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A Fossil Snake With Four Legs

Snakes can famously disarticulate their jaws, and open their mouths to extreme widths. David Martill from the University of Portsmouth did his best impression of this trick while walking through the Bürgermeister Müller Museum in Solnhofen, Germany. He was pointing out the museum’s fossils to a group of students. “And then my jaw just dropped,” he recalls.

He saw a little specimen with a long sinuous body, packed with ribs and 15 centimetres from nose to tail. It looked like a snake. But it was stuck in unusual rock, with the distinctive characteristics of the Brazilian Crato Formation, a fossil site that dates to the early Cretaceous period. Snake fossils had been found in that period but never that location, and in South America but never that early. The combination of place and time was unusual.

Tetrapodophis specimen. Credit: Dave Martill.
Tetrapodophis specimen. Credit: Dave Martill.

“And then, if my jaw hadn’t already dropped enough, it dropped right to the floor,” says Martill. The little creature had a pair of hind legs. “I thought: bloody hell! And I looked closer and the little label said: Unknown fossil. Understatement!”

“I looked even closer—and my jaw was already on the floor by now—and I saw that it had tiny little front legs!” he says. Fossil-hunters have found several extinct snakes with stunted hind legs, and modern boas and pythons still have a pair of little spurs. “But no snake has ever been found with four legs. This is a once-in-a-lifetime discovery.”

Tetrapodophis forelimb. Credit: Dave Martill.
Tetrapodophis forelimb. Credit: Dave Martill.
Tetrapodophis hindlimb. Credit: Dave Martill.
Tetrapodophis hindlimb. Credit: Dave Martill.


Martill called the creature Tetrapodophis: four-legged snake. “This little animal is the Archaeopteryx of the squamate world,” he says. (Squamates are the snakes and lizards.) Archaeopteryx is the feathered fossil whose mish-mash of features hinted at the evolutionary transition from dinosaurs to birds. In the same way, Martill says, the new snake hints at how these legless, slithering serpents evolved from four-legged, striding lizards.

There are two competing and fiercely contested ideas about this transition. The first says that snakes evolved in the ocean, and only later recolonised the land. This hypothesis hinges on the close relationship between snakes and extinct marine reptiles called mosasaurs (yes, the big swimming one from Jurassic World). The second hypothesis says that snakes evolved from burrowing lizards, which stretched their bodies and lost their limbs to better wheedle their way through the ground. In this version, snakes and mosasaurs both independently evolved from a land-lubbing ancestor—probably something like a monitor lizard.

Tetrapodophis supports the latter idea. It has no adaptations for swimming, like a flattened tail, and plenty of adaptations for burrowing, like a short snout. It swam through earth, not water.

It hunted there, too. Its backward-pointing teeth suggest that it was an active predator. So does the joint in its jaws, which would have given it an extremely large gape and allowed it to swallow large prey. And tellingly, it still contains the remains of its last meal: there are little bones in its gut, probably belonging to some unfortunate frog or lizard. This animal was a bona fide meat eater, and suggests that the first snakes had a similar penchant for flesh.

Martill thinks that Tetrapodophis killed its prey by constriction, like many modern snakes do. “Why else have a really long body?” he says. In particular, why have a long body with an extreme number of vertebrae in your midsection? None of the other legless lizards have that, even burrowing ones. Martill thinks that this feature made early snakes incredibly flexible, allowing them to throw coils around their prey.

Their stumpy legs may even have helped. It’s unlikely that Tetrapodophis used these limbs to move about, and they don’t seem to have any adaptations for burrowing. With tiny “palms” and long “fingers”, they look a little like the prehensile feet of sloths or climbing birds. Martill thinks that the snake may have used these “strange, spoon-shaped feet” to restrain struggling prey—or maybe mates.

Tetrapodophis catching a lizard. Credit: James Brown, University of Portsmouth
Tetrapodophis catching a lizard. Credit: James Brown, University of Portsmouth

But is it even a snake? “I honestly do not think so,” says Michael Caldwell from the University of Alberta, who also studies ancient snakes. He says that Tetrapodophis lacks distinctive features in its spine and skull that would seal the case. “I think the specimen is important, but I do not know what it is,” he adds. “I might be wrong, but that will require me to see the specimen first hand. I’m looking forward to visiting Solnhofen.”

It’s certainly possible that Tetrapodophis could be something else. In the squamates alone, a snake-like body has independently evolved at least 26 times, producing a wide menagerie of legless lizards. These include the slow worm of Europe, and the bizarre worm-lizard Bipes, which has lost its hind legs but has kept the stubby front pair. True snakes represent just one of these many forays into leglessness.

Susan Evans from University College London, who studies reptile evolution, is on the fence. “This happens every time a possible early snake is described,” she says. “Opinions on snake evolution are highly polarised.”  She says that Tetrapodophis has some features you’d expect from an early snake, and doesn’t easily fit into any other known group of squamates. The specimen is also more complete than many other recently alleged snakes, some of which are known only from fragments of vertebrae or jaw. “Unfortunately, the skull is poorly preserved and this complicates interpretation,” says Evans. “The most important thing is that it is now brought to notice and it will be thoroughly scrutinised by other workers.” Above all, she hopes that someone finds one with a better skull.

Martill insists that Tetrapodophis has “got loads of little things that tell you it’s a snake.” There’s the backwards-pointing teeth, the single row of belly scales, the way the 150 or so vertebrae connect to each other, and the unusually short tail. (In lizards and crocodiles, the tail can be as long as the entire body, but a snake’s tail—everything after the hip—is relatively short.) Some of these features are found in other legless lizards, but only snakes have all of them. And Martill adds that you just wouldn’t expect an ancestral snake to have all the features that its descendants picked up over millions of years of evolution.

He also teamed up with Nick Longrich at the University of Bath to compare Tetrapodophis’s features to those of both modern and fossil snakes. Their analysis produced a family tree in which Tetrapodophis came after the earliest known snakes like Eophis, Parviraptor, and Diablophis, but is still very much a snake.

But how could that be? Eophis and the others only have two legs, so how could four-legged Tetrapodophis have come after them? The answer is that evolution doesn’t proceed along simple, straight lines. Even if four-legged lizards gave rise to four-legged snakes, then two-legged snakes, then legless ones, the later stages don’t displace the former ones. For a long time, they would all exist together, in the same way that birds co-existed with the feathered dinosaurs that gave rise to them. (This, incidentally, is also the answer to that tired question: “If we evolved from monkeys, why are there still monkeys?”)

“At any one time in the Cretaceous, chances are you’ve got ten, twenty, maybe thirty species [of early snakes], all going off on their own evolutionary paths,” says Martill. “There would be a whole bunch of very snake-like lizards, all with the potential to become today’s snakes. One of them does. Maybe one of them goes off and loses its front legs and retains its back legs for 20 million years. One maybe loses its back legs and keeps its front legs—and we haven’t found that one yet.”

Reference: Martill, Tischlinger & Longrich. 2015. A four-legged snake from the Early Cretaceous of Gondwana. Science http://dx.doi.org/10.1126/science.aaa9208

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Giant Jurassic fleas sucked but couldn’t jump

The shortest poem ever written is known as Lines on the Antiquity of Microbes or, more simply, as Fleas. It goes: Adam/  Had ‘em. It’s a cute verse, but we don’t need Blblical references to know what the first fleas fed upon. As with many questions about ancient life, we can turn to fossils.

Among a horde of insect fossils recovered from China and Mongolia, Diying Huang from the Chinese Academy of Sciences has discovered several species of giant fleas. There are nine individuals from three different species, and they hail from the middle Jurassic and early Cretaceous periods.  “These outcrops have given us thousands of exquisitely preserved insects, but fewer than ten fleas,” says Andre Nel, who led the study.

The fossilised insects had many features that identify them as fleas – ancient precursors to the ones we know and loathe. But they had many unusual traits too. For a start, they were much bigger. While modern fleas are just a few millimetres long, some of these ancient forms were ten times bigger. The males grew between 8 and 15 millimetres in length and the females reached between 14 and 20 millimetres.


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I am virus – animal genomes contain more fossil viruses than ever expected

EbolaIf you think about fossils, you probably picture a piece of bone or shell, turned to stone and buried in the ground. You visit them in museums; some of you may even have found some. But your closest fossils are inside you, scattered throughout your genome. They are the remains of ancient viruses, which shoved their genes among those of our ancestors. There they remained, turning into genetic fossils that still lurk in our genomes to this day.

We’ve known about our viral ancestors for 40 years, but a new study shows that their genetic infiltration was far more extensive than anyone had realised. The viral roots of our family tree have just become a lot bigger.


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Do new discoveries ever “rewrite evolutionary history”?


You can’t go for a month without seeing a claim that some new discovery has rewritten evolutionary history. If headlines are to be believed, phylogeny – the business of drawing family trees between different species – is an etch-a-sketch science. No sooner are family trees drawn before they’re rearranged. It’s easy to rile against these seemingly sensationalist claims, but James Tarver from the University of Bristol has found that the reality is more complex.

Tarver focused on two popular groups of animals – dinosaurs and catarrhines, a group of primates that includes humans, apes and all monkeys from Asia and Africa. Together with Phil Donoghue and Mike Benton, Tarver looked at how the evolutionary trees for these two groups have changed over the last 200 years. They found that the catarrhine tree is far more stable than that of the dinosaurs. For the latter group, claims about new fossils that rewrite evolutionary history (while still arguably hyperbolic) have the ring of truth about them.


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Whales evolved from small aquatic hoofed ancestors

This article is reposted from the old WordPress incarnation of Not Exactly Rocket Science.

Travel back in time to about 50 million years ago and you might catch a glimpse of a small, unassuming animal walking on slender legs tipped with hooves, by the rivers of southern Asia. It feeds on land but when it picks up signs of danger, it readily takes to the water and wades to safety.


The animal is called Indohyus (literally “India’s pig”) and though it may not look like it, it is the earliest known relative of today’s whales and dolphins. Known mostly through a few fossil teeth, a more complete skeleton was described for the first time last week by Hans Thewissen and colleagues from the Northeastern Ohio Universities. It shows what the missing link between whales and their deer-like ancestors might have looked like and how it probably behaved.Whales look so unlike other mammals that it’s hard to imagine the type of creature that they evolved from. Once they took to the water, their evolutionary journey is fairly clear. A series of incredible fossils have documented their transformation into the masterful swimmers of today’s oceans from early four-legged forms like Pakicetus and Ambulocetus (also discovered by Thewissen). But what did their ancestors look like when they still lived on land?

Hooves to flippers

Until now, we had little idea and their modern relatives have provided few clues. According to molecular evidence, the closest living relatives of whales are, quite surprisingly, the artiodactyls, a group of hoofed mammals that includes deer, cows, sheep, pigs, giraffes, camels and hippos.

They all have a characteristic even number of toes on each hoof and not a single one of them bears even a passing resemblance to whales and dolphins. Among the group, the hippos are evolutionarily closest and while they are at least at home in water, their family originated some 35 million years after the first whales and dolphins did.

Enter Indohyus, a small animal about 70cm long that lived 47 million years ago. It was a member of a family of mammals called the raoellids, prehistoric artiodactyls that lived at the same time as the earliest whales and hailed from the same place of origin – southern Asia. By analysing a fossilised skull and limbs collected from India, Thewissen found compelling evidence that the raoellids were a sister group to the ancestors of whales.

Even though Indohyus had the elegant legs of a small deer and walked around on hooves, it also had features found only in modern and fossil whales. Its jaws and teeth were similar to those of early whales, but the best evidence was the presence of a thickened knob of bone in its middle ear, called an involucrum. This structure helps modern whales to hear underwater, it’s only found in whales and their ancestors, and acts as a diagnostic feature for the group.

Based on these physical similarities, Thewissen suggests that the raoellids are a sister group to the whales. Both of these groups are evolutionary cousins to all modern artiodactyls. (As a note for journalists and creationists, Indohyus is not a direct ancestor of whales, as many news sites are claiming, and nor did whales ‘evolve from deer’!)

A swimming Indohyus

Life in the water

Indohyus‘s skeleton also suggests that it was partially adapted for life in the water. Its leg bones were unusually thick, a feature shared by other aquatic animals including hippos, sea otters and manatees. These heavier bones stop swimming mammals from floating by default and allow them to hang in the water and dive more easily.

Because Indohyus had slender legs and not paddle-shaped ones, Thewissen pictures it wading in shallow water, walking hippo-style along the river floor while its heavy bones provided ballast.

Thewissen found more clues about the animal’s lifestyle from its teeth, and particularly the levels of certain isotopes in their enamel. Levels of oxygen isotopes matched those of water-going mammals, providing further support for Indohyus‘s aquatic tendencies. Its large crushing molars are typical of plant-eaters and levels of carbon isotopes in them suggested that Indohyus either came onto land to graze (like hippos) or fed on plants and invertebrates in the water (like muskrats). In terms of behaviour, they were close to the modern mousedeer, a tiny, secretive deer that feeds on land but flees into streams when danger threatens.

Put together, this portrait of Indohyus‘s life also tells us about the changes that drove the evolution of whales, and it looks like it wasn’t a move to water. Whales and raoellids are evolutionary sisters and since early members of both groups were happy in the water, aquatic lifestyles must have pre-dated the origin of whales.

Instead, Thewissen suggests that the key step was a switch in diet. He speculates that whales developed from an Indohyus-like ancestor that fed on plants and possibly small invertebrates on land, but fled to water to escape predators. Over time, they slowly turned into meat-eaters and evolved to swim after nimble aquatic prey.

Video: Have a look at Thewissen talking about Indohyus and the origin of whales.

Images of Indohyus are painted by the extraordinary Carl Buell

Reference: Thewissen, J.G., Cooper, L.N., Clementz, M.T., Bajpai, S., Tiwari, B.N. (2007). Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature, 450(7173), 1190-1194. DOI: 10.1038/nature06343

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


Around 395 million years ago, a group of four-legged animals strode across a Polish coast. These large, amphibious creatures were among the first invaders of the land, the first animals with true legs that could walk across solid ground. With sprawling gaits and tails held high, they took pioneering footsteps. Their tracks eventually fossilised and their recent discovery yields a big surprise that could rewrite what we know about the invasion of land. These animals were walking around 18 million years earlier than expected.

The evolution of four-legged creatures – tetrapods – is one of the most evocative in life’s history. It has been illustrated by a series of beautiful fossils that vividly show the transition from swimming with fins to walking on legs. These include Panderichthys, a fish with a large tetrapod-like head and a muscular pair of front fins. Tiktaalik expanded on these themes. Its head could turn about a solid neck. Its limbs had the fin rays of its fishy predecessors but clear wrist bones and basic fingers too. Tiktaalik could support itself on strong shoulder bones, bend its fins at the wrists, and splay out its hand-like bones.

These animals – the elpistostegids – have largely been seen as transitional fossils. Tetrapods supposedly evolved from these intermediate forms and eventually replaced them. You could draw all of their skeletons in the corner of a book and flick the pages to see the move from sea to land happen before your eyes. But the new fossil tracks tell a very different story. As one reviewer writes, they “lob a grenade into that picture”.

The earliest true tetrapods so far discovered were around 375 million years old and the earliest elpistostegids hail from around 386 million years ago. But the Polish tracks are 10 million years older still. These dates suggest that the elpistostegids weren’t transitional forms at all. They weren’t early adopters of new biological technology, but late-surviving relics that stayed in their fish-like state while other species had evolved new bodies and, quite literally, run with them. Per Ahlberg, who led the study, says, “I’ve been working on the origin of tetrapods for about 25 years, and this is the biggest discovery I have ever been involved in. It is enomously exciting.”

It would be tempting to cast animals like Pandericthys or Tiktaalik in the role of biological luddites, outstaying their welcome with outmoded bodies. But that would be an injustice. If these animals co-existed with tetrapods for at least 10 million years, it suggests that their bodies were stable, well-adapted structures in their own right. They weren’t just brief flirtations with sturdiness on the way to full-blown walking.

Ahlberg discovered the fossil tracks along with researchers from Warsaw University, led by Grzegorz Niedzwiedzki. The tracks are found in the disused Zachelmie Quarry, nestled among Poland’s Holy Cross Mountains. The area used to be part of a tidal plain. Rocks from the site and a few rare fossils allowed the team to confidently date the track-ridden layer to around 395 million years ago, the middle of the Devonian period.

Among this layer, Niedzwiedzki found several tracks of different shapes and sizes. He also found several isolated handprints and footprints that clearly show signs of toes and ankles. Many of these tracks (such as in the diagram at the top) were clearly made by an animal walking with powerful, diagonal strides, powered by sprawling right-angled limbs.


They weren’t the work of any elpistostegid, whose straight limbs and backward-pointing shoulders and hips would have created far narrower tracks. Elpistostegids would also have dug long central troughs as they laboriously dragged themselves along. No such troughs exist at the quarry. This tells us that the track-makers strode along using strong hips and shoulders to hold their bodies and tails off the ground.

Niedzwiedzki thinks that they were undoubtedly tetrapods, and big ones too. The animal that created the tracks above was just 40-50 cm long. But some of the footprints were 15cm wide and hinted at creatures that were around 2.5 metres in length. The largest print is 26cm wide and its maker was probably a giant.

The implications of the Polish tracks are so controversial that reactions from other palaeontologists have been, understandably, mixed. Ted Daeschler and Neil Shubin, who discovered Tiktaalik, both find the study intriguing, but not definitive.

For Shubin, the deal-breaker would be identifying the animals that made the trackways and establishing where they sit on the evolutionary tree. He says, “The skeletal anatomy, let alone evolutionary relationships, of a trackmaker is hard to interpret from a track or print.” For example, he says that a model of Tiktaalik‘s skeleton would produce a print much like the one in the paper if it’s mushed into sand, and different consistencies or angles would produce an even closer match. He adds, “There is nothing in Tiktaalik’s described anatomy that suggests it didn’t have a stride.” 

Daeschler agrees that “trace fossils such as these presumed tracks… are a notoriously difficult class of evidence to interpret with full confidence”. Nonetheless, he’s keeping an open mind and a keen eye on future developments. “Paleontology is a lively field in which new discoveries constantly refine our knowledge of the history of life on earth,” he says.  

Jenny Clack, the Cambridge scientist who discovered Acanthostega, has seen the Polish tracks for herself and finds them more convincing. Her only reservation is that the detailed prints don’t have any trackways to show how their maker moved, while the trackways themselves consist of blobs. “But so do lots of previously known tracks,” she says. “If you’d found those in other deposits in the last part of the Devonian, you wouldn’t have any qualms about them.” She’d like to see trackways of the detailed prints but she’s nonetheless excited. “It’s going to change all our ideas about why tetrapods emerged from the water, as well as when and where.”

On the question of where, many scientists have suggested that the invasion of land began at the margins of freshwater – at river banks, deltas, lakes or flooded forests. But the Zachelmire quarry wasn’t any of these. Most likely, it was a shallow tidal flat or perhaps a saltwater lagoon. The first tetrapods didn’t lurk in rivers, but trampled the mud of coral-reef lagoons.

Niedzwiedzki thinks that this revised locale makes a better staging ground for the invasion of land. Twice a day, the zone between high and low tide is awash with stranded marine animals that would provide a feast for marine creatures experimenting with life on land. He argues that life was driven aground by the rich availability of snacks.

This new setting for the rise of the tetrapods also helps to answer a big question raised by the tracks. If tetrapods were walking around 18 million years earlier than we thought, they and the elpistostgids must have large “ghost lineages” – periods when they must have existed but for which no fossils have been found. Actually, very few fossils have been found at Zachelmie Quarry at all. These sites, where tetrapods first marched onto land, may have been good at preserving footprints, but they haven’t been equally kind to bones.

But why do the fossils that have been found make it look a lot like the elpistostegids preceded the tetrapods? That’s more of a stumper, but Niedzwiedzki has a possible answer. He thinks that elpistostegids may have colonised new environments before their tetrapod peers (or at least those environments that would preserve their bones). It’s a nice hypothesis, but for the moment, it’s just that. There’s no clear answer, although the hunt for new fossils or tracks will hopefully provide one.

Clack is certainly excited by the new doors opened by this discovery. “People are now going to start looking in different places from where they traditionally looked,” she says. “The Polish trackways were only discovered by accident. Nobody had ever looked at these Devonian deposits in detail before. Now the same team are starting to look for body fossils and they’ve started to find some, but no tetrapods yet. I’m expecting stuff to come out from other parts of the world too, like China.”

And here, even the sceptics agree. “All scenarios are intruiging, but we simply do not know for sure,” says Shubin. “All the more excuse to continue to go out in the field and find skeletons!”


Reference: Niedzwiedzki. 2009. Tetrapod trackways from the early Middle Devonian period of Poland. Nature doi:10.1038/nature08623

All images: copyright of Nature

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Raptorex shows that T.rex body plan evolved at 100th the size

Meet Raptorex, the “king of thieves”. It’s a new species of dinosaur that looks, for all intents and purposes¸ like the mighty Tyrannosaurus rex, complete with large, powerful skull and tiny, comical forearms. But there’s one very important difference – it’s 100 times smaller. Unlike the ever-shrinking world of music players and phones, it seems that evolution crafted tyrannosaur technology with much smaller specifications before enlarging the design into the giant predators of the late Cretaceous.

Raptorex is a new species of meat-eating dinosaur, discovered in northwest China by Paul Sereno from the University of Chicago. The specimen is a young adult, but it wouldn’t have grown to more than 3 metres in length. It stood about as tall as a human, and wouldn’t have weighed much more. And yet Raptorex looked very much like a scaled-down version of its giant future relatives. All the features that made tyrannosaurs so recognisable and such efficient killers (except their enormous size) were present in this animal.

It really is a beautiful transitional fossil. As Sereno says, “Raptorex really is a pivotal moment in the history of the group where most of the biologically meaningful features of tyrannosaurs came into being, and the surprising thing is that they came into being in such a small animal.” Raptorex clearly shows that natural selection initially honed the distinct body shape of these giant predators at a 1/100th scale. This design was then scaled up with remarkably few modifications.

It had a skull that had clearly been developed into the animal’s primary weapon.  It was unusually big for its body size (40% of its torso length), it was structurally reinforced against the stresses of heavy bites, it had large places where powerful jaw-closing muscles attached and it was armed with sharp teeth.

Its limbs also had classic T.rex proportions – strong hind legs that that were fit for running, but miniscule forearms. In contrast, other early tyrannosaurids, such as Guanlong, Dilong, Eotyrannus and Stokesosaurus, looked very different with arms that were long and useful, and proportionally smaller heads (just 30% of its torso length). Only a few distinctive parts of their skeleton mark them out as early tyrannosaurids.

Raptorex brain was also large for its size. For comparison, the Jurassic predator Allosaurus had a brain that was just 60% bigger, despite having a body that was 10 times heavier! Raptorex‘s sense of smell was particularly well-developed, just as Tyrannosaurus‘s was. A scan of its skull showed a large area for its olfactory bulbs – the parts of its brain devoted to smell. These bulbs take up a full 20% of the brain’s total volume, a proportion that exceeds that of all meat-eating dinosaurs except the giant tyrannosaurs.

Despite what many newspapers will assuredly tell you, Raptorex isn’t the ancestor of Tyrannosaurus although it probably looked very much like what this hypothetical animal would have done. It’s more like an early cousin, but one that’s clearly more closely related to T.rex and its giant kin than any of the other smaller species so far discovered.

Based on his new fossil, Sereno tells a three-act story of tyrannosaur evolution. Act One was set in the Jurassic and early Cretaceous periods, with a cast that included Eotyrannus and Dilong.  Their snouts had become stronger and their jaws more powerful, but they were typical of other predators of the time. It was only during Act Two, around 125 million years ago, that this dynasty of predators started to become truly specialised, enhancing the skull, lengthening the legs, and shrinking the forearms.

All of these features were present in Raptorex, setting the stage of the final act in tyrannosaur evolution – getting really big. The lineage grew in bulk by around 100 times. By the end of the Cretaceous, the meat-eating scene in the northern continents was dominated by tyrannosaurids – predators such as Albertasaurus, Gorgosaurus, Daspletosaurus and Tarvosaurus, each weighing in at 2.5 tons or more.

It would be fascinating to see if the same story could be told for other lineages of predators, if the abelisaurids, carcharodontosaurids and spinosaurids all had their own mini-prototypes.

Reference: Science 10.1126/science.1177428

Images: Reconstruction by Todd Marshall; other images from Science/AAAS

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Darwinius changes everything

Darwinius-on-toastYesterday, the entire world changed noticeably as the media, accompanied by some scientists, unveiled a stunning fossilised primate. The creature has been named Darwinius masillae, but also goes by Ida, the Link, the Chosen One and She Who Will Save Us All.

The new fossil is remarkably complete and well-preserved, although the media glossed over these facts in favour of the creature’s ability to cure swine flu. Ida was hailed as a “missing link” in human evolution, beautifully illustrating our transition from leaping about in trees to rampant mass-media sensationalism.

Speaking to a group of international reporters, the scientists who discovered Ida described the animal in painstaking detail to the sound of Wagner’s Ride of the Valkyries played from 50-foot speakers. As a barrage of fireworks launched in the background, one journalist said, “The release of 30 doves just at the right moment really helped to drive home the unique paleoecological perspective that Ida provides.”

Evolutionary biologist Stephen Wilton added, “Ida has been waiting for us for 47 million years so I’m grateful that the publication of the paper wasn’t rushed and that the whole thing didn’t turn into some sort of media circus. You never know when that might happen.”

Businesses around the world are also hoping that demand for Ida merchandise will stimulate an ailing global economy out of recession. Retailer Bud Hornblower said, “We’re seeing a massive spike in demand for fainting couches as ordinary lay people fail to cope with the total change brought on by this small, weird-lookin’ monkey thing.”

Scientists and people who actually know a thing or two about evolution warned of hype and exaggeration but were forced to abandon their reason and critical analysis in the face of incontrovertible speculation that Ida could convert base metals into gold and has already led to the invention of flying cars.

“I didn’t believe it at first,” said Professor Adam Templesmith from the University of Slough. “When I read the press release about a fossil that would change everything, I naturally assumed that it was some sort of poorly conceived and overly exaggerated PR claim. But now that the total reversal of climate change is underway, I’m forced to reconsider my prejudices.”

Already the star of her own website, book and documentary, little Ida will soon have her own action figure, underwear range, three-album deal and seat in Parliament. “Ida’s brand is a hot as Obama’s right now,” said Don Chumleigh, market analyst. “I’m just sad that her fossilised hand isn’t doing that fist-bump thing.”

Recreated through CGI, Ida is also set to play a pivotal role in the climax of the new Harry Potter film, where she will be voiced by Keira Knightley and wield a powerful ‘Changus Totalus’ spell. Special effects will also be used to insert Ida into previous seasons of the Wire and past G8 summits.

Around the world, signs that everything has changed have already begun to appear. Jeanette Gould from Stoke-on-Trent was shocked to discover the outline of Darwinius emblazoned on her morning toast. “Well, it ruined breakfast,” said Ms Gould, failing to appreciate the detail of the creature’s stomach contents outlined in bread crumbs. “I couldn’t very well spread raspberry jam over the direct ancestor of my children, could I?”

For actual details about Ida, look no further than excellent takes from Brian Switek, PZ and Carl Zimmer. Brian in particular has serious reservations about the paper itself. I’m too weary to tackle it.

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Puijila, the walking seal – a beautiful transitional fossil


Blogging on Peer-Reviewed ResearchSeals and sea-lions gracefully careen through today’s oceans with the help of legs that have become wide, flat flippers. But it was not always this way. Seals evolved from carnivorous ancestors that walked on land with sturdy legs; only later did these evolve into the flippers that the family is known for. Now, a beautifully new fossil called Puijila illustrates just what such early steps in seal evolution looked like. With four legs and a long tail, it must have resembled a large otter but it was, in fact, a walking seal.

Natalia Rybczynski unearthed the new animal at Devon Island, Canada and worked out that it must have swam through the waters of the Arctic circle around 20-24 million years ago. She named it Puijila darwini after an Inuit word referring to a young seal, and some obscure biologist. The skeleton has been beautifully preserved, with over 65% of the animal intact, including its limbs and most of its skull.

Puijila is a massive boon for biologists trying to understand the evolution of pinnipeds, the group that includes seals, sea lions and walruses. It’s not itself a direct ancestor, having branched off the evolutionary path that led to modern pinnipeds. It did, however, retain many of the same features that a direct ancestor would have had. “Puijila is a transitional fossil,” Rybczynski explains. “It gives us a glimpse of what the earliest stages of pinniped evolution looked like, before pinnipeds had flippers. And it suggests that in the land-to-sea transition, pinnipeds went through a freshwater phase.”

This familiar group evolved from land-dwelling carnivores and their closest living relatives are the bears and the mustelids (otters, weasels, skunks and badgers). For other marine mammals like whales and dolphins, the fossil record has given us dramatic visuals for the gradual transformation from land-dweller to full-time swimmer. But for pinnipeds, that transition is much murkier because until now, the earliest known seal Enaliarctos already had a full set of true flippers. Puijila changes all of that.

In the Origin of the Species, the ever-prescient Darwin wrote, “A strictly terrestrial animal, by occasionally hunting for food in shallow water, then in streams or lakes, might at last be converted into an animal so thoroughly aquatic as to brave the open ocean”. This year, on the 150th anniversary of the book’s publication, the walking seal that bears his name pays a fitting tribute to Darwin’s insight.



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Fossil foetus shows that early whales gave birth on land

Blogging on Peer-Reviewed ResearchNine years ago, a team of fossil-hunters led by Philip Gingerich from the University of Michigan uncovered something amazing – the petrified remains of an ancient whale, but one unlike any that had been found before. Within the creature’s abdomen lay a collection of similar but much smaller bones. They were the fossilised remains of a foetal whale, perfectly preserved within the belly of its mother. Gingerich says, “This is the ‘Lucy‘ of whale evolution.”

The creatures are new to science and Gingerich have called them Maiacetus inuus. The genus name is an amalgamation of the Greek words “maia” meaning “mother” and “ketos” meaning “whale”, while Inuus, the Roman god of fertility, gave his name to the species.

The foetus’s teeth were the first to be uncovered and only as the surrounding (and much larger) bones were revealed, did Gingerich realise what his team had found – the first ever foetal skeleton of an ancestral ancient whale (see video). Alongside the mother and calf, the group also discovered another fossil of the same species in even better condition. Its larger size and bigger teeth identified it as a male.

This trio of skeletons is so complete and well-preserved that Gingerich likens them to the Rosetta Stone. They provide an unparalleled glimpse at the lifestyle of an ancient whale before the group had made the permanent transition to the seas. How it gave birth, where it lived, how it competed for mates – all these aspects of its life are revealed by these beautiful new finds.


Maiacetuswasn’t quite like the whales we know and love. It was an intermediate form between the group’s earliest ancestors and the fully marine versions that swim about today. For a start, still had sturdy hind legs that were good for swimming but would have allowed it to walk on land.

Another piece of evidence tells us that Maiacetus was definitely amphibious – its foetus was facing backwards in the womb. If the mother had lived long enough to give birth (and judging by the foetus’s size, that wasn’t far off), the infant would have greeted the world face-first. No living whale or dolphin does that – all of their young emerge backwards, leading with their tails, to minimise the risk of drowning in the event of a prolonged labour. A head-first delivery means that Maiacetus gave birth as a landlubber.


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Beipaiosaurus was covered in the simplest known feathers

Blogging on Peer-Reviewed ResearchBeipaiosaurus was among the strangest of dinosaurs. It looked like a fusion of body parts taken from several other species and united in the unlikeliest of proportions. It had a stocky body, long arms adorned with massive claws, a long neck topped by an incongruously small head, and a beaked mouth. Bizarre as this cocktail of features is, it’s the animal skin that has currently warrants attention.

Beipaosaurus.jpgFossils of Beipaiosaurus include impressions of its skin and these clearly show long, broad filaments clumped around its head, neck, rump and tail. They are feathers, but most unusual ones. Traces of feathers have been found on other dinosaurs (including the infamous Velociraptor) and they come in a variety of shapes and forms. But all are composite structures consisting of several slender filaments that either sprout from a single base or branch off a central stem.

Beipaiosaurus was also covered in some of these complex feathers, but it had other plumes that were far simpler. Each of these was a single, unbranched, hollow filament – exactly the sort of structure that palaeontologists had predicted as the first step in the evolution of feathers.

Until now, their existence was merely hypothetical – this is the first time that any have actually been found in a fossil. Other, more advanced stages in feather evolution have been described, so Beipaiosaurus provides the final piece in a series of structures that takes us from simple filaments to the more advanced feathers of other dinosaurs to the complex quills that keep modern birds aloft.


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Heroes in a half-shell show how turtles evolved

Blogging on Peer-Reviewed ResearchClad in hard, armoured shells, turtles have a unique body plan unlike that of any other animal. Their shells have clearly served them well and the basic structure has gone largely unchanged since the time of the dinosaurs. But this unchanging nature poses a problem for anyone trying to understand how they evolved and until now, fossil turtles haven’t provided any clues. All of them, just like their living descendants, have fully formed two-part shells.

Cowabunga.jpgBut three stunning new fossils are very different. They belong to the oldest turtle ever discovered, which lived about 220 million years ago in the area that would become China. Unlike today’s species, its mouth had a full complement of small, peg-like teeth but even more amazingly, it had a feature that distinguishes it from any other turtle, either living or extinct – it only had half a shell.

The ancient turtle was unearthed by Chun Li (no, not that one) from the Chinese Academy of Sciences, who called it Odontochelys semitestacea, a name that literally means “toothed turtle in a half-shell”. It was a small animal, just 35 cm from snout to tail, and its shell consisted of just a plastron (the bottom half) and not a carapace (the top half).

Li’s team believes that this incomplete shell represents an intermediate step along the evolutionary path to the modern version. To them, Odontochelys‘s anatomy settles debates about how the group’s distinctive shell evolved, which animals they were most closely related to and what sort of lifestyles the earliest members had. It’s a true hero in a half-shell.


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Microraptor – the dinosaur that flew like a biplane

Many of us believe dinosaurs to be extinct but in truth, they surround us every day. All the world’s birds, from the pigeons of our cities to the gulls of our seasides, are descended from dinosaurs, and modern science now classifies the birds with their long-dead kin. The gulf between dinosaurs and modern birds may seem huge, but the discovery of several feathered dinosaurs are seriously blurring the line between the two. And now, new research on the feathered dinosaur Microraptor reveals that birds may have evolved from dinosaur ancestors that flew not on two wings, but on four.

The link between dinosaur and bird was cemented in the last two decades, when palaeontologists unearthed hundreds of beautifully preserved fossils in the Liaoning province of China. Many of the newcomers were small predators, belonging to the same group as the famous Velociraptor (and indeed, most scientists believe that this Hollywood star was also covered in primitive feathers).

The new species run the full evolutionary gamut from flightless dinosaurs to flying birds. They range from Sinosauropteryx with its primitive, downy, proto-feathers to Caudipteryx, a dinosaur with proper flight-capable feathers, to Confuciusornis, a true bird. Together, these species provide a tantalising snapshot of how small prehistoric predators transformed into the familiar fliers of today’s skies.

One of these species, Microraptor, stood out among the rest, for it had winged legs as well as arms. The animal’s metatarsal bones were covered in long, asymmetric flight feathers. Their shape is clearly designed to produce lift during flight, but how Microraptor used its four wings has puzzled scientists. The species’ discoverers believed that by splaying its legs out sideways from its body, it held its wings in tandem like a dragonfly. But for Sankar Chatterjee and R. Jack Templin of Texas Tech University, the facts didn’t add up.



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Early flatfish has eye that’s moved halfway across its head

Blogging on Peer-Reviewed ResearchImagine watching a movie where every now and then, key frames have been cut out. The film seems stilted and disjointed and you have to rely on logic to fill in the gaps in the plots. Evolutionary biologists face a similar obstacle when trying to piece together how living species arose from their common ancestors. It’s like watching a film with a minimum of footage; the species alive today are just a few frames at the very end, and the fossil record represents a smattering of moments throughout the film’s length.

Heteronectes_head.jpgBut the gaps, while plentiful, are being slowly filled in. With amazing regularity, new fossils are being unearthed that bridge the gap between existing specimens. These “transitional fossils” are always greeted with great relish for their intermediate nature provides yet more examples of gradual evolution from one form to another. They act as handy visual aids for explaining the story of evolution to those with a dearth of imagination.

Now, Matt Friedman from the University of Chicago has described a new transitional fossil that is one of the most dramatic yet. Its name is Heteronectes (meaning “different swimmer”) and it’s a flatfish, but not as you know it.

You’ve probably eaten flatfish before but tasty fillets of plaice, sole or halibut give few hints about their extraordinary physical specialisations. They are fish that live on their sides and their flat profiles make them both efficient hunters and difficult prey. For other fish, lying sideways would give one eye a useless view of sand but flatfish have adapted accordingly. Their fry resemble those of other fish but as they grow, one of their eyes makes an amazing journey to the other side of its head. The adults look like they’ve swum out of a Picasso painting.

But Heteronectes is a half-committed flatfish. Like modern representatives, its skull is asymmetrical and one eye has begun migrating to the other side of its head. But it hasn’t made it all the way round and stops near the midline without crossing to the other side. No living flatfish has eyes arranged in such a way. We couldn’t have wished for a better intermediate form – it’s a marvellous half-way form between the standard fish body plan and the distorted visages of flounders and soles.