FOSSILS
Analysis of fossil by Harvard researcher’s team sheds light on reptile evolution
New species of fossil reptile identified from 231 million years ago
Peer-Reviewed PublicationIMAGE: ILLUSTRATION OF TAYTALURA ALCOBERI view more
CREDIT: JORGE BLANCO
It’s not uncommon for scientists to have to run experiments numerous times to see whether they have a big discovery on their hands. Every once in a while, though, a researcher makes a big find by more or less eyeballing it. That’s essentially what Tiago R. Simões did when he was shown pictures of a 231-million-year-old reptile skull.
“I knew right away because of its age, locality, and some of its anatomical aspects that it was extremely important,” said Simões, a researcher in the lab of Harvard paleontologist Stephanie Pierce. “I knew we needed to give this priority and get the CT scan data to see exactly what we have.”
His suspicion was right. Analysis of the scans showed the fossil belonged to a new species of a lizard-like reptile, representing the earliest evolving member of a lineage that today includes all lizards, snakes, and their closest relatives. That’s nearly 11,000 species altogether.
Unearthed in the moonlike desert landscape of Ischigualasto Provincial Park in northwest Argentina, the fossil is of a lepidosaur, one of the major evolutionary branches of reptiles. It is the first three-dimensionally intact skull of a primitive member of this lineage ever found, and its discovery can help researchers better understand the early evolutionary history of this vast group.
“We have very few fossils from 240 or 250 million years ago when this entire group is expected to have originated and the very few fossils that we have are extremely fragmented. You have only pieces of jaws and teeth here and there,” said Simões, who is a fellow at Harvard and funded by the National Sciences and Engineering Research Council of Canada. “The first thing that this provides is this missing piece of the puzzle, which is an amazingly well-preserved skull of a primitive member of this lineage that lived in Argentina.”
Results of his analysis were published Wednesday in the journal Nature and was a collaboration between Simões and scientists from Argentina and Germany.
Understanding the significance of this find requires a little background. There are two main branches of reptile: archosaurs and lepidosaurs. Archosaurs include all crocodile and dinosaur lineages while lepidosaurs include squamates (lizards, snakes) and sphenodontians, which have only one living species today, the tuatara of New Zealand.
The lepidosaur fossil was not just any lepidosaur, but the first member of this group that evolved away from the others. That puts it at the top of that lineage and provides key evidence as to how lizards first evolved from more primitive reptiles. That kind of respect is shown in the name the scientists chose for it, Taytalura alcoberi, meaning father of the lizards in the Quechua and Kakán languages of the native Andean people of Argentina.
Taytalura is the earliest evolving lepidosaur, but it is not the oldest lepidosaur fossil ever found. That honor belongs to a 242 million-year-old squamate and a 234 million-year-old sphenodontian. That suggests an older Taytalura fossil may one day be found.
Regardless, the age discrepancy shows that these very early lepidosaurs lived side-by-side with squamates and sphenodontians, known as “true” lepidosaurs, for at least 10 million years during the Triassic period, a fact that was previously unknown.
The researchers used micro-CT scans of the three dimensionally preserved head to analyze the fossil. It allowed them to compare this early lepidosaurian skull with later lepidosaur and other reptiles. The researchers, for instance, noticed the skull of the first lepidosaurs looked substantially more like those of sphenodontians than squamates and that squamates represent a major deviation from the older skull patterns. They also found Taytalura teeth differed from those in any living or extinct group of lepidosaurs.
Another surprising finding involved where the fossil was discovered. Till now, almost all fossils of Triassic lepidosaurs have been found in Europe. This is the first early lepidosaur found in South America. It suggests lepidosaurs were able to migrate across the planet (which then was all still one super continent) very early in their evolutionary history.
That type of mileage is impressive for such a small creature. While it’s impossible to accurately estimate the total body length of this lizard-like reptile, the one-inch head suggests it likely could fit in the palm of a human hand. The creature most likely fed on insects from desert environments that it shared with some of the oldest dinosaurs in the planet, said Simões. “[It] was most likely preyed upon by some of the first dinosaurs to walk on Earth,” he said.
The researchers hope to explore older rocks in Argentina or other parts of South America and find older members of this lineage. The hope is to get the exact time of when the entire group originated, which will be critical in understanding the long evolutionary history of reptiles to help those that exist today.
“Lepidosaurs survived across three out of the five big mass extinctions on earth’s history during the last 260 million years,” Simões said. “By accurately reconstructing the long evolutionary history of lepidosaurs, we may be able to tell in much greater detail how they successfully survived and flourished across major environmental shifts in Earth’s past and how they may be impacted by modern human-induced climate change.”
JOURNAL
Nature
SUBJECT OF RESEARCH
Animals
ARTICLE TITLE
A Triassic stem lepidosaur illuminates the origin of lizard-like reptiles
ARTICLE PUBLICATION DATE
25-Aug-2021
The dawn of modern reptiles
International team of researchers describe a new fossil species representing the ancient forerunner of most modern reptiles
Peer-Reviewed PublicationIMAGE: LIFE RECONSTRUCTION OF TAYTALURA IN ITS NATURAL HABITAT WITH THE EXTINCT CONIFER RHEXOXYLON IN ISCHIGUALASTO (ARGENTINA) DURING THE LATE TRIASSIC, HIDING FROM THE PRIMITIVE DINOSAUR EODROMAEUS (IN THE BACKGROUND) INSIDE THE SKULL OF A MAMMALIAN ANCESTOR. view more
CREDIT: ORIGINAL ARTWORK CREATED BY SCIENTIFIC ILLUSTRATOR JORGE BLANCO.
Lizards and snakes are a key component of most terrestrial ecosystems on earth today. Along with the charismatic tuatara of New Zealand (a “living fossil” represented by a single living species), squamates (all lizards and snakes) make up the Lepidosauria—the largest group of terrestrial vertebrates in the planet today with approximately 11,000 species, and by far the largest modern group of reptiles. Both squamates and tuataras have an extremely long evolutionary history. Their lineages are older than dinosaurs having originated and diverged from each other at some point around 260 million years ago. However, the early phase of lepidosaur evolution 260-150 million years ago, is marked by very fragmented fossils that do not provide much useful data to understand their early evolution, leaving the origins of this vastly diverse group of animals embedded in mystery for decades.
In a study published August 25 in Nature an international team of researchers describe a new species that represents the most primitive member of lepidosaurs, Taytalura alcoberi, found in the Late Triassic deposits of Argentina. Discovered by lead author Dr. Ricardo N. Martínez, Universidad Nacional de San Juan, Argentina, and curator at the Instituto y Museo de Ciencias Naturales, Taytalura is the first three-dimensionally preserved early lepidosaur fossil. It allowed scientists to infer with great confidence it’s placement in the evolutionary tree of reptiles and aids in closing the gap of our knowledge of the origin and early evolution of lepidosaurs.
Martínez and co-author Dr. Sebastián Apesteguía, Universidad Maimónides, Buenos Aires, Argentina, conducted high-resolution CT scans of Taytalura which provided confirmation that it was something related to ancient lizards. They then contacted co-author Dr. Tiago R. Simões, postdoctoral fellow in The Department of Organismic and Evolutionary Biology, Harvard University, to help identify and analyze the fossil. Simões specializes in studying these creatures and in 2018 published the largest existing dataset to understand the evolution of the major groups of reptiles (living and extinct) in Nature.
“I knew the age and locality of the fossil and could tell by examining some of its external features that it was closely related to lizards, but it looked more primitive than a true lizard and that is something quite special,” said Simões.
The researchers then contacted co-author Dr. Gabriela Sobral, Department of Palaeontology, Staatliches Museum für Naturkunde Stuttgart, Germany, to process the CT scan data. Sobral, a specialist in processing CT data, created a mosaic of colors for each bone of the skull allowing the team to understand the fossil’s anatomy in high-detail resolution on a scale of only a few micrometers – about the same thickness as a human hair.
With Sobral’s data, Simões was able to apply a Bayesian evolutionary analysis to determine the proper placement of the fossil in the reptile dataset. Simões had recently applied the Bayesian method – which was adapted from methods originally developed in epidemiology to study how viruses like COVID-19 evolve – to precisely estimate the time and rates of anatomical evolution during the rise of tetrapods. The statistical analysis confirmed their suspicions that Taytalura was in fact the most primitive member of the lineage that eventually originated all lizards and snakes. “It’s not even a lizard in the evolutionary tree,” said Simões, “but it’s the very next thing there, between true liizards and tuataras, and all other reptiles.”
"This beautifully 3D preserved fossil is really an important finding. It is the most complete fossil representing the early stages of lepidosaur evolution that we have so far. All other known fossils are too incomplete, which makes it difficult to classify them for sure, but the complete and articulated nature of Taytalura makes its relationships much more certain,” said Sobral.
Simões agreed, “Taytalura is a major point in the reptile tree of life that was previously missing. Because these fossils are so small they are very difficult to preserve in the fossil record. And what candidate fossils we do have are very fragmented and poorly preserved, so they don’t provide as much useful data for analysis.”
CAPTION
Reconstruction of the skull of Taytalura based on high-resolution CT scans (left) and its placement in the evolutionary tree of reptiles (right).
CREDIT
Left) Gabriela Sobral, Jorge Blanco, and Ricardo Martínez; Right) Tiago Simões
Taytalura’s skull reveals that the first lepidosaurs looked substantially more like the tuataras than squamates, and therefore, that squamates represent a major deviation from this ancestral pattern. Further, it has a unique dentition, differing from the teeth found in any living or extinct group of lepidosaurs. “What our analyses tells us, besides some other anatomical traits that we could see on it, in the skull specifically, is that this sphenodontian body type, at least for the skull, is the ancestral pattern for lepidosaurs. The ancestral pattern seems to be more similar to tuataras,” said Simões.
“Taytalura preserves a composition of features that we were not expecting to find in such an early fossil. For instance, it shows some features that we thought were exclusive for the tuatara group. On the other hand, it made us question how truly "primitive" certain lizard features are, and it will make scientists reconsider several points in the evolution of this group,” said Sobral.
“The almost perfectly preserved Taytalura skull shows us details of how a very successful group of animals, including more than 10,000 species of snakes, lizards, and tuataras, originated,” said Martínez. “But it also highlights the paleontological importance of the paleontological site of Ischigualasto Formation, known for preserving some of the most primitive dinosaurs known in the world. The extraordinary quality of preservation of the fossils at this site allowed something as fragile and tiny as this specimen to be preserved for 231 million years.”
“Contrary to almost all fossils of Triassic lepidosaurs found in Europe, this is the first early lepidosaur found in South America, suggesting lepidosaurs were able to migrate across vastly distant geographic regions early in their evolutionary history,” agreed Simões.
"We are accustomed to accept that the Mesozoic Era was an age of gigantic reptiles, enormous proto-mammals, and huge trees, and thus we commonly look for fossils that are visible at human height, just walking,” said Apesteguía. “However, the largest part of the ancient ecosystem components was small, as today. There was a universe of fauna sneaking among bigger, clawed or hoofy paws. Taytalura teaches us that we were missing important information by looking not only for bigger animals, but for also thinking that the origin of lizards occurred only in the Northern Hemisphere as evidence seemed to support until now."
While Taytalura is primitive, it is not the oldest lepidosaur. The fossil is 231 million years old, but there are also fossils of true lizards from 11 million years earlier. The team plans to next explore older sites in hopes of finding similar or different species from the same lineage that branch just before the origin of true lizards.
####
JOURNAL
Nature
ARTICLE TITLE
A Triassic stem lepidosaur illuminates the origin of lizard-like reptiles
ARTICLE PUBLICATION DATE
25-Aug-2021
Peabody fossils illuminate dinosaur
evolution in eastern North America
Tyrannosaurus rex, the fearsome predator that once roamed what is now western North America, appears to have had an East Coast cousin.
A new study by Yale undergraduate Chase Doran Brownstein describes two dinosaurs that inhabited Appalachia — a once isolated land mass that today composes much of the eastern United States — about 85 million years ago: an herbivorous duck-billed hadrosaur and a carnivorous tyrannosaur. The findings were published Aug. 25 in the journal Royal Society Open Science.
The two dinosaurs, which Brownstein described from specimens housed at Yale’s Peabody Museum of Natural History, help fill a major gap in the North American fossil record from the Late Cretaceous and provide evidence that dinosaurs in the eastern portion of the continent evolved distinctly from their counterparts in western North America and Asia, Brownstein said.
“These specimens illuminate certain mysteries in the fossil record of eastern North America and help us better understand how geographic isolation— large water bodies separated Appalachia from other landmasses — affected the evolution of dinosaurs,” said Brownstein, who is entering his junior year at Yale College. “They’re also a good reminder that while the western United States has long been the source of exciting fossil discoveries, the eastern part of the country contains its share of treasures.”
For most of the second half of the Cretaceous, which ended 66 million years ago, North America was divided into two land masses, Laramidia in the West and Appalachia in the East, with the Western Interior Seaway separating them. While famous dinosaur species like T. rex and Triceratops lived throughout Laramidia, much less is known about the animals that inhabited Appalachia. One reason is that Laramidia’s geographic conditions were more conducive to the formation of sediment-rich fossil beds than Appalachia’s, Brownstein explained.
The specimens described in the new study were discovered largely during the 1970s at the Merchantville Formation in present day New Jersey and Delaware. They constitute one of the only known dinosaur assemblages from the late Santonian to early Campanian stages of the Late Cretaceous in North America. This fossil record period, dating from about 85 to 72 million years ago, is limited, Brownstein noted.
Brownstein examined a partial skeleton of a large predatory therapod, concluding that it is probably a tyrannosaur. He noted that the fossil shares several features in its hind limbs with Dryptosaurus, a tyrannosaur that lived about 67 million years ago in what is now New Jersey. The dinosaur has different hands and feet than T. rex, including massive claws on its forelimbs, suggesting that it represents a distinct family of the predators that evolved solely in Appalachia.
“Many people believe that all tyrannosaurs must have evolved a specific set of features to become apex predators,” Brownstein said. “Our fossil suggests they evolved into giant predators in a variety of ways as it lacks key foot or hand features that one would associate with western North American or Asian tyrannosaurs.”
The partial skeleton of the hadrosaur provided important new information on the evolution of the shoulder girdle in that group of dinosaurs, Brownstein found. The hadrosaur fossils also provide one of the best records of this group from east of the Mississippi and include some of the only infant/perinate (very young) dinosaur fossils found in this region.
Brownstein, who works as a research associate at the Stamford Museum and Nature Center in Stamford, Connecticut, has previously published his paleontological research in several peer-journals, including Scientific Reports, the Journal of Paleontology, and the Zoological Journal of the Linnaean Society. In addition to eastern North American fossils, he currently focuses his research on the evolution of fishes, lizards, and birds. He is particularly interested in how geographic change and other factors contribute to how fast different types of living things evolve.
He currently works in the lab of Thomas J. Near, curator of the Peabody Museum’s ichthyology collections and professor and chair of the Department of Ecology and Evolutionary Biology at Yale. Brownstein also collaborates with Yale paleontologists Jacques Gauthier and Bhart-Anjan Bhullar in the Department of Earth and Planetary Sciences.
While Brownstein is considering pursuing an academic career in evolutionary biology, he says his research is driven by enjoyment.
“Doing research and thinking about these things makes me happy,” he said. “Like biking, it’s something I love to do.”
JOURNAL
Royal Society Open Science
ARTICLE TITLE
Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America
CT scan of an ancient reptile skull reveals little evolutionary change over 22 million years
3D imaging analysis done by SMU shows skull is nearly
identical to one much older
Peer-Reviewed PublicationIMAGE: ELASMOSAURIDS, LIKE THE CARDIOMORAX MUKULU REPTILES SEEN HERE, LIVED DURING THE CRETACEOUS PERIOD. THEY WERE PREDATORS, THRIVING ON FISH AND OTHER MARINE LIFE. view more
CREDIT: KAREN CARR STUDIO INC.
DALLAS (SMU) — A CT scan of the skull of a long-necked plesiosaur shows the cranial architecture of these long-extinct marine reptiles didn’t evolve much over 22 million years that they lived during the Cretaceous time.
That’s very unusual, said SMU paleontologist Louis Jacobs, one of the world's foremost authorities on prehistoric creatures and co-author of a study published in PLOS One.
“Basically, in anything except living fossils, you don't go 22 million years without evolving,” said Jacobs, professor emeritus of Earth Sciences at SMU and president of ISEM at SMU.
Elasmosaurid plesiosaurs, lookalikes of the mythical Loch Ness monster, were the largest of the long-necked plesiosaurs, growing as long as 43 feet with half of that length deriving from their small heads and very long necks. Paleontologists from SMU (Southern Methodist University), as part of an international team called Projecto PaleoAngola, based their findings on a CT scan of the 71.5 million year old skull from a species of elasmosaurid called Cardiocorax mukulu.
This detailed 3D model allowed the paleontologists to compare the well-preserved skull of C. mukulu found in Angola to that of other species of elasmosaurids. They found that C. mukulu looked nearly identical to skulls that came from much older elasmosaurids, including one found at Cedar Hill, Texas, in 1931, whose 93-million-years old remains can be found at SMU’s Shuler Museum of Paleontology.
“The skull shape, organization of muscles, and the shape and arrangement of the teeth largely reflect how an animal acquired prey,” said co-author Michael J. Polcyn, research associate and director of SMU’s Digital Earth Sciences Laboratory “The interesting aspect of Cardiocorax mukulu is that it appears that this animal’s predecessors adopted a particular feeding style early in their evolutionary history, and then maintained the same basic skull structure for the next 22 million years”
It will take more research to pinpoint why elasmosaurids might have been different from other reptiles in their evolutionary journey.
Elasmosaurids lived during the Cretaceous Period, which spanned from 145 million years ago to 66 million years ago. They were predators, thriving on fish and other marine life. Projecto PaleoAngola paleontologists first discovered C. mukulu in Angola in 2015.
The lead author of the CT scan study is Miguel P. Marx, who will be starting a Ph.D. program at Lund University in Sweden later this month and was a researcher in SMU’s Earth Science department during this study. Other co-authors include Jacobs and Polcyn of SMU.; Octávio Mateus of Universidade Nova de Lisboa and Museu da Lourinhã, Portugal; Anne S. Schulp of the Naturalis Biodiversity Center and Utrecht University in the Netherlands; and A. Olímpio Gonçalves of the Universidade Agostinho Neto in Angola.
Skull found in the same area that yielded Smithsonian Museum exhibit
Mateus found the nearly complete cranium and jaw of C. mukulu, along with 12 associated teeth and other fossilized parts of the reptile’s body in Bentiaba, Angola in 2017. That area is on the coast of Angola that Jacobs has called a “museum in the ground,” because so many fossils have been found in the rocks there.
Many of those fossils are currently on display at the Smithsonian’s National Museum of Natural History. The museum’s “Sea Monsters Unearthed” exhibit, co-produced with SMU, features large marine reptiles from the Cretaceous Period — mosasaurs, turtles, and plesiosaurs.
Jacobs and Polcyn forged the Projecto PaleoAngola partnership with collaborators in Angola, Portugal, and the Netherlands to explore and excavate Angola’s rich fossil history and began laying the groundwork for returning the fossils to the West African nation. Back in Dallas, Jacobs, Polcyn, and research associate Diana Vineyard went to work over a period of 13 years with a small army of SMU students to prepare the fossils excavated by Projecto PaleoAngola.
Like the Smithsonian exhibit, the discovery of the Cardiocorax mukulu remains were the result of that collaboration.
CT scan shows jaws and teeth of elasmosaurids didn’t evolve much
Marx’s computed tomography (CT) scan of the skull was designed to reveal parts of the skull that are otherwise difficult to see, such as the braincase. Only part of the skull was actually freed from the Angolan rock in which it was discovered because elasmosaurids skulls are so fragile. So the CT scan was taken largely through the rock that preserved the specimen.
However, “the good resolution of the resulting CT images allowed me to discriminate between the bone, the rock matrix, and the plaster jacket the skull was protected in,” Marx said. “Thus, I could build a 3D model of the skull and be able to study the fragile parts of it, such as the braincase and palate, without touching it.”
The team’s conclusions about the cranial anatomy of C. mukulu were drawn from comparisons to the skull of Libonectes morgani, a much older elasmosaurid housed at SMU.
“The skull of L. morgani at SMU is so complete that the sutures between different bones can clearly be delineated,” he said. “The skull of Libonectes morgani worked as a guide for me when making the skull model of Cardiocorax mukulu. This made the process of building the model much faster.”
Marx and the PaleoAngola team also compared the 3D imaging to the skulls of Styxosaurus snowii and Thalassomedon haningtoni – all elasmosaurids from different time periods.
The similarity between the jaws, teeth and other skull anatomy of C. mukulu and its predecessors was a surprising discovery, Marx said.
For example, the skull of Cardiocorax mukulu and Libonectes morgani both exhibit a tall dorsal ramus of the maxilla, and the organization of the skull bones around the orbits is identical, Marx said. The skulls of these two species only differed in a couple of key aspects, including a slightly different number of teeth in the upper and lower tooth rows, the location of the premaxillary-parietal suture, and the presence or absence of the pterygoids contacting each other beneath the basioccipital bone.
“It appears that the skull of elasmosaurids did not undergo significant evolutionary change throughout their history, which is very cool,” Marx said.
###
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JOURNAL
PLoS ONE
METHOD OF RESEARCH
Imaging analysis
SUBJECT OF RESEARCH
Animals
ARTICLE TITLE
The cranial anatomy and relationships of Cardiocorax mukulu (Plesiosauria: Elasmosauridae) from Bentiaba, Angola
ARTICLE PUBLICATION DATE
17-Aug-2021
COI STATEMENT
No conflict for the researchers.
How the first roots developed more than 400 million years ago
Peer-Reviewed PublicationIMAGE: 3D RECONSTRUCTION OF ASTEROXYLON MACKIEI MADE FROM DIGITALLY RE-ASSEMBLING THIN SLICES OF ROCK. THE RECONSTRUCTION SHOWS THE HIGHLY BRANCHED LEAFY SHOOT IN GREEN AND THE ROOTING SYSTEM IN BLUE AND PURPLE. 3D SCALE BAR 1 X 0.1 X 0.1 CM. IMAGE TAKEN BY DR SANDY HETHERINGTON. view more
CREDIT: SANDY HETHERINGTON
A plant fossil from a geological formation in Scotland sheds light on the development of the earliest known form of roots. A team led by researchers at GMI – the Gregor Mendel Institute of Molecular Plant Biology of the Austrian Academy of Sciences, the University of Edinburgh and the University of Oxford realise the first 3D reconstruction of a Devonian plant based exclusively on fossil evidence. The findings demonstrate that the appearance of different axis types at branching points resulted in the evolution complexity soon after land plants evolved sometime before 400 million years ago. The results are published in eLife.
New research demonstrates how the oldest known root axed developed more than 400 million years ago. The evolution of roots at this time was a dramatic event that impacted our planet and atmosphere and resulted in transformative ecological and climate change.
The first evidence-based 3D reconstruction of the fossil Asteroxylon mackiei, the most structurally complex plant from the Rhynie chert has shown how roots and other types of axes developed in this ancient plant. The fossil is preserved in chert (a type of flint) found near village of Rhynie in Aberdeenshire, Scotland. The specimens are exceptionally well-preserved in the 407-million-year-old rocks from the Early Devonian period.
The extinct genus Asteroxylon belongs to the group of plants called the lycophytes, a class that also comprises living representatives such as isoetes and selaginella. The reconstruction has allowed researchers, for the first time, to glean both anatomical and developmental information of this mysterious fossil. This is of particular significance because previous interpretations of the structure of this fossil plant were based to a large extent on comparisons of fragmentary images with extant plants.
CAPTION
Artist's reconstruction of what Asteroxylon mackiei would have looked like in life. Each leafy shoot is roughly 1 cm in diameter. Illustrations by Matt Humpage (https://twitter.com/Matt_Humpage).
CREDIT
Matt Humpage
CAPTION
Thin slice of the 407 million-year-old Rhynie chert mounted on a glass slide showing the amazing preservation of fossil plants preserved within. Specimen number 4178 in the palaeobotanical collection at the University of Münster, Germany. Each interval on the scale bar is 1 mm. Image taken by Dr Sandy Hetherington.
CREDIT
Sandy Hetherington
The reconstruction demonstrates that these plants developed roots in an entirely different way than extant plants develop roots today. The rooting axes of A. mackiei are the earliest known types of plant roots. “These are the oldest known structures that resemble modern roots and now we know how they formed. They developed when a shoot-like axis formed a fork where one prong maintained its shoot identity and the second developed root identity,” says Dolan. This mechanism of branching, called “dichotomous branching”, is known in living plants within tissues that share structural identity. However, as Dolan stresses: “No roots develop in this way in living plants, demonstrating that this mechanism of root formation is now extinct”. Their findings demonstrate how a now extinct rooting system developed during the evolution of the first complex land plant.
“100 Years after the discovery of the fossils in Rhynie, our reconstruction demonstrates what these enigmatic plants really looked like! The reconstruction also demonstrates how the roots formed” exclaims GMI group leader Liam Dolan, co-corresponding author on the work. Understanding the structure and evolution of these plants from the Early Devonian period provides us with an insight into events at a key time in Earth history just after plants colonised the dry surfaces of the continents as they began to spread – radiate – across the land.
“Their evolution, radiation and spread across all continents had a dramatic impact on the Earth system. Plant roots reduced atmospheric CO2 levels, stabilized the soil and revolutionised water circulation across the surfaces of continents,” states first author and co-corresponding author Alexander (Sandy) J. Hetherington, group leader at the University of Edinburgh. At the root of the environmental and ecological impact of plant evolution are the plant roots themselves!
Hetherington highlighted how his research was enabled by fossils that were collected by generations of palaeontologists that are housed in many different museums and universities. “The answers to so many of the key questions of evolution are lying in shelves in these institutions” said the scientist who is now based at the University of Edinburgh. “Using digital 3D techniques, it is possible for the first time to visualise the complex body plan of A. mackiei allowing us to discover how these enigmatic plants developed. It was brilliant to finally see details that had previously been hidden.”
CAPTION
View over the village of Rhynie in Aberdeenshire, Scotland. The fossil deposit known as the Rhynie chert is named after the village of Rhynie were it was first discovered just over a century ago. Photo taken by Dr Sandy Hetherington.
CREDIT
Sandy Hetherington
Original Publication:
Hetherington A. J. et al., “An evidence-based 3D reconstruction of Asteroxylon mackiei the most complex plant preserved from the Rhynie chert”. eLife 2021. https://doi.org/10.7554/eLife.69447
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
An evidence-based 3D reconstruction of Asteroxylon mackiei, the most complex plant preserved from the Rhynie chert
ARTICLE PUBLICATION DATE
23-Aug-2021
Evolutionary ‘time travel’ reveals enzyme’s origins, possible future designs
IMAGE: TRIMERIC STRUCTURE OF AN ANCIENT ENZYME FROM ODIN ARCHAEA, WITH SUBSTRATE MOLECULES SHOWN IN GREEN. view more
CREDIT: MAGNUS WOLF-WATZ
ATLANTA, Aug. 25, 2021 — “The distinction between the past, present and future is only a stubbornly persistent illusion,” Albert Einstein wrote. Perhaps this is nowhere more evident than in protein evolution, where past and present versions of the same enzyme exist in different species today, with implications for future enzyme design. Now, researchers have used evolutionary “time travel” to learn how an enzyme evolved over time, from one of Earth’s most ancient organisms to modern-day humans.
The researchers will present their results today at the fall meeting of the American Chemical Society (ACS). ACS Fall 2021 is a hybrid meeting being held virtually and in-person Aug. 22-26, and on-demand content will be available Aug. 30-Sept. 30. The meeting features more than 7,000 presentations on a wide range of science topics.
“If a person lives in present-day Rome, they might want to learn about ancient Rome to better understand who they are,” says Magnus Wolf-Watz, Ph.D., the project’s principal investigator. “In the same way, we can look backward in time at more ancient forms of enzymes to understand how the proteins are working today and how we might engineer new versions in the future.”
Wolf-Watz, who is at Umeå University in Sweden, looked back some 2 to 3 billion years to primitive organisms known as archaea. These single-celled life forms, which still exist today, have characteristics of both prokaryotes (bacteria, which lack a cell nucleus) and eukaryotes (organisms like plants, animals and fungi that have a nucleus in their cells). A branch of archaea known as the Asgard phylum, discovered in 2015, comprises the closest known ancestors to eukaryotic cells. Four types of Asgard archaea have been identified, including Odin archaea, found in hydrothermal vents deep in the Atlantic Ocean.
Odin archaea have an enzyme called adenylate kinase (AK), which is also found in prokaryotes and eukaryotes. Wolf-Watz previously studied two human types of this enzyme, AK1 and AK3. Both are important in maintaining the energy balance in cells, but AK1 is in the cytoplasm, where it transfers a phosphate group from adenosine triphosphate (ATP, the main energy carrier in cells) to adenosine monophosphate (AMP). In contrast, AK3 resides within mitochondria, where it transfers a phosphate group from guanosine triphosphate (GTP, a molecule similar to ATP but with distinct roles) to AMP.
Wolf-Watz’s team used X-ray crystallization and nuclear magnetic resonance spectroscopy to study the structures of AK1 and AK3, finding that although the enzymes are very similar, they have a subtle difference in a short loop region that causes AK1 to prefer ATP and AK3 to prefer GTP. “Now we can take any AK enzyme, look at the structure of that loop, and predict whether it’s going to use ATP or GTP,” Wolf-Watz says. The next step was to examine a more ancient version of an AK enzyme –– from Odin archaea –– to learn how AK1 and AK3 evolved to prefer different nucleotide substrates.
The researchers purified the archaea AK and determined its structure. They found that the loop important for discriminating ATP and GTP is much longer in the archaeal enzyme, and it has chemical groups that can bind either nucleotide. “What we found is an early ancestor of the human AKs that contains two capacities –– it can use both ATP and GTP,” Wolf-Watz says. “During the course of evolution, it became specialized to become specific for one or the other, depending on the cellular compartment where it resides.” The archaea AK can actually use all naturally occurring nucleotide triphosphates (NTPs). “We’ve discovered a universal NTP binding motif that could be a building block for the future design of novel enzymes,” Wolf-Watz says.
The archaeal AK contains three copies of the enzyme (known as a trimer) that bind to each other through a helical structure. In human AKs, a mutation in this region makes the enzyme copies unable to stick to each other. The human enzymes, which function independently, are almost 1,000-fold more active. The trimer could have been more stable in the extreme environment of hydrothermal vents, but the human enzymes might have traded this thermostability for higher activity, which is important in a cooler environment, Wolf-Watz says.
Next, the researchers want to engineer novel enzymes that could be useful in organic synthesis or drug development. They also want to examine other enzymes from Odin archaea and study how they might have evolved over the eons. “We studied one enzyme and made this fantastic discovery,” Wolf-Watz says. “Of course, there’s more to find. It’s like we’re digging through a treasure chest.”
A recorded media briefing on this topic will be posted Wednesday, Aug. 25 at 9 a.m. Eastern time at www.acs.org/acsfall2021briefings.
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The researchers acknowledge support and funding from the Swedish Research Council, the Kempe Foundations and the Carl Trygger Foundation.
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Title
Evolutionary origins of enzymatic specificity and dynamics
Abstract
"Time-travel” is a concept that carry significant potential to decode previously unknown aspects of protein function. Archeological “backwards-looking” can be performed with evolutionary analysis, while a glimpse into the future can be obtained from directed evolution and enzyme design. Here, I will present our evolutionary approach that is centered on the enzyme adenylate kinase (AK) isolated from organisms from all three kingdoms of life; bacteria, archaea and eukarya. For the archaeal organism we have selected Odinarchaeota, a member of the recently discovered Asgard archaeal family that is believed to be the closest evolutionary ancestor to modern eukaryotic organisms. Comparative structural and functional analysis between AK from these three domains has enabled us to uncover novel principles in enzymatic catalysis. I will specifically present findings for the evolutionary origin of nucleoside triphosphate (NTP) specificity, but also for the evolutionary origin of large-scale conformational dynamics. The findings have been possible through an integrative structural biology approach where we utilize state-of-the-art quantitative 19F NMR spectroscopy (relaxation dispersions) for determination of microscopic rate-constants for conformational dynamics of a large (69 kDa) assembly.
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