Artist’s impression of two Troodons with a common nest. Illustration: Alex Boersma/PNAS
In millions of years and with a long sequence of small changes, evolution has shaped a particular group of dinosaurs, the theropods, into the birds we watch fly around the planet today. In fact, birds are the only descendants of dinosaurs which survived the catastrophic extinction 66 million years ago that ended the Cretaceous period.
Troodon was such a theropod. The carnivorous dinosaur was about two meters long and populated the vast semi-arid landscapes of North America about 75 million years ago. Like some of its dinosaur relatives, Troodon presented some bird-like features like hollow and light bones. Troodon walked on two legs and had fully developed feathery wings, but its relatively large size precluded it from flying. Instead, it probably ran quite fast and caught its prey using its strong claws. Troodon females laid eggs more similar to the asymmetric eggs of modern birds than to round ones of reptiles, the oldest relatives of all dinosaurs. These eggs were coloured and have been found half buried into the ground, probably allowing Troodon to sit and brood them.
An international team of scientists led by Mattia Tagliavento and Jens Fiebig from Goethe University Frankfurt, Germany, has now examined the calcium carbonate of some well-preserved Troodon eggshells. The researchers used a method developed by Fiebig’s group in 2019 called “dual clumped isotope thermometry.” By using this method, they could measure the extent to which heavier varieties (isotopes) of oxygen and carbon clump together in carbonate minerals. The prevalence of isotopic clumping, which is temperature-dependent, made it possible for scientists to determine the temperature at which the carbonates crystallized.
When analyzing Troodon eggshells, the research team was able to determine that the eggshells were produced at temperatures of 42 and 30 degrees Celsius. Mattia Tagliavento, leading author of the study, explains: “The isotopic composition of Troodon eggshells provides evidence that these extinct animals had a body temperature of 42°C, and that they were able to reduce it to about 30°C, like modern birds.”
The scientists then compared isotopic compositions of eggshells of reptiles (crocodile, alligator, and various species of turtle) and modern birds (chicken, sparrow, wren, emu, kiwi, cassowary and ostrich) to understand if Troodon was closer to either birds or reptiles. They revealed two different isotopic patterns: reptile eggshells have isotopic compositions matching the temperature of the surrounding environment. This is in line with these animals being cold-blooded and forming their eggs slowly. Birds, however, leave a recognizable so-called non-thermal signature in the isotopic composition, which indicates that eggshell formation happens very fast. Tagliavento: “We think this very high production rate is connected to the fact that birds, unlike reptiles, have a single ovary. Since they can produce just one egg at the time, birds have to do it more rapidly.”
When comparing these results to Troodon eggshells, the researchers did not detect the isotopic composition which is typical for birds. Tagliavento is convinced: “This demonstrates that Troodon formed its eggs in a way more comparable to modern reptiles, and it implies that its reproductive system was still constituted of two ovaries.”
The researchers finally combined their results with existing information concerning body and eggshell weight, deducing that Troodon produced only 4 to 6 eggs per reproductive phase. “This observation is particularly interesting because Troodon nests are usually large, containing up to 24 eggs,” Tagliavento explains. “We think this is a strong suggestion that Troodon females laid their eggs in communal nests, a behaviour that we observe today among modern ostriches.”
These are extremely exciting findings, Jens Fiebig comments: “Originally, we developed the dual clumped isotope method to accurately reconstruct Earth’s surface temperatures of past geological eras. This study demonstrates that our method is not limited to temperature reconstruction, it also presents the opportunity to study how carbonate biomineralization evolved throughout Earth’s history.”
Reference:
Mattia Tagliavento, Amelia J. Davies, Miguel Bernecker, Philip T. Staudigel, Robin R. Dawson, Martin Dietzel, Katja Götschl, Weifu Guo, Anne S. Schulp, François Therrien, Darla K. Zelenitsky, Axel Gerdes, Wolfgang Müller, Jens Fiebig. Evidence for heterothermic endothermy and reptile-like eggshell mineralization in Troodon , a non-avian maniraptoran theropod. Proceedings of the National Academy of Sciences, 2023; 120 (15) DOI: 10.1073/pnas.2213987120
An illustration showing how some Earth’s signature features, such as its abundance of water and its overall oxidized state could potentially be attributable to interactions between the molecular hydrogen atmospheres and magma oceans on the planetary embryos that comprised Earth’s formative years. Illustration by Edward Young/UCLA and Katherine Cain/Carnegie Institution for Science.
Our planet’s water could have originated from interactions between the hydrogen-rich atmospheres and magma oceans of the planetary embryos that comprised Earth’s formative years, according to new work from Carnegie Science’s Anat Shahar and UCLA’s Edward Young and Hilke Schlichting. Their findings, which could explain the origins of Earth’s signature features, are published in Nature.
For decades, what researchers knew about planet formation was based primarily on our own Solar System. Although there are some active debates about the formation of gas giants like Jupiter and Saturn, it is widely agreed upon that Earth and the other rocky planets accreted from the disk of dust and gas that surrounded our Sun in its youth.
As increasingly larger objects crashed into each other, the baby planetesimals that eventually formed Earth grew both larger and hotter, melting into a vast magma ocean due to the heat of collisions and radioactive elements. Over time, as the planet cooled, the densest material sank inward, separating Earth into three distinct layers — the metallic core, and the rocky, silicate mantle and crust.
However, the explosion of exoplanet research over the past decade informed a new approach to modeling the Earth’s embryonic state.
“Exoplanet discoveries have given us a much greater appreciation of how common it is for just-formed planets to be surrounded by atmospheres that are rich in molecular hydrogen, H2, during their first several million years of growth,” Shahar explained. “Eventually these hydrogen envelopes dissipate, but they leave their fingerprints on the young planet’s composition.”
Using this information, the researchers developed new models for Earth’s formation and evolution to see if our home planet’s distinct chemical traits could be replicated.
Using a newly developed model, the Carnegie and UCLA researchers were able to demonstrate that early in Earth’s existence, interactions between the magma ocean and a molecular hydrogen proto-atmosphere could have given rise to some of Earth’s signature features, such as its abundance of water and its overall oxidized state.
The researchers used mathematical modeling to explore the exchange of materials between molecular hydrogen atmospheres and magma oceans by looking at 25 different compounds and 18 different types of reactions — complex enough to yield valuable data about Earth’s possible formative history, but simple enough to interpret fully.
Interactions between the magma ocean and the atmosphere in their simulated baby Earth resulted in the movement of large masses of hydrogen into the metallic core, the oxidation of the mantle, and the production of large quantities of water.
Even if all of the rocky material that collided to form the growing planet was completely dry, these interactions between the molecular hydrogen atmosphere and the magma ocean would generate copious amounts of water, the researchers revealed. Other water sources are possible, they say, but not necessary to explain Earth’s current state.
“This is just one possible explanation for our planet’s evolution, but one that would establish an important link between Earth’s formation history and the most common exoplanets that have been discovered orbiting distant stars, which are called Super-Earths and sub-Neptunes,” Shahar concluded.
This project was part of the interdisciplinary, multi-institution AEThER project, initiated and led by Shahar, which seeks to reveal the chemical makeup of the Milky Way galaxy’s most common planets — Super-Earths and sub-Neptunes — and to develop a framework for detecting signatures of life on distant worlds. Funded by the Alfred P. Sloan Foundation, this effort was developed to understand how the formation and evolution of these planets shape their atmospheres. This could — in turn — enable scientists to differentiate true biosignatures, which could only be produced by the presence of life, from atmospheric molecules of non-biological origin.
“Increasingly powerful telescopes are enabling astronomers to understand the compositions of exoplanet atmospheres in never-before-seen detail,” Shahar said. “AEThER’s work will inform their observations with experimental and modeling data that, we hope, will lead to a foolproof method for detecting signs of life on other worlds.”
Reference:
Edward D. Young, Anat Shahar, Hilke E. Schlichting. Earth shaped by primordial H2 atmospheres. Nature, 2023; 616 (7956): 306 DOI: 10.1038/s41586-023-05823-0
How did the Andes — the world’s longest mountain range — reach its enormous size? This is just one of the geological questions that a new method developed by researchers at the University of Copenhagen may be able to answer. With unprecedented precision, the method allows researchers to estimate how Earth’s tectonic plates changed speed over the past millions of years.
The Andes is Earth’s longest above-water mountain range. It spans 8900 kilometres along South America’s western periphery, is up to 700 kilometres wide, and in some places, climb nearly seven kilometres into the sky. But exactly how this colossal mountain range emerged from Earth’s interior remains unclear among geologists.
University of Copenhagen researchers come with a new hypothesis. Using a novel method developed by one of the researchers, they closely studied the tectonic plate upon which the range is saddled. Their finding has shed new light on how the Andes came into being.
Tectonic plates cover Earth’s surface like massive puzzle pieces. They shift a few centimeters each year, at about the same pace as our nails grow. From time to time, these plates can suddenly speed up or slow down. However, we know little about the fierce forces behind these events. The UCPH researchers arrived at estimates that are more precise than ever, both with regards to how much and how often the plates changed velocity historically.
The researchers’ new calculations demonstrate that the South American plate suddenly and spectacularly shifted gears and slowed on two significant occasions over the past 15 million years. And this may have contributed to the widening of the enormous chain. The study’s results have been published in the journal Earth and Planetary Science Letters.
Remarkably, the two sudden slowdowns occurred between periods when the Andean range was under compression and growing rapidly taller:
“In the periods up until the two slowdowns, the plate immediately to the west, the Nazca Plate, plowed into the mountains and compressed them, causing them to grow taller. This result could indicate that part of the preexistent range acted as a brake on both the Nazca and the South-American plate. As the plates slowed down their speed, the mountains instead grew wider,” explains first author and PhD student Valentina Espinoza of the Department of Geosciences and Natural Resource Management.
According to the new study, the South American plate slowed down by 13% during a period that occurred 10-14 million years ago, and 20% during another period 5-9 million years ago. In geologic time, these are very rapid and abrupt changes. According to the researchers, there are mainly two possible reasons for South America’s sudden slowdowns.
One could, as mentioned, be related to the extension of the Andes, where the pressure relaxed and the mountains grew wider. The researchers’ hypothesis is that the interaction between the expansion of the mountains and the lower speed of the plate was due to a phenomenon called delamination. That is, a great deal of unstable material beneath the Andes tore free and sank into the mantle, causing major readjustments in the plate’s configuration.
This process caused the Andes to change shape and grow laterally. It was during these periods that the mountain chain expanded into Chile to the west and Argentina to the east. As the plate accumulated more mountain material and became heavier, the plate’s movement slowed.
“If this explanation is the right one, it tells us a lot about how this huge mountain range came to be. But there is still plenty that we don’t know. Why did it get so big? At what speed did it form? How does the mountain range sustain itself? And will it eventually collapse?” says Valentina Espinoza.
According to the researchers, another possible explanation for why the plate slowed is that there was a change in the pattern flow of heat from the Earth’s interior, known as convection, that moved up into the uppermost viscous layer of the mantle which tectonic plates float on top of. That change manifested itself as a change in the plate’s movement.
The researchers now have the information and tools to begin testing their hypotheses through modelling and experimentation.
May become a new standard model
The method to calculate the changes of tectonic plate motion builds upon the previous work of associate professor and study co-author Giampiero Iaffaldano and Charles DeMets in 2016. The special thing about the method is that it utilises high-resolution geological data, typically used only to calculate the motion of plates relative to each other. Here, the same data has been used to calculate changes in the motion of plates relative to the planet itself. It provides estimates with unprecedented accuracy.
After testing the method with a combination of six other tectonic plates, the researchers believe that it could become a new standard method:
“This method can be used for all plates, as long as high-resolution data are available. My hope is that such method will be used to refine historic models of tectonic plates and thereby improve the chance of reconstructing geological phenomena that remain unclear to us,” says Giampiero Iaffaldano, who concludes:
“If we can better understand the changes that have occurred in the motions of plates over time, we can have a chance at answering some of the greatest mysteries of our planet and its evolution. We still know so little about, for example: the temperature of Earth’s interior, or about when plates began moving. Our method can most likely be used to find pieces for this great big puzzle.”
FACT BOX: ABOUT THE METHOD
Tectonic plates change speed often, but high-resolution data is needed to identify their rapid changes over time spans of less than a couple million years.
One key aspect of the method developed by Giampiero Iaffaldano and Charles DeMets in 2016 differs from others. Typically, high-resolution data is only used to calculate the relative motion of plates, i.e. their motion relative to other plates. Their method uses this same kind of data to calculate the absolute motion of plates, i.e. the movement of plates relative to Earth itself. This results in far more accurate estimates than the ones currently obtained through hotspot volcanic chains.
FACT BOX: ABOUT PLATE TECTONICS
The theory of plate tectonics, first recognized in the 1960s, states that Earth is covered by an outer shell (the lithosphere), divided into a number of rigid plates that float on top the upper part of Earth’s mantle (the asthenosphere).
Observations show that plates come in all sorts of sizes, from the Pacific plate covering an area of 100 million square meters, to microplates with a hundredth times smaller. Tectonic plates may comprise a continental portion, that can reach up to 350 kilometers thick, and oceanic part, which rarely exceeds 100 kilometers thick.
Reference:
Valentina Espinoza, Giampiero Iaffaldano. Rapid absolute plate motion changes inferred from high-resolution relative spreading reconstructions: A case study focusing on the South America plate and its Atlantic/Pacific neighbors. Earth and Planetary Science Letters, 2023; 604: 118009 DOI: 10.1016/j.epsl.2023.118009
Earthquakes and volcanism occur as a result of plate tectonics. The movement of tectonic plates themselves is largely driven by the process known as subduction. The question of how new active subduction zones come into being, however, is still under debate. An example of this is the volcanic Lesser Antilles arc in the Caribbean. A research team including geophysicists Dr. Nicolas Riel and Professor Boris Kaus of Johannes Gutenberg University Mainz (JGU) as well as researchers from Universidade de Lisboa (ULisboa) recently developed models that simulated the occurrences in the Caribbean region during the Cretaceous, when a subduction event in the Eastern Pacific led to the formation of a new subduction zone in the Atlantic. The computer simulations show how the collision of the old Caribbean plateau with the Greater Antilles arc contributed to the creation of this new Atlantic subduction zone. Some 86 million years ago, the triggered processes subsequently resulted in a major mantle flow and thus to the development of the Caribbean large igneous province.
Subduction is a geological process in which the cold oceanic lithosphere, which is part of the rocky and about 100 kilometer thick outermost layer of the planet, runs into the edge of a continental plate and slides beneath it to be recycled back into the Earth’s mantle. Together with the release of hot mantle material in the form of mantle plumes and new oceanic floor generation at mid-ocean ridges, subduction events form the backbone of plate tectonics. However, it is largely unknown how active subduction zones form mainly because there are very few examples of ongoing subduction initiation currently here on Earth. With this in view, Dr. Nicolas Riel and Professor Boris Kaus of the JGU Institute of Geosciences decided to investigate the geodynamic conditions that would have predominated in the Caribbean region in the late Cretaceous period. “In terms of its plate tectonics, the Caribbean is a particularly interesting location,” said Professor Boris Kaus, head of the Geodynamics & Geophysics group at Mainz University. The Caribbean region can be seen as a kind of natural laboratory in which, over millions of years, plate tectonics resulted in the transfer of a subduction zone from the Pacific to the Atlantic. This was associated with very extensive magmatic activity that accounted for the origin of the Caribbean large igneous province (or CLIP for short). This structure of magmatic rock is now the center of the Caribbean plate.
For their computer simulations, the researchers selected a point in time 140 million years ago when the so-called Farallon plate, an ancient major plate in the Eastern Pacific, began to move east and subduct beneath the South American margin, thus shifting the old Caribbean plateau in the direction of the Farallon trench. About 135 million years ago, the old Caribbean plateau came into collision with the proto-Caribbean plate. As the simulations showed, the subduction of the Farallon plate was then temporarily interrupted while the subduction of the proto-Caribbean plate was initiated. Several subsequent phases follow over a period of some 50 million years, including the renewed subduction of the Farallon plate at the western end of the old plateau, the formation of a mantle plume, and the transfer of the Greater Antilles arc onto the retreating proto-Caribbean plate.
Simultaneous subduction of two plates forced part of the mantle upwards
“With the help of our computer simulations, we can better understand the physical process,” added Dr. Nicolas Riel, the lead author of the corresponding article recently published in Nature Communications. “We were all surprised by the results showing that 90 to 86 million years ago the renewal of the Farallon plate subduction led to a major mantle flow, triggering the formation of a plume. This produced a huge amount of magma.” This molten rock material added to the thickness of the crust of the Caribbean plate, making it up to 22 kilometers in depth, thus 8 to 10 kilometers thicker than the standard for the oceanic crust. It was previously assumed that the mantle plume induced the renewal of the Farallon plate subduction.
“We are in the unique situation of being able to carry out very realistic simulations,” said Boris Kaus. His team is one of the few groups worldwide that can use supercomputer modeling to test to the plausibility of their physical assumptions and thus to analyze what plate tectonic events actually occurred in the Caribbean. For their complex calculations, the researchers had access to the MOGON II supercomputer operated by Johannes Gutenberg University Mainz and the Helmholtz Institute Mainz (HIM), one of the fastest high-performance computers in the world.
Research under the aegis of TeMaS
The geophysical research was undertaken under the aegis of the Terrestrial Magmatic Systems (TeMaS) research platform, a joint project of the universities of Mainz, Frankfurt, and Heidelberg. TeMaS coordinates interdisciplinary research on magmatic processes in the broadest sense, from the generation of magma in the Earth’s mantle through to its eruption in volcanoes and how this impacts the atmosphere and climate. TeMaS is a High-potential Research Area at JGU, funded by the Ministry of Science and Health of Rhineland-Palatinate.
Boris Kaus is Head of the Geodynamics & Geophysics group at the JGU Institute of Geosciences. In 2018, he was granted an ERC Consolidator Grant, one of the most richly endowed EU funding awards, to support his research into magmatic processes. As part of the ERC project MAGMA, short for “Melting And Geodynamic Models of Ascent,” Kaus and his team developed numerical models that enabled them to simulate magmatic events. The geophysicist is also a Fellow of the Gutenberg Research College (GRC) of JGU.
Reference:
Nicolas Riel, João C. Duarte, Jaime Almeida, Boris J. P. Kaus, Filipe Rosas, Yamirka Rojas-Agramonte, Anton Popov. Subduction initiation triggered the Caribbean large igneous province. Nature Communications, 2023; 14 (1) DOI: 10.1038/s41467-023-36419-x
The massive Feb. 6 quake in Eastern Turkey killed more than 50,000 people and toppled more than 100,000 buildings. (Photo/Ahmet Ertas via Pixabay)
Researchers know a lot about Turkey’s next major earthquake. They can pinpoint the probable epicenter, estimate its strength and see the spatial footprint of where damage is most likely to occur.
They just can’t say when it will happen.
That’s the main takeaway from a new USC-led study that appears today (April 20) in Seismica.
Using remote sensing, USC geophysicist Sylvain Barbot and his fellow researchers documented the massive Feb. 6 quake that killed more than 50,000 people in Eastern Turkey and toppled more than 100,000 buildings.
Alarmingly, researchers found that a section of the fault remains unbroken and locked — a sign that the plates there may, when friction intensifies, generate another magnitude 6.8 earthquake when it finally gives way.
“We know a little bit better what to prepare for. We don’t know the timing, but we know where it can happen,” Barbot said.
Major earthquakes are caused by the slipping of tectonic plates. The plates, slowly moving pieces of the earth’s crust, press against each other, gradually accumulating force over the course of decades, centuries and eons. When the plates finally slip, the energy explodes in traveling waves through the earth’s crust.
The Kahramanmaras, Turkey, magnitude 7.8 mainshock occurred Feb. 6, followed by a magnitude 7.6 aftershock on a separate fault further west. Another quake occurred two weeks later, a magnitude 6.4 on Feb. 20. A plotting of data (see above) shows seismic activity and the amount of slippage along the faults.
The area beneath Turkey’s Pütürge district shows a swarm of seismic activity along the fault — but no slippage. That means that part of the fault is locked, or stuck, but it is likely to slip sometime — anytime — in the future.
“What we’ve seen in photos of the buildings that collapsed is that some of them were pancakes but others were literally pulverized,” Barbot said. “So that means another degree of failure; even the concrete itself disintegrated. There is the possibility that this earthquake produced more shaking than was anticipated in the building codes. We won’t know without more research.
“So, we have this region where we can expect a 6.8 magnitude earthquake and two things can happen from here. The population needs to be prepared for that. But also the scientific community because that gives us an opportunity to prepare a monitoring experiment to see how an earthquake starts and ends.”
Reference:
Sylvain Barbot, Heng Luo, Teng Wang, Yariv Hamiel, Oksana Piatibratova, Muhammad Tahir Javed, Carla Braitenberg, Gokhan Gurbuz. Slip distribution of the February 6, 2023 Mw 7.8 and Mw 7.6, Kahramanmaraş, Turkey earthquake sequence in the East Anatolian Fault Zone. Seismica, 2023; 2 (3) DOI: 10.26443/seismica.v2i3.502
Ridgecrest seismic station deployed in 2019. | USGS
Faults in the Ridgecrest, California area were very sensitive to solid earth tidal stresses in the year and a half before the July 2019 Ridgecrest earthquake sequence, researchers reported at the Seismological Society of America (SSA)’s 2023 Annual Meeting.
“The signal of tidal modulation becomes extremely strong” after 2018, said Eric Beauce of Lamont-Doherty Earth Observatory, who noted that the signal was identified with seismicity that occurred around the faults that broke in the 2019 magnitude 7.1 earthquake.
The link does not mean that tidal stresses — which are very small compared to other tectonic stresses — triggered the earthquake, however.
“We don’t know if something started to happen in the fault zone, something that is an indicator of the upcoming earthquake,” Beauce said. “Maybe that process changed the properties of the crust in a way that made the crust be more sensitive to tidal stresses.”
Pulled by the same gravitational forces of sun and moon that create ocean tides, the solid earth also deforms in the same periodic way. People can’t feel the changes, but the ground deforms between 10 to 20 centimeters a day.
These solid tides “induce very, very small stress changes in the crust,” Beauce explains, “which can induce stress changes in all the faults within the crust.”
Although researchers have known about these tiny stress changes for more than a century, it has been difficult to extract their signal from the seismic record, and to determine whether they modulate seismicity.
In the past ten years, however, better earthquake detection and analysis techniques have made it possible to search through earthquake catalogs to find the signal of tidal stresses, Beauce said.
He and his colleagues built a rich, high-resolution earthquake catalog, using machine learning algorithms along with other techniques, for the past decade of microseismicity in the Ridgecrest area. (Microseismicity usually refers to earthquakes of magnitude 2.0 or smaller).
They found that “there is suggestive evidence that peak seismicity happens when tidal stresses are maximum,” Beauce said, “but this modulation is weak, and because it is weak, it is only suggested.”
Other researchers looking at the 2004 Indian Ocean and 2011 Tohoku megathrust earthquakes have detected an increase in modulation of seismicity connected to tidal stresses, decades before the earthquakes, said Beauce. And some scientists have been able to generate similar results in lab-created earthquake experiments.
The tidal findings do not have direct implications for earthquake forecasting, “as we do not know if we are looking at a general phenomenon or one specific to the Ridgecrest earthquake only, said Beauce, “but I see it as a way of getting new observational constraints on the physics of earthquakes, possibly the preparation and nucleation of earthquakes.”
A juvenile Edmontosaurus disappears into the enormous, lipped mouth of Tyrannosaurus. Credit Dr Mark Witton
A new study suggests that predatory dinosaurs, such as Tyrannosaurus rex, did not have permanently exposed teeth as depicted in films such as Jurassic Park, but instead had scaly, lizard-like lips covering and sealing their mouths.
Researchers and artists have debated whether theropod dinosaurs, the group of two-legged dinosaurs that includes carnivores and top predators like T. rex and Velociraptor, as well as birds, had lipless mouths where perpetually visible upper teeth hung over their lower jaws, similar to the mouth of a crocodile.
However, an international team of researchers challenge some of the best-known depictions, and say these dinosaurs had lips similar to those of lizards and their relative, the tuatara — a rare reptile found only in New Zealand, which are the last survivors of an order of reptiles that thrived in the age of the dinosaurs.
In the most detailed study of this issue yet, the researchers examined the tooth structure, wear patterns and jaw morphology of lipped and lipless reptile groups and found that theropod mouth anatomy and functionality resembles that of lizards more than crocodiles. This implies lizard-like oral tissues, including scaly lips covering their teeth.
These lips were probably not muscular, like they are in mammals. Most reptile lips cover their teeth but cannot be moved independently — they cannot be curled back into a snarl, or make other sorts of movements we associate with lips in humans or other mammals.
Study co-author Derek Larson, Collections Manager and Researcher in Palaeontology at the Royal BC Museum in Canada, said: “Palaeontologists often like to compare extinct animals to their closest living relatives, but in the case of dinosaurs, their closest relatives have been evolutionarily distinct for hundreds of millions of years and today are incredibly specialised.
“It’s quite remarkable how similar theropod teeth are to monitor lizards. From the smallest dwarf monitor to the Komodo dragon, the teeth function in much the same way. So, monitors can be compared quite favourably with extinct animals like theropod dinosaurs based on this similarity of function, even though they are not closely related.”
Co-author Dr Mark Witton from the University of Portsmouth said: “Dinosaur artists have gone back and forth on lips since we started restoring dinosaurs during the 19th century, but lipless dinosaurs became more prominent in the 1980s and 1990s. They were then deeply rooted in popular culture through films and documentaries — Jurassic Park and its sequels, Walking with Dinosaurs and so on.
“Curiously, there was never a dedicated study or discovery instigating this change and, to a large extent, it probably reflected preference for a new, ferocious-looking aesthetic rather than a shift in scientific thinking. We’re upending this popular depiction by covering their teeth with lizard-like lips. This means a lot of our favourite dinosaur depictions are incorrect, including the iconic Jurassic Park T. rex.”
The results, published in the journal Science, found that tooth wear in lipless animals was markedly different from that seen in carnivorous dinosaurs and that dinosaur teeth were no larger, relative to skull size, than those of modern lizards, implying they were not too big to cover with lips.
Also, the distribution of small holes around the jaws, which supply nerves and blood to the gums and tissues around the mouth, were more lizard-like in dinosaurs than crocodile-like. Furthermore, modelling mouth closure of lipless theropod jaws showed that the lower jaw either had to crush jaw-supporting bones or disarticulate the jaw joint to seal the mouth.
“As any dentist will tell you, saliva is important for maintaining the health of your teeth. Teeth that are not covered by lips risk drying out and can be subject to more damage during feeding or fighting, as we see in crocodiles, but not in dinosaurs,” said co-author Kirstin Brink, Assistant Professor of Palaeontology at the University of Manitoba.
She added: “Dinosaur teeth have very thin enamel and mammal teeth have thick enamel (with some exceptions). Crocodile enamel is a bit thicker than dinosaur enamel, but not as thick as mammalian enamel. There are some mammal groups that do have exposed enamel, but their enamel is modified to withstand exposure.”
Thomas Cullen, Assistant Professor of Paleobiology at Auburn University and study lead author, said: “Although it’s been argued in the past that the teeth of predatory dinosaurs might be too big to be covered by lips, our study shows that, in actuality, their teeth were not atypically large. Even the giant teeth of tyrannosaurs are proportionally similar in size to those of living predatory lizards when compared for skull size, rejecting the idea that their teeth were too big to cover with lips.”
The results provide new insights into how we reconstruct the soft-tissues and appearance of dinosaurs and other extinct species. This can give crucial information on how they fed, how they maintained their dental health, and the broader patterns of their evolution and ecology.
Dr Witton said: “Some take the view that we’re clueless about the appearance of dinosaurs beyond basic features like the number of fingers and toes. But our study, and others like it, show that we have an increasingly good handle on many aspects of dinosaur appearance. Far from being clueless, we’re now at a point where we can say ‘oh, that doesn’t have lips? Or a certain type of scale or feather?’ Then that’s as realistic a depiction of that species as a tiger without stripes.”
The researchers point out that their study doesn’t say that no extinct animals had exposed teeth — some, like sabre-toothed carnivorous mammals, or marine reptiles and flying reptiles with extremely long, interlocking teeth, almost certainly did.
Reference:
Thomas M. Cullen, Derek W. Larson, Mark P. Witton, Diane Scott, Tea Maho, Kirstin S. Brink, David C. Evans, Robert Reisz. Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology. Science, 2023; 379 (6639): 1348 DOI: 10.1126/science.abo7877
Water makes up 71% of Earth’s surface, but no one knows how or when such massive quantities of water arrived on Earth.
A new study published in the journal Nature brings scientists one step closer to answering that question. Led by University of Maryland Assistant Professor of Geology Megan Newcombe, researchers analyzed melted meteorites that had been floating around in space since the solar system’s formation 4 1/2 billion years ago. They found that these meteorites had extremely low water content — in fact, they were among the driest extraterrestrial materials ever measured.
These results, which let researchers rule them out as the primary source of Earth’s water, could have important implications for the search for water — and life — on other planets. It also helps researchers understand the unlikely conditions that aligned to make Earth a habitable planet.
“We wanted to understand how our planet managed to get water because it’s not completely obvious,” Newcombe said. “Getting water and having surface oceans on a planet that is small and relatively near the sun is a challenge.”
The team of researchers analyzed seven melted, or achondrite, meteorites that crashed into Earth billions of years after splintering from at least five planetesimals — objects that collided to form the planets in our solar system. In a process known as melting, many of these planetesimals were heated up by the decay of radioactive elements in the early solar system’s history, causing them to separate into layers with a crust, mantle and core.
Because these meteorites fell to Earth only recently, this experiment was the first time anyone had ever measured their volatiles. UMD geology graduate student Liam Peterson used an electron microprobe to measure their levels of magnesium, iron, calcium and silicon, then joined Newcombe at the Carnegie Institution for Science’s Earth and Planets Laboratory to measure their water contents with a secondary ion mass spectrometry instrument.
“The challenge of analyzing water in extremely dry materials is that any terrestrial water on the sample’s surface or inside the measuring instrument can easily be detected, tainting the results,” said study co-author Conel Alexander, a scientist at the Carnegie Institution for Science.
To reduce contamination, researchers first baked their samples in a low-temperature vacuum oven to remove any surface water. Before the samples could be analyzed in the secondary ion mass spectrometer, the samples had to be dried out once again.
“I had to leave the samples under a turbo pump — a really high-quality vacuum — for more than a month to draw down the terrestrial water enough,” Newcombe said.
Some of their meteorite samples came from the inner solar system, where Earth is located and where conditions are generally assumed to have been warm and dry. Other rarer samples came from the colder, icier outer reaches of our planetary system. While it was generally thought that water came to Earth from the outer solar system, it has yet to be determined what types of objects could have carried that water across the solar system.
“We knew that plenty of outer solar system objects were differentiated, but it was sort of implicitly assumed that because they were from the outer solar system, they must also contain a lot of water,” said Sune Nielsen, a study co-author and geologist at the Woods Hole Oceanographic Institution. “Our paper shows this is definitely not the case. As soon as meteorites melt, there is no remaining water.”
After analyzing the achondrite meteorite samples, researchers discovered that water comprised less than two millionths of their mass. For comparison, the wettest meteorites — a group called carbonaceous chondrites — contain up to about 20% of water by weight, or 100,000 times more than the meteorite samples studied by Newcombe and her co-authors.
This means that the heating and melting of planetesimals leads to near-total water loss, regardless of where these planetesimals originated in the solar system and how much water they started out with. Newcombe and her co-authors discovered that, contrary to popular belief, not all outer solar system objects are rich in water. This led them to conclude that water was likely delivered to Earth via unmelted, or chondritic, meteorites.
Newcombe said their findings have applications beyond geology. Scientists of many disciplines — and especially exoplanet researchers — are interested in the origin of Earth’s water because of its deep connections with life.
“Wateris considered to be an ingredient for life to be able to flourish, so as we’re looking out into the universe and finding all of these exoplanets, we’re starting to work out which of those planetary systems could be potential hosts for life,” Newcombe said. “In order to be able to understand these other solar systems, we want to understand our own.”
Reference:
M. E. Newcombe, S. G. Nielsen, L. D. Peterson, J. Wang, C. M. O’D. Alexander, A. R. Sarafian, K. Shimizu, L. R. Nittler, A. J. Irving. Degassing of early-formed planetesimals restricted water delivery to Earth. Nature, 2023; DOI: 10.1038/s41586-023-05721-5
Model by Dr Tristan Salles, School of Geosciences.
Climate, tectonics and time combine to create powerful forces that craft the face of our planet. Add the gradual sculpting of the Earth’s surface by rivers and what to us seems solid as rock is constantly changing.
However, our understanding of this dynamic process has at best been patchy.
Scientists today have published new research revealing a detailed and dynamic model of the Earth’s surface over the past 100 million years.
Working with scientists in France, University of Sydney geoscientists have published this new model in the journal Science.
For the first time, it provides a high-resolution understanding of how today’s geophysical landscapes were created and how millions of tonnes of sediment have flowed to the oceans.
Lead author Dr Tristan Salles from the University of Sydney School of Geosciences, said: “To predict the future, we must understand the past. But our geological models have only provided a fragmented understanding of how our planet’s recent physical features formed.
“If you look for a continuous model of the interplay between river basins, global-scale erosion and sediment deposition at high resolution for the past 100 million years, it just doesn’t exist.
“So, this is a big advance. It’s not only a tool to help us investigate the past but will help scientists understand and predict the future, as well.”
Using a framework incorporating geodynamics, tectonic and climatic forces with surface processes, the scientific team has presented a new dynamic model of the past 100 million years at high resolution (down to 10 kilometres), broken into frames of a million years.
Second author Dr Laurent Husson from Institut des Sciences de la Terre in Grenoble, France, said: “This unprecedented high-resolution model of Earth’s recent past will equip geoscientists with a more complete and dynamic understanding of the Earth’s surface.
“Critically, it captures the dynamics of sediment transfer from the land to oceans in a way we have not previously been able to.”
Dr Salles said that understanding the flow of terrestrial sediment to marine environments is vital to comprehend present-day ocean chemistry.
“Given that ocean chemistry is changing rapidly due to human-induced climate change, having a more complete picture can assist our understanding of marine environments,” he said.
The model will allow scientists to test different theories as to how the Earth’s surface will respond to changing climate and tectonic forces.
Further, the research provides an improved model to understand how the transportation of Earth sediment regulates the planet’s carbon cycle over millions of years.
“Our findings will provide a dynamic and detailed background for scientists in other fields to prepare and test hypotheses, such as in biochemical cycles or in biological evolution.”
Authors Dr Salles, Dr Claire Mallard and PhD student Beatriz Hadler Boggiani are members of the EarthColab Group and Associate Professor Patrice Rey and Dr Sabin Zahirovic are part of the EarthByte Group. Both groups are in the School of Geosciences at the University of Sydney.
The research was undertaken in collaboration with French geoscientists from CNRS, France, Université Lyon and ENS Paris.
Reference:
Tristan Salles, Laurent Husson, Patrice Rey, Claire Mallard, Sabin Zahirovic, Beatriz Hadler Boggiani, Nicolas Coltice, Maëlis Arnould. Hundred million years of landscape dynamics from catchment to global scale. Science, 2023; 379 (6635): 918 DOI: 10.1126/science.add2541
Therizinosaurs claw hooking and pulling trees Credit: Shuyang Zhou for the 3D modelling and functional scenario restoration
Dinosaur claws had many functions, but now a team from the University of Bristol and the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing has shown some predatory dinosaurs used their claws for digging or even for display.
The study focused on two groups of theropod dinosaurs, the alvarezsaurs and therizinosaurs, that had weird claws whose function had been a mystery up to now. It turns out that alvarezsaurs used their rock-pick-like claws for digging, but their close relatives, the giant therizinosaurs, used their overdeveloped, metre-long, sickle-like claws for display.
The new work is led by Zichuan Qin, a PhD student at the University of Bristol and the IVPP. He developed a new, computational approach in biomechanics to identify functions based on detailed comparison with living animals. First, the claws were modelled in three dimensions from CT scans, then modelled for stress and strain using engineering methods, and finally matched to functions of pulling, piercing and digging by comparison with modern animals whose claw functions are known.
“Alvarezsaurs and therizinosaurs are definitely the strangest cousins among dinosaurs,” said Professor Michael Benton, one of Zichuan’s supervisors. “Alvarezsaurs were the tiniest dinosaurs ever, the size of chickens, with stubby forelimbs and robust single claws, but their closest relative, the therizinosaurs, evolved in the exact opposite path.”
“Therizinosaurus is famous for its sickle-like claws, each as long as a samurai sword: Edward Scissor-hands on speed. We all saw Therizinosaurus in ‘Jurassic World’ hitting deer and killing the giant predator Giganotosaurus. However, this is unlikely. These long, narrow claws were too weak for combat.” said Dr Chun-Chi Liao, an expert on therizinosaurs from IVPP who co-authored this study. “Our engineering simulation shows that these claws could not withstand much stress.”
“Not all therizinosaur hand claws were so useless in combat, but most other related species could use their claws as powerful hooking tools when feeding on leaves from the trees.,” Dr Chun-Chi Liao added, “so, we conclude that the largest claws of any animal ever were actually useless in mechanical function, and so must have evolved under sexual selection to be used in display. The adult Therizinosaurus I guess could wave the claws at a competitor and effectively say, ‘look at me, back off’ or wave them around in some way like a peacock can use its tail in display to attract females for mating.”
“Our previous work has shown that alvarezsaurs evolved to become the tiniest dinosaurs by the end of the Cretaceous, and these [dinosaurs] were using their punchy little claws for digging into ant hills and termite mounds. They were ant-eaters,” said Zichuan Qin.
“Our study shows that the early alvarezsaurs, like Haplocheirus from the Jurassic, had multifunctional hands, but they were not good at digging. Their much smaller descendants had the efficient digging hands so they could feast on the Late Cretaceous termites.” added Zichuan Qin.
“Science and technology cannot bring dinosaurs back to life, but advanced computing and engineering techniques can show us how extinct animals lived,” said Professor Emily Rayfield, one of Zichuan’s supervisors, and an expert of dinosaur biomechanics. “Especially for extinct animals like alvarezsaurs and therizinosaurs, they are so bizarre that we even can’t find any living animals like them. Luckily, advanced technology can help us to simulate, on a computer, the functioning of extinct animals using fundamental engineering and biomechanical principles. This study shows very well how selection for function can lead to the emergence of specific, sometime very bizarre, forms.”
Reference:
Zichuan Qin, Chun-Chi Liao, Michael J. Benton, Emily J. Rayfield. Functional space analyses reveal the function and evolution of the most bizarre theropod manual unguals. Communications Biology, 2023; 6 (1) DOI: 10.1038/s42003-023-04552-4
Compass readings that do not show the direction of true north and interference with the operations of satellites are a few of the problems caused by peculiarities of the Earth’s magnetic field.
The magnetic field radiates around the world and far into space, but it is set by processes that happen deep within the Earth’s core, where temperatures exceed 5,000-degress C.
New research from geophysicists at the University of Leeds suggests that the way this super-hot core is cooled is key to understanding the causes of the peculiarities — or anomalies, as scientists call them — of the Earth’s magnetic field.
In the extremely hot temperatures found deep in the Earth, the core is a mass of swirling, molten iron which acts as a dynamo. As the molten iron moves, it generates the Earth’s global magnetic field.
Convective currents keep the dynamo turning as heat flows out of the core and into the mantle, a rock layer that extends 2900 kilometres up to the Earth’s crust.
Research by Dr Jonathan Mound and Professor Christopher Davies, from the School of Earth and Environment at Leeds, has found that this cooling process does not happen in a uniform way across the Earth — and these variations cause anomalies in the Earth’s magnetic field.
Variations in earth’s magnetic field
Seismic analysis has identified that there are regions of the mantle, under Africa and the Pacific for instance, that are particularly hot. Computer simulations by the researchers have revealed that these hot zones reduce the cooling effect on the core — and this causes regional or localised changes to the properties of the magnetic field.
For example, where the mantle is hotter, the magnetic field at the top of the core is likely to be weaker.
And this results in a weaker magnetic field which is projected into space above the South Atlantic, which causes problems for orbiting satellites.
Interference with space technology
Dr Mound, who led the study, said: “One of the things that the magnetic field in space does is deflect charged particles emitted from the sun. When the magnetic field is weaker, this protective shield is not so effective.
“So, when satellites pass over that area, these charged particles can disrupt and interfere with their operations.”
Scientists have known about the anomaly over the South Atlantic since they started monitoring and observing the magnetic field, but it is not known if it is a long-lived feature or something that has happened more recently in the history of the Earth.
As the study at Leeds has revealed, the anomalies are likely to be caused by differences in the rate at which heat is flowing from the Earth’s core into the mantle. Whereabouts in the Earth’s inner structure these heat flow differences happen is likely to dictate how long they could last.
Dr Mound added: “Processes in the mantle happen very slowly, so we can expect the temperature anomalies in the lower mantle will have stayed the same for tens of millions of years. Therefore, we would expect the properties of the magnetic field they create also to have been similar over tens of millions of years.
“But the hotter, outer core is quite a dynamic fluid region. So, the heat flows and the magnetic field properties they cause will probably fluctuate on shorter time scales, perhaps for 100’s to 1000’s of years.”
The paper — Longitudinal structure of Earth’s magnetic field controlled by lower mantle heat flow — is published in Nature Geoscience. When the embargo lifts, it can be downloaded from the Nature Geoscience website.
Reference:
Jonathan E. Mound, Christopher J. Davies. Longitudinal structure of Earth’s magnetic field controlled by lower mantle heat flow. Nature Geoscience, 2023; DOI: 10.1038/s41561-023-01148-9
Microsphere from the meteorite: The iron oxide spherule found in the “Domaine du Météore” crater has a core composed of minerals typical for the crater environment and also contains a large number of microdiamonds. Photo: Frank Brenker, Goethe University Frankfurt
With the aim of creating an appealing brand, the name of the ‘Domaine du Météore’ winery near the town of Béziers in Southern France points to a local peculiarity: one of its vineyards lies in a round, 200-metre-wide depression that resembles an impact crater. By means of rock and soil analyses, scientists led by cosmochemist Professor Frank Brenker from Goethe University Frankfurt have now established that the crater was indeed once formed by the impact of an iron-nickel meteorite. In doing so, they have disproved a scientific opinion almost 60 years old, because of which the crater was never examined more closely from a geological perspective.
Countless meteorites have struck Earth in the past and shaped the history of our planet. It is assumed, for example, that meteorites brought with them a large part of its water. The extinction of the dinosaurs might also have been triggered by the impact of a very large meteorite.
Meteorite craters which are still visible today are rare because most traces of the celestial bodies have long since disappeared again. This is due to erosion and shifting processes in Earth’s crust, known as plate tectonics. The “Earth Impact Database” lists just 190 such craters worldwide. In the whole of Western Europe, only three were previously known: Rochechouart in Aquitaine, France, the Nördlinger Ries between the Swabian Alb and the Franconian Jura, and the Steinheim Basin near Heidenheim in Baden-Württemberg (both in Germany). Thanks to millions of years of erosion, however, for laypersons the three impact craters are hardly recognisable as such.
Geologist and cosmochemist Professor Frank Brenker from Goethe University Frankfurt is convinced: the new meteorite crater will now extend the list. While on holiday, the “Domaine du Météore” winery caught his attention. One of its vineyards lies in a round depression about 220 metres in diameter and 30 metres deep, and the proprietors use the scientific hypothesis that it is the impact crater of a meteorite — seemingly long disproved — as a marketing gag for their wine. Although this hypothesis was proposed by several geologists in the 1950s, it was dismissed by acclaimed colleagues a few years later.
Frank Brenker explains: “Craters can form in many ways, and meteorite craters are indeed very rare. However, I found the various other interpretations of how this depression could have formed unconvincing from a geological perspective.” That is why he and his wife collected rock samples for analysis in the labs at Goethe University Frankfurt — and indeed found the first signs of an impact crater. Brenker: “The microanalysis showed that dark-coloured layers in one of the shists, which usually simply comprise a larger percentage of mica, might be shock veins produced by the grinding and fracturing of the rock, which in turn could have been caused by an impact.” He also found evidence of breccia, angular rock debris held together by a kind of “cement,” which can also occur during a meteorite impact.
The following year, Brenker took his colleague Andreas Junge, Professor of Applied Geophysics at Goethe University Frankfurt, and a group of students with him to Southern France to examine the crater in detail. They discovered that Earth’s magnetic field is slightly weaker in the crater than in the surrounding area. This is typical for impact craters because the impact shatters or even melts the rock, which can thus contribute less to Earth’s magnetic field.
With the help of strong magnets attached to a plate, the researchers also found tiny iron oxide spherules of up to one millimetre in diameter. Such spherules had already been found in other impact craters. Later laboratory analysis showed that the ones here also contained nickel-bearing iron and encased a core of minerals typical for the crater environment. In addition, the researchers discovered numerous shock microdiamonds produced through the high pressure during the meteorite’s impact.
Frank Brenker explains: “Such microspheres form either through abrasion of the meteorite in the atmosphere or only upon impact, when a large part of the iron meteorite melts and then reacts with the oxygen in the air. On impact, material shattered at the point of impact might then also be encased. This, together with the lower magnetic field and the other geological and mineralogical finds, allows us to draw hardly any other conclusion: a meteorite did indeed strike here.” This makes the crater very exciting for geological laypeople too, says Brenker, because “every visitor can experience here the immense energies released upon such an impact.”
Microscopic view of a carnivorous dinosaur’s shin bone, showing growth rings that get more closely spaced towards the outside of the bone, indicating that this individual reached adulthood.
The meat-eating dinosaurs known as theropods that roamed the ancient Earth ranged in size from the bus-sized T. rex to the smaller, dog-sized Velociraptor. Scientists puzzling over how such wildly different dinosaur sizes evolved recently found — to their surprise- that smaller and larger theropod dinosaurs like these didn’t necessarily get that way merely by growing slower or faster.
In a new paper published in Science, “Developmental strategies underlying gigantism and miniaturization in non-avialan theropod dinosaurs,” researchers including Ohio University professor Patrick O’Connor and Ph.D. student Riley Sombathy discovered through examining the bones of dinosaurs that there was no relationship between growth rate and body size.
“Most animals are thought to evolve to be larger by growing faster than their ancestors, but this study shows that it’s just as likely that bigger and smaller animals grew for longer or shorter periods of time during growth spurts,” said Michael D. D’Emic, a paleontologist at Adelphi University and lead author of the study.
The bones of many animals, including dinosaurs, slowed or paused growth every year, leaving marks like tree rings that indicate the animal’s age and can be used to estimate the rate of growth. “Rings like these are called cortical growth marks,” said D’Emic. “Widely spaced rings indicate faster growth and narrowly spaced rings tell us that an animal was growing more slowly.”
D’Emic, O’Connor, Sombathy and a team of international researchers measured about 500 such growth rings in about 80 different theropod bones, the two-legged, mostly meat-eating species of dinosaurs closely related to birds.
“We found that there was no relationship between growth rate and size,” said D’Emic. “Some gigantic dinosaurs grew very slowly, slower than alligators do today. And some smaller dinosaurs grew very fast, as fast as mammals that are alive today.” This made sense to co-author Thomas Pascucci, whose graduate thesis contributed to the project: “Extinct animals like dinosaurs inspire awe because of how different they seem from our modern world, but they were animals that grew under similar constraints and environmental factors as those that exist today.”
According to O’Connor, this study opens the door to future investigations of how animals regulate their growth. “Alteration of different growth control mechanisms, at molecular or genetic levels, likely accounts for the range of developmental strategies our team observed in theropod dinosaurs. Future studies of living organisms provide an opportunity to elucidate mechanisms related to the evolution of body size in vertebrates more generally.”
Sombathy hopes to take up some of those investigations, adding “One of the things that interests me most about the results is the apparent decoupling between growth rate and body size. My Ph.D. dissertation will investigate the impacts of growth rate and body size on bone shape and function.”
“This has really important implications because changes in rate versus timing can correlate to many other things, like how many or how large your offspring are, how long you live, or how susceptible to predators you are,” D’Emic added. “Hopefully this research spurs investigations into other groups, both alive and extinct, to see what developmental mechanisms are most important in other types of animals.”
In addition to O’Connor, Sombathy, and D’Emic, the paper was co-authroed by Ignacio Cerda of Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional de Río Negro in Argentina, David Varricchio of Montana State University; Diego Pol of CONICET-Museo Paleontológico Egidio Feruglio in Argentina, Rodolfo Coria of Museo Carmen Funes in Argentina; and Kristina A. Curry Rogers of Macalester College in Minnesota. The study was funded, in part, by the US National Science Foundation and Adelphi University.
Reference:
Michael D. D’Emic et al. Developmental strategies underlying gigantism and miniaturization in non-avialan theropod dinosaurs. Science, 2023 DOI: 10.1126/science.adc8714
Seismogram being recorded by a seismograph at the Weston Observatory in Massachusetts, USA. Credit: Wikipedia
Data captured from seismic waves caused by earthquakes has shed new light on the deepest parts of Earth’s inner core, according to seismologists from The Australian National University (ANU).
By measuring the different speeds at which these waves penetrate and pass through the Earth’s inner core, the researchers believe they’ve documented evidence of a distinct layer inside Earth known as the innermost inner core — a solid “metallic ball” that sits within the centre of the inner core.
Not long ago it was thought Earth’s structure was composed of four distinct layers: the crust, the mantle, the outer core and the inner core. The findings, published in Nature Communications, confirm there is a fifth layer.
“The existence of an internal metallic ball within the inner core, the innermost inner core, was hypothesized about 20 years ago. We now provide another line of evidence to prove the hypothesis,” Dr Thanh-Son Phạm, from the ANU Research School of Earth Sciences, said.
Professor Hrvoje Tkalčić, also from ANU, said studying the deep interior of Earth’s inner core can tell us more about our planet’s past and evolution.
“This inner core is like a time capsule of Earth’s evolutionary history — it’s a fossilised record that serves as a gateway into the events of our planet’s past. Events that happened on Earth hundreds of millions to billions of years ago,” he said.
The researchers analysed seismic waves that travel directly through the Earth’s centre and “spit out” at the opposite side of the globe to where the earthquake was triggered, also known as the antipode. The waves then travel back to the source of the quake.
The ANU scientists describe this process as similar to a ping pong ball bouncing back and forth.
“By developing a technique to boost the signals recorded by densely populated seismograph networks, we observed, for the first time, seismic waves that bounce back-and-forth up to five times along the Earth’s diameter. Previous studies have documented only a single antipodal bounce,” Dr Phạm said.
“The findings are exciting because they provide a new way to probe the Earth’s inner core and its centremost region.”
One of the earthquakes the scientists studied originated in Alaska. The seismic waves triggered by this quake “bounced off” somewhere in the south Atlantic, before travelling back to Alaska.
The researchers studied the anisotropy of the iron-nickel alloy that comprises the inside of the Earth’s inner core. Anisotropy is used to describe how seismic waves speed up or slow down through the material of the Earth’s inner core depending on the direction in which they travel. It could be caused by different arrangement of iron atoms at high temperatures and pressures or preferred alignment of growing crystals.
They found the bouncing seismic waves repeatedly probed spots near the Earth’s centre from different angles. By analysing the variation of travel times of seismic waves for different earthquakes, the scientists infer the crystallised structure within the inner core’s innermost region is likely different to the outer layer.
They say it might explain why the waves speed up or slow down depending on their angle of entry as they penetrate the innermost inner core.
According to the ANU team, the findings suggest there could have been a major global event at some point during Earth’s evolutionary timeline that led to a “significant” change in the crystal structure or texture of the Earth’s inner core.
“There are still many unanswered questions about the Earth’s innermost inner core, which could hold the secrets to piecing together the mystery of our planet’s formation,” Professor Tkalčić said.
The researchers analysed data from about 200 magnitude-6 and above earthquakes from the last decade.
Reference:
Phạm, TS., Tkalčić, H. Up-to-fivefold reverberating waves through the Earth’s center and distinctly anisotropic innermost inner core. Nat Commun, 2023 DOI: 10.1038/s41467-023-36074-2
Artist’s impression of Ceratosuchops & orientation of skull endocast. Credit: Anthony Hutchings
Researchers from the University of Southampton and Ohio University have reconstructed the brains and inner ears of two British spinosaurs, helping uncover how these large predatory dinosaurs interacted with their environment.
Spinosaurs are an unusual group of theropod dinosaurs, equipped with long, crocodile-like jaws and conical teeth. These adaptations helped them live a somewhat-aquatic lifestyle that involved stalking riverbanks in quest of prey, among which were large fish. This way of life was very different from that of more familiar theropods, like Allosaurus and Tyrannosaurus.
To better understand the evolution of spinosaur brains and senses, the team scanned fossils of Baryonyx from Surrey and Ceratosuchops from the Isle of Wight. These two are the oldest spinosaurs for which braincase material is known. The huge creatures would have been roaming the planet about 125 million years ago years ago. The braincases of both specimens are well preserved, and the team digitally reconstructed the internal soft tissues that had long rotted away.
The researchers found the olfactory bulbs, which process smells, weren’t particularly developed, and the ear was probably attuned to low frequency sounds. Those parts of the brain involved in keeping the head stable and the gaze fixed on prey were possibly less developed than they were in later, more specialised spinosaurs.
Findings are due to be published in the Journal of Anatomy.
“Despite their unusual ecology, it seems the brains and senses of these early spinosaurs retained many aspects in common with other large-bodied theropods — there is no evidence that their semi-aquatic lifestyles are reflected in the way their brains are organised,” said University of Southampton PhD student Chris Barker, who led the study.
One interpretation of this evidence is that the theropod ancestors of spinosaurs already possessed brains and sensory adaptations suited for part-time fish catching, and that ‘all’ spinosaurs needed to do to become specialised for a semi-aquatic existence was evolve an unusual snout and teeth.
“Because the skulls of all spinosaurs are so specialised for fish-catching, it’s surprising to see such ‘non-specialised’ brains,” said contributing author Dr Darren Naish. “But the results are still significant. It’s exciting to get so much information on sensory abilities — on hearing, sense of smell, balance and so on — from British dinosaurs. Using cutting-edged technology, we basically obtained all the brain-related information we possibly could from these fossils,” Dr Naish said.
Over the last few years, the EvoPalaeo Lab at the University of Southampton has conducted substantial research on new spinosaurs from the Isle of Wight. Ceratosuchops itself was only announced by the team in 2021, and its discovery was followed up by the publication of another new spinosaur — the gigantic White Rock spinosaur — in 2022. The braincase of Ceratosuchops was scanned at the ?-Vis X-ray Imaging Centre at the University of Southampton, home to some of the most powerful CT scanners in the country, and a model of its brain will be on display alongside its bones at Dinosaur Isle Museum in Sandown, on the Isle of Wight.
“This new research is just the latest in what amounts to a revolution in palaeontology due to advances in CT-based imaging of fossils,” said co-author Lawrence M. Witmer, professor of anatomy at the Ohio University Heritage College of Osteopathic Medicine, who has been CT scanning dinosaurs — including Baryonyx — for over 25 years. “We’re now in a position to be able to assess the cognitive and sensory capabilities of extinct animals and explore how the brain evolved in behaviourally extreme dinosaurs like spinosaurs.”
“This new study highlights the significant role British fossils have in our constantly evolving, fast-moving understanding of dinosaurs, and shows how the UK — and the University of Southampton in particular — is at the forefront of spinosaur research,” said Dr Neil Gostling who leads the University of Southampton’s EvoPalaeoLab. “Spinosaurs themselves are one of the most controversial of all dinosaur groups, and this study is a valuable addition to ongoing discussions of their biology and evolution.”
Reference:
Chris Tijani Barker, Darren Naish, Jacob Trend, Lysanne Veerle Michels, Lawrence Witmer, Ryan Ridgley, Katy Rankin, Claire E. Clarkin, Philipp Schneider, Neil J. Gostling. Modified skulls but conservative brains? The palaeoneurology and endocranial anatomy of baryonychine dinosaurs (Theropoda: Spinosauridae). Journal of Anatomy, 2023; DOI: 10.1111/joa.13837
A new study from a University of Chicago scientist suggests there may be a layer of surprisingly fluid rock ringing the Earth, at the very bottom of the upper mantle.
The finding was made by measuring the lingering movement registered by GPS sensors on islands in the wake of a deep earthquake in the Pacific Ocean near Fiji. Published Feb. 22 in Nature, the study demonstrates a new method to measure the fluidity of the Earth’s mantle.
“Even though the mantle makes up the largest part of Earth, there’s still a lot we don’t know about it,” said Sunyoung Park, a geophysicist with the University of Chicago and the lead author on the study. “We think there’s a lot more we can learn by using these deep earthquakes as a way to probe these questions.”
Mantle mysteries
We still know surprisingly little about the Earth beneath our feet. The furthest anyone has managed to dig down is about seven and a half miles before the increasing heat literally melts the drill. Thus scientists have had to use clues like how seismic waves move to infer the different layers that make up the planet, including the crust, mantle, and core.
One thing that has stymied scientists is a precise measurement of how viscous the mantle layer is. The mantle is the layer below the crust. It’s made of rock, but at the intense temperature and pressures at that depth, the rock actually becomes viscous — flowing very slowly like honey or tar.
“We want to know exactly how fast the mantle flows, because that influences the evolution of the entire Earth — it affects how much heat the planet retains for how long, and how the Earth’s materials are cycled over time,” explained Park. “But our current understanding is very limited and includes a lot of assumptions.”
Park thought there might be a unique way to get a measurement of the mantle’s properties by studying the aftermath of very deep earthquakes.
Most of the earthquakes we hear about on the news are relatively shallow, originating in the top crust of the Earth. But occasionally, there are earthquakes that originate deep within the Earth — down to 450 miles below the surface. These earthquakes are not as well-studied as shallower ones, because they’re not as destructive to human settlements. But because they reach down into the mantle, Park thought they might offer a way to understand the behavior of the mantle.
Park and her colleagues looked at one particular such earthquake, which occurred off the coast of Fiji in 2018. The quake was magnitude 8.2, but it was so deep — 350 miles down — that it did not cause any major damage or deaths.
However, when the scientists carefully analyzed the data from GPS sensors on several nearby islands, they found the Earth kept moving — after the earthquake was over.
The data revealed that in the months following the quake, the Earth was still moving, settling in the wake of the disturbance. Even years later, Tonga is still moving slowly down at a rate of about 1 centimeter per year.
“You can think of it like a jar of honey that slowly comes back to level after you dip a spoon in it — except this takes years instead of minutes,” said Park.
This is the first solid observation of the deformation following deep quakes; the phenomenon had been observed before for shallow earthquakes, but experts thought the effect would be too small to be observable for deep earthquakes.
Park and her colleagues used this observation to infer the viscosity of the mantle.
By examining how the Earth deformed over time, they found evidence of a layer about 50-miles thick that is less viscous (that is, “runnier”) than the rest of the mantle, sitting at the bottom of the upper mantle layer. They think this layer may extend around the entire globe.
This low-viscosity layer could explain some other observations by seismologists that suggested there are “stagnant” slabs of rock that don’t move very much, located around the same depth at the bottom of the upper mantle. “It has been hard to reproduce those features with models, but the weak layer found in this study makes it easier to do so,” Park said.
It also has implications for how Earth transports heat, cycles and mixes materials between the crust, core, and mantle over time.
“We’re really excited,” Park said. “There’s a lot more to find out with this technique.”
The other co-authors on the paper were Jean-Philippe Avouac and Zhongwen Zhan of California Institute of Technology and Adriano Gualandi of Italy’s National Institute of Geophysics and Volcanology.
Reference:
Park, S., Avouac, JP., Zhan, Z. et al. Weak upper-mantle base revealed by postseismic deformation of a deep earthquake. Nature, 2023 DOI: 10.1038/s41586-022-05689-8
Image of fruit belonging to Palaeophytocrene chicoensis. The Sierra College Museum of Natural History is the permanent repository for this fossil. Credit: Brian Atkinson.
The discovery of an 80-million-year-old fossil plant pushes back the known origins of lamiids to the Cretaceous, extending the record of nearly 40,000 species of flowering plants including modern-day staple crops like coffee, tomatoes, potatoes and mint.
Brian Atkinson, assistant professor of ecology & evolutionary biology at the University of Kansas and curator of paleobotany at the KU Biodiversity Institute, recently published a study of the fossil plant, named Palaeophytocrene chicoensis, in the peer-reviewed journal Nature Plants.
“This fossil tells us a really diverse group of flowering plants evolved prior to our original understanding,” Atkinson said. “The fossil belongs to a group of lianas, which are woody vines that add structural complexity to rainforests. It shows us this group of flowering plants appeared super early in the fossil record. There’d been some hypotheses that they were around in the Cretaceous period — but no good clear evidence. This is a great indicator that structurally complex, modern-type rainforests may have been around as early as 80 million years ago.”
According to the KU researcher, the fossil fruit sheds new light on a “critical interval” in the history of life on Earth.
“It’s a time when forests are transitioning from being dominated by gymnosperms such as conifers to being dominated by flowering plants,” Atkinson said. “We know these ecological transitions occurred during the Late Cretaceous — but we still need critical pieces of evidence, like how certain ecosystems formed, such as rainforests, which today comprise over half of plant species that are alive today. This fossil shows this diverse group of plants, the lamiids, were older than previously thought, and Cretaceous ecosystems on the west coast of North America may have resembled structurally complex rainforests.”
The well-preserved fossil was unearthed in the 1990s by construction crews building housing near Granite Bay in Sacramento, California. Located in deposits of the Chico Formation tied to the Campanian (fifth of six ages of the Late Cretaceous epoch), the fossil was collected by Richard Hilton and Patrick Antuzzi of Sierra College and housed at their natural history museum.
“I spent seven years looking for these things [Cretaceous lamiids], and I couldn’t find them,” Atkinson said. “I’d been collecting and studying Cretaceous plants on the West Coast to better understand the evolution of flowering plants. Somebody said, ‘Oh, you should check out the Sierra College Museum of Natural History,’ as it wasn’t on my radar to contact them. They gladly had me over to look at their fossil plant collection, and I was just kind of blown away by the diversity of plants that these guys were able to dig up in this housing development.”
It wasn’t until Atkinson saw the fossil plant recovered decades earlier from the construction site that the specimen’s potential significance was understood.
“As I was opening this drawer, I noticed this fruit with really striking patterns on its surface,” the KU researcher said. “I immediately recognized it as belonging to this lamiid family called Icacinaceae, which is well-known in younger, post-Cretaceous deposits after the mass-extinction event. It’s all over the place. But before, there are no clear known fossils that belong to that family. And I thought, ‘Oh my God, this is it!’ You know, this family of plants have just these really striking fruits.”
To confirm his thinking about the fossil, Atkinson needed to take a closer look. He studied the fossil fruit’s structures using light microscopy, which allowed him to generate beautiful photographs of the specimen. By scrutinizing its arrangement of ridges, pits, rows and tubercles, the KU investigator could make comparisons to previously described fossils to place it correctly within its family tree. The work challenged Atkinson because he’d never described a “compression fossil” of its kind.
“I’m used to working on fossils that preserve in a different mode called ‘permineralization,'” Atkinson said. “This is my first paper on a compression fossil, and it was a little bit nerve-wracking, working in a different preservation type than you’re used to. Imaging it is a whole different process — I’m glad this turned out so well.”
After placing the fossil plant within the genus Palaeophytocrene, Atkinson named the species chicoensis after the Chico Formation where it was found.
“I just named it after the formation it was recovered from,” he said. “Part of my job is coming up with scientific names for new species that I describe, but I’m not that creative about it — usually I look up the location where it was discovered. Has that name been taken already?”
If the fossil fruit’s name is humdrum, it’s significance isn’t. The KU researcher said the findings help establish that one of the most diverse flowering plant groups survived the cataclysm that killed the dinosaurs to evolve into thousands of familiar modern species, including vital food crops for humanity.
“My research involves understanding deep time to better reconcile how modern biodiversity came to be — and potentially how it will fare in the future with climate change,” said Atkinson. “I’ve been trying to characterize these evolutionary events of flowering plants in the Cretaceous period, when the diversity of these plants just exploded. The Cretaceous record of lamiids has been hard to establish, but I knew these fossils had to be around. The West Coast of North America is under-sampled for Cretaceous plants compared to the Western Interior and East Coast of North America. By broadening our sampling geographically, we’ll come across more and more plants to help us understand Cretaceous diversification that led to modern biodiversity.”
Reference:
Brian A. Atkinson. Icacinaceae fossil provides evidence for a Cretaceous origin of the lamiids. Nature Plants, 2022; 8 (12): 1374 DOI: 10.1038/s41477-022-01275-y
A diagram of the asthenosphere, which aids plate tectonics, where researchers at the UT Austin Jackson School of Geosciences say they detected a global layer of partial melt (shown in speckled red). Credit: Junlin Hua, UT Jackson School of Geosciences
Scientists have discovered a new layer of partly molten rock under the Earth’s crust that might help settle a long-standing debate about how tectonic plates move.
Researchers had previously identified patches of melt at a similar depth. But a new study led by The University of Texas at Austin revealed for the first time the layer’s global extent and its part in plate tectonics.
The research was published Feb. 6, 2023, in the journal Nature Geoscience.
The molten layer is located about 100 miles from the surface and is part of the asthenosphere, which sits under the Earth’s tectonic plates in the upper mantle. The asthenosphere is important for plate tectonics because it forms a relatively soft boundary that lets tectonic plates move through the mantle.
The reasons why it is soft, however, are not well understood. Scientists previously thought that molten rocks might be a factor. But this study shows that melt, in fact, does not appear to notably influence the flow of mantle rocks.
“When we think about something melting, we intuitively think that the melt must play a big role in the material’s viscosity,” said Junlin Hua, a postdoctoral fellow at UT’s Jackson School of Geosciences who led the research. “But what we found is that even where the melt fraction is quite high, its effect on mantle flow is very minor.”
According to the research, which Hua began as a graduate student at Brown University, the convection of heat and rock in the mantle are the prevailing influence on the motion of the plates. Although the Earth’s interior is largely solid, over long periods of time, rocks can shift and flow like honey.
Showing that the melt layer has no influence on plate tectonics means one less tricky variable for computer models of the Earth, said coauthor Thorsten Becker, a professor at the Jackson School.
“We can’t rule out that locally melt doesn’t matter,” said Becker, who designs geodynamic models of the Earth at the Jackson School’s University of Texas Institute for Geophysics. “But I think it drives us to see these observations of melt as a marker of what’s going on in the Earth, and not necessarily an active contribution to anything.”
The idea to look for a new layer in Earth’s interior came to Hua while studying seismic images of the mantle beneath Turkey during his doctoral research.
Intrigued by signs of partly molten rock under the crust, Hua compiled similar images from other seismic stations until he had a global map of the asthenosphere. What he and others had taken to be an anomaly was in fact commonplace around the world, appearing on seismic readings wherever the asthenosphere was hottest.
The next surprise came when he compared his melt map with seismic measurements of tectonic movement and found no correlation, despite the molten layer encompassing almost half the Earth.
“This work is important because understanding the properties of the asthenosphere and the origins of why it’s weak is fundamental to understanding plate tectonics,” said coauthor Karen Fischer, a seismologist and professor at Brown University who was Hua’s Ph.D. advisor when he began the research.
The research was funded by the U.S. National Science Foundation. Collaborating institutions included the UT Oden Institute for Computational Engineering and Sciences and Cornell University.
Reference:
Junlin Hua, Karen M. Fischer, Thorsten W. Becker, Esteban Gazel, Greg Hirth. Asthenospheric low-velocity zone consistent with globally prevalent partial melting. Nature Geoscience, 2023; DOI: 10.1038/s41561-022-01116-9
What once appeared as a fossil of the primitive animal Dickinsonia turned out to be notihng more than a decaying beehive, shown falling off the rock on the right just a couple years later. (Gregory Retallack/Joe Meert)
In 2020, amid the first pandemic lockdowns, a scientific conference scheduled to take place in India never happened.
But a group of geologists who were already on site decided to make the most of their time and visited the Bhimbetka Rock Shelters, a series of caves with ancient cave art near Bhopal, India. There, they spotted the fossil of Dickinsonia¸ a flat, elongated and primitive animal from before complex animals evolved. It marked the first-ever discovery of Dickinsonia in India.
The animal lived 550 million years ago, and the find seemed to settle once and for all the surprisingly controversial age of the rocks making up much of the Indian subcontinent. The find attracted the attention of The New York Times, The Weather Channel and the scientific journal Nature as well as many Indian newspapers.
Only, it turns out, the “fossil” was a case of mistaken identity. The true culprit? Bees.
University of Florida researchers traveled to the site last year and discovered the object had seemingly decayed significantly — quite unusual for a fossil. What’s more, giant bee’s nests populate the site, and the mark spotted by the scientists in 2020 closely resembled the remains of these large hives.
“As soon as I looked at it, I thought something’s not right here,” said Joseph Meert, a UF professor of geology and expert on the geology of the area. “The fossil was peeling off the rock.”
The erstwhile fossil was also lying nearly vertical along the walls of the caves, which didn’t make sense. Instead, Meert says, fossils in this area should only be visible flat on the floor or ceiling of the cave structures.
Meert collaborated on the investigation with his graduate students Samuel Kwafo and Ananya Singha and University of Rajasthan professor Manoj Pandit. They documented the rapid decay of the object and photographed similar remains from nearby beehives. The team published their findings of the mistaken identity Jan. 19 in the journal Gondwana Research, which previously published the report of the serendipitous Dickinsonia fossil find.
Gregory Retallack, professor emeritus at the University of Oregon and lead author of the original paper, says he and his co-authors agree with Meert’s findings that the object is really just a beehive. They are submitting a comment in support of the new paper to the journal.
This kind of self-correction is a bedrock principle of the scientific method. But the reality is that admitting errors is hard for scientists to do, and it doesn’t happen often.
“It is rare but essential for scientists to confess mistakes when new evidence is discovered,” Retallack said in an email.
Correcting the fossil record puts the age of the rocks back into contention. Because the rock formation doesn’t have any fossils from a known time period, dating it can be difficult.
Meert says the evidence continues to point to the rocks being closer to one billion years old. His team has used the radioactive decay of tiny crystals called zircons to date the rocks to that time period. And the magnetic signature of the rocks, which captures information about the Earth’s magnetic field when the rocks formed, closely matches the signatures of formations confidently dated to a billion years ago.
Other scientists have reported findings supporting a younger age. The time period is essential to understand because of its implications for the evolution of life in the area and how the Indian subcontinent formed.
“You might say, ‘Okay, well what’s the big deal if they are 550 million or a billion years old?’ Well, there are lots of implications,” Meert said. “One has to do with the paleogeography at the time, what was happening to continents, where the continents were located, how they were assembled. And it was a period when life was going through a major change, from very simple fossils to more complex fossils.”
“So trying to figure out the paleogeography at the time is very, very important. And in order to figure out the paleogeography, we have to know the age of the rocks,” he said.
Reference:
Joseph G. Meert, Manoj K. Pandit, Samuel Kwafo, Ananya Singha. Stinging News: ‘Dickinsonia’ discovered in the Upper Vindhyan of India not worth the buzz. Gondwana Research, 2023; 117: 1 DOI: 10.1016/j.gr.2023.01.003
The fossilized skull of Coccocephalus wildi, an early ray-finned fish that swam in an estuary 319 million years ago. The fish is facing to the right, with the jaws visible in the lower right portion of the fossil. The eye socket is the circular, bumpy feature above the jaws. This fish would have been 6 to 8 inches long, about the size of a bluegill. Photo credit: Jeremy Marble, University of Michigan News.
The CT-scanned skull of a 319-million-year-old fossilized fish, pulled from a coal mine in England more than a century ago, has revealed the oldest example of a well-preserved vertebrate brain.
The brain and its cranial nerves are roughly an inch long and belong to an extinct bluegill-size fish. The discovery opens a window into the neural anatomy and early evolution of the major group of fishes alive today, the ray-finned fishes, according to the authors of a University of Michigan-led study scheduled for publication Feb. 1 in Nature.
The serendipitous find also provides insights into the preservation of soft parts in fossils of backboned animals. Most of the animal fossils in museum collections were formed from hard body parts such as bones, teeth and shells.
The CT-scanned brain analyzed for the new study belongs to Coccocephalus wildi, an early ray-finned fish that swam in an estuary and likely dined on small crustaceans, aquatic insects and cephalopods, a group that today includes squid, octopuses and cuttlefish. Ray-finned fishes have backbones and fins supported by bony rods called rays.
When the fish died, the soft tissues of its brain and cranial nerves were replaced during the fossilization process with a dense mineral that preserved, in exquisite detail, their three-dimensional structure.
“An important conclusion is that these kinds of soft parts can be preserved, and they may be preserved in fossils that we’ve had for a long time — this is a fossil that’s been known for over 100 years,” said U-M paleontologist Matt Friedman, a senior author of the new study and director of the Museum of Paleontology.
The lead author is U-M doctoral student Rodrigo Figueroa, who did the work as part of his dissertation, under Friedman, in the Department of Earth and Environmental Sciences.
“Not only does this superficially unimpressive and small fossil show us the oldest example of a fossilized vertebrate brain, but it also shows that much of what we thought about brain evolution from living species alone will need reworking,” Figueroa said.
“With the widespread availability of modern imaging techniques, I would not be surprised if we find that fossil brains and other soft parts are much more common than we previously thought. From now on, our research group and others will look at fossil fish heads with a new and different perspective.”
The skull fossil from England is the only known specimen of its species, so only nondestructive techniques could be used during the U-M-led study.
The work on Coccocephalus is part of a broader effort by Friedman, Figueroa and colleagues that uses computed tomography (CT) scanning to peer inside the skulls of early ray-finned fishes. The goal of the larger study is to obtain internal anatomical details that provide insights about evolutionary relationships.
In the case of C. wildi, Friedman was not looking for a brain when he fired up his micro-CT scanner and examined the skull fossil.
“I scanned it, then I loaded the data into the software we use to visualize these scans and noticed that there was an unusual, distinct object inside the skull,” he said.
The unidentified blob was brighter on the CT image — and therefore likely denser — than the bones of the skull or the surrounding rock.
“It is common to see amorphous mineral growths in fossils, but this object had a clearly defined structure,” Friedman said.
The mystery object displayed several features found in vertebrate brains: It was bilaterally symmetrical, it contained hollow spaces similar in appearance to ventricles, and it had multiple filaments extending toward openings in the braincase, similar in appearance to cranial nerves, which travel through such canals in living species.
“It had all these features, and I said to myself, ‘Is this really a brain that I’m looking at?'” Friedman said. “So I zoomed in on that region of the skull to make a second, higher-resolution scan, and it was very clear that that’s exactly what it had to be. And it was only because this was such an unambiguous example that we decided to take it further.”
Though preserved brain tissue has rarely been found in vertebrate fossils, scientists have had better success with invertebrates. For example, the intact brain of a 310-million-year-old horseshoe crab was reported in 2021, and scans of amber-encased insects have revealed brains and other organs. There is even evidence of brains and other parts of the nervous system recorded in flattened specimens more than 500 million years old.
The preserved brain of a 300-million-year-old shark relative was reported in 2009. But sharks, rays and skates are cartilaginous fishes, which today hold relatively few species compared to the ray-finned fish lineage containing Coccocephalus. Early ray-finned fishes like Coccocephalus can tell scientists about the initial evolutionary phases of today’s most diverse fish group, which includes everything from trout to tuna, seahorses to flounder.
There are roughly 30,000 ray-finned fish species, and they account for about half of all backboned animal species. The other half is split between land vertebrates — birds, mammals, reptiles and amphibians — and less diverse fish groups like jawless fishes and cartilaginous fishes.
The Coccocephalus skull fossil is on loan to Friedman from England’s Manchester Museum. It was recovered from the roof of the Mountain Fourfoot coal mine in Lancashire and was first scientifically described in 1925. The fossil was found in a layer of soapstone adjacent to a coal seam in the mine.
Though only its skull was recovered, scientists believe that C. wildi would have been 6 to 8 inches long. Judging from its jaw shape and its teeth, it was probably a carnivore, according to Figueroa.
When the fish died, scientists suspect it was quickly buried in sediments with little oxygen present. Such environments can slow the decomposition of soft body parts.
In addition, a chemical micro-environment inside the skull’s braincase may have helped to preserve the delicate brain tissues and to replace them with a dense mineral, possibly pyrite, Figueroa said.
Evidence supporting this idea comes from the cranial nerves, which send electrical signals between the brain and the sensory organs. In the Coccocephalus fossil, the cranial nerves are intact inside the braincase but disappear as they exit the skull.
“There seems to be, inside this tightly enclosed void in the skull, a little micro-environment that is conducive to the replacement of those soft parts with some kind of mineral phase, capturing the shape of tissues that would otherwise simply decay away,” Friedman said.
Detailed analysis of the fossil, along with comparisons to the brains of modern-fish specimens from the U-M Museum of Zoology collection, revealed that the brain of Coccocephalus has a raisin-size central body with three main regions that roughly correspond to the forebrain, midbrain and hindbrain in living fishes.
Cranial nerves project from both sides of the central body. Viewed as a single unit, the central body and the cranial nerves resemble a tiny crustacean, such as a lobster or a crab, with projecting arms, legs and claws.
Notably, the brain structure of Coccocephalus indicates a more complicated pattern of fish-brain evolution than is suggested by living species alone, according to the authors.
“These features give the fossil real value in understanding patterns of brain evolution, rather than simply being a curiosity of unexpected preservation,” Figueroa said.
For example, all living ray-finned fishes have an everted brain, meaning that the brains of embryonic fish develop by folding tissues from the inside of the embryo outward, like a sock turned inside out.
All other vertebrates have evaginated brains, meaning that neural tissue in developing brains folds inward.
“Unlike all living ray-finned fishes, the brain of Coccocephalus folds inward,” Friedman said. “So, this fossil is capturing a time before that signature feature of ray-finned fish brains evolved. This provides us with some constraints on when this trait evolved — something that we did not have a good handle on before the new data on Coccocephalus.”
Comparisons to living fishes showed that the brain of Coccocephalus is most similar to the brains of sturgeons and paddlefish, which are often called “primitive” fishes because they diverged from all other living ray-finned fishes more than 300 million years ago.
Friedman and Figueroa are continuing to CT scan the skulls of ray-finned fish fossils, including several specimens that Figueroa brought to Ann Arbor on loan from institutions in his home country, Brazil. Figueroa said his doctoral dissertation was delayed by the COVID-19 pandemic but is expected to be completed in summer 2024.
The Nature study includes data produced at U-M’s Computed Tomography in Earth and Environmental Science facility, which is supported by the Department of Earth and Environmental Sciences and the College of Literature, Science, and the Arts.
The other authors of the paper are Sam Giles of London’s Natural History Museum and the University of Birmingham; Danielle Goodvin and Matthew Kolmann of the U-M Museum of Paleontology; and Michael Coates and Abigail Caron of the University of Chicago.
Friedman and Figueroa said the discovery highlights the importance of preserving specimens in paleontology and zoology museums.
“Here we’ve found remarkable preservation in a fossil examined several times before by multiple people over the past century,” Friedman said. “But because we have these new tools for looking inside of fossils, it reveals another layer of information to us.
“That’s why holding onto the physical specimens is so important. Because who knows, in 100 years, what people might be able to do with the fossils in our collections now.”
Reference:
Rodrigo T. Figueroa, Danielle Goodvin, Matthew A. Kolmann, Michael I. Coates, Abigail M. Caron, Matt Friedman, Sam Giles. Exceptional fossil preservation and evolution of the ray-finned fish brain. Nature, 2023; DOI: 10.1038/s41586-022-05666-1
