. It’s an animal that’s coming to life.”

Pierce built her virtual skeleton by putting dozens of Ichthyostega specimens in powerful CT-scanners, choosing only the best preserved ones out of the 300 or so in existence. “The front end of the animal was mainly composed from one beautifully preserved specimen called ‘Mr Magic’,” she says.

It was painstaking work. These fossils are so old that chemically, they are almost identical to the rocks around them. By eye, the bones stand out. To the scanners, they blend in. Pierce spent over two years scanning the specimens and building her model, but the results were worth it. “This has been on the wish-list for years,” says Michael Coates, who studies tetrapod evolution at the University of Chicago.

Those boots weren’t made for walking…

The model showed that Ichthyostega’s shoulders and hips were oddly restricted. They could move back and forth, and up and down, but they couldn’t rotate about their long axis. Hold your arm out and rotate your palm so it faces up then down—Ichthyostega’s shoulder couldn’t do that.

Most modern tetrapods need long-axis rotation in order to walk. Without it, their legs can’t be thrown forward or pulled backward. Ichthyostega’s limitations meant that despite having four limbs, it probably couldn’t have taken a step. It hind feet would never have been planted flat against the ground or supported its weight. It had invaded the land, but it wasn’t striding across it.

“It highlights the fact that the earliest tetrapods are not just ‘gigantic salamanders’, despite a vague similarity in outline,” says Per Ahlberg from Uppsala University. “The limbs and girdles are very different from anything now living.”

Pierce thinks that Ichthyostega moved by paddle with its front limbs, using powerful muscles and flexible elbows to make rowing motions. The closest living analogue is probably the mudskipper – a fish that drags itself along muddy land with its front fins (as in the video below).

Pierce also compared Ichthyostega’s joints and limbs to those of other living animals with sinuous bodies and interesting gaits, including a salamander, crocodile, seal, otter and platypus. Compared to these modern species, Ichthyostega’s hips and shoulders were similarly flexible in most planes of movements, but along their long axis, they could barely rotate.

Some scientists think that the tetrapods evolved limbs before they could walk, and their first members lived in shallow water. Others think that it’s the other way round, and that muscular limbs, hips and shoulders evolved while fish still had fins. The virtual Ichthyostega supports the former idea, since it had limbs but couldn’t walk. But Coates cautions against “fitting a smooth transition from swimmers to walkers.” He says, “Evolutionary transitions needn’t follow linear routes. Ichthyostega probably represents one of multiple experiments among the first tetrapods with limbs, trying-out life in the shallows.”

So… what made those tracks?

Other early tetrapods had similar shoulders and hips, so they probably had the same limitations too. John Hutchinson, who led the new study, plans to find out. His lab is busy reconstructing other early tetrapods including Acanthostega, one of Ichthyostega’s contemporaries, and Pederpes, a later model.

But Ahlberg notes that Ichthyostega had a very unusual and rigid spine, and may not have been representative of other early tetrapods. “Other tetrapods are known to have had more flexible spines” he says, “and this probably allowed them to overcome the limitations of their shoulders and hips”.

This might explain why Ahlberg and others have discovered tracks that pre-date Ichthyostega by around 20 million years, and had become fairly common by the time it evolved. Many of these tracks showed precisely the kind of salamander-like movements that Ichthyostega was apparently incapable of making. They were clearly made by early four-legged tetrapods, and to this date, we don’t know what made them.

Pierce agrees that the final word on Ichthyostega’s movements will have to wait until she can animate its entire skeleton. “The ultimate goal would be to try and create some sort of dynamic movement,” she says. She has applied for a grant to do just that, to model the motions of the entire animal, and compare them to salamanders or crocodiles. “That’s going to take so much time, but it’ll be very interesting,” she says.

PS: I want to point out that in researching this story, I spent a good minute on my living room floor trying to walk without long-axis rotation. It was really hard, and I looked like an idiot. I did a similar thing when I was writing about hummingbird wing movements for Nature. I’m going to christen this Method Science Journalism.

Reference: Pierce, Clack & Hutchinson. 2012. Three-dimensional limb joint mobility in the early tetrapod Ichthyostega. Nature http://dx.doi.org/10.1038/nature11124

Image by Julie Molnar

More on tetrapods:

Fossil tracks push back the invasion of land by 18 million years

Fish fins and mouse feet controlled by the same ancient genetic switch

 

Jurassic bends – the rise of fast predators bubbled the blood of prehistoric reptiles

By Ed Yong | May 15, 2012 9:00 am

Experienced divers know that rising too quickly can be a fatal mistake. The changing pressure yanks previously dissolved gases out of one’s blood and forms tiny bubbles, like the fizz in a newly opened can of soda. Depending on where they emerge, the bubbles can cause everything from a rash (the skin) to seizures (the brain). To avoid this condition, known as decompression sickness or “the bends”, divers rise slowly.

Then again, if you’re being chased by a gigantic prehistoric shark, you may have no choice.

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CATEGORIZED UNDER: Palaeontology
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