Tag Archives: #fossils

The Oldest Fossils Of Methanogenic Bacteria Discovered (Paleontology)

By analyzing the rocks present in the Unesco site known as the Barberton Green Rock Belt, in South Africa, one of the oldest geological structures in the world, a team of researchers led by Barbara Cavalazzi of the University of Bologna has discovered the oldest remains fossils of methanogenic archaea – microorganisms that lived 3.42 billion years ago within a system of hydrothermal venules

There is a place on our planet where one of the oldest geological complexes in the world is located. A place where the rocks present, of volcanic and sedimentary origin, tell how the Earth was between 3.2 and 3.6 billion years ago. We are talking about the Barberton Green Rock Belt : an area located in South Africa, included in the Unesco World Heritage List since 2018 – the list of World Heritage Sites.

It is an environment with unique chemical-physical characteristics, and therefore ideal for astrobiology studies, aimed at searching for life forms that existed long ago, when the Earth was very young. And it is precisely by conducting similar studies that an international team of researchers led by the University of Bologna, analyzing rock samples taken on the site, discovered the oldest remains ever identified of methanogenic bacteria , ancestral microorganisms capable of converting molecular hydrogen and carbon dioxide into methane through a process known as  methanogenesis . A discovery that expands the frontiers of potentially habitable environments on early Earth and other planets, such as Mars.

According to what is reported in the article describing the discovery, published yesterday in Science Advances , it would be archaea that lived 3.42 billion years ago in a system of venules carved into the rock by the activity of hydrothermal springs – environments in which the interaction of the seabed water with hot water heated by volcanic activities creates suitable conditions for the life of various microorganisms.

“We found exceptionally well-preserved evidence of microbial fossils that appear to have thrived along the walls of cavities created by the warm water of hydrothermal systems present a few meters below the seabed,” explains Barbara Cavalazzi , geologist and astrobiologist at the University of Bologna. and first author of the study. “These subsurface habitats, heated by volcanic activity, have probably hosted some of the earliest microbial ecosystems on Earth, and this is the oldest example we have found to date.”

Image of the outcrop from which the rock sample examined in the study was taken. Credits: Cavalazzi et al., 2021

That these are precisely fossilized remains of bacteria are suggested by the chemical analyzes that the researchers conducted on filamentous structures, similar to a biofilm , found in two thin layers of the rocks examined. The results show that the filaments include most of the structural elements necessary for life: a carbon-rich outer coating, consistent with a cell wall  or with what remains of the extracellular polymeric substance , substances secreted by microorganisms in their environment and considered the Fundamental component that determines the physico-chemical properties of a biofilm; and a chemically distinct core structure which may be condensed cytoplasmic matter .

That they are, more specifically, methanogenic archaea is indicated by the presence in the filaments of organic compounds of nickel, a cofactor of enzymes involved in the metabolism of methane, the organic molecule which, as mentioned, these microorganisms produce and use as a source of “food”. The concentrations of nickel measured in the filaments, the researchers explain, are similar to those found in the methanogens that now populate some extreme environments of our planet.

Filamentous microfossils observed under an optical microscope. Credits: B. Cavalazzi

The specific combination of the site where they were observed, their morphological complexity in three dimensions, their kerogenic nature (kerogen is a mixture of chemical compounds produced by the decomposition of organic matter), the spectroscopically observed ultrastructures and their specific metal signature -organic, the researchers add, exclude that they may be abiotic pseudofossils , that is structures produced by natural physical and chemical processes, therefore of a non-biological nature, which however resemble fossils of primitive life forms.

“We know that archaea can be fossilized, however we have few direct examples,” concludes Cavalazzi. “Our findings could extend, for the first time, the Archaea fossil record to the time when life emerged on Earth.”

Featured image: The Barberton Belt of Green Rocks, South Africa. Credits: A. Hofmann.

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Provided by INAF

Discovery of the Oldest Plant Fossils of the African Continent! (Paleontology)

Analysis of very ancient plant fossils found in South Africa dating from the Lower Devonian allows us to learn more about the transition from barren continents to the green planet we know today. A study in which Cyrille Prestianni, paleobotanist at the EDDy Lab at ULiège, participated, and the results of which have just been published in the journal Scientific Reports .

The greening of the continents – or terrestrialization – is undoubtedly one of the most important processes that our planet has known. While for most of Earth’s history the continents were devoid of macroscopic life, starting in the Ordovician (480 million years ago) green algae have gradually adapted to life outside of the aquatic environment. The conquest of the land emerged by plants was a very long process during which the plants gradually acquired the ability to stand erect, to breathe in the air or to disperse their spores. Plant fossils that document these transitions are very rare. In 2015, during the expansion of the Mpofu Dam (South Africa), researchers discovered numerous plant fossils in geological strata dated to the Lower Devonian (420 – 410 million years ago), making this a truly exceptional discovery.

Mtshaelo kougaensis is a plant that bears complicated sporangia gathered at the end of the axes. © University of Liège

”  Quickly, the discovery turned out to be out of the ordinary ,” explains Cyrille Prestianni, paleobotanist within the EDDy Lab * (Geology / F aculty of Sciences research unit ) at the University of Liège, since we are in the presence of the oldest fossil flora in Africa and that it is very diverse and of exceptional quality  ”. It is thanks to a collaboration between the University of Liège, the IRSNB (Royal Institute of Natural Sciences of Belgium) and the New Albany Museum (South Africa) that this incredible discovery was able to be studied. The study just published in the journal Scientific Reports describes this particularly diverse fossil flora with no less than fifteen species analyzed, three of which are new to science.  “This flora is also particularly interesting by the quantity of more or less complete specimens which could be discovered there,” continues the researcher. These plants are small in size, with the largest specimens not exceeding 10cm in height. They are simple plants, made up of axes that divide two to three times and end in reproductive structures called sporangia. ” 

The fossil flora of Mpofu, allows us today to imagine what the world could look like when the largest plants did not exceed the height of our ankles and that almost no animal had yet been able to free itself from the aquatic environment. . It allows us to better understand how our Earth went from a red boulder devoid of life to the green planet we know today. These plants, as simple as they are, are a crucial step in building the environments that welcomed the first arthropods. They are the basis of the long history of life on Earth, which continues today from dense tropical forests to arid tundra in the north.

* The Evolution and Diversity Dynamics Lab (EDDy Lab) of the University of Liège is the heir to a long paleontological tradition, particularly in the study of Terrestrialization processes. The work presented here is the result of a long collaboration between ULiège and IRSNB, which are the two French-speaking Belgian institutions that are leaders in the field of paleontological sciences.  

Featured image: Uskiella spargen a small plant whose axes divide several times before bearing oval sporangia. Credit: Cyrille Prestianni

Scientific Reference

Robert W. Gess & Cyrille Prestianni, An Early Devonian Flora from the Baviaanskloof Formation (Table Mountain Group) of South Africa , Scientific Reports , June 2021.

Provided by Liege University

Quartz Crystals in the Stomach of Fossil Bird Complicates the Mystery of its Diet (Paleontology)

It’s hard to know what prehistoric animals’ lives were like—even answering seemingly simple questions, like what they ate, can be a challenge. Sometimes, paleontologists get lucky, and pristine fossils will preserve an animal’s stomach contents or provide other clues. In a new study in Frontiers in Earth Science, researchers investigating the fossil of a bird that lived alongside the dinosaurs got more questions than answers when they found quartz crystals in the bird’s stomach.

“I would say it’s some kind of bizarre form of soft tissue preservation that we’ve never seen before,” says Jingmai O’Connor, the associate curator of fossil reptiles at Chicago’s Field Museum. “Figuring out what’s in this bird’s stomach can help us understand what it ate and what role it played in its ecosystem.”

“This paper tells us that the Enantiornithes, one important clade of fossil birds, still have no direct stomach traces or evidence,” says Shumin Liu, a student at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, and the paper’s first author. “I was excited, it is a breakthrough about them.”

The fossil bird the researchers focused on is a specimen of Bohaiornis guoi. “They’re part of an early lineage of birds from the Cretaceous, about 120 million years ago,” says O’Connor, who worked on the paper while at IVPP, where Liu was her Master’s student. “They still retain teeth and claws on their hands, but they’re small, about the size of a pigeon, so they’re not particularly terrifying.” Bohaiornis was part of a group called the enantiornithines that were once the world’s most common birds; thousands of enantiornithine specimens have been found in northeastern China’s Jehol Group deposits.

Despite the vast number of finely preserved enantiornithines, none have been preserved with traces of food in their stomachs that could tell researchers what these birds ate. “We can identify the diet and reconstruct the digestive system for all these other groups of birds found in the deposits that record the Jehol Biota, except the enantiornithines, even though you have more enantiornithines than any other group,” says O’Connor. “For these guys, we have no specimens or preserved evidence of diet, which is really weird.” In the specimen O’Connor and her colleagues examined in this new paper, though, there was a clue: a previous study pointed out the presence of small rocks in its stomach.

Many living birds have an organ called a gizzard—a thick, muscular part of the stomach helps them digest food. They swallow small rocks, called gizzard stones, and these rocks make their way to the gizzard, where they help to crush up tough food. These gizzard stones, called gastroliths, have been found in some dinosaur and bird fossils, providing clues about what those animals ate—they’ve been associated with diets of tough plant materials and seeds.

X-ray image of crystals in the stomach of Bohaiornis guoi. © Liu et al, IVPP.

But rocks in an animal’s stomach aren’t necessarily a sign that it’s using them to crush up food. Some modern birds of prey swallow rocks called rangle to help dislodge matter from their digestive tract to clean it out. And sometimes, rocks have been found near the stomach cavities of dinosaur fossils that the creature swallowed accidentally, or the stones were just coincidentally near the fossil. “You have to make a differentiation between just a gastrolith and a gastrolith that’s used as a gizzard stone,” says O’Connor.

While there’s no clear evidence of gastroliths in the enantiornithine birds, a paper published in 2015 posited that a specimen of Bohaiornis guoi contained rocks in its stomach used as rangle (gastroliths ingested by raptorial birds to clean the stomach, but not to digest food). O’Connor was skeptical; the photos of the rocks didn’t look right. Gastroliths are usually made of different kinds of rock and are slightly different colors and shapes; these rocks were all similar in composition to each other and to the fossilized bone itself. They also didn’t seem to be shaped or grouped quite right—they were too round and too scattered. “I didn’t know what they were, but I was like, they’re not gastroliths,” she says. So, she and her colleagues set out to figure out what these rocks were and compare them with gastroliths from other fossil birds and dinosaurs.

The researchers extracted a sample of the rocks in Bohaiornis’s stomach and examined them under a scanning electron microscope. They then exposed the rocks to X-rays to determine which wavelengths the rocks absorbed. Since each mineral absorbs different wavelengths, this helped the researchers narrow down what these rocks were made of.

“We found that those pieces of rock that had been called gastroliths were chalcedony crystals,” says O’Connor. “Chalcedony is basically quartz crystals that grow in sedimentary rocks. There hasn’t been any evidence of this in the Jehol but there’s plenty of evidence of it within the fossil record where chalcedony crystals will form within a clamshell, or sometimes chalcedony will replace the minerals making up the bones in a fossil.” What’s more, the chalcedony was all interconnected in one thin sheet of crystal, rather than separate rocks that the bird had swallowed.

The fossil specimen of Bohaiornis with crystals in its stomach. © Liu et al, IVPP.

The amount of chalcedony present was wrong, too, if it were used to help with digestion. Scientific literature suggests that the rocks that birds consume as rangle account for about 3% of their body mass; since Bohaiornis was likely about 300 grams, the team would be looking for up to 9 grams worth of rangle. O’Connor says, “We weren’t able to extract the entire sample and figure out how much it weighed, but Shumin was really clever, and she took a piece of chalcedony that weighed 3 grams, and it was huge” —way bigger than the combined size of the bits of chalcedony in Bohaiornis’s stomach.

The combined evidence suggests that Bohaiornis didn’t have gastroliths for helping crush food or rangle to help clean out its stomach after all. Or, at least, this specimen of Bohaiornis doesn’t contain those gastroliths.

“We just have this absence of evidence, and paleontologists always say absence of evidence is not evidence of absence. But I always counter with, whoever came up with that adage never imagined having thousands of specimens that are complete and articulated, some preserving soft tissue,” says O’Connor. If Early Cretaceous enantiornithines did employ gastroliths, it’s awfully strange that none of the thousands of fossils show them.

O’Connor notes that while none of the enantiornithine birds from the Jehol Formation show evidence of stomach contents, there’s one from Spain with bits of freshwater shellfish in its stomach. But the mystery of what Bohaiornis ate, and why none of the Jehol enantiornithines have anything in their stomachs, remains.

“This study is important because this fossil is the one and only fossil record of Enantiornithes containing possible gastroliths, even possible real stomach traces in the Jehol. What’s more, only this clade of fossil birds don’t have stomach traces so far, whereas most other clades have these traces,” says Liu.

“We’re always trying to find some evidence, and the specimens that have been suggested to fill this gap just unfortunately don’t do it,” says O’Connor. “It’s just part of the paleo game, part of science—constantly correcting. I’m happy when we don’t understand things, because it means there’s research to do, it’s exciting.”

Featured image: A reconstruction of the bohaiornithid Sulcavis, a close relative of Bohaiornis guoi, hunting an insect. © S. Abramowicz, Dinosaur Institute, Natural History Museum of Los Angeles County.

Reference: Shumin Liu, Zhiheng Li, Alida M. Bailleul, Min Wang and Jingmai O’Connor, “Investigating Possible Gastroliths in a Referred Specimen of Bohaiornis guoi (Aves: Enantiornithes)”, Front. Earth Sci., 19 February 2021 | https://doi.org/10.3389/feart.2021.635727

Provided by Field Museum

Stromatolites – Fossils of Earliest Life on Earth – May Owe Existence to Viruses (Paleontology)

As the Mars Rover sets out to look for evidence of life on another planet, scientists back on Earth suggest viruses played a key role in creating stromatolites, our planet’s earliest lifeforms.

It may pain us to hear this during a deadly viral pandemic, but life as we know it on this planet may never have occurred if it weren’t for viruses, scientists studying billion-year-old ‘living rocks’ say.

In a paper published in the March issue of Trends in Microbiology, a team of scientists from UNSW Sydney and the US looked at evidence of the world’s oldest lifeforms in fossils known as stromatolites, layered limestone rocks often found in shallow waters around the globe. They wanted to understand the mechanism that led colonies of single-celled organisms known as microbial mats to create these intriguing rock structures.

And they believe viruses may be the missing piece of the puzzle that could help explain how a soft microbial mat transitions – or lithifies – into the hard stromatolite features that are prevalent in such places as Shark Bay and the Pilbara, Western Australia.

Co-author on the paper, Associate Professor Brendan Burns from UNSW’s Australian Centre for Astrobiology, says stromatolites are one of the oldest known microbial ecosystems, dating back some 3.7 billion years.

“Stromatolites are pervasive in the fossil record and are some of our earliest examples of life on Earth,” he says.

“The microbial mats that created them were predominantly made up of cyanobacteria, which used photosynthesis – like plants do – to turn sunlight into energy, while producing so much oxygen over time they changed the early Earth’s atmosphere to make it habitable for complex life.

“You could say we owe our very existence to these living rocks.”

A shard of stromatolite rock found at Shark Bay showing layered sediments that was produced by microbial mats billions of years ago. Photo: UNSW/Brendan Burns

A/Prof. Burns and his colleagues wanted to understand the mechanism behind the microbial mats lithifying into stromatolites, not only because so little is known about the process, but because of what this could add to our knowledge about life on Earth – and possibly other planets.

“If we understand the mechanisms of stromatolite formation, we will have a better handle on the impact these ecosystems had on evolution of complex life,” he says.

“This knowledge may help us better interpret biosignatures – which you could call chemical or molecular fossils – that provide clues to the activities of early life, billions of years ago.

“It also has the potential to help us look for life on other planets – one of the jobs of the Mars 2020 mission is to look for evidence of biosignatures in Martian rock samples.”

In the paper, the authors postulate that microbial mat transition from soft cells to rock is enhanced by interactions with viruses.

“We propose viruses may have a direct or indirect impact on microbial metabolisms that govern the transition from microbial mat to stromatolite,” he says.

In the direct impact scenario, viruses infiltrate the nucleus of the cyanobacteria and influence the host metabolism, inserting and removing genes that increase the fitness of the virus and the host at the same time.

“This, in turn, increases survival of the microbial mat and selects for genes that potentially influence carbonate precipitation – basically the process of microbes pouring the concrete to make their stromatolite apartment blocks,” A/Prof. Burns says.

In the indirect scenario, the scientists talk about a process known as viral lysis, where viruses invade living cells and trigger the disintegration of their membranes and release of contents – effectively bringing about cell death.

“We think viral lysis may release material that promotes metabolism of organisms which results in mineral precipitation and eventual stromatolite formation.”

Whether viruses cause the microbial mats to harden into stromatolites directly or indirectly, or a combination of both, A/Prof. Burns says more research is needed.

“We’re hoping to do more studies in the lab to test this.

“We want to be able to identify what viruses are actually involved and see if we can then manipulate potential virus-host interaction to find out whether or not they can, in fact, change some of the metabolisms that might result in stromatolite formation,” A/Prof. Burns says.

Featured image: Stromatolites at Shark Bay, Western Australia. Photo: UNSW Sydney/Brendan Burns

Read the full paper in Trends in MicrobiologyBetween a Rock and a Soft Place: The Role of Viruses in Lithification of Modern Microbial Mats

Provided by UNSW

Researchers Discover 635 Million-year-old fungi-like Microfossil That Bailed Us Out of an Ice Age (Paleontology)

When you think of fungi, what comes to mind may be a crucial ingredient in a recipe or their amazing ability to break down dead organic matter into vital nutrients. But new research by Shuhai Xiao, a professor of geosciences with the Virginia Tech College of Science, and Tian Gan, a visiting Ph.D. student in the Xiao lab, highlights yet another important role that fungi have played throughout the Earth’s history: helping the planet recover from an ice age.

A team of scientists from Virginia Tech, the Chinese Academy of SciencesGuizhou Education University, and University of Cincinnati has discovered the remains of a fungi-like microfossil that emerged at the end of an ice age some 635 million years ago. It is the oldest terrestrial fossil ever found. To put it into perspective, this microfossil predates the oldest dinosaurs about three times over.

Their findings were published in Nature Communications on Jan. 28.

The fossil was found in small cavities within well-studied sedimentary dolostone rocks of the lowermost Doushantuo Formation in South China. Although the Doushantuo Formation has provided a plethora of fossils to date, researchers did not expect to find any fossils toward the lower base of the dolostones.

But against all odds, Gan found a few long, thread-like filaments – one of the key characteristics of fungi.

“It was an accidental discovery,” said Gan. “At that moment, we realized that this could be the fossil that scientists have been looking for a long time. If our interpretation is correct, it will be helpful for understanding the paleoclimate change and early life evolution.”

This discovery is key for understanding multiple turning points throughout Earth’s history: the Ediacaran period and the terrestrialization of fungi.

When the Ediacaran period began, the planet was recovering from a catastrophic ice age, also known as the “snowball Earth.” At that time, ocean surfaces were frozen to a depth of more than a kilometer and it was an incredibly harsh environment for virtually any living organism, except for some microscopic life that managed to thrive. Scientists have long wondered how life ever returned to normalcy – and how the biosphere was able to grow larger and more complex than ever before.

With this new fossil in hand, Tian and Xiao are certain that these microscopic, low profile cave dwellers played numerous roles in the reconditioning of the terrestrial environment in the Ediacaran time. One role involved their formidable digestive system.

Fungi have a rather unique digestive system that plays an even greater role in the cycling of vital nutrients. Using enzymes secreted into the environment, terrestrial fungi can chemically break down rocks and other tough organic matter, which can then be recycled and exported into the ocean.

“Fungi have a mutualistic relationship with the roots of plants, which helps them mobilize minerals, such as phosphorus. Because of their connection to terrestrial plants and important nutritional cycles, terrestrial fungi have a driving influence on biochemical weathering, the global biogeochemical cycle, and ecological interactions,” said Gan.

Although previous evidence stated that terrestrial plants and fungi formed a symbiotic relationship around 400 million years ago, this new discovery has recalibrated the timeline of when these two kingdoms colonized the land.

“The question used to be: ‘Were there fungi in the terrestrial realm before the rise of terrestrial plants’,” said Xiao, an affiliated faculty member of the Fralin Life Sciences Institute and the Global Change Center. “And I think our study suggests yes. Our fungus-like fossil is 240 million years older than the previous record. This is, thus far, the oldest record of terrestrial fungi.”

Now, new questions have arisen. Since the fossilized filaments were accompanied by other fossils, Gan will set out to explore their past relationships.

“One of my goals is to constrain the phylogenetic affinities of these other types of fossils that are associated with the fungal fossils,” said Gan.

Xiao is thrilled to tackle the environmental aspects of these microorganism. Sixty years ago, few believed that microorganisms, like bacteria and fungi, could be preserved as fossils. Now that Xiao has seen them with his very eyes, he plans to learn more about how they have been virtually frozen in time.

“It is always important to understand the organisms in the environmental context,” said Xiao. “We have a general idea that they lived in small cavities in dolostone rocks. But little is known about how exactly they lived and how they were preserved. Why can something like fungi, which have no bones or shells, be preserved in the fossil record?”

However, it can’t be said for sure if this fossil is a definitive fungus. Although there is a fair amount of evidence behind it, the investigation into these microfossils is ongoing.

“We would like to leave things open for other possibilities, as a part of our scientific inquiry,” said Xiao. “The best way to put it is that perhaps we have not disapproved that they are fungi, but they are the best interpretation that we have at the moment.”

Three distinct groups and labs at Virginia Tech were crucial for the identification and timestamping of this fossil. The Confocal Laser Scanning and Microscopy lab at the Fralin Life Sciences Institute helped Tian and Xiao perform initial analysis that prompted further investigation at the University of Cincinnati.

The Department of Biological Sciences’ Massey Herbarium, which houses over 115,000 specimens of vascular plants, fungi, bryophytes, and lichens, provided modern fungal specimens for comparison with the fossils.

The team called in technicians to conduct geochemical analysis using Secondary Ion Mass Spectrometry, which ionize nanomoles of material from small areas that are a fraction the thickness of a hair strand, to analyze the isotopic abundance of sulfur-32 and sulfur-34 in order to understand the fossilization environment.

Advanced computerized tomography was crucial to getting the 3D morphology of the filaments, which are just a few micrometers thick. And a combination of Focused Ion Beam Scanning Electron Microscopy and Transmission Electron Microscopy allowed researchers to cut samples with surgical precision and take an even closer look at every nanometer of the filaments.

“This wasn’t a single person or even a single lab that did this work,” said Xiao.

Xiao also emphasized the importance of interdisciplinary research in this study and many others.

“It’s very important to encourage the next generation of scientists to be trained in an interdisciplinary light because new discoveries always happen at the interface of different fields,” said Xiao.

Featured image: Microscopic image of the fungus-like filamentous microfossils. Credit: Andrew Czaja of University of Cincinnati.

Reference: Gan, T., Luo, T., Pang, K. et al. Cryptic terrestrial fungus-like fossils of the early Ediacaran Period. Nat Commun 12, 641 (2021). https://doi.org/10.1038/s41467-021-20975-1

Provided by Virginia Tech

New Fossil Provides Clarity to the History of Alligatoridae (Paleontology)

Families are complicated. For members of the alligatorid family, which includes living caimans and alligators – this is especially true. They are closely related, but because of their similarity, their identification can even stump paleontologists.

But after the recent discovery of a partial skull, the caimans of years past may provide some clarity into the complex, and incomplete, history of its relatives and their movements across time and space.

Michelle Stocker, an assistant professor of vertebrate paleontology in Virginia Tech’s Department of Geosciences in the College of Science, Chris Kirk of the University of Texas at Austin, and Christopher Brochu of the University of Iowa, have identified a 42 million year old partial skull that may have belonged to one of the last prehistoric caimans to roam the United States.

“Any fossil that we find has unique information that it contributes to understanding the history of life,” said Stocker, who is an affiliated faculty member of the Fralin Life Sciences Institute and the Global Change Center. “From what we have, we are able to understand a little bit more about the evolutionary history of caimans and the alligatorid group, which includes alligators and caimans.”

Their findings were published in PeerJ, an open access peer-reviewed scientific journal covering research in the biological and medical sciences.

Michelle Stocker and Rachel Wallace, a former graduate student at the University of Texas at Austin, are seen excavating the caiman fossil from sandstone in January of 2011. Photo courtesy of Chris Kirk.

The fossil was discovered in 2010 at Midwestern State University’s Dalquest Desert Research Site, which includes extensive exposures of the Devil’s Graveyard Formation, a geologic formation in the trans-Pecos volcanic field of West Texas. The Devil’s Graveyard Formation preserves fossils from the latter portion of the Eocene epoch, a period of time covering 15 million years of prehistory.

In 2011, Stocker and the team returned to the site to collect a key bone that remained in the hard sandstone block that once encapsulated the caiman skull.

“The Devil’s Graveyard Formation provides a unique window into the evolution of North American vertebrates during the middle and late Eocene,” said Kirk. “There are a host of extinct species that are only known from the Devil’s Graveyard, including several primates, rodents, lizards, and now this new fossil caiman.”

What they discovered was a partial skull. At the time of the discovery, paleontologists were convinced that the skull came from a closer relative to alligators than to caimans.

“When you are at the early diversification of groups, their features aren’t as differentiable,” said Stocker. “It was harder to tell if this is more closely related to caimans or to alligators because those two are really closely related already. And the differences between them are subtle, especially early in their evolutionary history.”

The skull’s braincase was a key component in the identification of the fossil. The braincase encases and protects the brain from injury. Since no two species have the same braincase, finding one can provide some much needed information for paleontologists.

After further investigation into this fossil’s braincase, Stocker and the team were able to determine that this was most likely a caiman. 

The caiman was deemed to be 42 million years old using a combination of investigative techniques, including radiometric dating, biochronology, and biostratigraphy, where paleontologists use the relative order of the fossilized animals to find out how old the rocks are.

With the age of the fossil and its location in mind, paleontologists are able to add to an ever-growing story about a large biogeographic range contraction, or a climate-related extirpation, that occurred millions of years ago.

Roughly 56 million years ago, the planet was experiencing temperatures so hot and methane levels so high that no polar ice caps could form. For large cool-blooded reptiles like alligators and caimans, it was their time to thrive and soak up the sun. In fact, the conditions were so favorable that these early reptiles roamed as far north as northern Canada.

“The presence of a fossil caiman in the Devil’s Graveyard, about 1200 kilometers north of where caimans are found today, really says something about how different the climate of West Texas was in the middle Eocene”, said Kirk.

But one epoch later, in the Oligocene, the entire world was experiencing cooler temperatures, forcing many species that require warm and humid conditions into more restricted geographic ranges.

Caiman populations, in particular, are now only found in South and Central America. Although, a small number of caimans have been found outside of this range and are thought to be invasive species.

“This caiman seems out of place,” said Brochu. “Caimans today are a South American radiation, and data from modern forms, including DNA, would suggest a very simple single origin from a North American ancestor. This new form, along with some older North American fossil caimans, suggests a far more complex early history with multiple crossings of the seaway that separated North and South America until fairly recently.”

There is even more to know about caiman history. Since the specimen was an incomplete skull, and far from a complete skeleton, paleontologists still have some knowledge gaps to fill about their relationships.

“If we can find another individual, we will get a better sense of its relationships, and it might be able to say something about what variation could be present in this taxon, or how they grow, or where else they might be found,” said Stocker. “This is a one and done kind of fossil right now. Hopefully there are more out there.”

Chris Kirk, a professor of the University of Texas at Austin and a member of Michelle Stocker’s team, with the recovered caiman fossil in January of 2010. Photo courtesy of Chris Kirk.

The fossil will be housed at the Texas Vertebrate Paleontology Collections at the University of Texas at Austin where it will be preserved and maintained in perpetuity.

There is more research to be done on other fossils that have been retrieved from Central and South American specimens, as well. Those fossils, in particular, are critical for understanding the early southern record of caiman history and clearing up the morphological and chronologic gaps that currently exist in the caiman fossil record.

In the end, all that lies on the horizon is to do more fieldwork, collect more fossils, and conduct more study.

Without museums, this identification couldn’t have been possible. When paleontologists find new fossils, they must travel to museums, where they compare the new fossils with other specimens that have been collected. Stocker maintains that the preservation and maintenance that museums do is just one reason that they need to be supported.

“Museums are important for science and for everybody who wants to understand our shared evolutionary history,” said Stocker. “And collaboration is the way that science moves forward.”

Provided by Virginia Tech

New Discovery Sheds Light on the Mysterious Family Life of Notorious Sabre-toothed Tiger (Paleontology)

Like many of today’s millennials, adolescent Sabre-Toothed Cats stayed with family longer than expected.

New research indicates adolescent offspring of the menacing sabre-toothed predator, Smilodon fatalis, were more momma’s cubs than independent warriors.

Sabre-toothed cubs playing together. Credit: Illustration by Danielle Dufault, © Royal Ontario Museum

A new study by scientists at the Royal Ontario Museum (ROM) and University of Toronto, published January 7, 2021 in iScience¸ documents a family group of the sabre-toothed cats whose remains were discovered in present-day Ecuador. By studying the fossils, collected for the ROM in the early 1960s, the scientists were able to show that while the supersized Ice Age cats grew quite quickly, they also appeared to stay with their mother for longer than some other large cats before forging their own path.

“This study started out as a simple description of previously unpublished fossils,” says Ashley Reynolds, a graduate student based at the Royal Ontario Museum who led the study while completing her PhD research in Ecology & Evolutionary Biology at the University of Toronto. “But when we noticed the two lower jaws we were working on shared a type of tooth only found in about five percent of the Smilodon fatalis population, we knew the work was about to become much more interesting.”

A comparison of the lower left jaw bones from the two young sabre-toothed cats, S. fatalis, that were buried together. They show similar tooth formation, suggesting that the two were related. Comparison of the two left dentaries, ROMVP 5100 and ROMVP 5101. Credit: Ashley Reynolds © Royal Ontario Museum

Encouraged by this new discovery, the researchers dug deeper and found that they were likely looking at three related individuals: one adult and two “teenaged” cats. What’s more, they were able to determine that the younger cats were at least two years old at the time of their death, an age at which some living big cats, such as tigers, are already independent.

To support this conclusion, the team studied the preservation and formation of the Ecuadorian site (an area of study called taphonomy), based on historic collecting records and the suite of clues on the fossil bones themselves.

Historically, Smilodon specimens that have largely been collected from “predator trap” deposits, such as the famous La Brea Tar Pits in Los Angeles, California. But the Ecuador deposit, which formed on an ancient coastal plain, is likely derived from a catastrophic mass death event. This means that, unlike the “traps,” all the fossils in the deposit died at the same time. As this preserves a snapshot of an ecosystem, fossils like these can provide new and unique insights into the behaviour of extinct species.

Sabre-toothed cat adult and subadult size comparison Credit: Ashley Reynolds © Royal Ontario Museum

“The social lives of these iconic predators have been mysterious, in part because their concentration in tar seeps leaves so much room for interpretation” says Dr. Kevin Seymour, Assistant Curator of Vertebrate Paleontology at the ROM and a co-author of this study, “This historic assemblage of sabre-cat fossils from Ecuador was formed in a different way, allowing us to determine the two juveniles likely lived, and died, together—and were therefore probably siblings”

The fossils were collected from Coralito, Ecuador in 1961 by A. Gordon Edmund, who was curator of Vertebrate Palaeontology at the ROM from 1954-1990, and Roy R. Lemon, who was curator of Invertebrate Palaeontology from 1957-1969. Together, Edmund and Lemon collected tonnes of tar-soaked sediment which was later prepared at the ROM.

“These world-famous collections made 60 years ago have been studied for years, but a measure of their importance is that they continue to produce new insights into the lives of these extinct animals” says Dr. David Evans, Temerty Chair of Vertebrate Palaeontology at the Royal Ontario Museum and Reynolds’s thesis supervisor.

Article Reference: Reynolds, A.R., Seymour, K.L., and Evans, D.C. 2021. Smilodon fatalis siblings reveal life history in a saber-toothed cat. iScience. doi: 10.1016/j.isci.2020.101916 .

Provided by Royal Ontario Museum

Primitive Fish Fossils Reveal Developmental Origins of Teeth (Paleontology)

High-resolution X-ray imaging of primitive bony fish fossils reveal the developmental and evolutionary relationship between teeth and dermal odontodes.

Teeth and hard structures called dermal odontodes are evolutionarily related, arising from the same developmental system, a new study published today in eLife shows.

Part of a jawbone of the 422-million-year-old fossil bony fish Lophosteus, visualised with a high-resolution X-ray technique. On the right, the surface of the jawbone is shown in grey. In the middle, exposed teeth are highlighted in gold and dermal odontodes in shades of purple, pink and red. On the left, the bone itself is made transparent, revealing internal blood vessels and pulp cavities, shown in blue and green, as well as the embedded teeth and dermal odontodes. ©Chen et al. (CC BY 4.0)

These findings in ancient fish fossils contradict established claims about the difference between the two structures based on modern sharks, and provide potential new insights into the origins and development of teeth.

Odontodes are hard structures made of dentine, the main substance in ivory, and are found on the outside surfaces of animals with backbones (vertebrates). Teeth are an example of odontodes but some animals also have them on their skin, such as the tooth-like ‘scales’ of sharks. These are known as dermal odontodes.

“Teeth and dermal odontodes are thought to have evolved separately because they seem to develop in different ways,” says lead author Donglei Chen, a researcher at the Department of Organismal Biology, Uppsala University, Sweden. “However, most of what we know is limited to modern sharks in which the difference between these structures has become very distinct. To understand the relationship between the two more clearly, we needed to turn to the fossil record.”

The team looked at fossils of one of the earliest bony fishes called Lophosteus which lived more than 400 million years ago. They chose this fish because it represents an early stage of tooth evolution, bringing them closer to the time when teeth and dermal odontodes could have separated in the hopes that any developmental similarities between the two would be more obvious.

The researchers used high-resolution X-ray imaging to look at the three-dimensional structure of odontodes in Lophosteus at different stages of development. They found that the appearance of odontodes were similar at the early stages of development but would change depending on whether they grew into the mouth or the face. This suggests there were different chemical signals in each area directing their development. At the later stages, some dermal odontodes would move from the face to the mouth and begin to look like teeth.

These findings suggest that both types of odontodes are able to respond to the same signals controlling each other’s development and are made by the same developmental system – not separate systems as previously thought.

“In addition to casting light on the early evolution of our own teeth, our results point to a previously unrecognised evolutionary-developmental relationship between teeth and dermal odontodes,” says senior author Per Ahlberg, PhD, Professor at the Department of Organismal Biology, Uppsala University. “This has potential implications for understanding the signalling that occurs during development and could inspire new lines of developmental research in other organisms.”

References: Donglei Chen , Henning Blom, Sophie Sanchez, Paul Tafforeau, Tiiu Märss, Per E Ahlberg, “The developmental relationship between teeth and dermal odontodes in the most primitive bony fish Lophosteus”, Evolutionary Biology, 2020. https://elifesciences.org/articles/60985

Provided by Elife

What Caused the Ice Ages? Tiny Ocean Fossils Offer Key Evidence (Biology)

The ocean’s role in past atmospheric carbon dioxide change comes into focus.

The last million years of Earth history have been characterized by frequent “glacial-interglacial cycles,” large swings in climate that are linked to the growing and shrinking of massive, continent-spanning ice sheets. These cycles are triggered by subtle oscillations in Earth’s orbit and rotation, but the orbital oscillations are too subtle to explain the large changes in climate.

Since the discovery that atmospheric carbon dioxide (CO2) concentrations were lower during past ice ages, the cause has been a mystery. Now, scientists have discovered that a weakening in upwelling in the Antarctic Ocean, the ocean around Antarctica, kept more CO2 in the deep ocean during the ice ages. This diatom species, Fragilariopsis kerguelensis, photographed both alive (left) and fossilized (right), is a floating algae that is abundant in the Antarctic Ocean and was the major species in the samples collected for this study. Nitrogen isotopes in their shells vary with the amount of unused nitrogen in the surface water. Researchers used that to trace nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods. Image of live diatom by Philipp Assmy (Norwegian Polar Institute) and Marina Montresor (Stazione Zoologica Anton Dohrn); fossilized diatoms (c) Michael Kloster, Alfred-Wegener-Institute

“The cause of the ice ages is one of the great unsolved problems in the geosciences,” said Daniel Sigman, the Dusenbury Professor of Geological and Geophysical Sciences. “Explaining this dominant climate phenomenon will improve our ability to predict future climate change.”

In the 1970s, scientists discovered that the concentration of the atmospheric greenhouse gas carbon dioxide (CO2) was about 30% lower during the ice ages. That prompted theories that the decrease in atmospheric CO2 levels is a key ingredient in the glacial cycles, but the causes of the CO2 change remained unknown. Some data suggested that, during ice ages, CO2 was trapped in the deep ocean, but the reason for this was debated.

Now, an international collaboration led by scientists from Princeton University and the Max Planck Institute for Chemistry (MPIC) have found evidence indicating that during ice ages, changes in the surface waters of the Antarctic Ocean worked to store more CO2 in the deep ocean. Using sediment cores from the Antarctic Ocean, the researchers generated detailed records of the chemical composition of organic matter trapped in the fossils of diatoms — floating algae that grew in the surface waters, then died and sank to the sea floor. Their measurements provide evidence for systematic reductions in wind-driven upwelling in the Antarctic Ocean during the ice ages. The research appears in the current issue of the journal Science.

For decades, researchers have known that the growth and sinking of marine algae pumps CO2 deep into the ocean, a process often referred to as the “biological pump.” The biological pump is driven mostly by the tropical, subtropical and temperate oceans and is inefficient closer to the poles, where CO2 is vented back to the atmosphere by the rapid exposure of deep waters to the surface. The worst offender is the Antarctic Ocean: the strong eastward winds encircling the Antarctic continent pull CO2-rich deep water up to the surface, “leaking” CO2 to the atmosphere.

This diatom species, Fragilariopsis kerguelensis, is a floating algae that is abundant in the Antarctic Ocean and was the major species in the samples collected for the study by Princeton University and the Max Planck Institute for Chemistry. These microscopic organisms live near the sea surface, then die and sink to the sea floor. The nitrogen isotopes in their shells vary with the amount of unused nitrogen in the surface water. The researchers used that to trace nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods. ©Philipp Assmy (Norwegian Polar Institute) and Marina Montresor (Stazione Zoologica Anton Dohrn)

The potential for a reduction in wind-driven upwelling to keep more CO2 in the ocean, and thus to explain the ice age atmospheric CO2 drawdown, has also been recognized for decades. Until now, however, scientists have lacked a way to unambiguously test for such a change.

The Princeton-MPIC collaboration has developed such an approach, using tiny diatoms. Diatoms are floating algae that grow abundantly in Antarctic surface waters, and their silica shells accumulate in deep sea sediment. The nitrogen isotopes in diatoms’ shells vary with the amount of unused nitrogen in the surface water. The Princeton-MPIC team measured the nitrogen isotope ratios of the trace organic matter trapped in the mineral walls of these fossils, which revealed the evolution of nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods.

“Analysis of the nitrogen isotopes trapped in fossils like diatoms reveals the surface nitrogen concentration in the past,” said Ellen Ai, first author of the study and a Princeton graduate student working with Sigman and with the groups of Alfredo Martínez-García and Gerald Haug at MPIC. “Deep water has high concentrations of the nitrogen that algae rely on. The more upwelling that occurs in the Antarctic, the higher the nitrogen concentration in the surface water. So our results also allowed us to reconstruct Antarctic upwelling changes.”

The data were made more powerful by a new approach for dating the Antarctic sediments. Surface water temperature change was reconstructed in the sediment cores and compared with Antarctic ice core records of air temperature.

This diatom species, Fragilariopsis kerguelensis, is a floating algae that is abundant in the Antarctic Ocean and was the major species in the samples collected for the study by Princeton University and the Max Planck Institute for Chemistry. These microscopic organisms live near the sea surface, then die and sink to the sea floor. The nitrogen isotopes in their shells vary with the amount of unused nitrogen in the surface water. The researchers used that to trace nitrogen concentrations in Antarctic surface waters over the past 150,000 years, covering two ice ages and two warm interglacial periods. (c) Michael Kloster, Alfred-Wegener-Institute

“This allowed us to connect many features in the diatom nitrogen record to coincident climate and ocean changes from across the globe,” said Martínez-García. “In particular, we are now able to pin down the timing of upwelling decline, when climate starts to cool, as well as to connect upwelling changes in the Antarctic with the fast climate oscillations during ice ages.”

This more precise timing allowed the researchers to home in on the winds as the key driver of the upwelling changes.

The new findings also allowed the researchers to disentangle how the changes in Antarctic upwelling and atmospheric CO2 are linked to the orbital triggers of the glacial cycles, bringing scientists a step closer to a complete theory for the origin of the ice ages.

“Our findings show that upwelling-driven atmospheric CO2 change was central to the cycles, but not always in the way that many of us had assumed,” said Sigman. “For example, rather than accelerating the descent into the ice ages, Antarctic upwelling caused CO2 changes that prolonged the warmest climates.”

Their findings also have implications for predicting how the ocean will respond to global warming. Computer models have yielded ambiguous results on the sensitivity of polar winds to climate change. The researchers’ observation of a major intensification in wind-driven upwelling in the Antarctic Ocean during warm periods of the past suggests that upwelling will also strengthen under global warming. Stronger Antarctic upwelling is likely to accelerate the ocean’s absorption of heat from ongoing global warming, while also impacting the biological conditions of the Antarctic Ocean and the ice on Antarctica.

“The new findings suggest that the atmosphere and ocean around Antarctica will change greatly in the coming century,” said Ai. “However, because the CO2 from fossil fuel burning is unique to the current times, more work is needed to understand how Antarctic Ocean changes will affect the rate at which the ocean absorbs this CO2.”

“Southern Ocean upwelling, Earth’s obliquity, and glacial-interglacial atmospheric CO2 change” by Xuyuan Ellen Ai, Anja S. Studer, Daniel M. Sigman, Alfredo Martínez-García, François Fripiat, Lena M. Thöle, Elisabeth Michel, Julia Gottschalk, Laura Arnold, Simone Moretti, Mareike Schmitt, Sergey Oleynik, Samuel L. Jaccard and Gerald H. Haug appears in the Dec. 11 issue of Science (DOI: 10.1126/science.abd2115). The research was supported by the National Science Foundation (grant PLR-1401489 to D.M.S.), ExxonMobil through the Andlinger Center for Energy and the Environment at Princeton University, the Swiss National Science Foundation (grant PBEZP2_145695 to A.S.S. and grants PP00P2_144811 and PP00P2_172915 to S.L.J.), a Global Research Fellowship from the German Research Foundation (DFG grant GO 2294/2-1 to J.G.), and the Max Planck Society. Other Princeton connections: Anja Studer and Francois Fripiat were both postdoctoral researchers in Sigman’s lab, and Sergey Oleynik is the isotope lab manager for Princeton’s Department of Geosciences.

Provided by Princeton University