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.

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.

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Were the mysterious dinosaurs known as spinosaurs excellent swimmers that could dive to catch prey? Or were they “hell herons” that plucked huge fish from shallow waters? Fossils of a new spinosaur species that lived around 1000 kilometres inland should settle the debate, say its discoverers, confirming that it was a wader. “Coup de grâce, as far as I’m concerned,” says at the University of Chicago.

The lifestyle of spinosaurs has been a contentious topic among palaeontologists, due to the animal having a strange combination of features, including a large sail, huge claws, broad feet and crocodile-like jaws. In 2025, the BBC series Walking With Dinosaurs depicted them as aquatic hunters.

In 2019, a local guide took Sereno’s team to a remote desert site in Niger, where they found fragments of jawbones that they later realised belonged to some kind of spinosaur. Because of the covid-19 pandemic and the remote location of the site, it was years before they could return.

On their second trip, Sereno and his colleagues found bones from around 10 individual spinosaurs. Within hours of the first finds, the team realised these spinosaurs had a large crest on top of their skulls, in addition to the characteristic sail along their backs.

“It was a glorious moment because we knew that this was a new spinosaur, something that would have a major impact on how we understand this animal,” says Sereno.

The new species, dubbed Spinosaurus mirabilis, lived around 95 million years ago and grew to about 10 to 14 metres in length, the team estimates – nearly as large as the most famous spinosaur, Spinosaurus aegyptiacus. “I wouldn’t want to be near this animal, because it would finish off a human in about 3 seconds,” says Sereno.

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S. aegyptiacus also had a crest, but that of the new species is much larger – the bony part of the skull crest would have been at least 40 centimetres high on large individuals. Based on comparisons with modern birds with crests, such as the helmeted guineafowl, the team thinks the bone would probably have been covered by a keratinous sheath, making the crest at least 50 centimetres high.

The crest is too delicate to be a weapon of any kind. “Probably it was brightly coloured,” says Sereno. “It is meant to say, ‘I am here; I am healthy.'”

It is thought that the large sails of spinosaurs were also for visual display, he says. “So, these animals are really into display, and the question is, why?”

The answer could be that spinosaurs hunted along rivers where they needed to defend territories. “The prevalence of visual cues in environments like beaches or riversides tends to be exaggerated because it’s there that you can look a mile, obstruction-free, and see your competitor, or your mate, much more easily than [in] a typical land environment,” says Sereno.

Modern waders, such as the great blue heron, are also extremely display-oriented, Sereno says, and other characteristics of spinosaurs also fit the wading hypothesis. When his team plotted a range of animals on a graph based on the relative length of the jaw, neck and hind limbs, spinosaurs came out next to waders like herons.

“It can’t swim well because it’s got this huge sail that makes it very unstable in water. But it can go into 10 feet [3 metres] of water as a full adult,” says Sereno.

Then there’s the fact that it lived far inland, whereas most other spinosaurs have been found nearer to where seas were. No marine predator weighing over a tonne has ever moved into freshwater, says Sereno. There are river porpoises and dolphins, but no river orcas. “And so, I think it’s all playing to the same story, that these animals are mega-heron-type animals.”

“The paper really confirms a lot of the consensus that has been building for these animals,” says at Queen Mary University of London. “They are not super swimmers or deep divers, but much more like a heron or stork, wading into water to catch prey, predominantly fish.”

“I think it’s fairly convincing that this is a new species. If it was just the crest, this could well be variation, but there are differences in the jaws and teeth too,” says Hone.

“At face value, the fact that the legs weren’t particularly short or undermuscled suggests that it was no less able to walk and wade than any other predatory dinosaur,” says at the University of Portsmouth, UK. “This doesn’t bode well for proposals of swimming lifestyles, which are already floundering with issues concerning the stability and propulsion of a swimming Spinosaurus.”

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