Paleontologists Reveal Multiple Instances of Marine Fish Migrating to Freshwater

The fish supergroup earball, recognized for its superior hearing abilities, includes two-thirds of freshwater fish species. They were previously believed to have originated in freshwater prior to the breakup of the supercontinent Pangaea. This suggests an almost 80 million-year span from their inception to the earliest known fossils. However, the discovery of Acronichthys MacCognoi—a newly identified freshwater ear fish species from the late Cretaceous period—challenges this assumption.



Reconstruction of the Weberian apparatus in Acronichthys MacCognoi. The central golden bone arises from the rib bones (indicated in grey) that connect the fish’s air bladder (left) to the inner ear (right). Image credit: University of California, Berkeley Ken Chronicle.

Underwater ears require a distinct anatomy compared to those that sense airborne sounds.

Many terrestrial vertebrates have evolved eardrum-like structures that vibrate in response to sound waves.

These eardrums amplify sounds, moving bone arrays, similar to the malleus, incus, and stapes found in human middle ears, which then stimulate the fluid-filled inner ear.

In contrast, sound waves travel through fish, which have a density similar to that of the surrounding water.

Consequently, fish have developed an air-filled bladder that vibrates in response to sound passing through it.

These vibrations are then transferred to the fish’s inner ear in a basic manner in most saltwater species.

However, specialized fish have developed bony structures known as “bones” between the air bladder and inner ear (a system called Weberian apparatus), enhancing the amplification and range of frequencies detectable by their ears. For instance, zebrafish can detect frequencies of up to 15,000 Hz, nearing the human limit of 20,000 Hz.

The reason for these fish’s need to hear high frequencies remains unclear, though it may relate to their existence in varied and complex environments, from swift currents to still lakes.

“reason Acronichthys Maccagnoi Professor Neil Banerjee, a researcher at Western University, noted:

“This represents the oldest known North American member of the group and offers invaluable data for documenting the origins and early evolution of numerous freshwater fish species existing today.”

Acronichthys Maccagnoi thrived in the late Cretaceous period roughly 67 million years ago.

The authors utilized microCT scans of 4 cm long fossils to investigate their Weber structure.

They also studied the genomes and morphology of contemporary fish to refine the evolutionary lineage of freshwater species and simulate frequency responses of the middle ear structures of fossil fish.

Their model indicates that even 67 million years ago, Otophysan fish may have possessed hearing sensitivity on par with today’s zebrafish.

“We were uncertain if this constituted a fully functional Weberian device, but the simulation proved effective,” stated Dr. Juan Liu, a paleontologist at the University of California, Berkeley.

“The Weberian apparatus suggests it’s less sensitive than that of zebrafish.”

“However, the peak sensitivity frequency is not as low as that of zebrafish (500-1,000 Hz). This is not an insignificant finding, and it’s conceivable that this ancient Otophysan fish achieved a higher hearing frequency.”

This discovery indicates that at least two transitions from marine to freshwater species occurred during the evolution of otolaryngology.

Researchers estimate the divergence times for ear plants migrating from ocean to freshwater habitats occurred around 154 million years ago (late Jurassic period), following the fragmentation of Pangaea around 200 million years ago.

“Dinosaurs are fascinating, attracting significant attention, which means we know a lot about them. However, there’s still much to uncover regarding the diversity of prehistoric freshwater fish.”

“Many keys to understanding the origins of the groups that currently dominate rivers and lakes worldwide can be found in Canadian fossil sites.”

A paper detailing these findings was published in the journal Science on October 2nd.

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Juan Liu et al. 2025. Marine origin and freshwater radiation of ENT. Science 390 (6768): 65-69; doi: 10.1126/science.adr4494

Source: www.sci.news

New Research Confirms Multiple Instances of Water Activity in Jezero Crater

Minerals constitute the building blocks of rocks, and the specific minerals and their chemical compositions reveal significant insights into rock formation and history. On Mars, NASA’s dedicated rover, equipped with X-ray lithochemistry (PIXL) instruments, produces geochemical maps of rock surfaces. A recent study examined over 90,000 chemical analyses collected by PIXL during its first 1,100 days on Mars, revealing that the minerals in Jezero Crater interact with various types of liquids over time. result This will be published in Journal of Geophysics: Planets.

This image from NASA’s Mars reconnaissance orbiter showcases the Jezero Crater on Mars. Image credits: NASA/JPL-CALTECH/MSSS/JHU-APL.

In this research, Eleanor Moreland, a Rice University graduate student, along with her team, utilized mineral identification through stoichiometry (MIST) algorithms to analyze PIXL data.

PIXL determines the chemical composition by bombarding Martian rocks with X-rays, yielding the most comprehensive geochemical measurements ever obtained from another planet.

“The minerals identified in Jezero Crater through MIST indicate that these volcanic rocks interacted with liquid water multiple times throughout Mars’ history, suggesting the potential for habitable conditions,” Moreland stated.

Minerals form under specific environmental conditions, such as temperature, pH, and the chemical composition of fluids, making them reliable narrators of planetary history.

Within Jezero Crater, 24 mineral species illustrate the volcanic characteristics of the Martian surface and their interactions with water over time.

Water chemically alters rocks, producing salt or clay minerals, with the specific minerals formed depending on environmental variables.

The minerals discovered in the crater showcase three different types of liquid interactions, each indicating distinct possibilities for habitability.

The first mineral suite, featuring green arilite, hizingerite, and ferroaluminoceradonite, shows localized high-temperature acidic fluids present only in crater bedrock, interpreted as among the oldest rocks studied.

The water involved in this scenario is regarded as the most conducive to life, given that research on Earth suggests high temperatures and low pH can harm biological structures.

“These hot, acidic conditions present the toughest challenges to life,” commented Kirsten Siebach, a researcher at Rice University.

“However, on Earth, life can thrive in extreme environments such as the acidic waters of Yellowstone, so this doesn’t negate the possibility of habitability.”

The second mineral suite favors more hospitable conditions and indicates a medium neutral fluid present over larger areas.

Minerals like Minnesotaite and Clinoptilolite were detected on both the crater floor and fan area, forming at lower temperatures with neutral pH, while Clinoptilolite was restricted to the crater floor.

Lastly, the third category represents a cold alkaline liquid, considered highly habitable from a modern Earth perspective.

Sepiolite, a common mineral change on Earth, was found to form under moderate temperature and alkaline conditions, widely distributed across all units explored by the rover.

The presence of sepiolite in all these units indicates multiple episodes of liquid water contributing to habitable conditions in Jezero Crater.

“These minerals demonstrate that Jezero Crater has undergone a transition from harsher, hotter, acidic liquid conditions to more neutral and alkaline environments over time.

Given that Mars samples cannot be prepared or scanned as accurately as Earth samples, the team developed an uncertainty propagation model to enhance the findings.

Using a statistical approach, MIST repeatedly assessed mineral identification while considering potential errors, analogous to how meteorologists predict hurricane paths by utilizing numerous models.

“Error analysis enables us to assign confidence levels to all mineral identifications,” Moreland remarked.

“MIST assists not just with the scientific and decision-making processes of Mars 2020, but also establishes a mineralogical archive of Jezero Crater, which will be invaluable if samples are returned to Earth.”

The findings affirm that Jezero Crater, once home to an ancient lake, has experienced a complex, dynamic aqueous history.

Each new mineral discovery brings us closer to determining whether Mars has ever supported life, while also refining strategies for sample collection and return.

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Eleanor L. Moreland et al. 2025. Multiple episodes of fluid changes in Jezero Crater indicated by the identification of MIST minerals in PIXL XRF data from the first 1100 SOL of the Mars 2020 mission. Journal of Geophysics: Planets 130 (9): e2024je008797; doi: 10.1029/2024je008797

Source: www.sci.news

Researchers have identified numerous instances of snow leopards dispersing from the Tibetan Plateau.

of snow leopard (panthera uncia) It is a large cat endemic to the Qinghai-Tibetan Plateau and surrounding areas. How this apex predator gradually adapted to its extreme environment remains a mystery due to Tibet’s sparse fossil record. In a new study, scientists examined five records outside Tibet of the snow leopard lineage. Their findings suggest that snow leopards dispersed from the Tibetan Plateau multiple times during the Quaternary period. The anatomy of modern snow leopards shows adaptation to steep slopes and cold/high-altitude environments. The new results suggest that snow leopards gradually strengthened such adaptations, especially since the Middle Pleistocene (800,000 years ago).

We predicted the appropriate distribution and morphospace of extant and fossil snow leopards. Image credit: Jianhao Ye.

The snow leopard is one of the emblematic animals of the Tibetan Plateau and is also distributed in the mountainous regions of Central Asia as well as the Mongolian Plateau.

It has distinctive features that clearly distinguish it from other members of the genus, including long, dense fur, long tail, short face, steep, broad forehead, and large cheek teeth. pantera.

Snow leopards typically live in alpine regions above 3,000 meters above sea level or above the tree line, but can also be found much lower, below 1,000 meters in some areas of Siberia.

The snow leopard’s status on the IUCN Red List is: vulnerablethere are 4,000 individuals. However, as global warming progresses, their distribution is expected to shift northward or to higher altitudes, which will have a major impact.

“Although the unique characteristics of the snow leopard have long been recognized, the correlation between these characteristics and their adaptation to the environment of the Tibetan Plateau, as well as their evolutionary history, remains largely unknown,” said the institute’s researchers. said Dr. Qigao Jianzuo. Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences and Peking University, and colleagues.

“This gap in understanding is primarily due to the rarity of snow leopard fossils on the Tibetan Plateau and surrounding areas.”

In this study, researchers described snow leopard fossils collected from five archaeological sites in Longdan, Gansu Province, China; Arago in France. Zhoukoudian area 3, Beijing, China. Manga Larga, Portugal. Niuyan Cave, Mendougou, Beijing, China.

With the exception of the Uyan Cave fossil, which can be classified as a modern snow leopard, the others show significant differences compared to extant snow leopards.

Scientists concluded that the snow leopards found outside the Qinghai-Tibetan Plateau are not an independent lineage, but rather consist of smaller branches from the main snow leopard branch.

These branches may indicate multiple dispersions of snow leopards from Tibet at different times.

To study the evolution of key morphological characters, the authors conducted a systematic analysis of the functional morphology of modern snow leopards using anatomy, geometric morphometrics, and finite element analysis. carried out.

Their findings show that snow leopards have large eye sockets and highly developed binocular vision, and have advanced stereopsis that allows them to quickly focus on prey even in complex terrain. It suggests that.

“Snow leopards have short snouts and steeply angled jaws, with canine teeth characterized by an approximately circular cross-section,” the researchers said.

“This structure allows them to exert great force and subdue strong prey, but it can also reduce their flexibility.”

“Furthermore, the snow leopard’s well-developed frontal sinus system warms the air it breathes, increasing its respiratory efficiency, making it a well-adapted animal to cold, low-oxygen environments.”

“Additionally, snow leopards have a prominent tympanic sac, which increases their sensitivity to infrasound and allows them to detect prey sounds from greater distances in open areas.”

“Thanks to their large cheek teeth (i.e. premolars and molars), they are able to eat most of the meat of their prey before it freezes in cold environments.”

“Additionally, these teeth improve the snow leopard’s ability to chew on already frozen carcasses.”

“The snow leopard’s scapula and pelvis are relatively small, but the bones in its distal limbs are elongated.”

“This suggests that although their forelimb strength is low, they have high movement flexibility, making them suitable for running and jumping in mountainous areas.”

“Most of these traits represent adaptations to the mountainous environment and their primary prey, Caprinae (sheep and their relatives). Capriidae tend to be slower, but shorter and shorter. It has sturdy limbs and strong horns that provide excellent resistance.

“Only some of the snow leopard’s adaptations are related to high-altitude, low-oxygen conditions.”

The researchers also studied the functional form of the fossil snow leopard by correlating its various morphological features with its functions.

They discovered early snow leopards, including the early Pleistocene. pantera Ah. Pirenaica From Longtan and early Middle Pleistocene Panthera Pirenaica The Frenchman’s lower jaw was already steeply angled, but not yet shortened.

Additionally, their cheek teeth were not enlarged. This suggests an early adaptation to caprine prey. However, no significant specialization for cold environments was evident at this stage.

Fossils from later periods such as the late Middle Pleistocene pantera Ah. anthea Zhoukoudian locality 3 and from the late Pleistocene Panthera Uncia Lusitanawas found to be very similar to modern snow leopards and exhibit comparable adaptations.

However, certain characteristics, such as the development of the ectotympanic cavity and the degree of forehead enlargement, were generally less pronounced in Europeans. Panthera Uncia Lusitana Compare it to the modern snow leopard.

“Bayesian analysis of the rate of morphological evolution indicates that snow leopards began to change rapidly during the Middle Pleistocene,” the authors said.

“This period coincides with the appearance of large ice sheets on the Qinghai-Tibet Plateau.”

“Since the Middle Pleistocene, global climate change has increased, resulting in more severe and prolonged ice ages.”

“These conditions have allowed the snow leopard to expand its range beyond the Qinghai-Tibet Plateau.”

“Notably, the Middle Pleistocene was also the time when many members of the Capriinae began to migrate from the Qinghai-Tibetan Plateau to northern China and Europe, paralleling the migration of snow leopards from the plateau.”

To determine whether fossil snow leopards have similar ecological adaptations to modern snow leopards, researchers analyzed the relationship between the distribution of modern snow leopards and climate data.

They took a random forest approach and trained a model known as species distribution modeling to predict how snow leopards would adapt based on climate conditions.

They then applied climate data from the Last Glacial Maximum to assess the potential maximum distribution of extant snow leopards during that period.

“This result indicates that the potential suitable distribution of snow leopards during the Last Glacial Maximum was significantly larger than it is today,” the scientists said.

“However, regions such as Europe and Beijing were outside of areas considered suitable for distribution.”

“This suggests that fossil snow leopards may have developed different ecological adaptations than modern snow leopards.”

“Therefore, the distribution of fossil snow leopards cannot be fully predicted using modern snow leopard models.”

“Furthermore, it should be noted that these fossil remains are generally located at relatively low altitudes (below 500 meters), but in mountainous environments, and usually contain fossils of the family Caprinae.” It’s important.”

“The only exception is archaeological sites in Portugal, where there are no animal records. This observation suggests that mountainous terrain and associated prey availability may be more important for snow leopards than high altitude, low oxygen conditions. This suggests that there is a possibility that

“Uuyan Cave is the only known place in the world that contains both snow leopard and leopard fossils.”

“We know that today’s snow leopards sometimes share habitat in transition zones near tree lines, so the Niuyang Cave discovery suggests that similar environmental conditions existed there when the fossils were deposited. It suggests possibility.”

“Tracing the evolutionary history and functional-morphological adaptations of the snow leopard, an important target for ecological conservation on the Qinghai-Tibetan Plateau, by integrating paleontology, molecular biology, finite element analysis, and species distribution modeling. I was able to do that.”

“Our findings reveal the evolutionary path of snow leopards and suggest that mountainous terrain may have played a more important role in their survival than climate factors alone.”

These insights are important for ongoing snow leopard conservation efforts and also demonstrate the utility of paleontological conservation.

Dr João Madurell Malapeira said: “Our analysis shows that altitude and snow are definitely not the limiting factors for the distribution of this species, but rather the presence of open and steep spaces. I have come to the conclusion that this may be the case.” Researchers at the University of Florence and the Autonomous University of Barcelona.

“In other words, snow leopards have always adapted to life in the mountains, but they don’t necessarily have to live at high altitude or in places with snow.”

“And this is an encouragement to ensure their survival in climate change conditions like the current one.”

team’s paper Published in a magazine scientific progress.

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Qigao Jiangzuo others. 2025. Insights into the evolution and adaptation to high altitude and cold environments in the snow leopard lineage. scientific progress 11(3);doi: 10.1126/sciadv.adp5243

Source: www.sci.news

Study finds evidence of multiple instances of Denisovan populations interbreeding with modern humans

The identification of a new human group called the Denisovans has been one of the most exciting discoveries in human evolution over the past decade. Unlike Neanderthal remains, the Denisovan fossil record consists of only a few skeletal fragments. Several Denisovan populations, which likely had vast geographic ranges, adapted to different environments and through multiple different interbreeding events that helped shape early human history, according to a new study. I passed on some of my genes.

Portrait of a young Denisovan woman based on a skeletal profile reconstructed from ancient DNA methylation maps. Image credit: Maayan Harel.

Denisovans are an extinct hominin group first identified through genome sequences determined from finger bone fragments found in the Denisova Cave in the Altai Mountains of southern Siberia.

“This was one of the most exciting discoveries in human evolution in the past decade,” said Dr Linda Ongaro, a researcher at Trinity College Dublin.

Subsequent genome analysis showed that Denisovans diverged from Neanderthals 400,000 years ago, and that at least two distinct Denisovan populations intermingled with the ancestors of modern Asians.

The only physical remains of Denisovans discovered so far are a finger bone fragment, three teeth, and a skull fragment from the Denisovan Cave. Jaw bones and rib bones from Baisiya Karst Cave on the northeastern edge of the Tibetan Plateau.

“It's a common misconception that humans evolved suddenly and cleanly from one common ancestor, but the more we learn, the more we realize that interbreeding with different hominins occurred and helped shape the humans we know today. ” said Dr. Ongaro.

“Unlike Neanderthal remains, the Denisovan fossil record consists only of finger bones, jaw bones, teeth, and skull fragments.”

“However, by exploiting the remaining Denisovan parts of modern humans' genomes, scientists have found evidence of at least three past events in which genes from different Denisovan populations invaded modern humans' genetic characteristics. I discovered.”

Each of these shows different levels of relatedness to the sequenced Altai Denisovans, illustrating the complex relationships between these sister lineages.

Dr. Ongaro and his colleague Professor Emilia Huerta Sánchez of Trinity College Dublin and Brown University, in their new paper, have a wide geographical range, from Siberia to Southeast Asia, and from Oceania to the south. We have reviewed evidence pointing to several likely Denisovan populations. America has adapted to a unique environment.

They also outlined a number of genes of Denisovan origin that conferred advantages to modern humans in different environments.

“Among these are genetic loci that confer tolerance to hypoxia or hypoxic conditions, which makes a lot of sense because we see it in the Tibetan population. Multiple genes that increase immunity. Another “Influences lipid metabolism and provides heat when stimulated by cold, providing benefits to Arctic Inuit populations,” Dr. Ongaro said.

“There are many directions for future research that will help us more fully understand how Denisovans influenced modern humans, including uncovering currently hidden traces of Denisovan ancestry. This includes more detailed genetic analyzes in understudied populations that have the potential to

“Additionally, by integrating more genetic data with archaeological information, finding more Denisovan fossils will certainly fill in some more gaps.”

of paper Published in a magazine natural genetics.

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L. Ongaro & E. Huerta-Sánchez. History of multiple Denisovan introgressions in modern humans. Nat Genetpublished on November 5, 2024. doi: 10.1038/s41588-024-01960-y

Source: www.sci.news