The extinct American cheetah wasn’t a true cheetah at all, say biologists in new research overturning our previous understanding of the legendary predator, revealing a cautionary tale about superficial scientific interpretations.
In a recent paper published in Current Biology, a research team led by scientists at the University of California, Santa Cruz, revealed that the so-called “American cheetah” is actually a relative of the Puma, adapted to Arctic conditions.
Scientifically known as Miracinonyx trumani, the American cheetah has turned out to be a fish-eating Puma relative and quite a distinct creature from the one envisioned by earlier researchers, as their suggestions were based primarily on the animal’s physical form. Using fossils discovered as far north as the Arctic Yukon, the team analyzed the species’ nuclear paleogenomes and stable isotopes, reconsidering the big cat at the genetic level.
M. trumani had long front legs and a slender body, weighing roughly 150 pounds and measuring about eight feet long and three feet tall. This sleek form allowed it to cross vast swathes of Pleistocene North America and achieve cheetah-like speeds.
While it may have developed a form similar to the cheetah, this is simply a case of convergent evolution, after the “American cheetah” split from the puma lineage some 2.6 million years ago. Fossils used in the research date from 23,000 to 31,000 years old, considerably more recent than that initial split.
Although the American cheetah is extinct today, its influence is still felt. One evolutionary theory is that the fastest North American land animal, the pronghorn, which can run up to 60 miles per hour, owes its tremendous speed to evolving to escape the swift predator.
One of the most intriguing elements of the new research is that it extends the cat’s habitat north by 20° latitude, into the Arctic Yukon. The team says that, depending on latitude, the species could occupy distinctly different ecological niches, demonstrating a high degree of adaptability to prevailing conditions.
To the south, the American cheetah had long been recognized as residing in Florida and Wyoming. In these areas, rich in temperate grasslands, the cat would have behaved as a generalist predator. However, in the harsher Arctic Yukon, it acted as a tertiary predator, living off fish like salmon.
“These cats were remarkably flexible, much like pumas are across their range today,” said lead author Molly Cassatt-Johnstone, a Ph.D. candidate in the Paleogenomics Lab at UC Santa Cruz. “We found loss-of-function mutations in certain genes that regulate circadian rhythms, suggesting they may have adapted to the extreme light cycles of summers and winters in northern latitudes.”
The genes revealed further peculiarities of M. Trumani. Generally, cats are known for a lack of interest in sweet foods, but this particular cat also lacked a sour taste receptor, a trait associated with specialized diets. Animals normally use this receptor to identify food that is safe to eat.
The fossils tell the story of a slow, steady decline in the species over the course of the Pleistocene. One notable factor could be their distinct lack of genetic diversity, which the researchers do not attribute to inbreeding.
“Miracinonyx persisted for a very long time without the signs of inbreeding we’d expect before a collapse,” senior author Beth Shapiro, professor of ecology and evolutionary biology at UC Santa Cruz and co-director of the Paleogenomics Lab, concluded. “The decline was slow, not sudden, and that may be what left it unable to adapt when the climate shifted.”
The paper, “Range and Diet Diversity in the Pleistocene American ‘Cheetah,’ Miracinonyx Trumani,” appeared in Current Biology on September 4, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.
Scientists have identified the first dinosaur fossil from a remote western section of the Bayan Gobi Formation in China’s Inner Mongolia, extending the known geographic range of dinosaur fossils in this important Early Cretaceous rock unit.
The post 115-Million-Year-Old Dinosaur Fossil Recovered from Deep Drill Core in China appeared first on Sci.News: Breaking Science News.
For several decades, paleontologists have described Miracinonyx trumani -- an extinct species of cheetah-like felid that roamed the North American prairies and steppe terrains more than 13,000 years ago -- as North America’s answer to the African cheetah (Acinonyx jubatus).
The post Ancient DNA Rewrites Story of Enigmatic ‘American Cheetah’ appeared first on Sci.News: Breaking Science News.
Paleontologists studying a fossil unearthed in southern Manitoba, Canada, have identified what they believe are two bite marks on the internal skeleton of the ancient giant cephalopod Enchoteuthis.
The post Fossil of Giant Squid-Like Creature from Cretaceous Period Bears Marks of Deadly Attack appeared first on Sci.News: Breaking Science News.
Long before the age of the Pharaohs and the monumental construction that defined the ancient Egyptian world, the famed Gift of the Nile was once a sea filled with hungry monsters.
Today, evidence of these ancient aquatic beasts can still be found in Egypt’s sands, as revealed in a new study appearing in Cretaceous Research, which sheds new light on the diversity of ancient shark communities that swam modern-day Egypt’s ancient oceans in the Late Cretaceous.
Adding to the known species of sharks from this era, the new research has revealed five additional species of ancient marine predators that once thrived there, fossils of which were among those unearthed in a fossil tomb very unlike those excavated by Egyptologists over the last two centuries.
During the Cretaceous period, Earth saw much higher temperatures, which also meant less ice accumulation around the poles. That abundance of liquid water caused by the greenhouse effect during this period in Earth’s history, therefore, led to much higher ocean levels than those seen today.
In Egypt’s Western Desert today, a vast tropical sea once existed 150 million years ago along what is recognized as the Abu-Tartur Plateau, which is home to the fossil-rich Duwi Formation. There, organic sediments collected over vast periods, which helped to create the phosphorite deposits that were conducive to fossil formation, thereby preserving a record of the ancient species that once thrived there.
Past studies had already documented several ancient shark species from the region’s Cretaceous oceans, prompting the additional research detailed in the new study. According to the team’s findings, more than a dozen new fossil shark teeth were recovered from the area around the Abu-Tartur mine, displaying a remarkable diversity.
Based on their individual characteristics, paleontologists have identified the new specimens based on existing records kept in museum collections and other record sources.
Of fourteen teeth the researchers uncovered from phosphorite beds during their field work, at least five extinct varieties of lamniform sharks—a variety known as mackerel sharks—were uncovered, which brings the number known to have once inhabited the region up to seven.
Of the five newly identified varieties, two species—Squalicorax bassanii and Serratolamna serrata—were previously unknown to Egypt, while one other variety, Scapanorhynchus raphiodon, appears to have been an ancient ancestor of the odd-looking goblin shark. Modern varieties of this species are known to thrive around continental shelves and seamounts throughout the Atlantic, Pacific, and Indian oceans, although the ancient relative identified in the new research had never previously been found anywhere on the African continent.
If confirmed, the recent Egyptian discovery could also indicate the earliest known presence of this species in Earth’s ancient oceans.
The new findings reveal new insights into the nature of Earth’s ancient seas, revealing that the prevalent nutrients in the tropical waters of the Cretaceous helped to foment a thriving ancient shark community.
“Collectively, this assemblage highlights a nutrient-enriched, high-productivity marine ecosystem along a phosphogenic shelf margin, most likely developed during a transgressive systems tract in the Late Cretaceous,” the study authors say.
The recent paper, “Egyptian shark graveyard: New Late Cretaceous Lamniform shark Assemblage from Duwi Formation of Abu-Tartur Area, Southwestern desert, Egypt,” appeared in Cretaceous Research.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.
A recent analysis of bones found in two separate underwater cave systems in South Australia has provided researchers with a new framework for investigating how animal remains, including those of extinct megafauna, came to rest in these submerged environments.
Well-preserved bones have often been found in submerged caves, but interpreting how they accumulated and what happened to them afterward has been difficult. Researchers have had limited tools for determining the environmental processes that alter remains over time.
The new study, led by Griffith University PhD candidate Meg Walker and Professor Julien Louys of the Australian Research Centre for Human Evolution, identifies physical, chemical, and molecular markers that can provide clues about the environmental conditions each specimen experienced. The findings were published in PLOS One.
With help from specialist cave divers from the Cave Divers Association of Australia, Walker’s team examined animal bones recovered from Green Waterhole and Gouldens Sinkhole, two underwater cave systems near Mount Gambier, South Australia. Gouldens Sinkhole reaches 63 meters deep through a nearly 30-meter-wide shaft.
The researchers used radiocarbon dating methods on 41 specimens and examined them at various scales, starting with a visual evaluation of spatial distribution and surface wear before progressing to portable X-ray fluorescence, scanning electron microscopy, and protein analysis. Using these techniques, the researchers identified chemical residue, signs of bacterial damage, and traces of ancient DNA. The group also identified changes associated with different preservation environments by comparing submerged bones with those recovered from nearby dry caves.
Light played an important role in some of the most noticeable changes to the bones. Near the cave entrances, where sunlight was available, algae and aquatic plants grew on the bone surfaces and left black biological stains, while cyanobacteria produced circular etchings and tunnels on the outer surfaces. Deeper within the caves, in areas where sunlight did not reach, the bones mostly stayed the same and retained their original characteristics.
This distinction is important because it shows that staining alone does not indicate that a bone was buried in sediment or fully submerged, as previously assumed. Instead, it shows that the bone was simply exposed to light.
Bones from the dry sections of the cave systems showed different patterns. In the absence of water and algae, land-based bacteria penetrated the bone from within, while plant roots created long grooves on the surface as they grew in search of nutrients. These features are distinct from those observed in submerged specimens.
The bones in the team’s study were not from ancient megafauna, belonging instead to cattle, kangaroos, emus, sheep, pigs, dingoes, rabbits, possums, quolls, and swamp rats. European settlers likely deposited the specimens in the caves after they arrived in the Mount Gambier region in the 1840s. DNA tests showed that one bone came from a Merino sheep.
The ultimate goal is to apply this framework to older material. Caves in the Mount Gambier region, such as Tank Cave and Englebrechts Cave, have yielded remains of Australia’s Pleistocene megafauna, including Diprotodon, a large marsupial similar in size to a rhinoceros, Thylacoleo carnifex, the largest known marsupial predator, and short-faced kangaroos that reached about 2 meters in height. Some of these fossils have remained undisturbed for more than 60,000 years.
Using Walker’s framework when looking at these specimens might help researchers understand how Australia’s megafauna fossils accumulated and could also provide a method for investigating factors such as human activity and environmental change that caused their extinction.
“This study has delivered the first framework for interpreting how megafauna fossils formed, survived, and changed in underwater caves,” Walker said. “It will provide archaeologists and paleontologists worldwide with a powerful new tool for reconstructing past environments and histories in these challenging conditions.”
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.
Horseshoe crabs are marine animals more closely related to spiders than crabs. These animals have existed for more than 450 million years, and are sometimes called “living fossils” because they appear to have changed very little throughout their evolutionary history. However, horseshoe crabs have a poor fossil record, so this apparent lack of change could also be due to a lack of evidence, particularly when it comes to their reproduction. Scientists want to know: Are horseshoe crabs truly living fossils?
Modern horseshoe crabs reproduce by releasing hundreds of eggs and sperm into tidal waters, via a process called external fertilization. Until now, scientists have assumed that horseshoe crabs have always reproduced this way. But paleontologists have only found 3 fossil horseshoe crabs from the past 252 million years with their reproductive systems preserved, so this assumption is mainly based on an absence of evidence to the contrary.
Scientists in the past interpreted the horseshoe crab’s long history of external fertilization as indicative of its evolutionary consistency. However, James Lamsdell and colleagues recently discovered a new fossil species of horseshoe crab in the 450 million-year-old Big Hill Formation in Michigan that challenges this assumption.
To study the specimen, the scientists photographed it under 2 types of microscopes. The first type of microscope used polarized light to see structures in the fossil that may have blended into the rock, like putting on special glasses to see subtle textures. The second type of microscope used fluorescent light to reveal soft tissue in the fossil. Only some tissues, like ovarian tissue and preserved eggs, glow under fluorescence, so this method helped the team rule out non-biological structures, like bubbles, cracks, or minerals.
The researchers found that their analytical techniques revealed remarkable details about the ancient horseshoe crab. One unique feature of the fossil was the shape of its exoskeleton. The fossil’s exoskeleton had a more shovel-like appearance than that of modern horseshoe crabs, which are less elongated and more round. It was also about 11 times smaller than a modern adult horseshoe crab.
The researchers also discovered that the fossil preserved an intricate network of ovaries containing unfertilized eggs. This ovarian network lined the interior surface of the shell in a band of interconnected tubes, preserving both unfertilized eggs and developing eggs. They noted that the fossil eggs were all about 0.1 to 0.15 millimeters in diameter, about the same width as a human hair. This size consistency suggested that all the eggs developed at the same time, via a process called synchronous development.
Since the fossil crab’s ovarian tubes contained developing eggs, it was an adult, meaning that the earliest adult horseshoe crabs were significantly smaller and shaped differently than modern adult horseshoe crabs. Despite their differences in size and shape, the fossil horseshoe crab’s reproductive system closely mirrored its modern one, in terms of its ovarian system and synchronous development of eggs. As in previous studies, it showed no evidence of internal fertilization.
The researchers concluded that the earliest horseshoe crabs also reproduced through external fertilization. This fossil horseshoe crab is more than 215 million years older than preexisting fossils preserving evidence of external fertilization, and suggests that the horseshoe crab’s mode of reproduction has been conserved for almost half a billion years!
However, the team’s findings reveal a more nuanced evolutionary history for the horseshoe crab than previously assumed. Although they’ve maintained the same reproductive system for almost half a billion years, the size and shape of their exoskeleton have changed. This discovery reveals that different parts of the horseshoe crab evolved at different rates. It seems that horseshoe crabs are not entirely the living fossils scientists once thought… while their bodies have evolved, their reproduction has endured.
The post Are horseshoe crabs truly “living fossils”? appeared first on Sciworthy.
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