At this time of the year, sea surface temperatures above 86 F are common in the western Pacific warm pool, a mass of water located northeast of Australia. But the Niño 3.4 region is nowhere near the warm pool and usually has much cooler temperatures. This latest data indicates "an exceptionally warm state for this part of the tropical Pacific," said Jin-Yi Yu, a professor of Earth system science at the University of California, Irvine.

"If the reported daily El Niño 3.4 temperature above 30°C is verified in the observational dataset, it would be an extraordinary record," Yu told Live Science in an email.

Other experts agreed. A Niño 3.4 sea surface temperature above 86 F is a "very significant" new record, Timothy Osborn, a professor of climate science and the director of the Climatic Research Unit at the University of East Anglia in the U.K., told Live Science in an email. Mat Collins, a professor of climate systems and the head of mathematics and statistics at the University of Exeter in the U.K., also called the temperature "very significant" in an email to Live Science.

But it's important to note that absolute temperature is not the standard way of measuring the strength of El Niño, Osborn said. Researchers usually assess El Niño intensity by comparing sea surface temperatures in the Niño 3.4 region with the average conditions there or with sea surface temperatures across the rest of the tropics, with the latter method removing a skew in the data caused by the climate-change-induced heating of oceans globally.

"On those measures, the current event is already close to being the strongest [El Niño] on record and will likely soon exceed previous records given that the event is forecast to strengthen further," Osborn said. "For some measures, it is already record-breaking for the time of year."

"Super" El Niño

El Niño events happen when warm water in the western tropical Pacific Ocean migrates eastward along the equator, toward South America. This boosts global temperatures, triggering heavy rainfall and floods in regions like East Africa, southern China, the southern U.S. and the Pacific coast of equatorial South America, while places such as Indonesia, the Philippines, southern Africa and northern South America experience drought.

"El Nino impacts are greatest across the tropics and in the lands around the Pacific Ocean," Osborn said. "An El Nino with record strength is very significant because it greatly disrupts the atmospheric circulation which controls the weather patterns including patterns of rainfall."

As of Oct. 6, the temperature anomaly in the Niño 3.4 region is 6 F (3.34 C) above average and rising. A typical El Niño increases Niño 3.4 temperatures by a maximum of 1.8 to 3.6 F (1 to 2 C) above average, so the current condition is "exceptionally large," Yu said. "This indicates that a very strong, or what is sometimes called a 'super,' El Niño is developing."

This year's El Niño is being amplified by human-driven global warming, which has increased background ocean temperatures. As a result, it's likely that sea surface temperatures in the Niño 3.4 region will keep rising over the coming weeks and peak in November or December, before declining again in 2027, Collins said.

"The Niño 3.4 anomaly is very likely to remain extremely large and may increase further," Yu said, echoing forecasters' suggestions that it could reach 7.2 F (4 C) by November.

A new kind of El Niño?

The world is on the brink of crossing a critical warming threshold, raising the question of whether the current conditions can be considered a new normal for future El Niños.

While it's likely that future El Niños will be more extreme than past ones, on average, not every El Niño will be record-breaking and as dramatic as the one unfolding now, because these events tend to be very variable, Collins said.

As climate change intensifies, the big worry is that certain regions will be primed for extreme conditions even before an El Niño strikes, Osborn said. For example, regions that are getting drier due to global warming could see catastrophic droughts if they overlap with areas that experience dryness during El Niño events. Likewise, places that are getting wetter could see worse deluges of rain and flooding if they coincide with areas with higher precipitation during El Niños. But that doesn't necessarily mean extreme El Niños are the new normal, he said.

Instead, the location and duration of El Niño events may be transforming, Yu suggested. "In research by my group and collaborators, we have documented changes not only in El Niño intensity, but also in where the warming occurs and how long events persist," he said.

Yu and his colleagues helped to introduce the idea that we are seeing the emergence of two distinct types of El Niño: the eastern Pacific El Niño and the central Pacific El Niño. "Many El Niño events in the earlier observational record were dominated by warming in the eastern tropical Pacific, whereas Central Pacific El Niño events became much more prominent in recent decades," he explained, adding that El Niños have also been lasting longer.

Global warming may be creating a new kind of El Niño by strengthening atmosphere-ocean interactions in the subtropical Pacific, Yu said. If these interactions combine with processes in the equatorial Pacific, where eastern Pacific El Niños emerge, they might trigger unusually strong events with extreme heating in the central Pacific.

"That provides a physical reason to take the possibility of more frequent extreme El Niño events in a warmer climate seriously," Yu said. "But I would distinguish that from saying that every El Niño will become progressively stronger."

'> The central Pacific Ocean just broke a temperature record. Experts say it might signal a new kind of El Niño. in early September, marking the state's first known dengue death in almost a century.

Prior to the past few years, most dengue cases reported in Florida were the result of travel. In other words, people caught the disease in other countries and then traveled to Florida, where their case was then diagnosed. At 245, the number of travel-related cases reported this year is not unusually high, Caroline Waddell, a public health researcher at the University of Florida, told Live Science in an email. However, the number of cases caught from local mosquitoes is more than five times higher than at this point in the year compared with any of the previous four years, she said.

Why are local dengue cases especially high this year? Live Science spoke with experts to find out.

A growing global health concern

Dengue fever is caused by the virus Orthoflavivirus denguei, which spreads from mosquitoes to people through the pests' bites; it doesn't spread from person to person. Aedes aegypti and Aedes albopictus mosquitoes transmit the virus to humans, and the same species can also carry the viruses behind yellow fever, Zika and chikungunya.

About 100 million to 400 million dengue infections happen annually worldwide, with about 800 cases reported in the U.S. historically, although that number has increased recently. Only about 1 in 4 people exposed to the dengue virus develop symptoms, which can include fever, headache, body aches, nausea and rash. About 1 in 20 cases become severe, and immunocompromised people, children, older adults and pregnant people are especially susceptible to these serious infections.

Severe symptoms can include abdominal pain, vomiting, difficulty breathing and bleeding of the gums or nose. The most severe forms of the infection can lead to leaky blood vessels, severe bleeding, shock, organ dysfunction and death. There is no specific treatment for dengue, so care focuses on managing symptoms and maintaining patients' vital signs.

Dengue has escalated as a global health concern in the past few decades. Between 2000 and 2019, global cases of dengue increased tenfold; between 1990 and 2021, dengue-related deaths doubled. Scientists say this surge is likely driven by climate change, since rising temperatures expand Ae. aegypti mosquitoes' range, in turn exposing more people to the insects' bites. Plus, warmer conditions speed up mosquitoes' life cycles and the dengue virus's replication rate, thereby boosting transmission.

International travel also factors into these rising case counts. In 2023, dengue spikes around the world were attributed to the resurgence of global travel following the COVID-19 pandemic.

Zooming in on Florida

As the global picture has worsened, dengue cases in the U.S. have also increased.

Nearly 3,800 cases were reported in 2024 ‪—‬ an increase of more than 300% above the annual average for the previous 10 years. The uptick was tied to a rise in travel-associated cases, reflecting the wider global surge, as well as to warming temperatures that brought dengue-carrying mosquitoes to new regions of the U.S.

Each year, Florida experiences dengue outbreaks in the southernmost parts of the state, such as Miami and the Florida Keys, Panpim Thongsripong, a disease ecologist at the University of Florida, told Live Science. Historically, outbreaks in Miami typically totaled around 50 or fewer cases. But then a 2019 outbreak resulted in over 200 cases, and from 2022 to 2024, outbreak totals have ranged from about 500 to 675 cases.

The outbreak currently unfolding in Florida centers on Hillsborough County, which is farther north and includes Tampa. This is unusual, Thongsripong said, as this region of the state normally sees just a few sporadic cases. Hillsborough County has reported 223 of the state's 252 locally acquired cases this year, and it's where the one dengue-related death took place.

Florida's health department regularly traps mosquitoes and tests them for viruses. So far this year, 20 pools of mosquitoes have tested positive for dengue across seven counties, and 19 of those positive pools were sampled from the greater Tampa area. In 2025, only four mosquito pools throughout the state tested positive, and in 2023, one mosquito pool did.

"Finding positive mosquito pools is rare in Florida because dengue is not endemic to the state," said Keira Lucas, deputy executive director of the Collier Mosquito Control District. "In many ways, it can be like looking for a needle in a haystack," she told Live Science.

Routine mosquito trapping is a relatively inefficient method for detecting viruses, though, Lucas said. As such, detecting dengue-positive mosquito pools may indicate that a large amount of transmission is already unfolding. "Since approximately 75% of dengue infections are asymptomatic, the virus can circulate within a community without being readily detected for some time," Lucas explained.

In addition to Hillsborough, neighboring Pasco and Pinellas counties have declared local states of emergency over dengue.

An unlucky combination of factors

So what's driving the unusual dengue activity this year?

In the past, Florida's local dengue outbreaks tended to be concentrated in the South, which saw moderate rainfall, warmer temperatures and more travel-related dengue cases compared with the rest of the state, according to a 2022 study in the journal Insects. With the outbreak concentrated farther north this year, that could suggest changing climatic patterns are making additional parts of the state especially hospitable to mosquitoes and the virus. That wouldn't necessarily explain why Tampa is seeing more local cases than Miami this year, but it could nonetheless be a factor in the overall trend.

For the virus to persist in local mosquitoes, dengue still needs to be reintroduced periodically through travel-related cases. Because the virus is not yet endemic to the state, it doesn't regularly circulate in local mosquitoes; however, a somewhat predictable "dengue season" has been emerging that coincides with upticks in international travelers carrying the virus to Florida.

This year, though, the high number of locally acquired dengue cases suggests a shift from predominantly imported infections toward outbreaks spurred by local Florida mosquitoes. Scientists hypothesize that climate change could increase local transmission in Florida even more in the future.

This year, Florida has also been enduring its most intense drought in over a decade. In theory, that might be expected to limit mosquito populations because the pests need water to breed, Lucas said. However, when it's dry, people tend to run their sprinklers more, creating mosquito breeding grounds when puddles form or containers fill up, she noted. This could bring mosquitoes closer to people, as it creates opportunities for them to breed.

Ae. aegypti mosquitoes are especially well adapted to living alongside humans, as they prefer to breed in human-made containers. Droughts can also drive dehydrated mosquitoes to bite more as they hunt for fluids.

"It's almost like an unlucky [combination]," Thongsripong said. "Everything coming together at the right time and right place, and boom, you have the conditions for an outbreak to occur."

The true number of dengue cases may be even higher than reported, Waddell said. The cases captured in the data include infected individuals who went to a doctor to get tested. Because many infections are mild or asymptomatic, additional people may have contracted the virus but never got counted.

What can be done

It's too early to definitively say what factors have increased Florida's dengue cases this year, Thongsripong said, as scientists are still gathering information. Despite the unknowns, she thinks the health and housing infrastructure in the U.S. will stop dengue from becoming too dangerous here.

To get dengue under control, it's key for government-level mosquito control efforts to coordinate and for the public to be aware of the virus, Lucas said. The mosquito control district coordinates with the health department for the latest data to best target where to spray larvicide, which kills mosquito offspring before they can bite people, she said.

It's important for people to use mosquito repellent when going outside, Thongsripong said, as well as to empty water from objects that can collect water and become a mosquito breeding ground, such as pets' water bowls, plant saucers, buckets or discarded tires.

Due to this year's strong El Niño, Florida is expecting a rainier winter, which could mean even more mosquitoes than usual, Lucas noted. That, in turn, could fuel additional dengue cases.

"Cases with September onsets are still being reported," Waddell said, "so we're not out of the woods."

This article is for informational purposes only and is not meant to offer medical advice.

'> Why are dengue cases surging in Florida this year? An 'unlucky' combination of factors, experts say

Amid revelations that safety concerns have forced the company to abandon the planned rollout of GPT-6.1 Astra, independent researchers and benchmark creators warn that GPT-6 Astra's record-breaking scores rely on heavy prompt optimization rather than true general intelligence. This comes as experts warn about the risks of future AI systems and AI executives jointly call for a slowdown in AI research.

In announcing the model's release, OpenAI President Greg Brockman suggested that Astra signaled a fundamental turning point in AI evolution. "If we fast-forward a couple years, and we look back and say when was it really that AGI was created, I think it's going to be about this time, and I think it might be about this model," Brockman said during a Sept. 3 news conference marking the launch.

How did the new model perform in benchmarking?

As part of the testing-and-verification process for the new model, OpenAI released benchmark results across a range of tests that measure the capabilities of AI models at various tasks. OpenAI representatives claimed in a statement that the company's new model delivers "state-of-the-art" performance across a variety of fields, including software engineering, the autonomous use of computer programs, mathematics problems, and even scientific research.

Demonstrations, for example, highlighted Astra's ability to generate 3D CAD code; lay out printed circuit boards in CAD (computer-aided design) software; convert digital 3D models into interactive, video-game-style environments; and deploy hosted web applications directly from prompts.

"In our early testing, Astra stood out by approaching legal work the way a discerning lawyer does: it distinguishes documents from established records, surfaces unsupported assumptions, and converts gaps into concrete drafting positions," said Niko Grupen, head of applied research at legal services AI developer Harvey as part of OpenAI’s announcement.

On ARC-AGI-3 ‪—‬ a benchmark designed to measure how efficiently AI systems acquire new skills in novel, abstract environments ‪—‬ Astra achieved a headline score of 99.9%. Independent testing by the nonprofit ARC Prize Foundation, which oversees the benchmark, revealed that Astra surpassed "human action-efficiency" baselines on 96% of levels, taking 51.7% fewer actions per level, on average, than human solvers.

"Not only is this the best model we've ever tested," ARC Prize Foundation President Greg Kamradt said as part of the OpenAI announcement, "but it also represents a meaningful step change in frontier-model performance — not only in its ability to navigate and solve novel environments but also in how efficiently it learns to do so."

How much can we read into test results?

Many researchers have highlighted that Astra's top ARC-AGI-3 performance relied on a proprietary "Provider Adapter" harness, a specialized software scaffolding layer that's inaccessible to rival developers. When tested using the benchmark's neutral Standard harness, this score dropped to 62.7%. ARC Prize organizers also noted that saturating the benchmark does not constitute proof of achieving AGI — emphasizing that its closed, deterministic puzzle environments do not capture the open-ended complexity of the real world.

"When we launched ARC-AGI-3, "we made it clear that saturating the benchmark would not represent 'proof of achieving AGI,'" Kamradt wrote in a blog post. "Therefore, while we believe Astra represents meaningful progress towards generalization, we are not claiming that it is AGI."

Discrepancies in the data were reportedly present even before the official announcement. As reported by Fortune, an embargoed draft provided to news organizations prior to the model's launch listed Astra's ARC-AGI-3 score at 98.6% before it jumped to 99.9% on the live site.

Anka Reuel and Mike Hardy, doctoral researchers in AI at Stanford University, also raised concerns over OpenAI quietly revising several published metrics post-launch, including halving Astra's reported hallucination rate from 4.2% to 2.0% before reverting it.

Speaking to Fortune, Reuel and Hardy attributed the shifting figures to "benchmaxxing" — an industry term that describes the practice of repeatedly rerunning evaluations under subtly tweaked prompts, scaffolds or compute allocations to hunt for peak theoretical scores.

In a 2025 paper published on pre-print server arXiv titled ‘Benchmarking is Broken -- Don't Let AI be its Own Judge’, experts including Princeton doctoral candidate Zerui Cheng and University of Luxembourg postdoctoral researcher Dr. Stella Wohnig warned that such practices create confusion and undermine trust, particularly when official technical documentation omits the basic methodology, making independent verification nearly impossible. Crucially, scores achieved through benchmaxxing reflect idealized performance ceilings under optimal lab conditions rather than practical, out-of-the-box reliability.

According to OpenAI's benchmark data, across specialized domain evaluations, GPT-6 Astra delivered 10% to 20% better performance than both its predecessor, GPT-5.6 Sol, and top market competitors.

Highlights include a 98% score on FrontierMath Tier 4 (v2), which evaluates expert-level mathematical reasoning; a perfect 100% on ExploitBench, which is designed to test offensive cybersecurity capabilities; 95.9% on BenchCAD, which measures an AI's ability to reconstruct 3D objects using CAD code; 57.9% on Terminal-Bench 4.0, which assesses complex terminal-based system administration and software engineering; and 41.4% on AutomationBench, which tests whether agents can complete multistep business workflows across applications.

But independent findings from external AI benchmarking firm Artificial Analysis contradict these results. Astra's score on the independent Artificial Analysis Intelligence Index — an aggregate metric that evaluates general reasoning across frontier models — remained completely flat, at 61, compared with GPT-5.6 Sol, while trailing competitors like Anthropic's Claude Fable 5.1 and Meta's Muse Spark 1.3.

While some benchmark results have seen improvement since the previous generation, Astra underperformed in other tests. Artificial Analysis' testing showed that against GDPval-AA v2 — an economically focused benchmark that measures real-world workplace tasks across 44 occupations — Astra suffered a significant drop in its relative leaderboard ranking compared with GPT-5.6 Sol. Additional regressions were observed in benchmarks that test customer service support, scientific Python programming, and long-context reasoning across large documents.

In terms of overall token use — the metering system that measures the fragments of text or data processed by AI models — OpenAI representatives said GPT-6 Astra achieved dramatic efficiency gains on complex, long-horizon tasks. Findings from Artificial Analysis confirmed that on software engineering benchmarks, Astra was approximately 70% more token-efficient than GPT-5.6 Sol, using roughly one-third the total tokens of its predecessor and one-fifth the tokens of Claude Opus 5.

On professional workplace evaluations like Agents' Last Exam, the new model reduced output token consumption by up to 65% compared with Opus 5, while on general intelligence evaluations, Astra achieved a roughly 10% output token reduction at max effort compared with Sol.

On the other hand, this achievement is offset by a 250% increase in the base API pricing for GPT-6 Astra compared with GPT-5.6 Sol. Token prices jumped from $4/$20 to $10/$50 per million input/output tokens. As a result, Astra ends up approximately 75% more expensive per task than its predecessor on general intelligence evaluations, despite using 10% fewer output tokens. This trade-off has led researchers at Artificial Analysis to question whether AI labs are relying on expensive computational brute force to squeeze out minor gains, rather than achieving true technical breakthroughs.

Does achieving AGI even matter?

With its latest model, OpenAI has placed a stronger emphasis on safeguards and controls. The move follows a series of high-profile incidents in which frontier AI models inadvertently hacked into third-party networks and computer systems as part of routine testing operations, after the models went beyond what humans expected they would do when encountering challenging tasks.

According to OpenAI representatives, Astra did not exceed the scope of its tasks in any security evaluations. For comparison, GPT-5.6 Sol went beyond its authorized parameters in almost 50% of test cases. Hallucination rates have also been reduced significantly, falling to 4.2% on internal tests, compared with 12.2% for GPT-5.6 Sol (with independent testing by Artificial Analysis showing a drop from 92% to 51% at max effort). The model also showed an improved ability to handle ambiguous prompts.

David Wood ‪—‬ chair of London Futurists, a non-profit that hosts discussion groups on emerging technology ‪—‬ argued that beyond individual test results, Astra highlights a fundamental shift in how humans will interact with AI as models move from answering questions to autonomously pursuing complex goals in digital environments.

"The impressive benchmark results matter, but what matters more is the combination of intelligence, autonomy, computer use, and cybersecurity capability," he said in an email to Live Science. "That combination also demands caution. The more useful these systems become, the greater the consequences when they misunderstand our intentions, are misused, or find ways around the safeguards we give them."

Wood suggested that whether Astra can be classified as AGI is less relevant than recognizing the need for AI control and governance to keep pace with technical development.

"The possibility that AI could progress from systems like Astra towards all-round superintelligence makes much greater human vigilance, awareness, and collaboration increasingly urgent," he said.

Help us improve Live Science Pro: We're always trying to make our content better. Leave us feedback about Pro here.

'> OpenAI claims we've entered the AGI era — has GPT-6 Astra really demonstrated general intelligence?

While mitochondrial function has long been linked to longevity and mitochondrial dysfunction has been tied to disease, Jonathan offers fresh insight into that dynamic, said study co-author Stephen Clark, chief scientist of the Kallel Foundation, a nonprofit in Nashville researching drug targets to promote human longevity.

Clark and colleagues published their findings Wednesday (Oct. 7) in the journal Science Advances.

Decoding Jonathan's secrets to long life

Nearly a decade ago, the researchers enlisted Joe Hollins, the vet tasked with Jonathan's care, to collect samples from the record-setting animal. Island authorities forbade the vet from drawing the tortoise's blood, fearing the risk of an infection.

"I didn't want to be the doctor that killed Jonathan," Clark told Live Science. Hollins collected samples via cheek swab instead.

When the samples arrived in the U.S., the researchers sequenced them, but when their computers kept crashing, they discovered that the DNA had been isolated from bacteria in Jonathan's mouth rather than the tortoise's own cells.

Clark "had to go back and beg" for permission to collect more data, he said. The vet then sent cheek scrape samples, which are collected with a slightly different tool than cheek swabs. This time, the DNA was in fact from Jonathan.

The DNA isolated from those cheek tissue samples was more fragmented than it would have been in a blood sample, so the researchers filled in the gaps using an existing reference genome from a 36-year-old Aldabra tortoise named Tank. They also compared Jonathan's DNA to that of a Galápagos tortoise (Chelonoidis abingdoni) named Lonesome George, who was believed to be over 100 years old at the time of his death in 2012.

The team found that, compared to Tank and Lonesome George, Jonathan carried 287 unique variants of genes that had previously been linked to aging-related pathways. These included genes involved in DNA repair and the function of telomeres — the protective tips at the end of chromosomes that tend to shorten with age.

These pathways are also related to aging processes in humans, highlighting a "broader signature of aging" across species, Greer Dolby, an assistant professor of biology at The University of Alabama at Birmingham, who was not involved with the study, told Live Science.

The researchers also looked at epigenetic changes, including DNA methylation, which is when a chemical tag called a methyl group binds the DNA. Certain patterns of DNA methylation can function as a "clock" in that they reflect an organism's biological age; scientists have recently harnessed these patterns in the study of human aging. In this case, the team compared the DNA methylation across Jonathan's genome to that of young and old Aldabra tortoises.

The methylation patterns were more disordered in the older tortoises, reflecting random changes acquired over time, the researchers found. Scientists call this phenomenon "methylation entropy." For most genes, Jonathan's DNA methylation patterns were more disordered than those of the young tortoises. But in a suite of genes tied to mitochondrial function — specifically the bits of those genes that switch them "on" — Jonathan had more organized methylation patterns. That might keep expression of these genes consistent over time, the researchers theorized.

Mitochondria produce energy that cells need to function properly, repair themselves and reduce further damage to DNA. "Keeping the entropy low in these mitochondrial genes, or keeping pristine mitochondria, is likely to be a contributor to longevity," Clark said.

However, the authors couldn't determine a causal relationship — they didn't run any tests that could definitively prove that Jonathon's lack of entropy in these genes explains his long life. Clark argued that additional experiments on a blood sample from Jonathan could offer a more comprehensive view of his genome.

Jonathan's full genetic profile can't be known until after the tortoise's death, when researchers can collect DNA from more tissues, said Vincent Lynch, a professor of biology at the University at Buffalo, who was not involved with the study.

"Some organs are more susceptible to different diseases of old age than other ones, and that happens because mutations accumulate over time," he told Live Science. "We would ideally like to know what those mutations are in those specific tissues."

Furthermore, Lynch questioned whether entropy was a useful characterization of age-related DNA methylation patterns, as methylation can be unpredictable. That said, he agreed that the genes flagged in the study offer helpful data for future work on longevity.

More experiments are needed to determine whether these mitochondrial genes actually play a role in longevity across all Aldabra tortoises, let alone in other animals, or if Jonathan is just an outlier.

"Maybe Jonathan is just really good at being old," Lynch said.

'> Jonathan the tortoise has lived to 194 years old — now scientists think they know why Zhe-Xi Luo, a paleontologist at the University of Chicago, told Live Science. "The back half of this animal is very much like a platypus. As are the limbs, which would be capable of swimming or digging tunnels in river banks."

But the teeth "are definitely not like a platypus," Luo said. It possessed robust canines and shearing cheek-teeth that would cut and chew meat in a different way from modern carnivorous mammals. "It's a predator with gigantic and very specialized canines," Luo said. "So, it's partly otter-like and partly platypus-like."

A revealing fossil

Tiny bits of vertebrate bones found in what would have been the animal's stomach and the surrounding fossil beds hint that M. sungei dined on salamanders, Luo said.

He added that M. sungei may have sheltered in burrows on land in the temperate plant-filled climate, and hunted in lakes and rivers for fish and invertebrates.

Another notable aspect of the fossil is its throat. Modern mammals, including humans, have hyoid bones in the throat arranged in a "U"-shaped saddle. These help us use throat muscles to swallow chewed food one chunk at a time, instead of gulping down huge bites or whole prey. The structures also enable babies to suckle their mother's milk.

M. sungei seems to have had the apparatus needed to do this, study co-author Thomas Martin, a paleontologist at the University of Bonn in Germany, told Live Science.

"This is an incredibly important evolutionary innovation," Luo said, adding that this capability is one of the things that helped early mammals diversify into carnivores, insectivores, herbivores or omnivores to take advantage of all sorts of foods.

Finding this in M. sungei suggests that the apparatus needed for suckling milk and swallowing had already evolved by the Middle Jurassic (around 174 million to 164 million years ago), Martin said.

This is before marsupials like kangaroos and placental mammals like primates and bears are thought to have diverged from each other 160 million years ago, after descending from an egg-laying common ancestor that lived approximately 180 million years ago.

"Now we push the history of it back to before the split of modern marsupials and modern eutherian [placental] mammals," Luo said.

"Neonatal suckling behaviour was previously thought of as being a hallmark of advanced mammals, but it now appears to have evolved well before then, in the common ancestor of docodontans and mammals at least 165 million years ago," said Sue Hand, a vertebrate paleontologist at the University of New South Wales in Australia who wasn’t involved in the study.

M. sungei is from an extinct lineage of docodonts, which are relatives of mammals from the dinosaur-dominated Jurassic and Cretaceous periods, living between about 200 million and 120 million years ago.

Docodonts adapted to a wide variety of habitats. For example, there was the Jurassic tree-dwelling shrew-like docodont called Microdocodon gracilis, and Docofossor brachydactylus, a tunnel-digger with shovel-like paws. Luo was also part of the team that described a semiaquatic "Jurassic beaver", Castorocauda lutrasimilis, which lived 164 million years ago.

"It seems that an aquatic lifestyle arose often in early mammal-like species," said Tim Flannery, a mammalogist at the Australian Museum Research institute who wasn't involved in the work.

If anything, the newly described "spectacular fossil" shows that docodonts were wide-ranging during the dinosaur age, Hand told Live Science in an email.

"This very detailed study adds to accumulating evidence that mammaliaforms occupied a wide range of ecological niches long before the evolution of living mammals," Hand said.

'> 'It looks like a chimera' — 168 million years ago, a strange platypus-like mammal relative lived in China alongside dinosaurs