Meet Callichimaera perplexa, the platypus of crabs

Meet Callichimaera perplexa, the platypus of crabs

Callichimaera perplexa Cretaceous
The diversity of body forms among crabs, including the enigmatic Callichimaera perplexa (center). Credit: Photos, Arthur Anker & Javier Luque; figure, Javier Luque, Yale University

New Haven, Conn. - The crab family just got a bunch of new cousins -- including a 95-million-year-old chimera species that will force scientists to rethink the definition of a crab.

An international team of researchers led by Yale paleontologist Javier Luque announced the discovery of hundreds of exceptionally well-preserved specimens from Colombia and the United States that date back to the mid-Cretaceous period of 90-95 million years ago. The cache includes hundreds of tiny comma shrimp fossils, several true shrimp, and an entirely new branch of the evolutionary tree for crabs.

The most intriguing discovery, according to the researchers, is Callichimaera perplexa, the earliest example of a swimming arthropod with paddle-like legs since the extinction of sea scorpions more than 250 million years ago. The name derives from a chimera, a mythological creature that has body features from more than one animal. Callichimaera's full name translates into "perplexing beautiful chimera."

Luque noted that Callichimaera's "unusual and cute" appearance, including its small size -- about the size of a quarter -- large compound eyes with no sockets, bent claws, leg-like mouth parts, exposed tail, and long body are features typical of pelagic crab larvae. This suggests that several of the larval traits seen in this "perplexing chimera" might have been retained and amplified in miniaturized adults via changes in the timing and rates of development. This is a process called "heterochrony," which may lead to the evolution of novel body plans.

"Callichimaera perplexa is so unique and strange that it can be considered the platypus of the crab world," said Luque. "It hints at how novel forms evolve and become so disparate through time. Usually we think of crabs as big animals with broad carapaces, strong claws, small eyes in long eyestalks, and a small tail tucked under the body. Well, Callichimaera defies all of these 'crabby' features and forces a re-think of our definition of what makes a crab a crab."

A study about the discovery appears in the April 24 online edition of the journal Science Advances.

"It is very exciting that today we keep finding completely new branches in the tree of life from a distant past, especially from regions like the tropics, which despite being hotspots of diversity today, are places we know the least about in terms of their past diversity," Luque said.

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Luque's team included researchers from the University of Alberta, Kent State University, the University of Montreal, the Smithsonian Tropical Research Institute in Panama, the Canadian Parks and Wilderness Society, the National Autonomous University of Mexico, the University of Nevada, and the College of Communication and Design in Boca Raton, Fla.

Artistic reconstruction of Callichimaera perplexa, the strangest crab that has ever lived. Credit: Elissa Martin, Yale Peabody Museum of Natural History

Press release from Yale University


Texas Serengeti

Ancient 'Texas Serengeti' had elephant-like animals, rhinos, alligators and more

Ancient 'Texas Serengeti' had elephant-like animals, rhinos, alligators and more

An artist's interpretation of ancient North American fauna. The new study led by The University of Texas at Austin Jackson School of Geosciences revealed that elephant-like gomphotheres, rhinos, horses and antelopes with slingshot-shaped horns were among the species recovered near Beeville, Texas, by Great Depression-era fossil hunters. Credit: Jay Matternes/ The Smithsonian Institution

During the Great Depression, some unemployed Texans were put to work as fossil hunters. The workers retrieved tens of thousands of specimens that have been studied in small bits and pieces while stored in the state collections of The University of Texas at Austin for the past 80 years.

Now, decades after they were first collected, a UT researcher has studied and identified an extensive collection of fossils from dig sites near Beeville, Texas, and found that the fauna make up a veritable "Texas Serengeti" - with specimens including elephant-like animals, rhinos, alligators, antelopes, camels, 12 types of horses and several species of carnivores. In total, the fossil trove contains nearly 4,000 specimens representing 50 animal species, all of which roamed the Texas Gulf Coast 11 million to 12 million years ago.

paper describing these fossils, their collection history and geologic setting was published April 11 in the journal Palaeontologia Electronica.

"It's the most representative collection of life from this time period of Earth history along the Texas Coastal Plain," said Steven May, the research associate at the UT Jackson School of Geosciences who studied the fossils and authored the paper.

In addition to shedding light on the inhabitants of an ancient Texas ecosystem, the collection is also valuable because of its fossil firsts. They include a new genus of gomphothere, an extinct relative of elephants with a shovel-like lower jaw, and the oldest fossils of the American alligator and an extinct relative of modern dogs.

A new study of fossils dug up in Texas during the Great Depression offers the best look yet of an ancient environment that was once home to a diverse array of animals including camels, rhinos, alligators and an ancient elephant relative. Glen Evans (left), who managed much of the Works Progress Administration's effort to collect Texas fossils, is pictured here carrying a fossil in a field jacket with a worker. Credit: The University of Texas at Austin Jackson School of Geosciences

The fossils came into the university's collection as part of the State-Wide Paleontologic-Mineralogic Survey that was funded by the Works Progress Administration (WPA), a federal agency that provided work to millions of Americans during the Great Depression. From 1939 to 1941, the agency partnered with the UT Bureau of Economic Geology, which supervised the work and organized field units for collecting fossils and minerals across the state.

Despite lasting only three years, the survey found and excavated thousands of fossils from across Texas including four dig sites in Bee and Live Oak counties, with the majority of their finds housed in what is now the Texas Vertebrate Paleontology Collections at the Jackson School Museum of Earth History. Over the years, a number of scientific papers have been published on select groups of WPA specimens. But May's paper is the first to study the entire fauna.

This extensive collection of fossils is helping to fill in gaps about the state's ancient environment, said Matthew Brown, the director of the museum's vertebrate paleontology collections.

The emphasis on big mammals is due in large part to the collection practices of the fossil hunters, most of whom were not formally trained in paleontology. Large tusks, teeth and skulls were easier to spot - and more exciting to find - than bones left by small species.

"They collected the big, obvious stuff," May said. "But that doesn't fully represent the incredible diversity of the Miocene environment along the Texas Coastal Plain."

In order to account for gaps in the collection, May tracked down the original dig sites so he could screen for tiny fossils such as rodent teeth. One of the sites was on a ranch near Beeville owned by John Blackburn. Using aerial photography and notes from the WPA program stored in the university's archives, May and the research team were able to track down the exact spot of an original dig site.

"We're thrilled to be a part of something that was started in 1939," Blackburn said. "It's been a privilege to work with UT and the team involved, and we hope that the project can help bring additional research opportunities."

Scores of WPA-era fossils in the UT collections are still secured in plaster field jackets, waiting to be unpacked for future research projects. Lab managers Deborah Wagner and Kenneth Bader are supervising their preparation, which includes teaching UT students fossil prep skills so they can pick up where the WPA workers left off.

Wagner said that the advantage of unpacking fossils decades later is that they are able to apply modern research techniques that scientists from past eras wouldn't have dreamed possible.

"We are able to preserve more detailed anatomy and answer questions that require higher resolution data," she said.

May said that he plans to continue to study the fossils as more are prepared.

Texas Serengeti
Fossilized skull parts from ancient elephant relatives in the collections of the Jackson School Museum of Earth History. The skull of a shovel-jawed gomphothere (pictured on bottom) collected by Great Depression-era fossil hunters is still wrapped in its field jacket. Credit: The University of Texas at Austin Jackson School of Geosciences

Press release from the University of Texas at Austin


Talking stones Alabama cave Manitou Cave Cherokee inscriptions

Researchers interpret Cherokee inscriptions in Alabama cave

Researchers interpret Cherokee inscriptions in Alabama cave

Talking stones Alabama cave Manitou Cave Cherokee inscriptions
Cherokee inscriptions found in Manitou Cave, Alabama. Photograph by A. Cressler

For the first time, a team of scholars and archaeologists has recorded and interpreted Cherokee inscriptions in Manitou Cave, Alabama. These inscriptions reveal evidence of secluded ceremonial activities at a time of crisis for the Cherokee, who were displaced from their ancestral lands and sent westward on the Trail of Tears in the 1830s.

"These are the first Cherokee inscriptions ever found in a cave context, and the first from a cave to be translated," said Jan Simek, president emeritus of the University of Tennessee System and Distinguished Professor of Science in UT's Department of Anthropology. Simek is a co-author of the study "Talking Stones: Cherokee Syllabary in Manitou Cave, Alabama," published recently in Antiquity. "They tell us about what the people who wrote on the walls were doing in the cave and provide a direct link to how some Native Americans viewed caves as sacred places."

The research team that worked to understand the nature and meaning of these historic inscriptions included scholars from the Eastern Band of Cherokee Indians, the United Keetoowah Band of Cherokees, and the Cherokee Nation of Oklahoma as well as Euro-American archaeologists.

The researchers concentrated on two main groups of Cherokee inscriptions found in Manitou Cave, a popular tourist site near Fort Payne, Alabama. Until now, indigenous uses of the cave had been unrecorded, as typical archaeological evidence like artifacts or deposits have been removed during its time as a tourist attraction.

The first inscription records an important ritual event that took place in 1828, translated as "The leaders of the stickball team on the 30th day in their month April 1828." A nearby inscription reads "We who are those that have blood come out of their nose and mouth."

Stickball is a Cherokee sport similar to lacrosse.

"It is far more than a simple game," Simek said. "It is a ceremonial event that often continues over days, focusing on competition between two communities who epitomize the spirit and power of the people and their ancestors."

A second series of inscriptions is located on the ceiling nearer to the entrance of the cave.

"The ceiling inscriptions are written backwards, as if addressing readers inside the rock itself," Simek said. "This corresponds with part of one inscription which reads 'I am your grandson.' This is how the Cherokee might formally address the Old Ones, which can include deceased Cherokee ancestors as well as comprise other supernatural beings who inhabited the world before the Cherokee came into existence."

The inscriptions analyzed by researchers indicate that caves like Manitou were seen by the Cherokee as spiritually potent places where wall embellishment was appropriate in the context of ceremonial action.

Since their work in Manitou Cave, the researchers have identified several caves with similar inscriptions. They will continue to collaborate as scholars from the three federally recognized Cherokee tribes and archaeologists.

"Our research has shown that the Cherokee voice in Alabama did in fact outlast the Trail of Tears," Simek said. "We will continue to document and protect these previously unknown records of indigenous American history and culture."

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Along with Simek, the study's authors are Beau Duke Carroll, who took part in the research as a graduate student in UT's Department of Anthropology; Alan Cressler of the US Geological Survey; Tom Belt, a member of the United Keetoowah Band of Cherokees and coordinator of the Cherokee Language program at Western Carolina University; and Julie Reed, a member of the Cherokee Nation of Oklahoma and former faculty member in UT's Department of History, now at Pennsylvania State University.

 

Press release from the University of Tennessee at Knoxville

 


farming agriculture

Food for thought: Why did we ever start farming?

Food for thought: Why did we ever start farming?

The reason that humans shifted away from hunting and gathering, and to agriculture -- a much more labor-intensive process -- has always been a riddle. It is only more confusing because the shift happened independently in about a dozen areas across the globe.

"A lot of evidence suggests domestication and agriculture doesn't make much sense," says Elic Weitzel, a Ph.D. student in UConn's department of anthropology. "Hunter-gatherers are sometimes working fewer hours a day, their health is better, and their diets are more varied, so why would anyone switch over and start farming?"

Weitzel sought to get to the root of the shift in his new paper in American Antiquity, by looking at one area of the world, the Eastern United States.In a nutshell, he looked for evidence to support either of two popular theories.

One theory posits that in times of plenty there may have been more time to start dabbling in the domestication of plants like squash and sunflowers, the latter of which were domesticated by the native peoples of Tennessee around 4,500 years ago.

The other theory argues that domestication may have happened out of need to supplement diets when times were not as good. As the human population grew, perhaps resources shifted due to reasons such as over-exploitation of resources or a changing climate. "Was there some imbalance between resources and the human populations that lead to domestication?"

Weitzel tested both hypotheses. He did this by analyzing animal bones from the last 13,000 years and taken from a half-dozen archeological sites in northern Alabama and the Tennessee River valley, where human settlements and their detritus give clues about how they lived, including what they ate. He coupled the findings with pollen data taken from sediment cores collected from lakes and wetlands, cores that serve as a record about the types of plants present at different points in time. The findings are ... mixed.

Weitzel found pollen from oak and hickory, leading to the conclusion that forests composed of those species began to dominate the region as the climate warmed, but also led to decreasing water levels in lakes and wetlands. Along with the decreasing lakes, the bone records showed a shift from diets rich in water fowl and large fishes to subsistence on smaller shellfish.

Taken together, that data provides evidence for the second hypothesis: There was some kind of imbalance between the growing human population and their resource base, effected perhaps by exploitation and also by climate change.

But Weitzel also saw support for the first hypothesis in that an abundance of oak and hickory forest supported an equally prevalent game species population. "That is what we see in the animal bone data," says Weitzel. "Fundamentally, when times are good and there are lots of animals present, you'd expect people to hunt the prey that is most efficient," says Weitzel. "Deer are much more efficient than squirrels for example, which are smaller, with less meat, and more difficult to catch."

A single deer or goose can feed several people, but if over-hunted, or if the landscape changes to one less favorable for the animal population, humans must subsist on other smaller, less efficient food sources. Agriculture, despite being hard work, may have become a necessary option to supplement diet when imbalances like these occurred.

Despite the mixed results, the findings supporting domestication happening in times when there was less than an ideal amount of food is significant, says Weitzel.

"I think that the existence of declining efficiency in even one habitat type is enough to show that ... domestication happening in times of plenty isn't the best way to understand initial domestication." The broader context of this research is important, says Weitzel, because looking to the past and seeing how these populations coped and adapted to change can help inform what we should do as today's climate warms in the coming decades.

"Having an archaeological voice backed by this deep-time perspective in policy making is very important."

farming agriculture
Image by Sasin Tipchai from Pixabay

Press release from the University of Connecticut


Chumash black abalone California

Scientists measure extent of recovery for critically endangered black abalone

Scientists measure extent of recovery for critically endangered black abalone

Team applies historical perspective to inform modern management

A 19th-century archaeological abalone fishing site on the Northern Channel Islands. Credit: © 2015 Hannah Haas

SAN FRANCISCO (April 2, 2018) - One critically endangered species of smooth-shelled abalone is making a comeback in certain parts of its range along the California coast. To better understand the extent of black abalone recovery, a collaborative team led by scientists at the California Academy of SciencesSan Diego State UniversityUniversity of Oregon, and Channel Islands National Park is turning to archeological sites on the Channel Islands. Their findings, published today in Ecology and Evolution, suggest that while the recent ecological rebound is encouraging, there's still work to do before the black abalone should be considered fully recovered.

"Our goal is to provide a deep historical lens for understanding black abalone across 10,000 years of human fishing," says Dr. Todd Braje, Academy Curator of Anthropology. "Documenting abalone populations across millennia helps resource managers put shorter-term decadal changes in context. We hope these data will serve as a new benchmark for setting management goals."

Black abalone play a critical role in the kelp ecosystem along the California coast. The marine snails are an important food source for key predators like the endangered sea otter. Historically, coastal Native Americans relied on abalone for over 10,000 years--the shellfish later became one of California's first commercial fisheries.

"Management goals are often set using modern data from fisheries already on the verge of collapse," says lead author Hannah Haas, a former Master's student at San Diego State University. "If we want to restore kelp ecosystems, we first have to understand what a healthy system actually looks like, and archeological data can help paint that picture."

To better understand the characteristics of a flourishing abalone population in a historically healthy ecosystem, the study team turned to the archeological record left behind along the rocky shorelines of the Channel Islands. San Miguel Island, the westernmost island in the archipelago, hosts archeological sites spanning the last 10,000 years where the Chumash and their ancestors once deposited abalone shells by the thousands into trash piles known as shell middens. The team recovered nearly 2,000 whole abalone shells from 26 shell middens and measured shell size. They then compared deep historical shell size to modern measurements of live abalone collected by Channel Island National Park biologists during recent ecological monitoring. Shell size indicates the ratio of juveniles to adults and the population structure through time, which can help scientists compare and contrast overall population health between deep historical and modern eras.

While there has been an encouraging rebound of black abalone in recent decades, current populations still pale in comparison to historical levels. Several thousand years ago, the distribution of juvenile to adult-sized abalone was more akin to what ecologists recognize as a healthy population. This was probably maintained by a delicate balance between competitors, predators, and prey that may have actually increased the productivity of black abalone over the long term.

"We hope that our long-term analyses over the 10,000-year history of black abalone fishing in Southern California may help resource managers determine whether current abalone populations are healthy," says Haas.

Millions of smooth-shelled abalone once clung to California's rocky coastline until a steep decline in the 1990s, driven by overfishing, warming waters, and a devastating infection known as withering foot syndrome. California closed commercial and recreational black abalone fisheries in 1993 and listed the species as endangered in 2009.

"A variety of perspectives and data are key to understanding how to manage toward ecological balance rather than an era defined by commercial fishing, sea otter extirpation, and ecosystem dysfunction," says Braje. "We're trying to put together a diverse group of scholars--archeologists, biologists, and resource managers--to combine data insights and all work toward the same goal of abalone recovery and restoring healthy California kelp forest ecosystems."

The study team conducts a shoreline survey of prehistoric Chumash sites, which often contain discarded abalone shell. Credit: © 2015 Todd Braje

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About Research at the California Academy of Sciences

The Institute for Biodiversity Science and Sustainability at the California Academy of Sciences is at the forefront of efforts to understand two of the most important topics of our time: the nature and sustainability of life on Earth. Based in San Francisco, the Institute is home to more than 100 world-class scientists, state-of-the-art facilities, and nearly 46 million scientific specimens from around the world. The Institute also leverages the expertise and efforts of more than 100 international Associates and 450 distinguished Fellows. Through expeditions around the globe, investigations in the lab, and analyses of vast biological datasets, the Institute's scientists work to understand the evolution and interconnectedness of organisms and ecosystems, the threats they face around the world, and the most effective strategies for sustaining them into the future. Through innovative partnerships and public engagement initiatives, they also guide critical sustainability and conservation decisions worldwide, inspire and mentor the next generation of scientists, and foster responsible stewardship of our planet.

 

Press release from the California Academy of Sciences


rock art X-ray vision

Uncovering the secrets of ancient rock art using 'X-ray vision'

Uncovering the secrets of ancient rock art using 'X-ray vision'

rock art X-ray vision
A portable X-ray device has revealed new insights about the pigments used in rock art without damaging the site. Credit: courtesy of Shumla Archaeological Research and Education Center

ORLANDO, Fla., April 1, 2019 -- Prehistoric rock paintings are a source of fascination across the world. Aside from their beauty, there's deep meaning in these strokes, which depict ancient rituals and important symbols. To learn more about these murals, researchers have historically resorted to sampling methods that are damaging to the artwork, contradicting the archaeological tenets of conservation. Today, scientists report use of "X-ray vision" to gain brand-new insights about the layers of paint in rock art in Texas without needless damage.

The researchers will present their results today at the American Chemical Society (ACS) Spring 2019 National Meeting & Exposition. ACS, the world's largest scientific society, is holding the meeting here through Thursday. It features nearly 13,000 presentations on a wide range of science topics.

"In this particular work, we used a technique called portable X-ray fluorescence spectroscopy (pXRF), in which a handheld instrument can be carried to a site and used right there, on the spot," says Karen Steelman, Ph.D., who led the study. "It gives you the elemental analysis of a specific material, and is the first step in figuring out how ancient artists used different materials to make their paintings."

Steelman's research focuses on the analysis of rock and cave art, particularly in the Lower Pecos Canyonlands in Texas. She and her colleagues at the Shumla Archaeological Research & Education Center have previously analyzed the composition of pigments at more than 10 sites in the region, but had been unable to see the bigger picture of how these pictographs were composed. Other pigment analysis methods, such as inductively coupled plasma mass spectrometry, require a sample of the rock art in question, which results in damage to the site, and field microscopes are unable to detect layers of paint in a complex mural.

For this particular study, Steelman and her colleagues visited the Rattlesnake Canyon Site along the Rio Grande, known for its array of pictographs. Using a 105-foot wide mural as their testing canvas, they used pXRF to measure 138 areas where the composition indicated overlapping pigments of red, black, white and yellow. In addition, measurements were taken at 90 locations of unpainted limestone, which provided insight into the makeup of the geological canvas.

Using the large amount of data collected from Rattlesnake Canyon, the team could determine a pattern to the layers of pigment, as well as their elemental makeup. The pXRF measurements revealed previously unseen layers of black pigment under layers of red, which were made with manganese and iron oxide, respectively. These complex layers of pigment indicated a level of sophistication seen in other Lower Pecos sites, which ethnographers have determined are a series of religious murals that revealed the complex nature of the hunter-gatherer society that occupied the region from 2500 BCE to 500 CE.

In addition to their findings on the composition of the pictographs, Steelman, along with fellow Shumla collaborators Victoria Roberts and Carolyn Boyd, Ph.D., discovered that the site appeared to contain gunshot damage. To confirm their suspicions, they again turned to pXRF to identify any trace elements that could have come from ammunition. "Unfortunately, we often see suspected bullet impacts at rock art sites," Steelman says. "Most of this is older types of vandalism from the early 1900s, and we used the portable X-ray to determine what trace elements were present." At the impact sites, pXRF revealed traces of lead, mercury and selenium, which were not present in the undamaged areas. There is a bright side to this discovery; finding damage at archaeologically significant sites is an opportunity to petition state and federal agencies for conservation funds to use for more extensive preservation measures, Steelman explains.

With over 350 known rock art sites in the Lower Pecos Canyonlands alone, Steelman and team plan to continue using pXRF to see the full picture of the tapestry of color and symbol woven throughout the region. Flooding along the Rio Grande is a major threat to what the researchers describe as "the oldest books in North America," and they are on a mission to document and analyze as many sites as possible to preserve these stories for future generations.

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Chicxulub impact dinosaur extinction Cretaceous

The terrible moments after the dinosaur-killing Chicxulub impact

66-million-year-old deathbed linked to dinosaur-killing meteor

Fossil site preserves animals killed within minutes of meteor impact

A meteor impact 66 million years ago generated a tsunami-like wave in an inland sea that killed and buried fish, mammals, insects and a dinosaur (Triceratops), the first victims of a cataclysm that led to Earth's last mass extinction. The death scene from within an hour of the impact has been excavated at an unprecedented fossil site in North Dakota. Credit: graphic courtesy of Robert DePalma

The beginning of the end started with violent shaking that raised giant waves in the waters of an inland sea in what is now North Dakota.

Then, tiny glass beads began to fall like birdshot from the heavens. The rain of glass was so heavy it may have set fire to much of the vegetation on land. In the water, fish struggled to breathe as the beads clogged their gills.

The heaving sea turned into a 30-foot wall of water when it reached the mouth of a river, tossing hundreds, if not thousands, of fresh-water fish -- sturgeon and paddlefish -- onto a sand bar and temporarily reversing the flow of the river. Stranded by the receding water, the fish were pelted by glass beads up to 5 millimeters in diameter, some burying themselves inches deep in the mud. The torrent of rocks, like fine sand, and small glass beads continued for another 10 to 20 minutes before a second large wave inundated the shore and covered the fish with gravel, sand and fine sediment, sealing them from the world for 66 million years.

This unique, fossilized graveyard -- fish stacked one atop another and mixed in with burned tree trunks, conifer branches, dead mammals, mosasaur bones, insects, the partial carcass of a Triceratops, marine microorganisms called dinoflagellates and snail-like marine cephalopods called ammonites -- was unearthed by paleontologist Robert DePalma over the past six years in the Hell Creek Formation, not far from Bowman, North Dakota. The evidence confirms a suspicion that nagged at DePalma in his first digging season during the summer of 2013 -- that this was a killing field laid down soon after the asteroid impact that eventually led to the extinction of all ground-dwelling dinosaurs. The impact at the end of the Cretaceous Period, the so-called K-T boundary, exterminated 75 percent of life on Earth.

Fossilized fish piled one atop another, suggesting that they were flung ashore and died stranded together on a sand bar after the wave from the seiche withdrew. Credit: photo courtesy of Robert DePalma

"This is the first mass death assemblage of large organisms anyone has found associated with the K-T boundary," said DePalma, curator of paleontology at the Palm Beach Museum of Natural History in Florida and a doctoral student at the University of Kansas. "At no other K-T boundary section on Earth can you find such a collection consisting of a large number of species representing different ages of organisms and different stages of life, all of which died at the same time, on the same day."

In a paper to appear next week in the journal Proceedings of the National Academy of Sciences, he and his American and European colleagues, including two University of California, Berkeley, geologists, describe the site, dubbed Tanis, and the evidence connecting it with the asteroid or comet strike off Mexico's Yucatan Peninsula 66 million years ago. That impact created a huge crater, called Chicxulub, in the ocean floor and sent vaporized rock and cubic miles of asteroid dust into the atmosphere. The cloud eventually enveloped Earth, setting the stage for Earth's last mass extinction.

"It's like a museum of the end of the Cretaceous in a layer a meter-and-a-half thick," said Mark Richards, a UC Berkeley professor emeritus of earth and planetary science who is now provost and professor of earth and space sciences at the University of Washington.

Richards and Walter Alvarez, a UC Berkeley Professor of the Graduate School who 40 years ago first hypothesized that a comet or asteroid impact caused the mass extinction, were called in by DePalma and Dutch scientist Jan Smit to consult on the rain of glass beads and the tsunami-like waves that buried and preserved the fish. The beads, called tektites, formed in the atmosphere from rock melted by the impact.

Tsunami vs. seiche

Richards and Alvarez determined that the fish could not have been stranded and then buried by a typical tsunami, a single wave that would have reached this previously unknown arm of the Western Interior Seaway no less than 10 to 12 hours after the impact 3,000 kilometers away, if it didn't peter out before then. Their reasoning: The tektites would have rained down within 45 minutes to an hour of the impact, unable to create mudholes if the seabed had not already been exposed.

Instead, they argue, seismic waves likely arrived within 10 minutes of the impact from what would have been the equivalent of a magnitude 10 or 11 earthquake, creating a seiche (pronounced saysh), a standing wave, in the inland sea that is similar to water sloshing in a bathtub during an earthquake. Though large earthquakes often generate seiches in enclosed bodies of water, they're seldom noticed, Richards said. The 2011 Tohoku quake in Japan, a magnitude 9.0, created six-foot-high seiches 30 minutes later in a Norwegian fjord 8,000 kilometers away.

"The seismic waves start arising within nine to 10 minutes of the impact, so they had a chance to get the water sloshing before all the spherules (small spheres) had fallen out of the sky," Richards said. "These spherules coming in cratered the surface, making funnels -- you can see the deformed layers in what used to be soft mud -- and then rubble covered the spherules. No one has seen these funnels before."

The tektites would have come in on a ballistic trajectory from space, reaching terminal velocities of between 100 and 200 miles per hour, according to Alvarez, who estimated their travel time decades ago.

"You can imagine standing there being pelted by these glass spherules. They could have killed you," Richards said. Many believe that the rain of debris was so intense that the energy ignited wildfires over the entire American continent, if not around the world.

"Tsunamis from the Chicxulub impact are certainly well-documented, but no one knew how far something like that would go into an inland sea," DePalma said. "When Mark came aboard, he discovered a remarkable artifact -- that the incoming seismic waves from the impact site would have arrived at just about the same time as the atmospheric travel time of the ejecta. That was our big breakthrough."

At least two huge seiches inundated the land, perhaps 20 minutes apart, leaving six feet of deposits covering the fossils. Overlaying this is a layer of clay rich in iridium, a metal rare on Earth, but common in asteroids and comets. This layer is known as the K-T, or K-Pg boundary, marking the end of the Cretaceous Period and the beginning of the Tertiary Period, or Paleogene.

Iridium

In 1979, Alvarez and his father, Nobelist Luis Alvarez of UC Berkeley, were the first to recognize the significance of iridium that is found in 66 million-year-old rock layers around the world. They proposed that a comet or asteroid impact was responsible for both the iridium at the K-T boundary and the mass extinction.

The impact would have melted the bedrock under the seafloor and pulverized the asteroid, sending dust and melted rock into the stratosphere, where winds would have carried them around the planet and blotted out the sun for months, if not years. Debris would have rained down from the sky: not only tektites, but also rock debris from the continental crust, including shocked quartz, whose crystal structure was deformed by the impact.

The iridium-rich dust from the pulverized meteor would have been the last to fall out of the atmosphere after the impact, capping off the Cretaceous.

"When we proposed the impact hypothesis to explain the great extinction, it was based just on finding an anomalous concentration of iridium -- the fingerprint of an asteroid or comet," said Alvarez. "Since then, the evidence has gradually built up. But it never crossed my mind that we would find a deathbed like this."

Key confirmation of the meteor hypothesis was the discovery of a buried impact crater, Chicxulub, in the Caribbean and off the coast of the Yucatan in Mexico, that was dated to exactly the age of the extinction. Shocked quartz and glass spherules were also found in K-Pg layers worldwide. The new discovery at Tanis is the first time the debris produced in the impact was found along with animals killed in the immediate aftermath of the impact.

"And now we have this magnificent and completely unexpected site that Robert DePalma is excavating in North Dakota, which is so rich in detailed information about what happened as a result of the impact," Alvarez said. "For me, it is very exciting and gratifying!"

Tektites

Jan Smit, a retired professor of sedimentary geology from Vrije Universiteit in Amsterdam in The Netherlands who is considered the world expert on tektites from the impact, joined DePalma to analyze and date the tektites from the Tanis site. Many were found in near perfect condition embedded in amber, which at the time was pliable pine pitch.

Tektites, 1 millimeter spheres of glass, recovered from the Tanis fossil bed. They were produced by the Chicxulub impact and fell within an hour of the impact. Credit: photo courtesy of Robert DePalma

"I went to the site in 2015 and, in front of my eyes, he (DePalma) uncovered a charred log or tree trunk about four meters long which was covered in amber, which acted as sort of an aerogel and caught the tektites when they were coming down," Smit said. "It was a major discovery, because the resin, the amber, covered the tektites completely, and they are the most unaltered tektites I have seen so far, not 1 percent of alteration. We dated them, and they came out to be exactly from the K-T boundary."

The tektites in the fishes' gills are also a first.

"Paddlefish swim through the water with their mouths open, gaping, and in this net, they catch tiny particles, food particles, in their gill rakers, and then they swallow, like a whale shark or a baleen whale," Smit said. "They also caught tektites. That by itself is an amazing fact. That means that the first direct victims of the impact are these accumulations of fishes."

Smit also noted that the buried body of a Triceratops and a duck-billed hadrosaur proves beyond a doubt that dinosaurs were still alive at the time of the impact.

"We have an amazing array of discoveries which will prove in the future to be even more valuable," Smit said. "We have fantastic deposits that need to be studied from all different viewpoints. And I think we can unravel the sequence of incoming ejecta from the Chicxulub impact in great detail, which we would never have been able to do with all the other deposits around the Gulf of Mexico."

"So far, we have gone 40 years before something like this turned up that may very well be unique," Smit said. "So, we have to be very careful with that place, how we dig it up and learn from it. This is a great gift at the end of my career. Walter sees it as the same."

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Co-authors with DePalma, Smit, Richards and Alvarez are David Burnham of the University of Kansas, Klaudia Kuiper of Vrije Universiteit, Phillip Manning of Manchester University in the United Kingdom, Anton Oleinik of Florida Atlantic University, Peter Larson of the Black Hills Institute of Geological Research in South Dakota, Florentin Maurrasse of Florida International University, Johan Vellekoop of Katholieke Universiteit Leuven in Belgium and Loren Gurche of the Palm Beach Museum of Natural History.

 

Press release from the University of California - Berkeley

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Stunning discovery offers glimpse of minutes following 'dinosaur-killer' Chicxulub impact

LAWRENCE -- A study to be published Monday in the Proceedings of the National Academy of Sciences offers a scientific first: a detailed snapshot of the terrible moments right after the Chicxulub impact -- the most cataclysmic event known to have befallen life on Earth.

At a site called Tanis in North Dakota's Hell Creek Formation, a team of paleontologists whose headquarters are at the University of Kansas unearthed a motherlode of exquisitely-preserved animal and fish fossils -- creatures that lived in and around a deeply chiseled river connected to the ancient Western Interior Seaway -- that were killed suddenly in events triggered by the Chicxulub impact.

The fossils were crammed into a "rapidly emplaced high-energy onshore surge deposit" along the KT boundary that contained associated ejecta and iridium impactite associated with the impact about 66 million years ago -- an impact that eradicated about 75 percent of Earth's animal and plant species.

"A tangled mass of freshwater fish, terrestrial vertebrates, trees, branches, logs, marine ammonites and other marine creatures was all packed into this layer by the inland-directed surge," said lead author Robert DePalma, a KU doctoral student in geology who works in the KU Biodiversity Institute and Natural History Museum. "Timing of the incoming ejecta spherules matched the calculated arrival times of seismic waves from the impact, suggesting that the impact could very well have triggered the surge."

DePalma, who discovered the fossil motherlode, said the find outlines how the impact could have devastated areas very far from the crater quite rapidly.

"A tsunami would have taken at least 17 or more hours to reach the site from the crater, but seismic waves -- and a subsequent surge -- would have reached it in tens of minutes," he said.

DePalma and his colleagues describe the rushing wave that shattered the Tanis site as a "seiche."

"As the 2011 Tohoku earthquake in Japan showed us, seismic shaking can cause surges far from the epicenter," he said. "In the Tohoku example, surges were triggered nearly 5,000 miles away in Norway just 30 minutes after impact. So, the KT impact could have caused similar surges in the right-sized bodies of water worldwide, giving the first rapid 'bloody nose' to those areas before any other form of aftermath could have reached them."

According to KU researchers, even before the surge arrived, Acipenseriform fish (sturgeon) found at the site already had inhaled tiny spherules ejected from the Chicxulub impact.

"The fish were buried quickly, but not so quickly they didn't have time to breathe the ejecta that was raining down to the river," said co-author David Burnham, preparator of vertebrate paleontology at the KU Biodiversity Institute. "These fish weren't bottom feeders, they breathed these in while swimming in the water column. We're finding little pieces of ejecta in the gill rakers of these fish, the bony supports for the gills. We don't know if some were killed by breathing this ejecta, too."

The number and quality of preservation of the fossils at Tanis are such that Burnham dubs it the "lagerstätte" of the KT event -- paleontologist-speak for a landmark sedimentary deposit with exceptionally intact specimens. He said this is especially true as the fish are cartilaginous, not bony, and are less prone to fossilization.

"The sedimentation happened so quickly everything is preserved in three dimensions -- they're not crushed," Burnham said. "It's like an avalanche that collapses almost like a liquid, then sets like concrete. They were killed pretty suddenly because of the violence of that water. We have one fish that hit a tree and was broken in half."

Indeed, the Tanis site contains many hundreds of articulated ancient fossil fish killed by the Chicxulub impact's aftereffects and is remarkable for the biodiversity it reveals alone.

"At least several appear to be new species, and the others are the best examples known of their kind," DePalma said. "Before now, fewer than four were known from the Hell Creek, so the site was already magnificently significant. But we quickly recognized that the surrounding sediment was deposited by a sudden, massive rush of water, and that the surge was directed inland, away from an ancient nearby seaway. When we noticed asteroid impact debris within the sediment and a compact layer of KT boundary clay resting on top of it from the long-term fallout, we realized that this unusual site was right at the KT boundary."

According to Burnham, the fossil trove fills a void in scientific knowledge with vivid new detail.

"We've understood that bad things happened right after the impact, but nobody's found this kind of smoking-gun evidence," he said. "People have said, 'We get that this blast killed the dinosaurs, but why don't we have dead bodies everywhere?' Well, now we have bodies. They're not dinosaurs, but I think those will eventually be found, too."

DePalma said his find provides spectacular new detail to what is perhaps the most important event to ever affect life on Earth.

"It's difficult not to get choked up and passionate about this topic," he said. "We look at moment-by-moment records of one of the most notable impact events in Earth's history. No other site has a record quite like that. And this particular event is tied directly to all of us -- to every mammal on Earth, in fact. Because this is essentially where we inherited the planet. Nothing was the same after that impact. It became a planet of mammals rather than a planet of dinosaurs.

"As human beings, we descended from a lineage that literally survived in the ashes of what was once the glorious kingdom of the dinosaurs. And we're the only species on the planet that has ever been capable of learning from such an event to the benefit of ourselves and every other organism in our world."

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At KU, DePalma and Burnham worked with Loren Gurche of the Biodiversity Institute. Other co-authors are Jan Smit and Klaudia Kuiper of VU University Amsterdam; Phillip Manning of the University of Manchester; Anton Oleinik of Florida Atlantic University; Peter Larson of the Black Hills Institute of Geological Research Inc.; Florentin Maurrasse of Florida International University; Johan Vellekoop of VU Leuven; and Mark A. Richards and Walter Alvarez of the University of California at Berkeley.

Press release from the University of Kansas