Fungal outbreak in marine mammals began on land

In the early 2000s, a fungus infected hundreds of animals and people in British Columbia and Washington State. Scientists found that the disease also killed porpoises and dolphins in the Salish Sea-perhaps affecting cetaceans even earlier than people.

A study published today in Diseases of Aquatic Organisms explores how human-caused changes on land can affect aquatic animals, specifically in the case of the fungal pathogen, Cryptococcus gattii. Led by the University of California, Davis, a team of scientists from Canada and the Pacific Northwest pieced together the history of the fungal outbreak in marine mammals. They assembled and analyzed data collected over decades by veterinarians, microbiologists, marine mammal biologists, and marine mammal stranding responders.

C. gattii can cause lung and brain disease. It lives in soil and in tree dwellings and is acquired by breathing in fungal spores. It is not considered contagious between individuals. Typically found in tropical and subtropical forests paralleling the distribution of eucalyptus trees, C. gattii was likely translocated to the Pacific Northwest in the early 1900's, although the exact mechanisms are unknown.

Beginning in 1999 on Vancouver Island, humans, domestic animals, and terrestrial wildlife became infected with C. gattii, progressively affecting individuals living on mainland British Columbia, Washington, Oregon, and California. The researchers found that 42 dolphins and porpoises in the Salish Sea also died from the fungal pathogen, including harbor porpoises, Dall's porpoises, and Pacific white-side dolphins.

Construction, deforestation, and other activities that disturb soil can aerosolize C. gattii spores, causing infection in people and animals that live near the disturbed sites and breathe in the spores.

"As we change the environment in unprecedented ways, we could see more diseases that affect people and wildlife," said lead author Sarah Teman, a research assistant at the SeaDoc Society, a program of the Karen C. Drayer Wildlife Health Center at the UC Davis School of Veterinary Medicine.

The marine mammals that died from C. gattii were found near terrestrial hotspots, suggesting that the spores settled on the surface of the sea, where the porpoises and dolphins inhaled them when they surfaced to breathe.

Researchers also found evidence that the first probable case of C. gattii in the Pacific Northwest could have occurred in a Dall's porpoise in 1997 -- two years before the identification of the first human case in the region in 1999.

"Often we study marine mammals because they play important roles in the ecosystem, and they are cool," said Joe Gaydos, UC Davis wildlife veterinarian at SeaDoc Society and co-investigator. "Too often we forget that they can also alert us to diseases that affect humans."

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Traces of an ancient road in a lake

Anyone traveling from the German city of Brandenburg via Berlin to Frankfurt an der Oder at the Polish-German border does so along an ancient route that reaches far into Poland. German and Polish researchers have now documented the influence of this East-West connection on the history of the landscape by examining the sediments of Lake Czechowskie in the Bory Tucholskie and also evaluating historical sources. According to the results, three phases of landscape development can be distinguished in the last eight hundred years: from an almost untouched landscape through an intermediate phase lasting several centuries -- characterized by alternations between strong settlement activity and the return of nature after wars -- to today's cultural landscape.

One of the two main authors, Achim Brauer of the GFZ German Research Centre for Geosciences in Potsdam, says: "Wars had a clear influence, as the Via Marchionis was repeatedly used for troop transports that led to local destruction and devastation. In this study, for the first time, we have shown the impact on the landscape for every war in the region's history. In general, wars have led to greater or lesser devastation ('renaturalization') of the landscape, which has also lasted for varying lengths of time."

At other times, it was political developments that left their mark on the landscape, such as an agrarian reform in 1343, which led, with a certain time lag, to an accelerated "anthropogenization" of the landscape, that is, to clearly visible human influence. In the sediments of Lake Czechowskie this is shown by a strong increase of rye pollen and the decrease of birch and pine pollen.

Because sediments in a lake exhibit annual stratification similar to tree rings, the German-Polish team was able to pinpoint the year from which pollen originated by counting the individual layers ("warves") down to a resolution of five years. According to this, the landscape remained largely untouched by humans until about 1350 AD. Extensive forests and natural grasses dominated. Then followed five turbulent centuries. The expansion of agriculture and the formation of larger towns were favored by a warm climate and politically calm times. However, between 1409 and 1435 there was war between the Teutonic Order and Poland -- fields became fallow land, forests expanded again. After peace was concluded, five quiet decades followed again, during which an increase in handicrafts was also evident. Hardwood was cut to obtain building material and potash -- thus, birch pollen disappeared from lake sediments, rye again increased massively.

Huge army campaigns with thousands of riders and foot soldiers, plague epidemics in several waves and some very cold years with crop failures are also documented. Then, from the middle of the 19th century, the influence of agriculture, settlements and economic activity took over to such an extent that one can speak of a predominantly human influence, which continues to this day.

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That primate’s got rhythm!

Songbirds share the human sense of rhythm, but it is a rare trait in non-human mammals. An international research team led by senior investigators Marco Gamba from the University of Turin and MPI’s Andrea Ravignani set out to look for musical abilities in primates. “There is longstanding interest in understanding how human musicality evolved, but musicality is not restricted to humans”, says Ravignani. “Looking for musical features in other species allows us to build an ‘evolutionary tree’ of musical traits, and understand how rhythm capacities originated and evolved in humans.”

To find out whether non-human mammals have a sense of rhythm, the team decided to study one of the few ‘singing’ primates, the critically endangered lemur Indri indri. The researchers wanted to know whether indri songs have categorical rhythm, a ‘rhythmic universal’ found across human musical cultures. Rhythm is categorical when intervals between sounds have exactly the same duration (1:1 rhythm) or doubled duration (1:2 rhythm). This type of rhythm makes a song easily recognisable, even if it is sung at different speeds. Would indri songs show this “uniquely human” rhythm?

Ritardando in the rainforest

Over a period of twelve years, the researchers from Turin visited the rainforest of Madagascar to collaborate with a local primate study group. The investigators recorded songs from twenty indri groups (39 animals), living in their natural habitat. Members of an indri family group tend to sing together, in harmonised duets and choruses. The team found that indri songs had the classic rhythmic categories (both 1:1 and 1:2), as well as the typical ‘ritardando’ or slowing down found in several musical traditions. Male and female songs had a different tempo but showed the same rhythm.

According to first author Chiara de Gregorio and her colleagues, this is the first evidence of a ‘rhythmic universal’ in a non-human mammal. But why should another primate produce categorical ‘music-like’ rhythms? The ability may have evolved independently among ‘singing’ species, as the last common ancestor between humans and indri lived 77.5 million years ago. Rhythm may make it easier to produce and process songs, or even to learn them.

Endangered species

“Categorical rhythms are just one of the six universals that have been identified so far”, explains Ravignani. “We would like to look for evidence of others, including an underlying ‘repetitive’ beat and a hierarchical organisation of beats—in indri and other species.” The authors encourage other researchers to gather data on indri and other endangered species, “before it is too late to witness their breath-taking singing displays.”

From Science Daily

Men, women ride the same emotional roller coaster

Contrary to widely held gender stereotypes, women are not more emotional than men, researchers say.

Feelings such as enthusiasm, nervousness or strength are often interpreted differently between the two genders. It's what being "emotional" means to men vs. women that is part of a new University of Michigan study that dispels these biases.

For instance, a man whose emotions fluctuate during a sporting event is described as "passionate." But a woman whose emotions change due to any event, even if provoked, is considered "irrational," says the study's senior author Adriene Beltz, U-M assistant professor of psychology.

Beltz and colleagues Alexander Weigard, U-M assistant professor of psychiatry, and Amy Loviska, a graduate student at Purdue University, followed 142 men and women over 75 days to learn more about their daily emotions, both positive and negative. The women were divided into four groups: one naturally cycling and three others using different forms of oral contraceptives.

The researchers detected fluctuations in emotions three different ways, and then compared the sexes. They found little-to-no differences between the men and the various groups of women, suggesting that men's emotions fluctuate to the same extent as women's do (although likely for different reasons).

"We also didn't find meaningful differences between the groups of women, making clear that emotional highs and lows are due to many influences -- not only hormones," she said.

The findings have implications beyond everyday people, the researchers say. Women have historically been excluded from research participation in part due to the assumption that ovarian hormone fluctuations lead to variation, especially in emotion, that can't be experimentally controlled, they say.

"Our study uniquely provides psychological data to show that the justifications for excluding women in the first place (because fluctuating ovarian hormones, and consequently emotions, confounded experiments) were misguided," Beltz said.

From Science Daily

Infant planet discovered

One of the youngest planets ever found around a distant infant star has been discovered by an international team of scientists led by University of Hawaii at Manoa faculty, students, and alumni.

Thousands of planets have been discovered around other stars, but what sets this one apart is that it is newly-formed and can be directly observed. The planet, named 2M0437b, joins a handful of objects advancing our understanding of how planets form and change with time, helping shed new light on the origin of the Solar System and Earth. The in-depth research was recently published in Monthly Notices of the Royal Astronomical Society.

"This serendipitous discovery adds to an elite list of planets that we can directly observe with our telescopes," explained lead author Eric Gaidos, a professor in the UH Manoa Department of Earth Sciences. "By analyzing the light from this planet we can say something about its composition, and perhaps where and how it formed in a long-vanished disk of gas and dust around its host star."

The researchers estimate that the planet is a few times more massive than Jupiter, and that it formed with its star several million years ago, around the time the main Hawaiian Islands first emerged above the ocean. The planet is so young that it is still hot from the energy released during its formation, with a temperature similar to the lava erupting from Kilauea Volcano.

Key Maunakea telescopes

In 2018, 2M0437b was first seen with the Subaru Telescope on Maunakea by UH Institute for Astronomy (IfA) visiting researcher Teruyuki Hirano. For the past several years, it has been studied carefully utilizing other telescopes on the mauna.

Gaidos and his collaborators used the Keck Observatory on Maunakea to monitor the position of the host star as it moved across the sky, confirming that planet 2M0437b was truly a companion to the star, and not a more distant object. The observations required three years because the star moves slowly across the sky.

The planet and its parent star lie in a stellar "nursery" called the Taurus Cloud. 2M0437b is on a much wider orbit than the planets in the Solar System; its current separation is about one hundred times the Earth-Sun distance, making it easier to observe. However, sophisticated "adaptive" optics are still needed to compensate for the image distortion caused by Earth's atmosphere.

"Two of the world's largest telescopes, adaptive optics technology and Maunakea's clear skies were all needed to make this discovery," said co-author Michael Liu, an astronomer at IfA. "We are all looking forward to more such discoveries, and more detailed studies of such planets with the technologies and telescopes of the future."

Future research potential

Gathering more in-depth research about the newly-discovered planet may not be too far away. "Observations with space telescopes such as NASA's Hubble and the soon-to-be-launched James Webb Space Telescope could identify gases in its atmosphere and reveal whether the planet has a moon-forming disk," Gaidos added.

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A new Earth bombardment model

A team led by Southwest Research Institute has updated its asteroid bombardment model of the Earth with the latest geologic evidence of ancient, large collisions. These models have been used to understand how impacts may have affected oxygen levels in the Earth's atmosphere in the Archean eon, 2.5 to 4 billion years ago.

When large asteroids or comets struck early Earth, the energy released melted and vaporized rocky materials in the Earth's crust. The small droplets of molten rock in the impact plume would condense, solidify and fall back to Earth, creating round, globally distributed sand-size particles. Known as impact spherules, these glassy particles populated multiple thin, discrete layers in the Earth's crust, ranging in age from about 2.4 to 3.5 billion years old. These Archean spherule layers are markers of ancient collisions. "In recent years, a number of new spherule layers have been identified in drill cores and outcrops, increasing the total number of known impact events during the early Earth," said Dr. Nadja Drabon, a professor at Harvard University and a co-author of the paper.

"Current bombardment models underestimate the number of late Archean spherule layers, suggesting that the impactor flux at that time was up to 10 times higher than previously thought," said SwRI's Dr. Simone Marchi, lead author of a paper about this research in Nature Geoscience. "What's more, we find that the cumulative impactor mass delivered to the early Earth was an important 'sink' of oxygen, suggesting that early bombardment could have delayed oxidation of Earth's atmosphere."

The abundance of oxygen in Earth's atmosphere is due to a balance of production and removal processes. These new findings correspond to the geological record, which shows that oxygen levels in the atmosphere varied but stayed relatively low in the early Archean eon. Impacts by bodies larger than six miles (10 km) in diameter may have contributed to its scarcity, as limited oxygen present in the atmosphere of early Earth would have been chemically consumed by impact vapors, further reducing its abundance in the atmosphere.

"Late Archean bombardment by objects over six miles in diameter would have produced enough reactive gases to completely consume low levels of atmospheric oxygen," said Dr. Laura Schaefer, a professor at Stanford University and a co-author of the paper. "This pattern was consistent with evidence for so-called 'whiffs' of oxygen, relatively steep but transient increases in atmospheric oxygen that occurred around 2.5 billion years ago. We think that the whiffs were broken up by impacts that removed the oxygen from the atmosphere. This is consistent with large impacts recorded by spherule layers in Australia's Bee Gorge and Dales Gorge."

SwRI's results indicate that the Earth was subject to substantial numbers of large impacts throughout the late Archean era. Around 2.4 billion years ago, during the tail end of this bombardment, the Earth went through a major shift in surface chemistry triggered by the rise of atmospheric oxygen, dubbed the Great Oxidation Event (GOE), which is attributed to changes in the oxygen production-sink balance. Among the proposed scenarios are a presumed increase in oxygen production and decrease in gases capable of removing oxygen, either from volcanic sources or through their gradual loss to space.

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‘Raptor-like’ dinosaur discovered in Australian mine, actually uncovered as a timid vegetarian

Fossil footprints found in an Australian coal mine around 50 years ago have long been thought to be that of a large 'raptor-like' predatory dinosaur, but scientists have in fact discovered they were instead left by a timid long-necked herbivore.

University of Queensland palaeontologist Dr Anthony Romilio recently led an international team to re-analyse the footprints, dated to the latter part of the Triassic Period, around 220 million-year-ago.

"For years it's been believed that these tracks were made by a massive theropod predator that was part of the dinosaur family Eubrontes, with legs over two metres tall," Dr Romilio said.

"This idea caused a sensation decades ago because no other meat-eating dinosaur in the world approached that size during the Triassic period."

However, findings made by a team of international researchers, published today in the peer-reviewed journal Historical Biology, in fact shows the tracks were instead made by a dinosaur known as a Prosauropod - a vegetarian dinosaur that were smaller, with legs about 1.4 metres tall and a body length of six metres.

The research team suspected there was something not-quite-right with the original size estimates and there was a good reason for their doubts.

"Unfortunately, most earlier researchers could not directly access the footprint specimen for their study, instead relying on old drawings and photographs that lacked detail," Dr Romilio said.

The dinosaur fossils were discovered more than half a century ago around 200 metres deep underground at an Ipswich coal mine, just west of Brisbane.

"It must have been quite a sight for the first miners in the 1960s to see big bird-like footprints jutting down from the ceiling," Dr Romilio said.

Hendrik Klein, co-author and fossil expert from Saurierwelt Paläontologisches Museum in Germany, said the footprints -- referred to as 'Evazoum', scientifically, the footprint type made by prosauropod dinosaurs -- were made on the water-sodden layers of ancient plant debris with the tracks later in-filled by silt and sand.

"This explains why today they occur in an upside-down position right above our heads," Mr Klein said.

"After millions of years, the plant material turned into coal which was extracted by the miners to reveal a ceiling of siltstone and sandstone, complete with the natural casts of dinosaur footprints."

The mine has long since closed, but fortunately, in 1964, geologists and the Queensland Museum mapped the trackway and made plaster casts, now used in current research.

"We made a virtual 3D model of the dinosaur footprint that was emailed to team members across the world to study," Mr Klein said.

"The more we looked at the footprint and toe impression shapes and proportions, the less they resembled tracks made by predatory dinosaurs -- this monster dinosaur was definitely a much friendlier plant-eater.

"This is still a significant discovery even if it isn't a scary Triassic carnivore.

"This is the earliest evidence we have for this type of dinosaur in Australia, marking a 50-million-year gap before the first quadrupedal sauropod fossils known."

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Discovery of new tiny fish, lizard species

Two tiny new species that inhabited part of what is now the American south some 100 million years ago have been discovered by a team of researchers that includes a University of Wisconsin Oshkosh paleontologist.

Joseph Frederickson, a vertebrate paleontologist and director of the Weis Earth Science Museum on the Fox Cities campus, is among the authors on a recent paper published in PeerJ, highlighting these new discoveries in southwest Arkansas. The species are a small lizard researchers named Sciroseps pawhuskai and a fish named Anomoeodus caddoi.

The paper is titled A new vertebrate fauna from the Lower Cretaceous Holly Creek Formation of the Trinity Group, southwest Arkansas, USA. Celina Suarez, associate professor of geosciences at the University of Arkansas, served as primary author on the article, which pulls together decades of research in the area known as the Holly Creek Formation. Frederickson is the second author.

"The Holly Creek Formation is interesting because few fossils have been described in publications, even though it has produced dinosaur fossils in the past," Frederickson said. "Formations like these help us better understand how the continent was connected and the diversity of animals alive during the Early Cretaceous Period."

The discoveries serve both to underscore the variety of fossils found at this site, including dinosaurs, mammals, fish, amphibians and reptiles, and to reinforce the overall lack of variety of fossils found throughout North America from the period.

"The fish and lizard represent material, though small and fragmentary, that preserves enough detail to call them new species," he said. "The lizard jaw is specifically interesting because normally fossils are limited to small and broken bits, while the specimen we describe in this paper is most of a complete lower jaw."

Frederickson began work with the project in 2017. The previous year he started work with Suarez on a fossil-bearing site in Montana.

His part of the Arkansas project included investigating the micro-fossils, or small material that required microscopes to see in detail. This included the fish, amphibians, reptiles and dinosaurs teeth. He compared these fossils with those from similarly aged rocks in Oklahoma, Montana and Maryland to determine which species were present and then photographed the material using a scanning electron microscope.

This latest publish work comes a year after Frederickson made headlines for another published paper. In 2020, he presented evidence that Velociraptors likely did not hunt in large, coordinated packs as famously depicted in the Jurassic Park films. This latest research, of course, focuses in on creatures far less glamorous than the immortalized-by-Hollywood raptor.

"I think this paper is a good reminder that the fossil record preserves many different animals, not just dinosaurs," he said. "This paper focuses heavily on the tiny organisms crawling or swimming at the feet of giant dinosaurs, which too often go undocumented because they can be difficult to study. However, often it's these small animals that tell us the most about the environment in which they lived."

The study resulted from long-term investigations that began in Arkansas in the 1970s. That area is where thousands of sauropod and theropod tracks have been discovered, beginning in the 1980s.

Dinosaurs previously preserved from the site include at least one long-necked sauropod (likely Sauroposeidon), large theropods (a juvenile Acrocanthosaurus), an ankylosaur (armored dinosaur), and the small kickboxing raptor, Deinonychus.

A variety of very small fossils also was uncovered, including remains of sharks, bony fish, frogs, lizards, turtles, crocodilians and mammals. Although unspectacular, these tiny bones and teeth document the presence of numerous species critical to understanding the ecosystem that lived in Arkansas millions of years ago.

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Astronomers detect signs of an atmosphere stripped from a planet in a giant impact

Young planetary systems generally experience extreme growing pains, as infant bodies collide and fuse to form progressively larger planets. In our own solar system, the Earth and moon are thought to be products of this type of giant impact. Astronomers surmise that such smashups should be commonplace in early systems, but they have been difficult to observe around other stars.

Now astronomers at MIT, the National University of Ireland at Galway, Cambridge University, and elsewhere have discovered evidence of a giant impact that occurred in a nearby star system, just 95 light years from Earth. The star, named HD 172555, is about 23 million years old, and scientists have suspected that its dust bears traces of a recent collision.

The MIT-led team has observed further evidence of a giant impact around the star. They determined that the collision likely occurred between a roughly Earth-sized terrestrial planet and a smaller impactor at least 200,000 years ago, at speeds of 10 kilometers per second, or more than 22,000 miles per hour.

Crucially, they detected gas indicating that such a high-speed impact likely blew away part of the larger planet's atmosphere -- a dramatic event that would explain the observed gas and dust around the star. The findings, appearing today in Nature, represent the first detection of its kind.

"This is the first time we've detected this phenomenon, of a stripped protoplanetary atmosphere in a giant impact," says lead author Tajana Schneiderman, a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences. "Everyone is interested in observing a giant impact because we expect them to be common, but we don't have evidence in a lot of systems for it. Now we have additional insight into these dynamics."

A clear signal

The star HD 172555 has been an object of intrigue among astronomers because of the unusual composition of its dust. Observations in recent years have shown that the star's dust contains large amounts of unusual minerals, in grains that are much finer than astronomers would expect for a typical stellar debris disk.

"Because of these two factors, HD 172555 has been thought to be this weird system," Schneiderman says.

She and her colleagues wondered what the gas might reveal about the system's impact history. They looked to data taken by ALMA, the Atacama Large Millimeter Array in Chile, which comprises 66 radio telescopes, the spacing of which can be adjusted to increase or decrease the resolution of their images. The team looked through data from the ALMA public archive, seeking signs of carbon monoxide around nearby stars.

"When people want to study gas in debris disks, carbon monoxide is typically the brightest, and thus the easiest to find," Schneiderman says. "So, we looked at the carbon monoxide data for HD 172555 again because it was an interesting system."

In the aftermath

With a careful reanalysis, the team was able to detect carbon monoxide around the star. When they measured its abundance, they found the gas amounted to 20 percent of the carbon monoxide found in Venus' atmosphere. They also observed that the gas was circling in large amounts, surprisingly close to the star, at about 10 astronomical units, or 10 times the distance between the Earth and the sun.

"The presence of carbon monoxide this close requires some explanation," Schneiderman says.

That's because carbon monoxide is typically vulnerable to photodissociation, a process in which a star's photons break down and destroy the molecule. At close range, there would typically be very little carbon monoxide so close to a star. So, the group tested various scenarios to explain the gas' abundant, close-in appearance.

They quickly ruled out a scenario in which the gas arose from the debris of a newly formed star, as well as one in which the gas was produced by a close-in belt of icy asteroids. They also considered a scenario in which the gas was emitted by many icy comets streaking in from a far-out asteroid belt, similar to our own Kuiper belt. But the data didn't quite fit this scenario either. The last scenario the team considered was that the gas was a remnant of a giant impact.

"Of all the scenarios, it's the only one that can explain all the features of the data," Schneiderman says. "In systems of this age, we expect there to be giant impacts, and we expect giant impacts to be really quite common. The timescales work out, the age works out, and the morphological and compositional constraints work out. The only plausible process that could produce carbon monoxide in this system in this context is a giant impact."

The team estimates that the gas was released from a giant impact that occurred at least 200,000 years ago -- recent enough that the star would not have had time to completely destroy the gas. Based on the gas' abundance, the impact was likely massive, involving two proto-planets, likely comparable in size to the Earth. The impact was so great that it likely blew off part of one planet's atmosphere, in the form of the gas that the team observed today.

Read more at Science Daily

Early dinosaurs may have lived in social herds as early as 193 million years ago

To borrow a line from the movie "Jurassic Park:" Dinosaurs do move in herds. And a new study shows that the prehistoric creatures lived in herds much earlier than previously thought.

In a paper appearing in Scientific Reports, researchers from MIT, Argentina, and South Africa detail their discovery of an exceptionally preserved group of early dinosaurs that shows signs of complex herd behavior as early as 193 million years ago -- 40 million years earlier than other records of dinosaur herding.

Since 2013, members of the team have excavated more than 100 dinosaur eggs (about the size of chicken eggs) and the partial skeletons of 80 juvenile and adult dinosaurs from a rich fossil bed in southern Patagonia.

Using X-ray imaging, they were able to examine the eggs' contents without breaking them apart, and discovered preserved embryos within, which they used to confirm that the fossils were all members of Mussaurus patagonicus -- a plant-eating dinosaur that lived in the early Jurassic period and is classified as a sauropodomorph, a predecessor of the massive, long-necked sauropods that later roamed the Earth.

Surprisingly, the researchers observed that the fossils were grouped by age: Dinosaur eggs and hatchlings were found in one area, while skeletons of juveniles were grouped in a nearby location. Meanwhile, remains of adult dinosaurs were found alone or in pairs throughout the field site.

This "age segregation," the researchers believe, is a strong sign of a complex, herd-like social structure. The dinosaurs likely worked as a community, laying their eggs in a common nesting ground. Juveniles congregated in "schools," while adults roamed and foraged for the herd.

"This may mean that the young were not following their parents in a small family structure," says team member Jahandar Ramezani, a research scientist in MIT's Department of Earth, Atmospheric and Planetary Sciences. "There's a larger community structure, where adults shared and took part in raising the whole community."

Ramezani dated ancient sediments among the fossils and determined that the dinosaur herd dates back to around 193 million years ago, during the early Jurassic period. The team's results represent the earliest evidence of social herding among dinosaurs.

Living in herds may have given Mussaurus and other social sauropodomorphs an evolutionary advantage. These early dinosaurs originated in the late Triassic, shortly before an extinction event wiped out many other animals. For whatever reason, sauropodomorphs held on and eventually dominated the terrestrial ecosystem in the early Jurassic.

"We've now observed and documented this earliest social behavior in dinosaurs," Ramezani says. "This raises the question now of whether living in a herd may have had a major role in dinosaurs' early evolutionary success. This gives us some clues to how dinosaurs evolved."

A fossil flood

Since 2013, paleontologists on the team have worked in the Laguna Colorada Formation, a site in southern Patagonia that is known for bearing fossils of early sauropodomorphs. When scientists first discovered fossils within this formation in the 1970s, they named them Mussaurus for "mouse lizard," as they assumed the skeletons were of miniature dinosaurs.

Only much later did scientists, including members of the Argentinian team, discover bigger skeletons, indicating Mussaurus adults were much larger than their rodent namesakes. The name stuck, however, and the team has continued to unearth a rich collection of Mussaurus fossils from a small, square kilometer of the formation.

The fossils they have identified so far were found in three sedimentary layers spaced close together, indicating that the region may have been a common breeding ground where the dinosaurs returned regularly, perhaps to take advantage of favorable seasonal conditions.

Among the fossils they uncovered, the team discovered a group of 11 articulated juvenile skeletons, intertwined and overlapping each other, as if they had been suddenly thrown together. In fact, judging from the remarkably preserved nature of the entire collection, the team believes this particular herd of Mussaurus died "synchronously," perhaps quickly buried by sediments.

Based on evidence of ancient flora in the nearby outcrops, the Laguna Colorada Formation has long been assumed to be relatively old on the dinosaur timescale. The team wondered: Could these dinosaurs have been herding from early on?

"People already knew that in the late Jurassic and Cretaceous, the large herbivore dinosaurs exhibited social behavior -- they lived in herds and had nesting spots," Ramezani says. "But the question has always been, when was the earliest time for such herding behavior?"

A gregarious line

To find out, Diego Pol, a paleontologist at the Egidio Feruglio Paleontological Museum in Argentina who led the study, looked for samples of volcanic ash among the fossils to send to Ramezani's lab at MIT. Volcanic ash can contain zircon -- mineral grains contaning uranium and lead, the isotopic ratios of which Ramezani can precisely measure. Based on uranium's half-life, or the time it takes for half of the element to decay into lead, he can calculate the age of the zircon and the ash in which it was found. Ramezani successfully identified zircons in two ash samples, all of which he dated to around 193 million years old.

Since the volcanic ash was found in the same sediment layers as the fossils, Ramezani's analyses strongly suggest that the dinosaurs were buried at the same time the ash was deposited. A likely scenario may have involved a flash flood or windblown dust that buried the herd, while ash from a distant eruption happened to drift over and, luckily for science, deposit zircons in the sediments.

Taken together, the team's results show that Mussaurus and possibly other dinosaurs evolved to live in complex social herds as early as 193 million years ago, around the dawn of the Jurassic period.

Scientists suspect that two other types of early dinosaurs -- Massospondylus from South Africa and Lufengosaurus from China -- also lived in herds around the same time, although the dating for these dinosaurs has been less precise. If multiple separate lines of dinosaurs lived in herds, the researchers believe the social behavior may have evolved earlier, perhaps as far back as their common ancestor, in the late Triassic.

"Now we know herding was going on 193 million years ago," Ramezani says. "This is the earliest confirmed evidence of gregarious behavior in dinosaurs. But paleontological understanding says, if you find social behavior in this type of dinosaur at this time, it must have originated earlier."

Read more at Science Daily