Tag: fossil

A fossil penguin gets its colours

By Ed Yong | September 30, 2010 2:00 pm


All Almost all modern penguins wear a suit of black feathers, but prehistoric members of the group didn’t go for the dinner jacket look. A newly discovered penguin, known as Inkayacu, was dressed in grey and reddish-brown hues.

Inkayacu paracasensis is named after the Quechua words for “water king” and the Paracas National Park where it was discovered by Julia Clarke from the University of Texas. Clarke’s team are no strangers to giant fossil penguins. In 2007, they unveiled two extinct species: Perudyptes, about the size of the modern king penguin; and Icadyptes, which was larger than any living species and had an unusually long, spear-like beak. Like Icadyptes, Inkayacu also swam off the coast of ancient Peru, had a long beak, and was one of the largest penguins in history. It weighed around twice as much as the heaviest of today’s penguins – the emperor.

In many ways, Inkayacu is no more significant a find that Icadyptes was three years ago. It is neither the oldest nor the largest penguin fossil, it doesn’t hail from a new part of the world, and it provides few clues about the group’s evolution. However, it does have one stand-out feature that probably secured its unveiling in the pages of Science – its feathers.

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CATEGORIZED UNDER: Animals, Birds, Palaeontology

Pocket science – swordfish and flatfish are close kin, and ancient death-grip scars

By Ed Yong | August 17, 2010 7:00 pm

Marlin_turbot

Flatfish are the closest living relatives to swordfish and marlins

At first glance, a swordfish and a flounder couldn’t seem more different. One is a fast, streamlined hunter with a pointy nose, and the other is an oddly shaped bottom-dweller with one distorted eye on the opposite side of its face. Their bodies are worlds apart, but their genes tell a different story.

Alex Little from Queen’s University, Canada, has found that billfishes, like swordfish and marlin, are some of the closest living relatives to the flatfishes, like plaice, sole, flounder and halibut. This result was completely unexpected; Little was originally trying to clarify the relationship between billfishes and their supposed closest relatives – the tunas. That connection seems to make more sense. Both tunas and billfishes are among a handful of fish that are partially warm-blooded. They can heat specific body parts, such as eyes and swimming muscles, to continuously swim after their prey at extremely fast speeds with keen eyesight.

But it turns out that these similarities are superficial. Little sequenced DNA from three species of billfishes and three tunas, focusing on three parts of their main genome and nine parts of their mitochondrial one (a small accessory genome that all animal cells have). By comparing these sequences to those of other fish, Little found that the billfishes’ closest kin are the flatfish and jacks. Indeed, if you look past the most distinctive features like the long bills and bizarre eyes, the skeletons of these groups share features that tunas lack. Indeed, billfish and tuna proved to be only distant relatives. Their ability to heat themselves must have evolved independently and indeed, their bodies product and retain heat in quite different ways.

Little’s work is testament to the power of natural selection. Even closely related species, like marlins are flounders, can end up looking vastly different if they adapt to diverse lifestyles. And distantly related species like tuna and swordfish can end up looking incredibly similar because they’ve adapted to similar challenges – pursuing fast-swimming prey. This shouldn’t come as a surprise – a few months ago, a French team found that prehistoric predatory sea reptiles were probably also warm-blooded.

Reference: Molecular Phylogenetics and Evolution: http://dx.doi.org/10.1016/j.ympev.2010.04.022; images by Luc Viatour and NAOA

Ant_scars

Ancient death-grip scars caused by fungus-controlled ants

Forty-eight million years ago, some ants marched up to a leaf and gripped it tight in their jaws. It would be the last thing they would ever do. Their bodies had already been corrupted by a fungus that, over the next few days, fatally erupted from their heads. The fungus produced a long stalk tipped with spores, which eventually blew away, presumably to infect more ants. In time, all that was left of this grisly scene were the scars left by the ants’ death-grip. Today, David Hughes from Harvard University has found such scars in a fossilised leaf from Germany.

Today, hundreds of species of Cordyceps fungi infect a wide variety of insects, including ants. Like many parasites, they can manipulate the way their hosts behave. One species, Cordyceps unilateralis, changes the brains of its ant hosts so that they find and bite into leaves, some 25cm above the forest floor. The temperature and humidity in this zone are just right for the fungus to develop its spore capsules. In its dying act, the ant leaves a distinctive bite mark that’s always on one of the leaf’s veins on its underside. And that’s exactly what Hughes saw in his fossil leaf.

Hughes originally thought that the marks were made by an insect cutting the veins of the leaf to drain away any potential poisons, something that modern insects also do. But these marks look very different – those on the fossil leaf bear a much closer resemblance to those of Cordyceps-infected ants. This is the first fossil trace of a parasite manipulating its host, but it’s not the oldest evidence for such a relationship. In 2008, another American group found a 105-million-year-old piece of amber containing a scale insect, with two Cordyceps stalks sticking out of its head. The war between insects and their Cordyceps nemeses is an ancient one indeed.

Reference: Biology Letters http://dx.doi.org/10.1098/rsbl.2010.0521
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DNA from the largest bird ever sequenced from fossil eggshells

By Ed Yong | March 9, 2010 7:00 pm

Even extinction and the passing of millennia are no barriers to clever geneticists. In the past few years, scientists have managed to sequence the complete genome of a prehistoric human and produced “first drafts” of the mammoth and Neanderthal genomes. More controversially, some groups have even recovered DNA from dinosaurs. Now, a variety of extinct birds join the ancient DNA club including the largest that ever lived – Aepyornis, the elephant bird. 

In a first for palaeontology, Charlotte Oskam from Murdoch University, Perth, extracted DNA from 18 fossil eggshells, either directly excavated or taken from museum collections. Some came from long-deceased members of living species including the emu, an owl and a duck. Others belonged to extinct species including Madagascar’s 3-metre tall elephant bird and the giants moas of New Zealand. A few of these specimens are just a few centuries old, but the oldest came from an emu that lived 19,000 years ago.

It turns out that bird eggshells are an excellent source of ancient DNA. They’re made of a protein matrix that is loaded with DNA and surrounded by crystals of calcium carbonate. The structure shelters the DNA and acts as a barrier to oxygen and water, two of the major contributors to DNA damage. Eggshells also stop microbes from growing and it seems that ancient ones still do the same. Oskam found that the fossil shells had around 125 times less bacterial DNA than bones of the same species did.

This is important – bacteria are a major problem for attempts to extract ancient DNA and they force scientists to search for uncontaminated sources, like frozen hair. Eggshells, it seems, provide similarly bacteria-free samples. Still, Oskam’s team took every precaution to prevent contamination. They used clean rooms and many control samples. Many of their sequences, like those of Aepyornis, were checked by two independent laboratories.

The Aepyornis sequences are particularly encouraging because many scientists have previously tried to extract DNA from the bones of this giant and failed. Eggshells seem like a more promising source and it certainly helps that the eggs of many of these giant species were massive and thick. But Oskam did also recover DNA from a fossil duck egg, which suggests that it should be possible to sequence the genes of even small extinct birds, like the dodo.

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Fossil tracks show a pterosaur coming in for a landing

By Ed Yong | August 18, 2009 6:43 pm

Blogging on Peer-Reviewed ResearchSeveral million years ago, at a time when dinosaurs walked the earth, a flying reptile – a pterosaur – came in for a landing. As it approached, it used its powerful wings to slow itself down and hit the ground feet first. It took a short hopping step before landing a second time. On solid ground, it leant forward, put its arms down and walked away on all fours.

The landing made quite an impression on the underlying limestone mud and in the following millennia, the creature’s tracks became fossilised. Now, they have been unearthed by Jean-Michel Mazin from the University of Lyon at a site near Crayssac in southwestern France.

The area is home to at least 30 sets of pterosaur tracks, which have earned it the nickname of Pterosaur Beach.  Some of these tracks have confirmed that some pterosaurs walked on four legs while land-bound, in the manner of many modern bats. But one bizarre set stood out to Mazin – they simply didn’t fit the typical walking gait of the French pterosaurs. The most plausible explanation is that they preserved a landing, and they’re the first set of fossils that have done so.

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Titanoboa – thirteen metres, one tonne, largest snake ever.

By Ed Yong | February 4, 2009 10:40 am

Blogging on Peer-Reviewed Research This is sure to be one of the most amazing scientific images of the year. You’re looking at vertebrae from two species of snake. The smaller model on the left belongs to the anaconda, a giant serpent that can grow to 7 metres in length and weigh as much as 45kg. It’s arguably the largest snake alive, so just think about how big the owner of the fossilised vertebra on the right would have been! There’s a good reason why this new discovery – the largest snake that ever slithered – has been named Titanoboa.

Titanoboa cerrejonesis is new to science and was discovered by a team of North American scientists led by Jason Head at the University of Toronto. It’s the latest fossil to emerge from Colombia’s Cerrejon coal mine, one of the world’s largest open-pit mines and an unexpected bonanza of prehistoric reptile fossils.

The giant serpent is closely related to today’s boas and anacondas, snakes that kill their prey with suffocating coils. Living boas come in various sizes, but their similar proportions gave Head the data he needed to work out how big Titanoboa actually was. The backbones of boas are similar enough that, with help from a computer, you can tell where any individual vertebra sits down the length of the snake by looking at its shape. And you can take an accurate stab at the length of the entire snake based on the size of each vertebra – all members have the same number of segments, and their size is proportional to the animal’s length.

Titanoboa‘s fossilised vertebra showed that it was a whopping 13 metres (42 feet) long. By comparison, the largest verifiable record for a living snake belongs to a 10-metre-long reticulated python, and that was probably a striking exception.  Large population surveys of reticulated pythons have failed to find individuals longer than 6 metres. By contrast, Head’s team analysed vertebrae from eight different specimens of Titanoboa and found that all of them were roughly the same size. A length of 13 metres was fairly ordinary for this extraordinary serpent. Not quite Jormungandr, but amazing nonetheless.

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CATEGORIZED UNDER: Animals, Palaeontology, Reptiles, Snakes
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