Rare fossilized algae, discovered unexpectedly, fill in evolutionary gaps
When geobiology graduate student Katie Maloney trekked into the mountains of Canada’s remote Yukon territory, she was hoping to find microscopic fossils of early life. Even with detailed field plans, the odds of finding just the right rocks were low. Far from leaving empty-handed, though, she hiked back out with some of the most significant fossils for the time period.
Eukaryotic life (cells with a DNA-containing nucleus) evolved over two billion years ago, with photosynthetic algae dominating the playing field for hundreds of millions of years as oxygen accumulated in the Earth’s atmosphere. Geobiologists think that algae evolved first in freshwater environments on land, then moved to the oceans. But the timing of that evolutionary transition remains a mystery, in part because the fossil record from early Earth is sparse.
Maloney’s findings were published yesterday in Geology. She and her collaborators found macroscopic fossils of multiple species of algae that thrived together on the seafloor about 950 million years ago, nestled between bacterial mounds in a shallow ocean. The discovery partly fills in the evolutionary gap between algae and more complex life, providing critical time constraints for eukaryotic evolution.
Although the field site was carefully chosen by Maloney’s field team leader, sedimentologist Galen Halverson, who has worked in the region for years, the discovery was an unexpected stroke of luck.
“I was thinking, ‘maybe we’ll find some microfossils,'” Maloney said. The possibility of finding larger fossils didn’t cross her mind. “So as we started to find well-preserved specimens, we stopped everything and the whole team gathered to collect more fossils. Then we started to find these big, complex slabs with hundreds of specimens. That was really exciting!”
Determining if traces like the ones Maloney found are biogenic (formed by living organisms) is a necessary step in paleobiology. While that determination is ultimately made in the lab, a few things tipped her off in the field. The traces were very curvy, which can be a good indicator of life, and there were visible structures within them. The fact that there were hundreds of them twisted together sealed the deal for her.
Few people would likely have noticed the fossils that day.
“We were really lucky that Katie was there to find them because at first glance, they don’t really look like anything,” Maloney’s advisor, Marc Laflamme, said. “Katie is used to looking at very weird looking fossils, so she has a bit of an eye for saying, ‘This is something worth checking out.'”
Maloney and her colleagues in the field wrestled the heavy slabs into their helicopter for safe transport back to the lab at the University of Toronto-Mississauga. She, Laflamme, and their collaborators used microscopy and geochemical techniques to confirm that the fossils were indeed early eukaryotes. They then mapped out the specimens’ cellular features in detail, allowing them to identify multiple species in the community.
While Maloney and her coauthors were writing up their results, they were confident they had found the first macroscopic specimens from this critical time period. During the peer review process, though, they received word from a collaborator that another group in China had made a similar discovery at about the same time — macrofossils from a similar period. That did not dissuade them.
“What’s a few hundred million years between friends?” Laflamme laughed. “I think our fossils have more detail, which makes them easier to interpret… They’re beautiful. They’re huge, they’re well detailed, there’s anatomy. Your eyes are just drawn to them.”
Ultimately, having two sets of macrofossils from approximately the same time can only improve the timeline of eukaryotic evolution, serving as critical calibration points for DNA-based biologic dating techniques. The new fossils also push back the time when algae were living in marine environments, indicating that evolution had already occurred in lakes on land. But for Maloney, an expert in sedimentology, they also raise questions about what gets preserved in the rock record and why.
“Algae became really important early on because of their role in oxygenation and biogeochemical cycles,” Maloney said. “So why does it take them so long to show up reliably in the fossil record? It’s definitely making us think more about animal ecosystems and whether or not we’re seeing the whole picture, or if we’re missing quite a bit from a lack of preservation.”
The whole project has been engaging for Maloney, who pivoted to algae from more recent biota. “I never expected to be fascinated by algae,” she said. “But I was pleasantly surprised as I started investigating modern algae, finding what an important role they play in sustainability and climate change — all these big issues that we’re dealing with today. So it’s been amazing contributing to algae’s origin story.”
This fieldwork was carried out with permits on traditional lands of the First Nation of Na-Cho Nyak Dun with their consent.
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Cephalopods: Older than was thought?
Fossil find from Canada could rewrite the evolutionary history of invertebrate organisms
The possibly oldest cephalopods in the earth’s history stem from the Avalon Peninsula in Newfoundland (Canada). They were discovered by earth scientists from Heidelberg University. The 522 million-year-old fossils could turn out to be the first known form of these highly evolved invertebrate organisms, whose living descendants today include species such as the cuttlefish, octopus and nautilus. In that case, the find would indicate that the cephalopods evolved about 30 million years earlier than has been assumed.
“If they should actually be cephalopods, we would have to backdate the origin of cephalopods into the early Cambrian period,” says Dr Anne Hildenbrand from the Institute of Earth Sciences. Together with Dr Gregor Austermann, she headed the research projects carried out in cooperation with the Bavarian Natural History Collections. “That would mean that cephalopods emerged at the very beginning of the evolution of multicellular organisms during the Cambrian explosion.”
The chalky shells of the fossils found on the eastern Avalon Peninsula are shaped like a longish cone and subdivided into individual chambers. These are connected by a tube called the siphuncle. The cephalopods were thus the first organisms able to move actively up and down in the water and thus settle in the open ocean as their habitat. The fossils are distant relatives of the spiral-shaped nautilus, but clearly differ in shape from early finds and the still existing representatives of that class.
“This find is extraordinary,” says Dr Austermann. “In scientific circles it was long suspected that the evolution of these highly developed organisms had begun much earlier than hitherto assumed. But there was a lack of fossil evidence to back up this theory.” According to the Heidelberg scientists, the fossils from the Avalon Peninsula might supply this evidence, as on the one hand, they resemble other known early cephalopods but, on the other, differ so much from them that they might conceivably form a link leading to the early Cambrian.
The former and little explored micro-continent of Avalonia, which — besides the east coast of Newfoundland — comprises parts of Europe, is particularly suited to paleontological research, since many different creatures from the Cambrian period are still preserved in its rocks. The researchers hope that other, better preserved finds will confirm the classification of their discoveries as early cephalopods.
The research results about the 522 million-year-old fossils were published in the Nature journal Communications Biology. Logistic support was given by the province of Newfoundland and the Manuels River Natural Heritage Society located there. The publication in open-access format was enabled in the context of Project DEAL.
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Younger Tyrannosaurus Rex bites were less ferocious than their adult counterparts
By closely examining the jaw mechanics of juvenile and adult tyrannosaurids, some of the fiercest dinosaurs to inhabit earth, scientists led by the University of Bristol have uncovered differences in how they bit into their prey.
They found that younger tyrannosaurs were incapable of delivering the bone-crunching bite that is often synonymous with the Tyrannosaurus rex and that adult specimens were far better equipped for tearing out chunks of flesh and bone with their massive, deeply set jaws.
The team also found that tension from the insertion of the lower pterygoid muscle is linked to decreasing stresses near the front of the typical tyrannosaur jaw, where the animals may have applied their highest impact bite forces using their large, conical teeth.
This would be advantageous with the highly robust teeth on the anterior end of the tyrannosaur jaw, where, usually, they may have applied their highest impact bite forces. Crocodilians experience the reverse situation — they possess robust teeth near the posterior end of their mandible where they apply their highest bite forces.
Adult tyrannosaurids have been extensively studied due to the availability of relatively complete specimens that have been CT scanned.
The availability of this material has allowed for studies of their feeding mechanics. The adult Tyrannosaurus rex was capable of a 60,000 Newton bite (for comparison, an adult lion averages 1,300 Newtons) and there is evidence of it having actively preyed on large, herbivorous dinosaurs.
The team were interested in inferring more about the feeding mechanics and implications for juvenile tyrannosaurs.
Their main hypotheses were that larger tyrannosaurid mandibles experienced absolutely lower peak stress, because they became more robust (deeper and wider relative to length) as they grew, and that at equalized mandible lengths, younger tyrannosaurids experienced greater stress and strain relative to the adults, suggesting relatively lower bite forces consistent with proportionally slender jaws.
At actual size the juveniles experienced lower absolute stresses when compared to the adult, contradicting our first hypothesis. This means that in real life, adult tyrannosaurs would experience high absolute stresses during feeding but shrug it off due to its immense size. However, when mandible lengths are equalized, the juvenile specimens experienced greater stresses, due to the relatively lower bite forces typical in slender jaws.
Lead author Andre Rowe, a Geology PhD Student at the University of Bristol’s School of Earth Sciences, said: “Tyrannosaurids were active predators and their prey likely varied based on their developmental stage.
“Based on biomechanical data, we presume that they pursued smaller prey and fulfilled an environmental role similar to the ‘raptor’ dinosaurs such as the dromaeosaurs. Adult tyrannosaurs were likely subduing large dinosaurs such as the duckbilled hadrosaurs and Triceratops, which would be quickly killed by their bone-crunching bite.
“This study illustrates the importance of 3D modeling and computational studies in vertebrate paleontology — the methodology we used in our study can be applied to many different groups of extinct animals so that we can better understand how they adapted to their respective environments.”
There are two major components of this research that Andre and the team would like to see future researchers delve into continued CT and surface scanning of dinosaur cranial material and more application of 3D models in dinosaur biomechanics research.
Andre added: “There remains a plethora of unearthed dinosaur material that has not been utilized in studies of feeding and function — ideally, all of our existing specimens will one day be scanned and made widely available online to researchers everywhere.
“The current lack of 3D model availability is noticeable in dinosaur research; relatively few studies involving 3D models of carnivorous dinosaurs have been published thus far. There is still much work to be done concerning skull function in all extinct animals — not only dinosaurs.”
Story Source:
Materials provided by University of Bristol. Note: Content may be edited for style and length.
Journal Reference:
- Andre J. Rowe, Eric Snively. Biomechanics of juvenile tyrannosaurid mandibles and their implications for bite force: Evolutionary biology. The Anatomical Record, 2021; DOI: 10.1002/ar.24602
They found that younger tyrannosaurs were incapable of delivering the bone-crunching bite that is often synonymous with the Tyrannosaurus rex and that adult specimens were far better equipped for tearing out chunks of flesh and bone with their massive, deeply set jaws.
The team also found that tension from the insertion of the lower pterygoid muscle is linked to decreasing stresses near the front of the typical tyrannosaur jaw, where the animals may have applied their highest impact bite forces using their large, conical teeth.
This would be advantageous with the highly robust teeth on the anterior end of the tyrannosaur jaw, where, usually, they may have applied their highest impact bite forces. Crocodilians experience the reverse situation — they possess robust teeth near the posterior end of their mandible where they apply their highest bite forces.
Adult tyrannosaurids have been extensively studied due to the availability of relatively complete specimens that have been CT scanned.
The availability of this material has allowed for studies of their feeding mechanics. The adult Tyrannosaurus rex was capable of a 60,000 Newton bite (for comparison, an adult lion averages 1,300 Newtons) and there is evidence of it having actively preyed on large, herbivorous dinosaurs.
The team were interested in inferring more about the feeding mechanics and implications for juvenile tyrannosaurs.
Their main hypotheses were that larger tyrannosaurid mandibles experienced absolutely lower peak stress, because they became more robust (deeper and wider relative to length) as they grew, and that at equalized mandible lengths, younger tyrannosaurids experienced greater stress and strain relative to the adults, suggesting relatively lower bite forces consistent with proportionally slender jaws.
At actual size the juveniles experienced lower absolute stresses when compared to the adult, contradicting our first hypothesis. This means that in real life, adult tyrannosaurs would experience high absolute stresses during feeding but shrug it off due to its immense size. However, when mandible lengths are equalized, the juvenile specimens experienced greater stresses, due to the relatively lower bite forces typical in slender jaws.
Lead author Andre Rowe, a Geology PhD Student at the University of Bristol’s School of Earth Sciences, said: “Tyrannosaurids were active predators and their prey likely varied based on their developmental stage.
“Based on biomechanical data, we presume that they pursued smaller prey and fulfilled an environmental role similar to the ‘raptor’ dinosaurs such as the dromaeosaurs. Adult tyrannosaurs were likely subduing large dinosaurs such as the duckbilled hadrosaurs and Triceratops, which would be quickly killed by their bone-crunching bite.
“This study illustrates the importance of 3D modeling and computational studies in vertebrate paleontology — the methodology we used in our study can be applied to many different groups of extinct animals so that we can better understand how they adapted to their respective environments.”
There are two major components of this research that Andre and the team would like to see future researchers delve into continued CT and surface scanning of dinosaur cranial material and more application of 3D models in dinosaur biomechanics research.
Andre added: “There remains a plethora of unearthed dinosaur material that has not been utilized in studies of feeding and function — ideally, all of our existing specimens will one day be scanned and made widely available online to researchers everywhere.
“The current lack of 3D model availability is noticeable in dinosaur research; relatively few studies involving 3D models of carnivorous dinosaurs have been published thus far. There is still much work to be done concerning skull function in all extinct animals — not only dinosaurs.”
Story Source:
Materials provided by University of Bristol. Note: Content may be edited for style and length.
Journal Reference:
- Andre J. Rowe, Eric Snively. Biomechanics of juvenile tyrannosaurid mandibles and their implications for bite force: Evolutionary biology. The Anatomical Record, 2021; DOI: 10.1002/ar.24602
Prehistoric killing machine exposed
Previously thought of as heavy, slow and sluggish, the 260-million-year-old predator, Anteosaurus, was a ferocious hunter-killer
Judging by its massive, bone-crushing teeth, gigantic skull and powerful jaw, there is no doubt that the Anteosaurus, a premammalian reptile that roamed the African continent 265 to 260 million years ago — during a period known as the middle Permian — was a ferocious carnivore.
However, while it was previously thought that this beast of a creature — that grew to about the size of an adult hippo or rhino, and featuring a thick crocodilian tail — was too heavy and sluggish to be an effective hunter, a new study has shown that the Anteosaurus would have been able to outrun, track down and kill its prey effectively.
Despite its name and fierce appearance, Anteosaurus is not a dinosaur but rather belongs to the dinocephalians — mammal-like reptiles predating the dinosaurs. Much like the dinosaurs, dinocephalians roamed and ruled the Earth in the past, but they originated, thrived, and died about 30 million years before the first dinosaur even existed.
The fossilised bones of Dinocephalians are found in many places in the world. They stand out by their large size and heavy weight. Dinocephalian bones are thick and dense, and Anteosaurus is no exception. The Anteosaurus’ skull was ornamented with large bosses (bumps and lumps) above the eyes and a long crest on top of the snout which, in addition to its enlarged canines, made its skull look like that of a ferocious creature. However, because of the heavy architecture of its skeleton, it was previously assumed that it was a rather sluggish, slow-moving animal, only capable of scavenging or ambushing its prey, at best.
“Some scientists even suggested that Anteosaurus was so heavy that it could only have lived in water,” says Dr Julien Benoit of the Evolutionary Studies Institute at the University of the Witwatersrand (Wits University).
By carefully reconstructing the skull of the Anteosaurus digitally using X-ray imaging and 3D reconstructions, a team of researchers investigated the internal structures of the skull and found that the specific characteristics of its brain and balance organs were developed in such a way that it was everything but slow-moving.
“Agile predators such as cheetahs or the infamous Velociraptor have always had a very specialised nervous systems and fine-tuned sensory organs that enable them to track and hunt down prey effectively,” says Benoit. “We wanted to find out whether the Anteosaurus possessed similar adaptations.”
The team found that the organ of balance in Anteosaurus (its inner ear) was relatively larger than that of its closest relatives and other contemporaneous predators. This indicates that Anteosaurus was capable of moving much faster than its prey and competitors. They also found that the part of the brain responsible for coordinating the movements of the eyes with the head was exceptionally large, which would have been a crucial trait to ensure the animal’s tracking abilities.
“In creating the most complete reconstruction of an Anteosaurus skull to date, we found that overall, the nervous system of Anteosaurus was optimised and specialised for hunting swiftly and striking fast, unlike what was previously believed,” says Dr Ashley Kruger from the Natural History Museum in Stockholm, Sweden and previously from Wits University.
“Even though Anteosaurus lived 200-million years before the famous dinosaur Tyrannosaurus rex, Anteosaurus was definitely not a ‘primitive’ creature, and was nothing short of a mighty prehistoric killing machine,” says Benoit.
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Materials provided by University of the Witwatersrand. Note: Content may be edited for style and length.
Journal Reference:
- Julien Benoit, Ashley Kruger, Sifelani Jirah, Vincent Fernandez, Bruce Rubidge. Palaeoneurology and palaeobiology of the dinocephalian Anteosaurus magnificus. Acta Palaeontologica Polonica, 2021; 66 DOI: 10.4202/app.00800.2020
Carbon dioxide dip may have helped dinosaurs walk from South America to Greenland
A new paper refines estimates of when herbivorous dinosaurs must have traversed North America on a northerly trek to reach Greenland, and points out an intriguing climatic phenomenon that may have helped them along the journey.
The study, published in the Proceedings of the National Academy of Sciences, is authored by Dennis Kent, adjunct research scientist at Columbia University’s Lamont-Doherty Earth Observatory, and Lars Clemmensen from the University of Copenhagen.
Previous estimates suggested that sauropodomorphs — a group of long-necked, herbivorous dinosaurs that eventually included Brontosaurus and Brachiosaurus — arrived in Greenland sometime between 225 and 205 million years ago. But by painstakingly matching up ancient magnetism patterns in rock layers at fossil sites across South America, Arizona, New Jersey, Europe and Greenland, the new study offers a more precise estimate: It suggests that sauropodomorphs showed up in what is now Greenland around 214 million years ago. At the time, the continents were all joined together, forming the supercontinent Pangea.
With this new and more precise estimate, the authors faced another question. Fossil records show that sauropodomorph dinosaurs first appeared in Argentina and Brazil about 230 million years ago. So why did it take them so long to expand into the Northern Hemisphere?
“In principle, the dinosaurs could have walked from almost one pole to the other,” explained Kent, who is also an emeritus professor at Rutgers University. “There was no ocean in between. There were no big mountains. And yet it took 15 million years. It’s as if snails could have done it faster.” He calculates that if a dinosaur herd walked only one mile per day, it would take less than 20 years to make the journey between South America and Greenland.
Intriguingly, Earth was in the midst of a tremendous dip in atmospheric CO2 right around the time the sauropodomorphs would have been migrating 214 million years ago. Until about 215 million years ago, the Triassic period had experienced extremely high CO2 levels, at around 4,000 parts per million — about 10 times higher than today. But between 215 and 212 million years ago, the CO2 concentration halved, dropping to about 2,000ppm.
Although the timing of these two events — the plummeting CO2 and the sauropodomorph migration — could be pure coincidence, Kent and Clemmensen think they may be related. In the paper, they suggest that the milder levels of CO2 may have helped to remove climatic barriers that may have trapped the sauropodomorphs in South America.
On Earth, areas around the equator are hot and humid, while adjacent areas in low latitudes tend to be very dry. Kent and Clemmensen say that on a planet supercharged with CO2, the differences between those climatic belts may have been extreme — perhaps too extreme for the sauropodomorph dinosaurs to cross.
“We know that with higher CO2, the dry gets drier and the wet gets wetter,” said Kent. 230 million years ago, the high CO2 conditions could have made the arid belts too dry to support the movements of large herbivores that need to eat a lot of vegetation to survive. The tropics, too, may have been locked into rainy, monsoon-like conditions that may not have been ideal for sauropodomorphs. There is little evidence they ventured forth from the temperate, mid-latitude habitats they were adapted to in Argentina and Brazil.
But when the CO2 levels dipped 215-212 million years ago, perhaps the tropical regions became more mild, and the arid regions became less dry. There may have been some passageways, such as along rivers and strings of lakes, that would have helped sustain the herbivores along the 6,500-mile journey to Greenland, where their fossils are now abundant. Back then, Greenland would have had a temperate climate similar to New York state’s climate today, but with much milder winters, because there were no polar ice sheets at that time.
“Once they arrived in Greenland, it looked like they settled in,'” said Kent. “They hung around as a long fossil record after that.”
The idea that a dip in CO2 could have helped these dinosaurs to overcome a climatic barrier is speculative but plausible, and it seems to be supported by the fossil record, said Kent. Sauropodomorph body fossils have not been found in the tropical and arid regions of this time period — although their footprints do occasionally turn up — suggesting they did not linger in those areas.
Next, Kent hopes to continue working to better understand the big CO2 dip, including what caused it and how quickly CO2 levels dropped.
Story Source:
Materials provided by Earth Institute at Columbia University. Original written by Sarah Fecht. Note: Content may be edited for style and length.
Journal Reference:
- Dennis V. Kent, Lars B. Clemmensen. Northward dispersal of dinosaurs from Gondwana to Greenland at the mid-Norian (215–212 Ma, Late Triassic) dip in atmospheric pCO2. Proceedings of the National Academy of Sciences, 2021; 118 (8): e2020778118 DOI:
Cite This Page:
- Earth Institute at Columbia University. “Carbon dioxide dip may have helped dinosaurs walk from South America to Greenland: Climate shift may have aided herbivores on a 6,500-mile trek.” ScienceDaily. ScienceDaily, 15 February 2021.
Pioneering prehistoric landscape reconstruction reveals early dinosaurs lived on tropical islands
A new study using leading edge technology has shed surprising light on the ancient habitat where some of the first dinosaurs roamed in the UK around 200 million years ago.
The research, led by the University of Bristol, examined hundreds of pieces of old and new data including historic literature vividly describing the landscape as a “landscape of limestone islands like the Florida Everglades” swept by storms powerful enough to “scatter pebbles, roll fragments of marl, break bones and teeth.”
The evidence was carefully compiled and digitised so it could be used to generate for the first time a 3D map showing the evolution of a Caribbean-style environment, which played host to small dinosaurs, lizard-like animals, and some of the first mammals.
“No one has ever gathered all this data before. It was often thought that these small dinosaurs and lizard-like animals lived in a desert landscape, but this provides the first standardised evidence supporting the theory that they lived alongside each other on flooded tropical islands,” said Jack Lovegrove, lead author of the study published today in Journal of the Geological Society.
The study amassed all the data about the geological succession as measured all round Bristol through the last 200 years, from quarries, road sections, cliffs, and boreholes, and generated a 3D topographic model of the area to show the landscape before the Rhaetian flood, and through the next 5 million years as sea levels rose.
At the end of the Triassic period the UK was close to the Equator and enjoyed a warm Mediterranean climate. Sea levels were high, as a great sea, the Rhaetian Ocean, flooded most of the land. The Atlantic Ocean began to open up between Europe and North America causing the land level to fall. In the Bristol Channel area, sea levels were 100 metres higher than today.
High areas, such as the Mendip Hills, a ridge across the Clifton Downs in Bristol, and the hills of South Wales poked through the water, forming an archipelago of 20 to 30 islands. The islands were made from limestone which became fissured and cracked with rainfall, forming cave systems.
“The process was more complicated than simply drawing the ancient coastlines around the present-day 100-metre contour line because as sea levels rose, there was all kinds of small-scale faulting. The coastlines dropped in many places as sea levels rose,” said Jack, who is studying Palaeontology and Evolution.
The findings have provided greater insight into the type of surroundings inhabited by the Thecodontosaurus, a small dinosaur the size of a medium-sized dog with a long tail also known as the Bristol dinosaur.
Co-author Professor Michael Benton, Professor of Vertebrate Palaeontology at the University of Bristol, said: “I was keen we did this work to try to resolve just what the ancient landscape looked like in the Late Triassic. The Thecodontosaurus lived on several of these islands including the one that cut across the Clifton Downs, and we wanted to understand the world it occupied and why the dinosaurs on different islands show some differences. Perhaps they couldn’t swim too well.”
“We also wanted to see whether these early island-dwellers showed any of the effects of island life,” said co-author Dr David Whiteside, Research Associate at the University of Bristol.
“On islands today, middle-sized animals are often dwarfed because there are fewer resources, and we found that in the case of the Bristol archipelago. Also, we found evidence that the small islands were occupied by small numbers of species, whereas larger islands, such as the Mendip Island, could support many more.”
The study, carried out with the British Geological Survey, demonstrates the level of detail that can be drawn from geological information using modern analytical tools. The new map even shows how the Mendip Island was flooded step-by-step, with sea level rising a few metres every million years, until it became nearly completely flooded 100 million years later, in the Cretaceous.
Co-author Dr Andy Newell, of the British Geological Survey, said: “It was great working on this project because 3D models of the Earth’s crust can help us understand so much about the history of the landscape, and also where to find water resources. In the UK we have this rich resource of historical data from mining and other development, and we now have the computational tools to make complex, but accurate, models.”
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