A 555-million-year-old worm had a predilection for turning right, possibly indicating the oldest known example of handedness.

Although these worms lacked limbs and so couldn’t be considered left- or right-handed in the way that we understand, the development of a tendency to favour one side over another is evidence of an advanced nervous system.

It remains a feature of free-living mobile life today, but until this discovery, it wasn’t thought to have emerged until the Cambrian Period, which began around 541 million years ago.

at the American Museum of Natural History in New York and his colleagues analysed 100 fossil specimens of a small flatworm-like creature, Spriggina floundersi, collected in South Australia over recent decades.

These animals lived during the Ediacaran Period, when multicellular life first became widespread. It preceded the Cambrian explosion, when animal life diversified dramatically and many groups of animals first appeared.

Spriggina lived in what was, half a billion years ago, a shallow ocean and is thought to have foraged on or close to the seafloor, moving by wriggling to the left or right.

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“We have around 50 specimens of Spriggina that are clearly bent,” says Evans. Twice as many of the fossilised worms are bent to the left than to the right, he says. This means the creature itself bent to the right, as the specimens are mirror-image impressions of the animals, made when storms buried them in sand.

“This appears to be statistically significant and matches what biologists find when they study handedness in different animals today,” says Evans. “Some specimens have multiple bends to both the right and left, suggesting that they all could bend both ways, which makes sense if you don’t want to be stuck moving in a circle.”

While the majority seem to demonstrate right-handedness, it is hard to tell if any were left-handed, he says. “I imagine it’s like taking a picture of 100 people waving with one hand today. You would likely be able to count that more people are waving with their right hand, but you wouldn’t be able to tell who is right- or left-handed.”

Discoveries like this demonstrate that many foundational characteristics that are common to a variety of animals today, such as the ability to move around, bilateral symmetry and handedness, evolved in the Ediacaran, says Evans.

In the Cambrian, organisms built on that foundation to become more complex, for example adding legs to move more efficiently, becoming “less alien and more like the major groups of animals we know today”, says Evans. “This is cool because it suggests that, while the Cambrian was an amazing time in animal evolution, those organisms didn’t just come out of nowhere: they built on the foundations established in the Ediacaran.”

“The presence of handedness in any kind of functional asymmetry, really deep into the fossil record, gives us important and interesting information about how these behaviours have evolved and how deeply in time they emerged,” says at Flinders University in Adelaide, Australia.

A set of exquisitely preserved 300-million-year-old fossils suggests that early four-limbed vertebrates did not undergo a metamorphosis between their juvenile and adult stages, challenging conventional ideas about the evolution of life on land.

“We have for a very long time assumed that these animals were broadly amphibian-like, and that this life cycle would have bridged the gap between life in the water and life on land,” says at the Field Museum of Natural History in Chicago.

Today’s reptiles, birds, mammals and amphibians belong to a group called tetrapods, which evolved from lobe-finned fish around 390 million years ago. But almost nothing was known about the early developmental stages of these ancestral lobe-finned fish, says at Flinders University in Adelaide, Australia.

Pardo and his colleague , also at the Field Museum, examined a collection of fossils that were unearthed between the 1960s and 1990s at the Mazon Creek fossil site, south-west of Chicago. The preserved animals lived 307 million to 309 million years ago, during the Carboniferous Period.

Embolomeres, which had a body around 2 metres long in adulthood, were the largest tetrapods in the Carboniferous and one of the top predators. They spent most of their time in water, but had small legs with which they could have clambered onto the land.

The fossils included two 2-centimetre-long baby embolomeres, which were so well preserved that the scientists could see soft tissues and even egg yolk.

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In tadpoles, the yolk sac remains inside the body for a few days after hatching as a store of energy. But the young embolomeres had a yolk sac outside the body, similar to the case for some young fish such as lungfish.

Amphibian larvae, such as tadpoles, have external gills that enable them to breathe underwater, but the young embolomeres did not. “The absence of external gills across early development in these animals is the smoking gun,” says Pardo.

The skull and skeleton have “all the important parts seen in an adult embolomere”, says Pardo. The fossils show that embolomeres remained more or less the same from the time they hatched from their eggs until they reached adulthood.

“Human bodies basically work the same way from birth through adulthood, but we get bigger and our proportions change, but we don’t undergo the sort of fast, rapid change you see in a frog or salamander,” says Pardo. “Our fossils show that this sort of life cycle was the norm for our earliest terrestrial ancestors, too.”

Although embolomeres were aquatic, Pardo argues that the evidence available suggests our earliest terrestrial ancestors did not have a tadpole-like stage either. The team also studied the fossil remains of two other early tetrapod species that were alive at the same time and in the same place as the embolomeres.

“None of these show any evidence of a tadpole-like stage,” says Pardo. “Neither do other fishy tetrapod relatives such as early lungfishes and coelacanths. So is it impossible that a tadpole stage showed up somewhere and was subsequently lost? Maybe, but it seems vanishingly unlikely with the data we have.”

This study fills in a much-needed knowledge gap, says Long. “It shows how early tetrapod-like fishes living about 308 million years ago did not need to develop a tadpole phase in order to invade land, as was previously thought by some scientists.”

Fossil hunting in the Australian outback

Join this extraordinary adventure through the heart of Australia’s fossil frontier. Once a shallow inland sea millions of years ago, eastern Australia is now a hotspot for fossils. Over 13 unforgettable days, you’ll travel deep into the outback, tracing the footsteps of prehistoric giants and uncovering the secrets of Earth’s ancient history.

Read more

The asteroid strike that wiped out the dinosaurs hit with such force that it took at least 8 million years for the impact site to cool down, creating a warm underground ecosystem where microscopic life thrived.

The Chicxulub asteroid, which collided with Earth 66 million years ago at what is now Mexico, is thought to have been as large as 15 kilometres in diameter. The strike caused so much climate chaos that it wiped out three-quarters of species on Earth. All the dinosaurs except the ancestors of birds became extinct and a nuclear winter gripped the planet for at least 15 years.

Its effects were also felt deep underground. “The Chicxulub impact was big enough to cause deformation at least 35 kilometres under the surface of the Earth, detectable using geophysical surveys,” says at the University of Glasgow, UK.

The impact melted about 10,000 cubic kilometres of rock, she says. The combination of melted rock and seawater created porous material filled with tiny pockets of hot water, known as a hydrothermal system.

Because of the presence of minerals that only form where there is liquid water and heat, we know that the asteroid would have created hydrothermal environments to depths of several kilometres. But the scale and lifespan of the heating and resulting hydrothermal system has, it seems, been massively underestimated.

Previously, it was thought it took only 2 million years for the impact site to cool down. Now, Pickersgill and her colleagues say it may have taken at least four times longer, giving hydrothermal life much more time to thrive.

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“One of the biggest unknowns about all impact-generated hydrothermal systems, and Chicxulub in particular, is how long the heat keeps water circulating through the structure,” says Pickersgill.

To figure this out, the team drilled 1 kilometre into the crater to obtain rock cores. Because potassium in the rocks has decayed into argon gas over time, the researchers could measure the amount of argon trapped in the samples to find out their age.

“We got a range of ages from the time of impact at 66 million years ago to about 58 million years ago,” says Pickersgill. “That told us that hydrothermal activity was ongoing in at least part of the Chicxulub structure for 8 million years after the impact.”

Sulphur isotopes in the cores provide evidence that microbial life existed in the hydrothermal system and recovered rapidly after the impact.

The results mean that the very earliest impact craters on the young Earth – and perhaps other worlds – may also have had habitable hydrothermal systems for longer than previously known.

“This provides more opportunity for life to develop, evolve and spread,” says Pickersgill. “It supports the concept that early life on Earth may have found a long-term home in impact craters, and possibly even life on other planets where these massive impact craters are dominant surface features.”

at Curtin University in Perth, Australia, says while there is “not an entirely unambiguous record of continuous hydrothermal activity” at Chicxulub, the evidence is strong that the impact site stayed hot for millions of years.

“Large impacts do not simply destroy environments,” he says. “They can also create long-lived underground systems where hot fluids circulate through shattered rock. These chemically rich settings may provide sheltered habitats for microbes and perhaps even favourable conditions for some of the early chemical steps towards life.”

Australia was once home to a second species of koala that lived only in the west of the continent, where it became extinct around 30,000 years ago.

Today, there is only one koala species: Phascolarctos cinereus. It is found almost exclusively in eucalyptus forests in eastern Australia and is threatened by habitat loss, disease, collisions with cars and predation by introduced species.

Numerous koala fossils, aged between 137,000 and 31,000 years old, have been collected in Western Australian caves over the past century. Until now, however, there wasn’t enough material to conclude that the remains were from a different species.

In the past 25 years, more fossils have become available to researchers, including skulls donated by the family of late speleologist Lindsay Hatcher, who discovered numerous ancient remains during his expeditions in caves in the south-west of Western Australia.

“Amongst the donation was a koala skull in very good condition,” says at the Western Australian Museum. “Upon examination of that skull, we noticed differences with modern koalas that got us to start working on the fossil material in the collection.”

To the untrained eye, the new species, named Phascolarctos sulcomaxilliaris, would have been difficult to distinguish from P. cinereus, but there are subtle differences.

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“In short, the Western Australian koalas were same-same but different,” says Travouillon. “They had shorter heads, for sure, and they seem to have less-well-developed chewing muscles than the east-coast koalas. But they simply chewed in a different way by having larger teeth and having a more efficient, shorter jaw to break down the leaves.”

A large groove on the cheek of P. sulcomaxilliaris suggests the animal had a larger muscle attached there that was used to either move a larger lip, with which it perhaps grabbed leaves, or inflate its nostrils to be able to smell leaves over a greater distance. Its skeleton was also less agile, suggesting it spent less time moving between trees.

When the climate dried and Western Australia’s forests disappeared about 30,000 years ago, P. sulcomaxilliaris vanished, along with many other animals that once shared its habitat. “There would have been [Tasmanian] devils, thylacines, giant echidnas, short-faced kangaroos and the giant marsupial Zygomaturus,” says Travouillon.

“Our first peoples in Western Australia would have lived amongst them and they would have been witness to their extinction.”

at the Australian Museum in Sydney says the study makes a “convincing case for the distinctiveness of the Western Australia koalas as a unique species”. “I look forward to seeing if any DNA can be extracted from the fossils,” he says.

Fossil hunting in the Australian outback

Join this extraordinary adventure through the heart of Australia’s fossil frontier. Once a shallow inland sea millions of years ago, eastern Australia is now a hotspot for fossils. Over 13 unforgettable days, you’ll travel deep into the outback, tracing the footsteps of prehistoric giants and uncovering the secrets of Earth’s ancient history.

Read more

Birds today have dinosaur DNA. They have dinosaur blood in their veins. Birds evolved directly from Velociraptor-type animals and are the only true dinosaurs that still exist. Steve Brusatte is a palaeontologist at the University of Edinburgh, UK, and has been studying 150 million years’ worth of bird evolution, from surviving the asteroid that wiped out their contemporaries to today’s adaptation into almost every niche. Brusatte introduces elephant birds, terror birds, demon ducks and penguins the size of gorillas, and why “when gulls dive bomb you and try to steal your pasty or your chips”, says Brusatte, “you really can sense in the nastiness, the cunning, the agility, the feistiness. You can sense that inner Velociraptor.”

Read more: The evolving science of dinosaurs

While dinosaurs ruled the land, Cretaceous oceans were home to a fierce and enormous octopus species that may have reached up to 19 metres in length, rivalling the size of the largest predators of the time, including sharks and marine reptiles like plesiosaurs and mosasaurs.

These octopuses were active predators, says at Hokkaido University in Japan.

“They could be thought of as the orcas or great white sharks of the invertebrate world – large, intelligent and highly effective apex predators,” says Iba. “These were animals over 10 metres long, with long arms, powerful jaws capable of crushing hard structures and probably advanced behaviour.”

Iba and his colleagues looked at 27 large, fossilised octopus jaws dating to between 100 million and 72 million years that had been collected in Japan and Vancouver Island, Canada.

A dozen of the octopus jaws were new to science and were locked inside rocks, says Iba. They became visible only when the researchers used high-tech scanning equipment and “digital fossil mining” combined with artificial intelligence to fully image the octopus remains hidden in the stone.

The octopus jaw, also called the beak, is often the only part of the animal to survive as a fossil because it is made primarily of durable chitin, while the rest of the animal is soft-bodied.

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Previously, it was thought that there were five species of octopus living in the Cretaceous Period, but the team found that, in fact, there were just two so far confirmed – Nanaimoteuthis jeletzkyi and N. haggarti.

“We realised early on that the jaws were unusually large,” says Iba. “In particular, the jaws of N. haggarti stood out even when compared with large modern cephalopods.”

However, he says, the full scale became clear only after the team estimated N. haggarti’s body size using the relationship between jaw size and the length of the mantle – the head-like structure above the arms – of modern, long-bodied finned octopuses. “That analysis showed that N. haggarti may have reached about 6.6 to 18.6 meters in total length,” says Iba. “Nanaimoteuthis haggarti may have been among the largest invertebrates in Earth’s history.”

at Flinders University, Australia, says he isn’t surprised by the findings, “as many creatures at this time went through gigantism – sharks, marine reptiles, ammonites – so the oceans were full of food for large predators”. But he says it is still a “gob-smacking” discovery. “Giant freaking killer octopi as apex predators were ruling the Cretaceous seas.”

Superficially, the ancient octopuses resembled today’s giant squid (Architeuthis dux), which reach lengths of over 12 metres. Like the giant squid, the ancient octopuses were open-water swimmers. But Iba says they were very different animals.

Squids typically have eight arms plus two long tentacles for prey capture, he says, while octopuses have eight arms and rely heavily on them all to capture prey.

“Nanaimoteuthis likely used long, flexible arms to seize prey and then processed it with powerful jaws, rather than chasing prey in the same way as a squid,” he says.

The team also analysed the scarring and wear on the ancient jaws, suggesting that it provides evidence of extensive “processing of hard materials”, says Iba, most likely animals with hard structures, such as large bivalves, ammonites, crustaceans, fish and other cephalopods.

“It is tempting to imagine them attacking very large animals, but we must be cautious,” he says. “We do not have direct evidence, such as stomach contents or bite marks on vertebrate bones, showing that they preyed on marine reptiles or sharks.”

Another interesting find that the team has noted is that there is uneven wear of the jaws, possibly indicating “lateralisation”, which means favouring one side of the body over the other, behaviour that can imply intelligence – a trait for which modern octopuses are renowned.

In general, lateralisation is associated with increased brain complexity and more efficient information processing.

“In our fossils, asymmetric jaw wear suggests that these animals may have favoured one side during feeding,” says Iba. “This implies that they were not only physically powerful, but also behaviourally complex, with potentially individual behavioural tendencies.”