Tag Archives: mammals

Two Similar Jurassic Mammals Featured Distinctively Shaped Jaw Joints

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According to recent analyses of fossils from two mammalian forms, the development of jaws in modern mammals proves to be more intricate than previously understood. (i) Polystodon chuananensis, a mid-Jurassic herbivorous tritylodont known for its relatively large size and possibly fossilized lifestyle, and (ii) Camulochondylus rufengensis, a newly identified Morganucodontan from the Early Jurassic.

Reconstructed illustration of Polystodon chuananensis. Image credit: Chuang Zhao / PNSO.

“In mammals, the joint connecting the skull to the lower jaw consists of two bones: the squamous bone and the dentary bone, where the lower jaw teeth are situated,” stated Dr. Jin Meng, a curator at the American Museum of Natural History and a researcher at the City University of New York, along with colleagues.

“This configuration replaced the older temporomandibular joint seen in reptiles, which is composed of two different bones: the quadrate and the articular bone.”

“As organisms transitioned from early mammal-like reptiles to true mammals, various ‘experimental’ versions of this new temporomandibular joint arose to withstand the forces of mastication.”

“Ultimately, this culminated in the formation of the bimandibular joint, with the new dentosquamous joint handling most of the chewing pressure, maintaining the joint functionality in reptiles, and establishing an initial system for detecting airborne sounds.”

“Over time, the dentate squamosal became the sole joint, transforming the quadratoid joint into a diminutive bone within the mammal’s middle ear, a critical feature that aids in hearing.”

However, scientists still lack a comprehensive understanding of how this new temporomandibular joint evolved, primarily due to the scarcity of fossils from this era.

“The evolution of the mammalian temporomandibular joint represents one of the most fascinating yet incomplete chapters in vertebrate history, with gaps in fossil records obscuring significant transitions,” remarked Dr. Meng.

Researchers utilized high-resolution computed tomography scans from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences.

One of these species, Polystodon chuananensis, is an opossum-sized creature featuring “horns” potentially used for digging.

The other, Camulochondylus rufengensis, is a newly described squirrel-sized animal that lived during the Early Jurassic, approximately 174 to 201 million years ago.

Paleontologists identified new jaw structures in both ancient species.

In Polystodon chuananensis, they discovered a uniquely formed secondary temporomandibular joint located between the zygoma and dentary. This marks the first identification of this joint structure in a tetrapod.

In Camulochondylus rufengensis, they characterized a simple articular head of the dentary bone that likely indicates an evolutionary step towards a morphology adaptable to the new temporomandibular joint socket.

“These discoveries enhance the diversity of temporomandibular joints in mammalian evolution and broaden our comprehension of the evolutionary lineage of key mammalian features crucial for understanding how mammals process food and perceive airborne sounds,” the authors concluded.

Their study was published in the journal Nature in September 2025.

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F. Mao et al. Convergent evolution of diverse temporomandibular joints in mammals. Nature published online on September 24, 2025. doi: 10.1038/s41586-025-09572-0

Source: www.sci.news

Fossilized Teeth Uncover How Extinct Carnivorous Mammals Adapted to Global Warming 56 Million Years Ago

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Around 56 million years ago, during a period of significant geological warming known as the Paleocene-Eocene Thermal Maximum (PETM), the mesonychid mammal Dissacus Praenuntius exhibited remarkable dietary changes—it began to consume more bones.

Dissacus Praenuntius. Image credit: DIBGD / CC by 4.0.

“I am a doctoral student at Rutgers University in New Brunswick,” stated Andrew Schwartz from the University of New Jersey.

“We are observing a similar trend: rising carbon dioxide levels, increasing temperatures, and the destruction of ecosystems.”

In their study, Schwartz and his team analyzed small pits and marks left on fossilized teeth using a method known as dental microwear texture analysis. The research focused on the extinct mammal Dissacus Praenuntius, part of the Mesonychidae family.

This ancient omnivore weighed between 12 and 20 kg, comparable in size to jackals and coyotes.

Common in the early Cenozoic forests, it likely had a diverse diet that included meat, fruits, and insects.

“They resembled wolves with large heads,” Schwartz remarked.

“Their teeth were similar to those of hyenas, though they lacked small hooves on their toes.”

“Before this phase of warming, Dissacus Praenuntius mainly consumed tough meat, akin to a modern cheetah’s diet.”

“However, during and after this ancient warming period, their teeth showed wear patterns consistent with crushing hard substances like bones.”

“Our findings indicate that their dental microwear is similar to that of lions and hyenas.”

“This suggests they were consuming more brittle food rather than their usual smaller prey, which became scarce.”

This shift in diet occurred alongside a slight decrease in body size, likely a result of food shortages.

“While earlier theories attributed body size reduction solely to rising temperatures, this latest research indicates that food scarcity was a significant factor,” Schwartz explained.

“The rapid global warming of this time lasted around 200,000 years, but the changes it caused were swift and dramatic.”

“Studying periods like this can offer valuable lessons for understanding current and future climatic changes.”

“Examining how animals have adapted and how ecosystems responded can reveal much about what might happen next.”

“The research underscores the importance of dietary flexibility; species that can consume a variety of foods are more likely to endure environmental pressures.”

“In the short term, excelling in a specific area can be beneficial,” Schwartz added.

“However, in the long run, generalists—animals that are adaptable across various niches—are more likely to survive environmental changes.”

This understanding can assist modern conservation biologists in identifying vulnerable species today.

Species with specialized diets, like pandas, may struggle as their habitats diminish, while more adaptable species, such as jackals and raccoons, might thrive.

“We’re already starting to see these trends,” Schwartz noted.

“Previous research has shown that African jackals have begun to consume more bones and insects over time, likely due to habitat loss and climate stress.”

The study also indicated that rapid climate change, reminiscent of historical events, could lead to significant shifts in ecosystems, influencing prey availability and predator behaviors.

This suggests that contemporary climate change could similarly disrupt food webs, pushing species to adapt and face extinction risks.

“Nonetheless, Dissacus Praenuntius was a robust and adaptable species that thrived for about 15 million years before eventually going extinct,” Schwartz said.

Scientists believe this extinction was driven by environmental changes and competition with other species.

The study was published in June 2025 in the journal Paleogeography, Paleoclimatology, Paleoecology.

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Andrew Schwartz et al. 2025. Dietary Changes in Mesonychids During the Eocene Heat Maximum: The Case of Dissacus Praenuntius. Paleogeography, Paleoclimatology, Paleoecology 675:113089; doi:10.1016/j.palaeo.2025.113089

Source: www.sci.news

Human wounds heal significantly slower than those of other mammals.

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Upon witnessing wild baboons in Kenya, Matsumotoda Ogawa, an evolutionary biologist and primate researcher at the University of Lycys in Japan, observed firsthand the violence among these creatures, particularly among the males.

“The frequency of injuries was striking,” she remarked.

In contrast to her experiences with Nick and Kat, the healing abilities of baboons appeared almost superhuman.

In a study published in the Royal Society B, Dr. Matsumoto and her team examined healing rates in humans, chimpanzees, monkeys, and mice. They discovered that human wounds heal more than twice as slowly as those of other mammals. This slower recovery may stem from evolutionary trade-offs dating back to when we lost our fur for naked, sweat-producing skin that helps us regulate temperature.

Researchers aimed to study healing in a more chaotic environment beyond what wild baboons provide.

To assess human healing, they enlisted 24 patients recovering from skin tumor removals at Lycys University Hospital. For chimpanzee data, considered one of our closest animal cousins, the researchers studied five captive chimpanzees at the Kumamoto Reserve of the Kyoto University Wildlife Research Center, where animals previously used in drug studies reside. Injuries in chimpanzees, akin to those of wild baboons, primarily resulted from conflicts among the animals.

Other primate subjects were housed at the Kenya Primate Research Institute. The researchers anesthetized the monkeys, induced surgical wounds, and monitored their recovery. “As an outdoor researcher, I believe invasive procedures should be minimized,” emphasized Dr. Matsumoto Oda, noting that the wounds from wild baboons are often similar in size to those inflicted surgically but deeper.

Finally, to compare distantly related mammals with humans and primates, the team anesthetized and surgically wounded mice and rats.

Drawing from her field observations, Dr. Matsumoto-Oda expected humans to exhibit slower healing than other species, noting that the 24 participants regenerated their skin at an average rate of about a quarter millimeter per day.

What astonished Dr. Matsumoto-Oda even further was the uniformity of healing rates among the animal subjects, including chimpanzees. There were no significant differences in the rapid regeneration of skin across the different primates, averaging about 0.62 mm of new skin daily, unlike humans, who were clear outliers.

Elaine Fuchs, a stem cell biologist at Rockefeller University who focuses on skin growth and repair and was not involved in the new research, expressed that the findings aligned with her expectations. This is largely because skin healing is influenced by hair.

Every hair grows from a follicle containing stem cells. Typically, these stem cells produce more hair. However, when necessary, they can facilitate new skin growth. “When the epidermis sustains damage, such as from scratches and scuffs, it’s the hair follicle stem cells that perform the repairs,” Dr. Fuchs explained.

Furry animals are covered in follicles, enabling quicker wound closure in mice and monkeys. In contrast, “human skin has a much lower density of hair follicles,” Dr. Fuchs noted. Our ancestors lost many of these follicles, replacing them with sweat glands. Although sweat glands also contain stem cells, they are significantly less effective at wound repair, according to Dr. Fuchs.

Why did we choose to evolve in this manner, sacrificing hair and its protective benefits? The glands responsible for producing watery, salty sweat that moistens our shirts on hot days are known as eccrine glands. Most furry mammals have them in limited areas, primarily on their feet. Conversely, early human ancestors were adaptations to sweating—modern humans possess millions of sweat glands, with a density ten times greater than that of chimpanzees.

“Many have enjoyed the benefits,” remarked Daniel Lieberman, an evolutionary biologist at Harvard University. Our extensive sweat glands and lack of fur enabled our ancestors to thrive in physically demanding, hot environments, aiding in cooling our larger brain functions, Dr. Lieberman stated.

The advantages of sacrificing hair for sweat appear to outweigh the downsides. Dr. Matsumoto-Oda and her colleagues theorize that social support among early humans may have helped those with injuries survive despite their slower healing process. (Or perhaps there were methods to treat wounds, akin to practices seen in orangutans and chimpanzees.)

“The drawback of evolution is that wound healing is slower,” Dr. Fuchs observed, yet humans have gained significant evolutionary advantages from losing their fur.

“If you wish, you can always wear a coat,” she added.

Source: www.nytimes.com

Mammals evolved to thrive on land in the late Cretaceous period.

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A recent study conducted by the University of Bristol presents evidence that many mammals had already transitioned towards a more ground-based lifestyle prior to the final Cretaceous mass extinction that eradicated the non-avian dinosaurs 66 million years ago.

Dryolestes late Jurassic relatives of Cretaceous treatment mammals. Image credits: James Brown/Pamelagill/University of Bristol.

Present-day mammals thrive in a varied environment mainly dominated by angiosperms (flowering plants).

In contrast to the habitats provided by coniferous vegetation, forests and woodland environments possess intricate lower levels and towering trees, offering rich biodiversity and resources for terrestrial mammals of all sizes.

Yet, the angiosperm-dominated habitat is relatively recent in Earth’s history, primarily characteristic of the Cenozoic era (66 million years ago to the present), with initial developments towards the end of the Cretaceous period.

“Mesozoic mammals were typically small, mostly weighing under 5 kg, with few surpassing 10 kg,” noted Professor Christine Janice from the University of Bristol and a colleague.

“While it holds true that the majority of present-day mammals are small, averaging around 0.5 kg, the Cenozoic era saw the evolution of greater mammal diversity.”

“The small size of Mesozoic mammals has commonly been attributed to dinosaur predation, but recent recognition of the late Cretaceous proliferation of angiosperms and the habitats they offered may be more crucial than dinosaurs in elucidating the patterns of Mesozoic mammal evolution and diversification.”

“Did these mammals prefer trees or terrestrial substrates? And did this preference alter towards the close of the Cretaceous period with the changes in angiosperm habitats?”

In their research, the authors scrutinized tiny bone fragments of ancient mammalian taxa (marsupials and placentals) unearthed in western North America, specifically the extremity bone edges.

They identified indications that these mammals were adapting to a terrestrial lifestyle.

The analysis of extremity bone edges entailed signatures of locomotive patterns that could be statistically compared to modern mammals.

“There was a known shift in plant life towards the Cretaceous boundary, characterized by angiosperms,” stated the researchers.

“It was also acknowledged that arboreal-dwelling mammals faced challenges post-asteroid impact.”

“However, what remained undocumented was whether mammals were inclining towards a more ground-dwelling lifestyle alongside habitat transformations.”

Former studies utilized complete skeletons to study the movement patterns of ancient mammals, but this study was among the first to employ small bone elements to track alterations across the community.

“The plant habitat appears to have played a pivotal role in the trajectory of Cretaceous mammal evolution beyond dinosaur influences,” remarked Professor Janice.

Published in the March/April 2025 issue of the journal Paleontology, the study unveils intriguing insights into ancient mammal adaptations.

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Christine M. Janice et al. 2025. Paleontology 68(2): E70004; doi: 10.1111/pala.70004

Source: www.sci.news

New research suggests early mammals possessed dark, dim greyish brown fur

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Fur colours, which serve many functions, are essential for the evolution of mammal behavior, physiology and habitat preferences. However, little is known about the colour of Mesozoic mammals that co-evolved with dinosaurs. In a new study, scientists from China, Belgium, the Netherlands, the UK and the US used the dataset Melanosome (Melanin-Containing Organelle) We quantitatively measured the morphology and quantitatively measured hair colours of 116 live mammals to reconstruct the colours of six Mesozoic mammals, including the species Yuhalamiidan mammals that were not previously described.

Reconstructing the life of Shenshou Luian extinct squirrel-like euhalamidian species from the Jurassic region of central China. Image credit: Tamuranobu, http://spinops.blogspot.com.

From communication to camouflage, animal colour plays an important role in many behavioral ecological functions.

Some animals exhibit distinct and vivid arrangements like birds, but mammalian fur is generally limited to muted tones due to their dependence on the single pigment melanin.

Mammals lack palettes, but have evolved a diverse and distinctive coat pattern.

However, due to lack of data on pigmentation in extinct mammals, the evolutionary history of hairy colour is not well understood.

Recent studies have shown that melanosomes, which cause pigmentation, can be preserved in fossilized specimens.

A similar technique has successfully reconstructed the colours of dinosaurs, but despite well-preserved fur specimens, it has not been widely applied to fossil mammals.

In the new study, Dr. Ruoshuang Li, a colleague of the Chinese University of Earth Sciences and colleague, analyzed melanosomes in 116 living mammals and created a predictive model to reconstruct the hairy colour based on melanosome morphology.

The authors applied the model to six Mesozoic mammalian forms of fossilized melanosomes, including the newly described euhalamyidan species that lived 158.5 million years ago (Late Jurassic Epoch).

The authors found that the fur of these early mammals was primarily and uniformly dark in colour, with no stripes and spots that adorn many modern mammals.

This suggests that despite evolutionary differences in phylogenetics and ecology, the early mammalian melanin colored systems remained little different.

This is in stark contrast to the diverse melanosome structures found in feathered dinosaurs, early birds and pterosaurs, indicating a distinct evolutionary pattern of mammalian colour.

“The typical modern nocturne mammals, such as the dark, uniformly dull fur found in these species – moles, mice, rats and nocturne bats, support the previous hypothesis that early mammals are also largely nocturne and colored for camouflage,” the researchers said.

“In addition, the high melanin content of the fur may have been beneficial in providing mechanical strength for thermoregulation and protection.”

“Following the Cretaceous – Fat extinction event, mammals rapidly diversified into niches previously occupied by dinosaurs, leading to more diverse melanosome structures and new perage colour strategies that are more suited to a more diverse environment.”

Survey results It was published in the journal today Science.

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rushuang li et al. 2025. Mesozoic mammalian forms illuminate the origin of the colour of the hair. Science 387 (6739): 1193-1198; doi: 10.1126/science.ads9734

Source: www.sci.news

New study reveals that Clovis people primarily consumed mammoths and other large mammals in their diet

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Paleoanthropologists believe that the Columbian mammoth (mammoth colombi) are the largest contributor to the diet of the Clovis people, the earliest widespread hunter-gatherer group inhabiting North America, followed by elk and bison/camels, but the contribution of small mammals is There were very few.

An artist's reconstruction of Clovis life 13,000 years ago shows the Anzick 1 infant eating mammoth meat with his mother near the hearth. Another individual crafting tool, such as a dart launch point or an atlatl. A huge slaughterhouse can be seen nearby. Image credit: Eric Carlson / Ben Potter / Jim Chatters.

The Clovis people lived in North America about 13,000 years ago.

During that time, giant animals such as mammoths lived in both northern Asia and the Americas.

Because they traveled long distances, they became a reliable source of fat and protein for highly mobile humans.

Some researchers argue that the Clovisians were some degree of megafauna experts, with a particular focus on mammoths, while others argue that such adaptations were not viable and therefore They argue that Clovisians were extensive foragers, likely incorporating small amounts of food into their diets on a regular basis. Prey, plants, and perhaps fish.

“Focusing on mammoths helps explain how the Clovis people spread from across North America to South America in just a few hundred years,” said Dr. James Chatters, a researcher at McMaster University. said.

“What's surprising to me is that this corroborates a lot of the data from other sites,” said Ben Potter, a professor at the University of Alaska Fairbanks.

“For example, the animal parts left at the Clovis site are dominated by megafauna, and the firing points are large ones attached to darts, which were effective long-range weapons.”

In the new study, Dr Chatters, Professor Potter and their colleagues used stable isotope analysis to investigate the effects of 18-month-old children found at the 13,000-year-old Clovis site in Anzick, Montana, USA. I modeled the meal. state.

Their findings support the hypothesis that the Clovis people specialized in hunting large animals, rather than primarily foraging on small animals and plants.

Professor Potter said: “Mammoth hunting provided a flexible way of life.”

“This allowed the Clovis people to move to new areas without relying on smaller, localized prey that could vary widely from region to region.”

“This mobility is consistent with what we are seeing with Clovis technology and payment patterns.”

“They were very mobile. They transported resources such as toolstone over hundreds of miles.”

“Isotopes provide a chemical fingerprint of a consumer's diet, and can be compared to the isotopes of potential dietary items to determine the proportional contributions of different dietary items,” said Dr. Matt Wooler of the University of Alaska Fairbanks. It can be estimated.”

The researchers compared the mothers' stable isotope fingerprints with those obtained from different food sources from the same time and region.

They found that about 40% of her diet came from mammoths, with other large animals such as elk and bison making up the rest.

Although small mammals were sometimes considered an important food source, they played a very minor role in her diet.

Finally, the scientists compared the mother's diet to that of other omnivores and carnivores from the same period, including American lions, bears, and wolves.

The mother's diet was most similar to that of the scimitar cat, a mammoth specialist.

The discovery also suggests that early humans may have contributed to the extinction of Ice Age megafauna, especially as environmental changes reduced their habitat.

“If the climate is changing in a way that reduces suitable habitat for some of these megafauna, they potentially become more susceptible to human predation. These people are highly capable. He was a great hunter,” Professor Potter said.

“It was a combination of a very sophisticated hunting culture that responded to a simple, large animal group under environmental stress, and techniques honed over 10,000 years in Eurasia,” Dr Chatters said.

of the team result Published in today's diary scientific progress.

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James C. Chatters others. 2024. Mammoths featured heavily in the diet of western Clovis. scientific progress 10(49);doi: 10.1126/sciadv.adr3814

Source: www.sci.news

Paleontologists discover significant discrepancies in growth patterns between ancient and modern mammals from the Jurassic era

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In a new study, paleontologists used synchrotron X-ray tomography of annual growth in dental cementum from fossil mammals belonging to three Jurassic animal groups to elucidate the origin of mammalian growth patterns that are intrinsically linked to mammals being warm-blooded.

Jurassic forest mammals. Image courtesy of © Zhao Chuang.

“This is the first time we've been able to reconstruct the growth patterns of early mammals in such detail,” said Dr Elise Newnham, a postdoctoral researcher at Queen Mary, University of London and the University of Bonn.

“By studying the spacing and texture of these growth rings, we can not only tell us how fast they grew at different stages of their life, but also make inferences about their metabolism and overall lifespan.”

The study calls into question previous assumptions about the growth patterns of our mammalian ancestors and the idea that these animals may have grown in a way similar to modern mammals.

Instead, the study answers a question raised by similar recent studies of early mammalian ancestors: when did modern mammalian life cycles evolve?

The researchers found that the first signs of modern mammalian growth patterns — high growth rates in young animals that stop at puberty — began in the earliest true mammals about 130 million years ago, compared with relatively little change throughout their lives in previously evolved mammalian forms.

However, like mammals, these animals grow slower and live much longer than modern small mammals such as mice and mice, with a maximum lifespan of 8 to 14 years.

The timing of this change in growth rate, combined with changes in tree-ring structure, indicates when these animals reached puberty and possibly sexual maturity.

“These data suggest that while all living small mammals reach sexual maturity within a few months of birth, the earliest mammals took several years to reach sexual maturity, supporting the results of a recent study on one of our study animals. Cruxatodon” Dr Pam Gill, a researcher at the Natural History Museum and University of Bristol, said:

“What's more, we find that this long, drawn-out life history was common to early mammals throughout the Jurassic Period.”

“Our results suggest that distinctive mammalian life history traits, such as high metabolic rate and extended parental care, evolved gradually over millions of years,” Dr Newnham said.

“The Jurassic period appears to have been a pivotal period in this evolution.”

The researchers used a technique called synchrotron X-ray tomography to image tiny growth rings in fossilized root cementum, the bone tissue that attaches teeth to the jaw. These rings are similar to those found in trees, but on a microscopic scale.

By counting the growth rings and analysing their thickness and texture, they were able to reconstruct the growth patterns and lifespan of the extinct animals.

“This work is a great example of how new technologies are revolutionizing our understanding of the distant past,” said Professor Thomas Martin from the University of Bonn.

“By closely examining these fossilized teeth, we can gain valuable insight into the lives of organisms that lived millions of years ago.”

“We are incredibly excited to be involved in this project,” said researcher Dr Jen Bright, from the University of Hull.

“Putting Jurassic fossils in a particle accelerator (synchrotron) to reconstruct the past sounds like science fiction, but it's actually possible!”

of Investigation result Published in a journal Scientific advances.

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Ellis Newham others2024. Origin of mammalian growth patterns during the Jurassic mammalian radiation. Scientific advances 10(32); doi: 10.1126/sciadv.ado4555

Source: www.sci.news

Efficient spread of avian influenza among cattle and other mammals uncovered in study

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summary

  • A new study explains how bird flu spreads between dairy cows and from them to other mammals.
  • Experts are concerned that the virus may be developing new capabilities that help it evolve so it can spread from person to person, something that has not yet been observed.
  • A new study has found that cats and raccoons have died from a virus, possibly from drinking raw milk.

A new study of an ongoing avian flu outbreak on dairy farms provides an unprecedented look into how efficiently the virus spreads among cows and from them to other mammals, including cats and raccoons.

This suggests the virus is developing new capabilities that have bird flu experts concerned.

Bird flu is a concern in the United States due to various poultry populations. Over the past few years, scientists have feared the virus could become more transmissible from person to person and spark the next pandemic.

To the best of researchers' knowledge, there has not yet been any human-to-human transmission, but the number of cases of person-to-person transmission is continuing to increase, Colorado health officials confirmed. 3 new cases Fourteen new cases of bird flu were confirmed on Thursday, bringing the total in the country to 14.

All of the human cases have been farm workers who became infected after coming into contact with sick animals, and all but one was diagnosed within the past four months. Little is still known about the three most recent infections, but the remaining infections are mild.

New research shows that the virus is spreading from one mammal species to another, a relatively new phenomenon that could make it difficult for authorities to control.

The longer the virus goes uncontrolled, the greater the chance it will evolve and adapt, becoming a greater threat to people, say the authors of the new study. The study was published Tuesday in the journal Nature.

“This virus is not very effective at infecting or transmitting to humans, but that could change if the virus continues to circulate among dairy cows and then from there to other mammals,” said study author Diego Diehl, head of the virology lab at Cornell University's Animal Health Diagnostic Center. “This is cause for concern.”

The new study assessed the first outbreaks of avian influenza among cows on nine farms in Texas, New Mexico, Kansas and Ohio, taking animal samples and comparing the genetic similarities of the viruses between them.

Researchers found that the virus, a specific strain of avian flu known as H5N1, spread rapidly between farms. When infected cows were moved from Texas to another farm in Ohio, the virus was soon found in the Ohio cows. Genetic sequences also suggest that cats and raccoons have died from the virus, possibly after drinking raw milk.

Studies have shown that sick cows eat less feed, chew their cud less, produce less milk, and the color of their milk changes. On some infected farms, cows died at twice the normal rate.

Andrew Bowman, a professor of veterinary preventive medicine at Ohio State University who was not involved in the study, said the research reflects the experience of veterinarians on many U.S. farms.

“It's consistent with the clinical picture,” Bowman said. “This is exactly what we've been seeing on dairy farms. This is really just the first documentation that's been published.”

The study adds to the growing evidence that handling and drinking unpasteurized milk is dangerous.

Diehl said infected cows shed incredible amounts of the virus from their mammary glands, at concentrations higher than could easily be cultured in a lab.

“Drinking raw milk is extremely dangerous,” Diehl said.

Various studies have detected live H5N1 virus in raw milk. Pasteurization has been shown to inactivate virusesCommercially produced milk will be safe to drink.

Farmers must not send potentially contaminated milk to production.

“Milk from sick cows should not be used in the milk supply,” Bowman said.

As scientists continue to study the avian flu outbreak, Bowman said he's interested to know whether cows can shed the virus before they start showing signs of illness and whether the virus can continue to spread from mammals infected by cows.

This is only the third time a virus has spread fairly quickly between groups of mammals, said Anise Loewen, a virologist and professor at the Emory University School of Medicine, who was also not involved in the new study. Spreading on mink farms and Between sea lions and fur seals last summer.

Some mammals have severe cases, such as sea lions. sealamong other species.

Lowen said health officials should also consider the risk that people could be infected with H5N1 and seasonal influenza at the same time this winter: When people are infected with more than one influenza virus, the viruses can exchange genetic information, a process called “reassortment.”

This process could give the virus an evolutionary shortcut and change how the virus spreads.

“The viruses currently infecting cattle pose a relatively low risk to humans — that's what the CDC says, and they're right,” Loewen said. “But the risk I see is viral evolution. Viruses change as they adapt to new hosts. They change as they reassort and swap genes.”

The Centers for Disease Control and Prevention declined to comment on the new study.

Source: www.nbcnews.com

Ancient fossils reveal slower growth rates in mammals compared to modern species from Jurassic period

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Cruxatodon kiltlingtonensisA small mammal from the Jurassic period

Maiya Carrara

During the Middle Jurassic, small mammals lived much longer than modern ones and received parental care for years rather than weeks, suggesting that at some point there was a major change in the growth rates of small mammals, although the exact cause is unknown.

The discovery is based on two fossil skeletons of extinct mouse-sized creatures. Cruxatodon kiltlingtonensis, It lived on the Isle of Skye in Scotland about 166 million years ago, and its fossils were unearthed decades apart, the first in the 1970s and the second in 2016.

The unusual discovery of two fossils of the same species, one adult and one juvenile, allowed the team to compare the specimens to study how the animals grew and developed. “That meant we could ask questions we never dreamed of with just one specimen,” he says. Elsa Panciroli At the National Museum of Scotland.

First, the scientists used X-ray images to count the growth rings on the specimens' teeth, which are similar to growth rings on tree trunks and can be used to estimate age. They found that the adult specimens were about 7 years old, and the juvenile specimens were between 7 months and 2 years old.

Panciroli said he expected the fossil to be much younger, since the pup still had its baby teeth. “This was quite surprising, as this animal is about the size of a squirrel or a shrew,” Panciroli said. “We would have expected its teeth to grow back within a few weeks or months, so we could see straight away that it must have been developing quite differently. [than modern species].”

This discovery K. Quiltrington Mice took up to two years to wean from their mothers, a big jump from the few weeks most small mammals require today. Analysis of the length and size of the fossil bones reveals that the animals “grew throughout their lives,” Panchiroli says. Today, small mammals like mice grow rapidly when they're young but then stop growing as adults.

It's unclear exactly when and why small mammals evolved this way, but Panchiroli said it could be linked to environmental changes or it could be the result of mammals having warmer blood and a faster metabolism.

Panciroli and her team return to Skye every year, and are optimistic that they will be able to better understand these changes: “Hopefully in the coming years we'll find more fossils and new ways to ask these questions,” she says.

topic:

Source: www.newscientist.com

New Study Shows Male Mammals Are Not Larger Than Females

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In his influential work Descent of Man, Charles Darwin confidently asserted that male mammals are generally larger than females. This concept, known as sexual size dimorphism (SSD), initially seemed logical. Darwin believed that females needed to invest a significant amount of energy in their offspring during pregnancy and after giving birth, while males needed to be bigger and stronger to compete with other males, particularly in scenarios involving physical combat.

For over 150 years, Darwin’s views on this matter have remained largely unchallenged. However, a recent study conducted by researchers at the City University of New York and Princeton University may radically alter this perspective. The research indicates that in most mammalian species, there is actually no significant difference in body size between males and females.

The study analyzed a total of 429 mammal species, with nine individuals from each species being examined. While in species where sexual dimorphism is present (such as lions and deer, where males and females exhibit distinct physical traits), males tended to be larger. However, this pattern did not hold true for the majority of species.

For instance, many species of bats and rodents show minimal dimorphism, with males and females displaying similar sizes.

“We were surprised to discover that almost half of all bat species have larger females and that half of all rodent species exhibit sexual size monomorphism, where males and females are the same size,” stated Dr. Kaia Tombak, the lead scientist behind the study, in an interview with BBC Science Focus. “These two groups make up the majority of all mammals.”

Past studies on dimorphism have often excluded these species from their findings.

“The concept of ‘larger males’ remains prevalent in evolutionary biology,” Tombak noted. “However, if this research receives sufficient attention, it could lead to significant changes in this area.”

Bat

Yellow-winged bat (Lavia front) in Kenya. In this species, like most bats, females tend to be larger than males. Photo credit: Severin Hex

The most extreme female-biased dimorphism (where females are larger than males) was observed in peninsular tube-nosed bats (Murina Peninsula). Female world leaf-nosed bats (Phyllostomidae) also tended to be larger than males.

Source: www.sciencefocus.com