Fossils: Past Preservers and Future Forecasters

Captivating remnants of ancient times, fossils offer a window into Earth’s history and the evolution of life. They document the past, providing clues about extinct species, vanished environments and the processes that shaped our planet. From dinosaur bones to prehistoric plant impressions, fossils are a source of fascination and wonder, inspiring scientific exploration and a deeper understanding of our world.

Less well-known, perhaps, is that fossils can also tell us about our future. By studying the fossil record, we can see how past ecosystems and species adapted to different conditions, helping us anticipate potential upcoming changes in biodiversity and ecosystem dynamics.

In short, fossils are the perfect blend of mystery and reality.

Why did some ancient animals fossilize while others vanished?

Fossils are more than just bones; some of the most remarkable finds include traces of soft tissues like guts, muscles and even brains. These rare fossils offer vivid glimpses into the past, but scientists have long puzzled over why such preservation happens only for certain animals and organs but not others.

To dig into this mystery, a team of scientists from the University of Lausanne in Switzerland turned to the lab. They conducted state-of-the-art decay experiments, allowing a range of animals including planarians (worms), shrimp, snails and starfish to decompose under precisely controlled conditions.

As the bodies broke down, the researchers used microsensors to monitor the surrounding chemical environment, particularly the balance between oxygen-rich (oxidizing) and oxygen-poor (reducing) conditions. The results were striking: the researchers discovered that larger animals and those with a higher protein content tend to create reducing (oxygen-poor) conditions more rapidly. These conditions are crucial for fossilization because they slow decay and trigger chemical reactions such as mineralization, which is tissue replacement by more durable materials.

This means that, in nature, two animals buried side by side could have vastly different fates as fossils, simply because of differences in body chemistry or size. One might vanish entirely, while the other could be immortalized in stone. Animals like large arthropods (arachnids, crustaceans and insects) are more likely to be preserved than small planarians or other aquatic worms. This could explain why fossil communities dating from the Cambrian and Ordovician Periods (around 500 million years ago) are dominated by arthropods, state the University of Lausanne scientists, who published their paper in the journal Nature Communications in April 2025.

These findings not only help explain the patchy nature of the fossil record but also offer valuable insights into the chemical processes that shape what ancient life we can reconstruct today. Pinpointing the factors that drive soft-tissue fossilization brings us closer to understanding how fossils form—and why we only see fragments of the past.

Fossils as time machines: ancient animals

1) Fossil tracks reveal when reptiles appeared on Earth. When researchers from Flinders University in Adelaide, Australia, recently identified the fossilized tracks of an amniote—the group that includes birds, mammals and reptiles—with clawed feet (most probably a reptile) from the Carboniferous Period, about 350 million years ago, they realized that they had found the oldest evidence in the world of reptilelike animals walking around on land. The report of this amazing find, published in the journal Nature in May 2025, pushes this group’s evolution back by 35 to 40 million years earlier than the records in the Northern Hemisphere. This discovery indicates that such animals originated in the ancient, southern supercontinent of Gondwanaland, of which Australia was a central part.

The crystal-clear fossil tracks, discovered in Australia’s Mansfield District of northern Victoria, were made by an animal that the scientists think would have been small and stumpy. At first, the researchers thought the tracks were from early amphibians, but one in the middle had a hooked claw coming off the digits, like a reptile; it’s an amniote, which rewrites this part of evolutionary history.

2) Marine fossils uncover a 506-million-year-old predator. Located within Canada’s Kootenay and Yoho National Parks, the Burgess Shale preserves some of the best records on Earth of marine life during the Cambrian Period. In 1980, the Burgess Shale was designated a UNESCO World Heritage site due to its outstanding universal value. It is now part of the larger Canadian Rocky Mountain Parks World Heritage site in British Columbia.

Recently, paleontologists at Winnipeg’s Manitoba Museum and Toronto’s Royal Ontario Museum discovered a remarkable 506-million-year-old predator from the Burgess Shale. Mosura fentoni was about the size of your index finger and had three eyes; spiny, jointed claws; a circular mouth lined with teeth; and a body with swimming flaps along its sides. These traits identify it as part of an extinct group known as the radiodonts, which also include the famous Anomalocaris canadensis, a three-foot-long predator that shared the waters with Mosura. However, Mosura also possessed a feature not seen in any other radiodont: an abdomen-like body region made up of multiple segments at its back end. This finding was announced in a paper published in the journal Royal Society Open Science in May 2025.

Mosura had 16, tightly packed segments lined with gills at the rear end of its body. This converges evolutionarily with modern groups, like horseshoe crabs, insects and wood lice, which share a batch of segments bearing respiratory organs at the ends of their bodies. The reason for this intriguing adaptation remains uncertain, but the researchers postulate it may be related to behavioral characteristics that required more efficient respiration or a particular habitat preference.

3) A saber-toothed fossil suggests a scramble for dominance. Two-hundred-and-fifty-two million years ago, Earth experienced a mass extinction so devastating that it’s become known as “the Great Dying.” Massive volcanic eruptions triggered catastrophic climate change, killing off nine out of every 10 species and eventually setting the stage for the dinosaurs. But the Great Dying was a long goodbye; the extinction event took place over the course of up to a million years at the end of the Permian Period. During that time, the fossil record shows drama and upheaval as species fought to get a foothold in their changing environments.

One animal that exemplifies this instability was a tiger-sized, saber-toothed creature called Inostrancevia: a new fossil discovery suggests that Inostrancevia migrated 7,000 miles across the supercontinent Pangaea, filling a gap in a faraway ecosystem that had lost its top predators, before going extinct itself.

In a study that was published in the journal Current Biology in June 2023, researchers from the Field Museum in Chicago explain that all the big, top predators in the late Permian in South Africa went extinct well before the end-Permian mass extinction. This vacancy in the niche was occupied, for a brief period, by Inostrancevia, a creature that looked very much like a top predator. Inostrancevia was a gorgonopsian, a group of protomammals that included the first saber-toothed predators on the planet. It was about the size of a tiger and likely had skin like an elephant or a rhino, but it was probably vaguely reptilian in appearance.

Prior to the paper in Current Biology, Inostrancevia had only ever been found in Russia. But while examining the fossil record of South Africa’s Karoo Basin, scientists identified the fossils of two, large, predatory animals that were different from those normally found in the region. It’s not clear how they made it from what’s now Russia, or how long it took them to cross Pangaea and arrive in what’s now South Africa. But being far from home was just one element of what made the fossils special. When the ages and ranges of the other top predators normally found in the area, the Rubidgeine gorgonopsians, were compared with the Inostrancevia fossils, it was found that the local carnivores went extinct quite a bit before even the main extinction in the Karoo; by the time the extinction begins in other animals, they’re gone.

The arrival of Inostrancevia from 7,000 miles away and its subsequent extinction indicates that these top predators were “canaries in the coal mine” for the larger extinction event to come. It shows that the shift in which groups of animals occupied apex predator roles occurred four times over less than 2 million years around the Permian-Triassic mass extinction, which is unprecedented in the history of life on land. This underlines how extreme this crisis was, with even fundamental roles in ecosystems in extreme flux.

The vulnerability of these top predators matches what we see today. Apex predators in modern environments tend to show high extinction risk and be among the first species that are locally extirpated due to human activities, such as habitat destruction or hunting. Examples are wolves in Europe or tigers in Asia, species which are slow to reproduce, grow and that require large geographic areas to hunt prey and roam, and which are now absent from most of their historic ranges. We should expect that ancient apex predators would have had similar vulnerabilities and would be among the species that first go extinct during mass extinction events.

In addition to shedding new light on the extinction event that helped lead to the rise of the dinosaurs, this study is important for what it can teach us about the ecological disasters the planet is currently experiencing. Without any modern analogs of what to expect with the sixth mass extinction happening today, the Permian-Triassic Extinction Event is instructional.

4) An Antarctica fossil exposes the earliest modern bird. Sixty-six million years ago, at the end of the Cretaceous Period, an asteroid impact near the Yucatan Peninsula of Mexico triggered the extinction of all known nonbird dinosaurs. But for the early ancestors of today’s waterfowl, location mattered—a lot. Antarctica may have served as a refuge, protected by its distance from the turmoil taking place elsewhere on the planet. Fossil evidence suggests the place had a temperate climate with lush vegetation, possibly serving as an incubator for the earliest members of the group that now includes ducks and geese.

In February 2025, the fossil discovery of a nearly complete, 69-million-year-old skull that belongs to an extinct bird named Vegavis iaai was described in a paper published in the journal Nature. The skull belongs to the oldest-known modern bird, an early relative of ducks and geese that lived in Antarctica at around the same time that Tyrannosaurus rex dominated North America.

The skull exhibits a long, pointed beak and a brain shape unique among all known birds previously discovered from the Mesozoic Era, when non-avian dinosaurs and a bizarre collection of early birds ruled the globe. Instead, these features place Vegavis in the group that includes all modern (also known as crown) birds, representing the earliest evidence of a now widespread and successful evolutionary radiation across the planet.

While this fossil skull shows beak bones and a brain shape that are consistent with modern birds—specifically, waterfowl—unlike most waterfowl today, the skull preserves traces of powerful jaw muscles useful for overcoming water resistance while diving to snap up fish. These skull features are consistent with clues from elsewhere in the skeleton, suggesting that Vegavis used its feet for underwater propulsion during pursuit of fish and other prey—a feeding strategy unlike that of modern waterfowl and more like that of grebes and loons.

Birds known from elsewhere on the planet at around the same time are barely recognizable by modern bird standards. Moreover, most of the handful of sites that preserve delicate bird fossils yield specimens that are so incomplete as to only give hints to their identity. Those few places with any substantial fossil records of Late Cretaceous birds, like Argentina and Madagascar, reveal an aviary of bizarre, now-extinct species with teeth and long, bony tails, only distantly related to modern birds. Something very different seems to have been happening in Antarctica, in many ways the final frontier for humanity’s understanding of life during the Age of the Dinosaurs.

5) A fossil penguin discloses wing evolution. As outlined in the Journal of the Royal Society of New Zealand in July 2024, researchers from New Zealand’s University of Otago and Japan’s Okayama University of Science and Osaka University have found a new species of penguin which lived in Otago about 24 million years ago. Named Pakudyptes hakataramea, the penguin was very small—about the same size as a little blue penguin, the smallest in the world—with anatomical adaptations that allowed it to dive.

An analysis of the three fossil bones that were found—a femur, humerus and ulna—in New Zealand’s Hakataramea Valley, South Canterbury, fill a morphological gap between fossil and modern penguins. Surprisingly, while the shoulder joints of the wing of Pakudyptes are very close to those of present-day penguins, the elbow joints are very similar to those of older types of fossil penguins. Pakudyptes is the first fossil penguin ever found with this combination, and scientists say it is the key to unlocking the evolution of penguin wings.

6) Elephant fossils depict what could have been in Europe. Elephants are among the largest land mammals on Earth and are often referred to as “ecosystem engineers” because they sustainably alter their surroundings through digging, grazing and trampling. Europe, too, had an elephant: the straight-tusked elephant (Palaeoloxodon antiquus) that lived on the continent for around 700,000 years. The species survived multiple ice ages before becoming extinct during the last one due to hunting pressures from humans.

But throughout its existence, the straight-tusked elephant helped shape Europe’s landscapes, maintaining open spaces and light woodlands. Many native plant species are still adapted to these conditions today. The German word waldelefant (forest elephant) originates from the assumption that this species primarily lived in the wooded regions of Europe. However, fossil evidence shows that Palaeoloxodon antiquus often inhabited open or semi-open habitats with mosaiclike vegetation like modern elephants.

To reconstruct the way of life of straight-tusked elephants and their actual habitat—known as the realized niche—a research team from Germany’s University of Bayreuth examined scientific literature and paleontological databases for fossil finds of Palaeoloxodon antiquus that could be assigned to specific Marine Isotope Stages, periods in the Earth’s history that reflect the climate, representing warm and cold stages. The Bayreuth research team assigned fossil finds from across Europe to either a warm or cold stage and then used climate models from these periods to reconstruct the realized niche of straight-tusked elephants. In their paper published in the journal Frontiers of Biogeography in April 2025, the researchers state that straight-tusked elephants would still be able to live in Europe today. The climate in Western and Central Europe would be particularly suitable, they say, except for mountainous regions such as the Alps and the Caucasus.

7) Giant marine lizard fossils detail changing oceans. Paleontologists recently discovered a strange, new species of marine lizard with daggerlike teeth that lived near the end of the Age of the Dinosaurs. Their findings, published in the journal Cretaceous Research in August 2024, show a dramatically different ocean ecosystem from that of today’s. In the past, numerous, giant top predators ate large prey, unlike modern ecosystems where a few apex predators—such as great white sharks, leopard seals and orcas—dominate.

Khinjaria acuta was a member of the family Mosasauridae, or mosasaurs. Mosasaurs weren’t dinosaurs but giant marine lizards, relatives of today’s anacondas and Komodo dragons, which ruled the oceans 66 million years ago. Khinjaria had powerful jaws and long, sharp teeth to seize prey. The elongation of the animal’s posterior part of the skull accommodating the jaw musculature suggests a fierce biting force. It was part of an extraordinarily diverse fauna of predators that inhabited the Atlantic Ocean off the coast of Morocco just before the dinosaurs went extinct.

The report of this discovery, led by researchers from England’s University of Bath, is based on a skull and parts of the skeleton collected from a phosphate mine southeast of Casablanca, Morocco. The sheer diversity of top predators here is remarkable; multiple species of them were larger than a great white shark, but they all had different teeth, suggesting they hunted in different ways. Some mosasaurs had teeth to pierce prey, others to crush, cut or tear. In contrast is Khinjaria, with a short face full of huge, jagged teeth.

Morocco’s diverse marine reptiles lived just before an asteroid struck the Yucatan Peninsula in Mexico. Dinosaurs were wiped out on land, and a handful of surviving species of birds, lizards and mammals diversified to take their place. Meanwhile, the same happened in the oceans. Mosasaurs, plesiosaurs and giant sea turtles disappeared, along with entire families of fish.

The ecosystem that evolved after the impact was different. Modern marine communities don’t have the incredible diversity of top predators that the Late Cretaceous had. We don’t know whether there was something about marine reptiles that caused the ecosystem to be different, or the prey, or perhaps the environment. But we do know that it was an incredibly dangerous time to be a fish, sea turtle or even a marine reptile.

8) Fossil teeth tell a Caribbean, croc-like tale. Imagine a crocodile built like a greyhound—that’s a sebecid. Standing tall, with some species reaching 20 feet in length, sebecids dominated South American landscapes after the extinction of dinosaurs until about 11 million years ago. Or at least, that’s what paleontologists thought, until they began finding strange, fossilized teeth in the Caribbean.

The initial confusion was warranted. Three decades ago, researchers uncovered two, 18-million-year-old teeth in Cuba. With a tapered shape and small, sharp serrations specialized for tearing into meat, they unmistakenly belonged to a predator at the top of the food chain. But for the longest time, scientists didn’t think such large, land-based predators ever existed in the Caribbean. The mystery deepened when another tooth turned up in Puerto Rico, this one 29 million years old. The teeth alone weren’t enough to identify a specific animal, and the matter went unresolved.

But in early 2023, a research team from the University of Florida and the Florida Museum of Natural History unearthed another fossilized tooth in the Dominican Republic. This time, it was accompanied by two vertebrae. The fossils belonged to a sebecid; and the Caribbean—far from never having large, terrestrial predators—became a known refuge for the last sebecid populations at least 5 million years after they went extinct everywhere else.

The sebecids—the last surviving members of the Notosuchia, a large and diverse group of extinct crocodilians—acted like carnivorous dinosaurs, sprinting after prey on their four, long, agile limbs and tearing through flesh with their notorious teeth. Some species could reach 20 feet in length and had protective armor made of bony plates embedded in their skin. The mass extinction event 66 million years ago that wiped out non-avian dinosaurs nearly destroyed Notosuchians, as well. In South America, only the sebecids endured; and with the dinosaurs gone, they quickly rose to be the apex predators.

The open sea separating the Caribbean islands and mainland South America would have posed a serious challenge for a terrestrial sebecid to swim across. In finding the fossils, the research team also found possible evidence in support of the GAARlandia hypothesis. This theory suggests that a pathway of temporary land bridges or a chain of islands once allowed land animals to travel from South America to the Caribbean.

If, as scientists hypothesize, the serrated teeth discovered on the other Caribbean islands also belonged to a sebecid, the history of these giant reptiles extends beyond the Dominican Republic. They would have occupied and shaped the region’s ecosystems for millions of years. Yet today, you’d be hard-pressed to find evidence of the large terrestrial predators. In their absence, smaller, endemic predators like birds, snakes and crocodiles have evolved to fill the gap in the food chain.

This revelation aligns with similar observations ecologists have described worldwide, say the authors of a paper published in the Proceedings of the Royal Society B in April 2025. Islands are known to act as “museums of biodiversity,” providing a haven that allows animals and plants to survive even after their related species have gone extinct on the mainland.

Fossils as landscapers: ancient plants

1) Fossil forest in England changes how rivers flow. The oldest fossilized forest known on Earth—dating from 390 million years ago—has been found in the high sandstone cliffs along the Devon and Somerset Coast of Southwest England. Discovered and identified by researchers from England’s University of Cambridge and Cardiff University in Wales, the fossilized forest is roughly 4 million years older than the previous record holder, which was found in New York State.

The fossils were found near Minehead, on the south bank of the Bristol Channel. At first glance, the fossilized trees, known as Calamophyton, look like palm trees, but they are a prototype of the kinds of trees we are familiar with today. Rather than solid wood, their trunks were thin and hollow in the center. They also lacked leaves, and their branches were covered in hundreds of twiglike structures. These trees were also much shorter than their descendants: the largest were between 6.5 and 13 feet tall. As the trees grew, they shed their branches, dropping lots of vegetation litter, which supported invertebrates on the forest floor.

Scientists had previously assumed this stretch of the English coast did not contain significant plant fossils, but in addition to its age, this particular find—described in the Journal of the Geological Society in July 2024—also shows how early trees helped shape landscapes and stabilize coastlines and riverbanks hundreds of millions of years ago.

The researchers say that compared to the forests of today, this one was weird. There wasn’t any undergrowth to speak of, and grass hadn’t yet appeared; but the twigs dropped by the densely packed trees had a big effect on the landscape. This period marked the first time that such close-knit plants were able to grow on land, and the sheer abundance of debris shed by the Calamophyton trees built up layers of sediment. The sediment affected the way that the rivers flowed across the landscape, the first time that the course of rivers could be influenced in this way.

The scientists conclude that the evidence contained in this fossilized forest preserves a key stage in Earth’s development, when rivers started to operate in a fundamentally different way than they had before, becoming the great erosive force that they are today.

2) Fossil discovery in Greenland means increased risk of sea-level catastrophe. The story of Greenland keeps getting greener—and scarier. A new study provides the first direct evidence that the center—not just the edges—of Greenland’s ice sheet melted away in the recent geological past and the now-ice-covered island was then home to a green, tundra landscape.

Recently, scientists from the University of Vermont reexamined a few inches of sediment from the bottom of a two-mile-deep ice core extracted at the very center of Greenland in 1993 and held for 30 years in a Colorado storage facility. They were amazed to discover soil that contained fungi, insect parts, a poppy seed and willow wood—all in pristine condition.

While the fossils are beautiful, what they imply about the impact of human-caused climate change on the melting of the Greenland ice sheet is alarming. The study, published in the Proceedings of the National Academy of Sciences in August 2024, confirms that Greenland’s ice melted and the island greened during a prior warm period, likely within the last million years, suggesting that the giant ice sheet is more fragile than scientists had realized.

If the ice covering the center of the island was once melted, then most of the rest of it had to be melted too—and probably for many thousands of years, which is enough time for soil to form and an ecosystem to take root. This new study confirms that a lot of sea-level rise occurred at a time when causes of warming were not especially extreme, providing a warning of what damage is ahead if we continue to warm the climate.

Sea level today is rising more than an inch each decade. It’s likely to be several feet higher by the end of this century, when today’s children are grandparents. And if the release of greenhouse gases—from burning fossil fuels—is not radically reduced, the near-complete melting of Greenland’s ice over the next centuries to a few millennia would lead to about 23 feet of sea-level rise.

3) Fossils in Florida assess seagrass health. The seagrass is greener along Florida’s Nature Coast; figuratively, that is. A new study published in May 2025 shows that seagrass ecosystems along the northern half of Florida’s Gulf Coast have remained relatively healthy and undisturbed for the last several thousand years.

This is not the case for most other seagrass ecosystems across the world, nearly 30% of which have disappeared since 1879. An estimated 7% of seagrass beds were lost each year between 1990 and 2009. Those that remain are generally not faring well, and the discovery of a healthy refugium is a rare event.

Figuring this out wasn’t easy, though. The extraordinary changes humans have made to the planet have not only jeopardized the health of entire ecosystems, but we’ve also made it nearly impossible for us to know what a healthy ecosystem should look like in the first place. We’ve also been altering our surroundings much longer than we’ve been systematically observing them. Fortunately, we aren’t the only ones keeping a record of the past. The Earth does a pretty good job of it, too.

That’s the idea behind a relatively new branch of science called “conservation paleobiology,” which uses the most recent fossil record to reconstruct past ecosystems. For this method to work well, scientists need to analyze large numbers of fossils, but there are only a few types of organisms that are preserved in sufficient quantities. Seagrasses, which are entirely composed of soft tissues that rapidly decompose after death, are not one of them.

This isn’t a hindrance to paleobiologists, however. Unlike modern grass lawns, which are ecologically barren and in which hardly anything lives but the grass itself, seagrass meadows are underwater oases for coastal marine organisms. This includes a variety of animals that produce hard shells, which are disproportionately represented in the fossil record. The shells of clams, oysters and other mollusks disintegrate so slowly that they stay around on the ocean floor from hundreds to millions of years.

The fossils of mollusks and other marine organisms with tough exteriors are so tightly connected and dependent on their environments that they can be used as a surrogate for species that don’t normally get preserved. If mollusks are doing well, it’s likely that everything else is, too. So, to find out if seagrass communities along Florida’s Nature Coast have recently degraded, the study’s authors sampled 21 locations in six estuaries, from the mouth of the Steinhatchee River in the north to that of the Weeki Wache in the south. At each site, they used a long hose made from PVC pipe to suction up sections of the seafloor. The sediment samples were then sieved to extract all materials, which were dominated by dead debris accumulated over many centuries. Typically, for every live bivalve or snail, there were thousands of dead specimens.

After years of counting and identifying the gathered materials, results showed that mollusk diversity—and the health of seagrass meadows, by extension—hasn’t changed much over the last several millennia, including the most recent one in which humans have left their mark on even the most challenging and inhospitable environments.

Only rarely do researchers find historical evidence that can make us optimistic about the current state of a local ecosystem. Most conservation paleobiology studies tell depressing stories about shrinking habitats, declining biodiversity and diminishing ecosystem services. For once, at least, this is not the case. What’s thrilling is that this system is shown to still be in very good condition, which makes it even more important to protect it.

Just 50 miles south of the study’s sampling area, seagrass communities haven’t been as lucky. Between 1950 and 1980, the city of Tampa’s population increased from about 125,000 people to 270,000. During that same period, 46% of seagrass meadows in Tampa Bay disappeared. Aggressive nutrient reduction efforts in the region between 1999 and 2018 led to water quality improvements and the recovery of seagrass in Tampa Bay; however, recent assessments have again shown significant reductions in seagrass followed by modest recoveries. On the opposite coast, a survey from 1999 indicated as much as 60% of seagrass coverage has been lost in a 56-mile stretch of the Indian River Lagoon.

These die-offs are primarily caused by nutrient pollution from inland farms and coastal cities. Plumes of single-celled microalgae and photosynthetic bacteria feast on excess nutrients and multiply in the water column, creating what are, in effect, marine clouds. This significantly reduces the amount of light that reaches the seafloor, which seagrasses don’t tolerate well. The Nature Coast, which was designated an aquatic preserve in 2020, has largely avoided these challenges.

Fossils as flashbacks and foretellers

Fossils are a bottomless treasure trove of information about the past—and significant signs of the future. If you want to know what went before and what is likely to come after, you just need to open a museum drawer or look at what’s under the microscope. For example, what had seemed to be no more than specks floating on the surface of a melted core sample of Greenland’s ice, was, in fact, a window into a bygone tundra landscape.

What else can simultaneously serve as a tangible link to our natural past—and a crystal ball into our manufactured future?

Here’s to finding your true places and natural habitats,

Candy