Excavated dolmen in Sweden one of the oldest in Scandinavia

The first analysis results now confirm that the grave in Tiarp is one of the oldest stone burial chambers in Sweden. "It's an early grave which dates to the Early Neolithic period, about 3500 BCE," says archaeologist Karl-Göran Sjögren. The researchers also noted that some parts of the people buried in the grave are missing, such as skulls and thigh bones, posing intriguing questions for archaeologists.

Last summer, archaeologists from Gothenburg University and Kiel University excavated a dolmen, a stone burial chamber, in Tiarp near Falköping in Sweden.

The archaeologists judge that the grave has remained untouched since the Stone Age.

However, the odd thing is that parts of the skeletons of the people buried are missing.

Skulls and large bones are missing and may have been removed from the grave.

Now that the researchers have examined the material from the grave, they have found that it contains bones from hands and feet, fragments of rib bones and teeth.

But skulls and larger bones such as thigh and arm bones are very few.

"This differs from what we usually see in megalith graves, i.e. stone burial chambers from the Neolithic period," Karl-Göran Sjögren explains.

"Usually, the bones that are missing are smaller bones from feet and hands."

Torbjörn Ahlström, Professor of Osteology at Lund University, studied the bone finds.

His conclusion is that the bones come from at least twelve people, including infants and the elderly.

But the archaeologists don't yet know why they died.

"We haven't seen any injuries on the people buried so we don't think violence is involved. But we are continuing to study their DNA and that will show whether they had any diseases," says Karl-Göran Sjögren.

Falköping has long been known for its many passage graves dating from a somewhat later period, approximately 3300 BCE.

Agriculture reached Falbygden in about 4000 BCE, i.e. about 500 years before the grave in Tiarp was built.

In all likelihood, the people buried in the dolmen were farmers.

"They lived by growing grain and keeping animals and they consumed dairy products," says Karl-Göran Sjögren.

Are the people buried in the grave related?

A number of samples were taken at the excavation last summer, including DNA from the skeletal remains.

"The preliminary DNA results show that the DNA in the bones is well preserved. This means we will be able to reconstruct the family relationships between the people in the grave and we are working on that now," says Karl-Göran Sjögren.

Falbygden is known for its many traces of people from the Stone Age.

There are more than 250 passage graves here, large graves built of blocks of stone.

"But this dolmen is older. It's about 200 to 150 years older than the passage graves, making it one of the oldest stone burial chambers in Sweden and across the whole of Scandinavia," says Karl-Göran Sjögren.

There is another thing that makes the grave unique.

"It's the way it is constructed. There's a little niche at each end. This is unique for graves in Falbygden," says Karl-Göran Sjögren.

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How did humans learn to walk? New evolutionary study offers an earful

Humans and our closest relatives, living apes, display a remarkable diversity of types of locomotion -- from walking upright on two legs to climbing in trees and walking using all four limbs.

While scientists have long been intrigued by the question of how humans' bipedal stance and movement evolved from a quadrupedal ancestor, neither past studies nor fossil records have permitted the reconstruction of a clear and definitive history of the early evolutionary stages that led to human bipedalism.

However, a new study, which centers on recently discovered evidence from skulls of a 6-million-year-old fossil ape, Lufengpithecus, offers important clues about the origins of bipedal locomotion courtesy of a novel method: analyzing its bony inner ear region using three-dimensional CT-scanning.

"The semicircular canals, located in the skull between our brains and the external ear, are critical to providing our sense of balance and position when we move, and they provide a fundamental component of our locomotion that most people are probably unaware of," explains Yinan Zhang, a doctoral student at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences (IVPP) and the lead author of the paper, which appears in the journal the Innovation. "The size and shape of the semicircular canals correlate with how mammals, including apes and humans, move around their environment. Using modern imaging technologies, we were able to visualize the internal structure of fossil skulls and study the anatomical details of the semicircular canals to reveal how extinct mammals moved."

"Our study points to a three-step evolution of human bipedalism," adds Terry Harrison, a New York University anthropologist and one of the paper's co-authors.

"First, the earliest apes moved in the trees in a style that was most similar to aspects of the way that gibbons in Asia do today. Second, the last common ancestor of apes and humans was similar in its locomotor repertoire to Lufengpithecus, using a combination of climbing and clambering, forelimb suspension, arboreal bipedalism, and terrestrial quadrupedalism. It is from this broad ancestral locomotor repertoire that human bipedalism evolved."

Most studies of the evolution of ape locomotion had focused on comparisons of the bones of the limbs, shoulders, pelvis, and spine and the way they are associated with the different types of locomotor behaviors seen in living apes and humans.

However, the diversity of locomotor behaviors in living apes and the incompleteness of the fossil record have hampered the development of a clear picture of human bipedalism's origins.

The skulls of Lufengpithecus -- originally discovered in China's Yunnan Province in the early 1980s -- have given scientists the opportunity to address, in new ways, unanswered questions about the evolution of locomotion.

However, the heavy compression and distortion of the skulls obscured the bony ear region and led previous researchers to believe that the delicate semicircular canals were not preserved.

To better explore this region, Zhang, Ni and Harrison, along with other researchers at IVPP and the Yunnan Institute of Cultural Relics and Archaeology (YICRA), used three dimensional scanning technologies to illuminate these portions of the skulls to create a virtual reconstruction of the inner ear's bony canals.

They then compared these scans to those collected from other living and fossil apes and humans from Asia, Europe, and Africa.

"Our analyses show that early apes shared a locomotor repertoire that was ancestral to human bipedalism," explains IVPP Professor Xijun Ni, who led the project.

"It appears that the inner ear provides a unique record of the evolutionary history of ape locomotion that offers an invaluable alternative to the study of the postcranial skeleton."

"Most fossil apes and their inferred ancestors are intermediate in locomotor mode between gibbons and African apes," adds Ni. "Later, the human lineage diverged from the great apes with the acquisition of bipedalism, as seen in Australopithecus, an early human relative from Africa."

By studying the rate of evolutionary change in the bony labyrinth, the international team proposed that climate change may have been an important environmental catalyst in promoting the locomotor diversification of apes and humans.

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Prehistoric fish fills 100 million year gap in evolution of the skull

A 455-million-year-old fossil fish provides a new perspective on how vertebrates evolved to protect their brains, a study has found.

In a paper published in Nature today (Wednesday 20th September), researchers from the University of Birmingham, Naturalis Biodiversity Centre in Leiden, Netherlands; and the Natural History Museum have pieced together the skull of Eriptychius americanus.

The research, funded by the Leverhulme Trust, suggests that the ancient jawless fish found in ancient deposits in Colorado, USA has a skull unlike that of any previously seen, and fills a gap currently spanning 100 million years in the evolutionary history of the vertebrate skull.

Using computed tomography, a form of x-ray technique, scientists recreated a detailed 3D representation of the skull of Eriptychius and is the first time that such a comprehensive recreation has been done on the specimen which was collected in the 1940s, originally described in the 1960s and is housed in the Field Museum of Natural History, Chicago.

This ancient fish had separated, independent cartilages encasing the brain, rather than the solid bone or cartilage structure of jawless and jawed fish that followed it.

While later specieshave a fully bound cage of cartilage that holds the brain, these results suggest that the early evolution of structures to separate the brain from other parts of the head may have begun with Eriptychius.

Dr Ivan Sansom, Senior Lecturer in Palaeobiology at the University of Birmingham and senior author of the paper said:

"These are tremendously exciting results that may reveal the early evolutionary history of how primitive vertebrates protected their brains. Eriptychius americanus appears to be the first evidence for a series of cartilages separating the brain from the rest of the head. This study emphasises the importance of museum collections and the application of new techniques in studying them."

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Face of Anglo-Saxon teen VIP revealed with new evidence about her life

The face of a 16-year-old woman buried near Cambridge (UK) in the 7th century with an incredibly rare gold and garnet cross (the 'Trumpington Cross') has been reconstructed following analysis of her skull. The striking image is going on public display for the first time on 21st June,* with new scientific evidence showing that she moved to England from Central Europe as a young girl, leading to an intriguing change in her diet.

Forensic artist Hew Morrison created the likeness using measurements of the woman's skull and tissue depth data for Caucasian females. Without DNA analysis, Morrison could not be sure of her precise eye and hair colour, but the image offers a strong indication of her appearance shortly before she died.

Hew Morrison said: "It was interesting to see her face developing. Her left eye was slightly lower, about half a centimetre, than her right eye. This would have been quite noticeable in life."

New "you are what you eat" isotopic analysis of the young woman's bones and teeth conducted by bioarchaeologists Dr Sam Leggett and Dr Alice Rose, and archaeologist Dr Emma Brownlee, during PhD research at the University of Cambridge also reveals that she moved to England from somewhere near the Alps, perhaps southern Germany, sometime after she turned 7 years old.

Leggett and Rose also found that once the girl had arrived in England, the proportion of protein in her diet decreased by a small but significant amount. This change occurred close to the end of her young life, showing that the period between her migration and burial near Cambridge was tragically short.

Dr Leggett, now at the University of Edinburgh, said: "She was quite a young girl when she moved, likely from part of southern Germany, close to the Alps, to a very flat part of England. She was probably quite unwell and she travelled a long way to somewhere completely unfamiliar -- even the food was different. It must have been scary."

Previous analysis indicated that the young woman had suffered from illness but her cause of death remains unknown. She was buried in a remarkable way -- lying on a carved wooden bed wearing the cross, gold pins (also on display) and fine clothing.

Hers is one of only 18 bed burials ever uncovered in the UK. Her ornate cross, combining gold and garnets (third quarter of the 7th century), is one of only five of its kind ever found in Britain and identifies her as one of England's earliest converts to Christianity and as a member of the aristocracy if not royalty. The best known example of such a cross was found in the coffin of St Cuthbert.

In 597 AD, the pope dispatched St Augustine to England on a mission to convert the pagan Anglo-Saxon kings, a process which continued for many decades.

Dr Leggett said: "She must have known that she was important and she had to carry that on her shoulders. Her isotopic results match those of two other women who were similarly buried on beds in this period in Cambridgeshire.

"So it seems that she was part of an elite group of women who probably travelled from mainland Europe, most likely Germany, in the 7th century, but they remain a bit of a mystery. Were they political brides or perhaps brides of Christ? The fact that her diet changed once she arrived in England suggests that her lifestyle may have changed quite significantly."

Dr Sam Lucy, a specialist in Anglo-Saxon burial from Newnham College, Cambridge, who published the Anglo-Saxon excavations at Trumpington**, said:

"These are intriguing findings, and it is wonderful to see this collaborative research adding to our knowledge of this period. Combining the new isotopic results with Emma Brownlee's research into European bed burials really does seem to suggest the movement of a small group of young elite women from a mountainous area in continental Europe to the Cambridge region in the third quarter of the seventh century.

"Southern Germany is a distinct possibility owing to the bed burial tradition known there. Given the increasingly certain association between bed burial, such cross-shaped jewellery, and early Anglo-Saxon Christianity, it is possible that their movement related to pan-European networks of elite women who were heavily involved in the early Church."

Dr Jody Joy, the exhibition's co-curator, said: "The story of this young woman goes to the very heart of what our exhibition is all about -- new research making visible the lives of people at pivotal moments of Cambridgeshire's history. MAA holds one of Britain's most important collections of Early Medieval archaeology and the Trumpington bed burial is so important. It looks like it still has much more to teach us."

In the exhibition, the 'Trumpington Cross' will be displayed together with the delicate gold and garnet pins connected by a gold chain, which were found near the teenager's neck. These pins probably secured a long veil to an outer garment of fine linen. The pins would have caught the light as she moved.The burial bed's decorativeheadboard will also be exhibited.

* The image and artefacts from the mysterious woman's burial -- discovered in 2012 by the Cambridge Archaeological Unit at Trumpington Meadows on Cambridge's southern limits -- including her famous cross will be unveiled in a major new exhibition at Cambridge's Museum of Archaeology and Anthropology (MAA). 'Beneath Our Feet: Archaeology of the Cambridge Region' will run from 21st June to 14th April 2024.

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True giant wombat gives Diprotodon podium a wobble

If you thought Australia was home to only one ancient 'giant wombat', think again.

While the Diprotodon -- the extinct megafauna species that is distantly related to wombats but was the size of a small car -- is commonly (but incorrectly) thought of as Australia's 'giant wombat', researchers from Griffith University have shed light on a large species that does belong in the modern-day wombat family.

The complete skull of this true fossil giant wombat, found in a Rockhampton cave in Queensland and estimated to be around 80,000 years old, has been described for the first time by a team led by Associate Professor Julien Louys from Griffith's Australian Research Centre for Human Evolution.

Associate Professor Louys said the discovery provided unprecedented insights into the biology and appearance of these previously little known 'gentle giants'.

"The extinct megafauna of Australia never ceases to amaze and intrigue not just Australians, but people all over the world," he said.

"Although one of the most charismatic of the giant mammals to go extinct, Diprotodon is commonly referred to as a 'giant wombat'. But this is incorrect as Diprotodon belongs to an entirely different family -- equivalent to saying a hippo is just a giant pig.

"There were however, true giant wombats. These have traditionally been poorly known, but the discovery of the most complete skull of one of these giants, Ramsayia, has provided us with an opportunity to reconstruct what this creature looked like, where and when it lived, and how the evolution of giant wombats took place in Australia."

The cranium and mandible of the Ramsayia magna fossil was discovered from the rear of the front chamber of Lower Johansons Cave in Rockhampton in the early 2000s, but it was only through subsequent excavations and analysis by Associate Professor Louys's team that is was confirmed as belonging to a previously described but very poorly known species.

Extinct giant wombats of the family Vombatidae (broadly defined as twice the size of modern wombats) are rarer than the fossil diprotodontids that are often popularly -- and incorrectly -- referred to as giant wombats.

Associate Professor Louys said this giant wombat -- Ramsayia -- had extensive cranial sinuses, which had not been previously reported for a wombat.

"This indicates that the wombat had a large, rounded skull for the attachment of specific and strong chewing muscles," he said.

"The giant wombat also possessed a 'premaxillary spine', an indication that it had a large, fleshy nose.

"In this paper, we show that all true giant wombats evolved large body sizes first, then individually became quite specialised to eat different types of grasses.

"We also dated this species as being about 80,000 years old. This is the first date for this species and is much earlier than human arrival in Australia, although we still don't know exactly when or why this species became extinct."

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Study of ancient skulls sheds light on human interbreeding with Neanderthals

Research has established that there are traces of Neandertal DNA in the genome of modern humans. Now an exploratory study that assessed the facial structure of prehistoric skulls is offering new insights, and supports the hypothesis that much of this interbreeding took place in the Near East -- the region ranging from North Africa to Iraq.

"Ancient DNA caused a revolution in how we think about human evolution," says Steven Churchill, co-author of the study and a professor of evolutionary anthropology at Duke University. "We often think of evolution as branches on a tree, and researchers have spent a lot of time trying to trace back the path that led to us, Homo sapiens. But we're now beginning to understand that it isn't a tree -- it's more like a series of streams that converge and diverge at multiple points."

"Our work here gives us a deeper understanding of where those streams came together," says Ann Ross, corresponding author of the study and a professor of biological sciences at North Carolina State University.

"The picture is really complicated," Churchill says. "We know there was interbreeding. Modern Asian populations seem to have more Neandertal DNA than modern European populations, which is weird -- because Neandertals lived in what is now Europe. That has suggested that Neandertals interbred with what are now modern humans as our prehistoric ancestors left Africa, but before spreading to Asia. Our goal with this study was to see what additional light we could shed on this by assessing the facial structure of prehistoric humans and Neandertals."

"By evaluating facial morphology, we can trace how populations moved and interacted over time," Ross explains. "And the evidence shows us that the Near East was an important crossroads, both geographically and in the context of human evolution."

For this study, the researchers collected data on craniofacial morphology from the published literature. This ultimately resulted in a data set including 13 Neandertals, 233 prehistoric Homo sapiens, and 83 modern humans.

The researchers focused on standard craniofacial measurements, which are reproducible, and used those measurements to assess the size and shape of key facial structures. This then allowed the researchers to do an in-depth analysis to determine whether a given human population was likely to have interbred with Neandertal populations, as well as the extent of that likely interbreeding.

"Neandertals had big faces," Churchill says. "But size alone doesn't establish any genetic link between a human population and Neandertal populations. Our work here involved a more robust analysis of the facial structures."

The researchers also accounted for environmental variables that are associated with changes in human facial characteristics, to determine the likelihood that connections they established between Neandertal and human populations were the result of interbreeding rather than other factors.

"We found that the facial characteristics we focused on were not strongly influenced by climate, which made it easier to identify likely genetic influences," Ross says. "We also found that facial shape was a more useful variable for tracking the influence of Neandertal interbreeding in human populations over time. Neandertals were just bigger than humans. Over time, the size of human faces became smaller, generations after they had bred with Neandertals. But the actual shape of some facial features retained evidence of interbreeding with Neandertals."

"This was an exploratory study," Churchill says. "And, honestly, I wasn't sure this approach would actually work -- we have a relatively small sample size, and we didn't have as much data on facial structures as we would have liked. But, ultimately, the results we got are really compelling.

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Earth's first giant

The two-meter skull of a newly discovered species of giant ichthyosaur, the earliest known, is shedding new light on the marine reptiles' rapid growth into behemoths of the Dinosaurian oceans, and helping us better understand the journey of modern cetaceans (whales and dolphins) to becoming the largest animals to ever inhabit the Earth.

While dinosaurs ruled the land, ichthyosaurs and other aquatic reptiles (that were emphatically not dinosaurs) ruled the waves, reaching similarly gargantuan sizes and species diversity. Evolving fins and hydrodynamic body-shapes seen in both fish and whales, ichthyosaurs swam the ancient oceans for nearly the entirety of the Age of Dinosaurs.

"Ichthyosaurs derive from an as yet unknown group of land-living reptiles and were air-breathing themselves," says lead author Dr. Martin Sander, paleontologist at the University of Bonn and Research Associate with the Dinosaur Institute at the Natural History Museum of Los Angeles County (NHM). "From the first skeleton discoveries in southern England and Germany over 250 years ago, these 'fish-saurians' were among the first large fossil reptiles known to science, long before the dinosaurs, and they have captured the popular imagination ever since."

Excavated from a rock unit called the Fossil Hill Member in the Augusta Mountains of Nevada, the well-preserved skull, along with part of the backbone, shoulder, and forefin, date back to the Middle Triassic (247.2-237 million years ago), representing the earliest case of an ichthyosaur reaching epic proportions. As big as a large sperm whale at more than 17 meters (55.78 feet) long, the newly named Cymbospondylus youngorum is the largest animal yet discovered from that time period, on land or in the sea. In fact, it was the first giant creature to ever inhabit the Earth that we know of.

"The importance of the find was not immediately apparent," notes Dr. Sander, "because only a few vertebrae were exposed on the side of the canyon. However, the anatomy of the vertebrae suggested that the front end of the animal might still be hidden in the rocks. Then, one cold September day in 2011, the crew needed a warm-up and tested this suggestion by excavation, finding the skull, forelimbs, and chest region."

The new name for the species, C. youngorum, honors a happy coincidence, the sponsoring of the fieldwork by Great Basin Brewery of Reno, owned and operated by Tom and Bonda Young, the inventors of the locally famous Icky beer which features an ichthyosaur on its label.

In other mountain ranges of Nevada, paleontologists have been recovering fossils from the Fossil Hill Member's limestone, shale, and siltstone since 1902, opening a window into the Triassic. The mountains connect our present to ancient oceans and have produced many species of ammonites, shelled ancestors of modern cephalopods like cuttlefish and octopuses, as well as marine reptiles. All these animal specimens are collectively known as the Fossil Hill Fauna, representing many of C. youngorum's prey and competitors.

C. youngorum stalked the oceans some 246 million years ago, or only about three million years after the first ichthyosaurs got their fins wet, an amazingly short time to get this big. The elongated snout and conical teeth suggest that C. youngorum preyed on squid and fish, but its size meant that it could have hunted smaller and juvenile marine reptiles as well.

The giant predator probably had some hefty competition. Through sophisticated computational modeling, the authors examined the likely energy running through the Fossil Hill Fauna's food web, recreating the ancient environment through data, finding that marine food webs were able to support a few more colossal meat-eating ichthyosaurs. Ichthyosaurs of different sizes and survival strategies proliferated, comparable to modern cetaceans' -- from relatively small dolphins to massive filter-feeding baleen whales, and giant squid-hunting sperm whales.

Co-author and ecological modeler Dr. Eva Maria Griebeler from the University of Mainz in Germany notes, "due to their large size and resulting energy demands, the densities of the largest ichthyosaurs from the Fossil Hill Fauna including C. youngourum must have been substantially lower than suggested by our field census. The ecological functioning of this food web from ecological modeling was very exciting as modern highly productive primary producers were absent in Mesozoic food webs and were an important driver in the size evolution of whales."

Whales and ichthyosaurs share more than a size range. They have similar body plans, and both initially arose after mass extinctions. These similarities make them scientifically valuable for comparative study. The authors combined computer modeling and traditional paleontology to study how these marine animals reached record-setting sizes independently.

"One rather unique aspect of this project is the integrative nature of our approach. We first had to describe the anatomy of the giant skull in detail and determine how this animal is related to other ichthyosaurs," says senior author Dr. Lars Schmitz, Associate Professor of Biology at Scripps College and Dinosaur Institute Research Associate. "We did not stop there, as we wanted to understand the significance of the new discovery in the context of the large-scale evolutionary pattern of ichthyosaur and whale body sizes, and how the fossil ecosystem of the Fossil Hill Fauna may have functioned. Both the evolutionary and ecological analyses required a substantial amount of computation, ultimately leading to a confluence of modeling with traditional paleontology."

They found that while both cetaceans and ichthyosaurs evolved very large body sizes, their respective evolutionary trajectories toward gigantism were different. Ichthyosaurs had an initial boom in size, becoming giants early on in their evolutionary history, while whales took much longer to reach the outer limits of huge. They found a connection between large size and raptorial hunting -- think of a sperm whale diving down to hunt giant squid -- and a connection between large size and a loss of teeth -- think of the giant filter-feeding whales that are the largest animals ever to live on Earth.

Ichthyosaurs' initial foray into gigantism was likely thanks to the boom in ammonites and jawless eel-like conodonts filling the ecological void following the end-Permian mass extinction. While their evolutionary routes were different, both whales and ichthyosaurs relied on exploiting niches in the food chain to make it really big.

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Golden ratio observed in human skulls

The Golden Ratio, described by Leonardo da Vinci and Luca Pacioli as the Divine Proportion, is an infinite number often found in nature, art and mathematics. It's a pattern in pinecones, seashells, galaxies and hurricanes.

In a new study investigating whether skull shape follows the Golden Ratio (1.618 ... ), Johns Hopkins researchers compared 100 human skulls to 70 skulls from six other animals, and found that the human skull dimensions followed the Golden Ratio. The skulls of less related species such as dogs, two kinds of monkeys, rabbits, lions and tigers, however, diverged from this ratio.

"The other mammals we surveyed actually have unique ratios that approach the Golden Ratio with increased species sophistication," says Rafael Tamargo, M.D., professor of neurosurgery at the Johns Hopkins University School of Medicine. "We believe that this finding may have important anthropological and evolutionary implications."

The researchers published their findings in the September issue of The Journal of Craniofacial Surgery.

The Golden Ratio can be calculated by taking a line and dividing it into two unequal parts, with the length of the longer part divided by the shorter length being equal to the entire length divided by the longer part. Tamargo's interest in history and anatomy led him in 2010 to publish on finding a human brain and spinal cord in the depiction of God in Michelangelo's Sistine Chapel painting.

Jonathan Pindrik, now a pediatric neurosurgeon at Nationwide Children's Hospital in Ohio, also contributed to the study.

From Science Daily

Coelacanth reveals new insights into skull evolution

This is the overall anterolateral view of the skull of the Coelacanth's foetus. The brain is in yellow.

An international team of researchers presents the first observations of the development of the skull and brain in the living coelacanth Latimeria chalumnae. Their study, published in Nature, provides new insights into the biology of this iconic animal and the evolution of the vertebrate skull.

The coelacanth Latimeria is a marine fish closely related to tetrapods, four-limbed vertebrates including amphibians, mammals and reptiles. Coelacanths were thought to have been extinct for 70 million years, until the accidental capture of a living specimen by a South African fisherman in 1938. Eighty years after its discovery, Latimeria remains of scientific interest for understanding the origin of tetrapods and the evolution of their closest fossil relatives -- the lobe-finned fishes.

One of the most unusual features of Latimeria is its hinged braincase, which is otherwise only found in many fossil lobe-finned fishes from the Devonian period (410-360 million years ago). The braincase of Latimeria is completely split into an anterior and posterior portion by a joint called the "intracranial joint." In addition, the brain lies far at the rear of the braincase and takes up only 1% of the cavity housing it. This mismatch between the brain and its cavity is totally unequalled among living vertebrates. How the coelacanth skull grows and why the brain remains so small has puzzled scientists for years. To answer these questions, researchers studied specimens at different stages of cranial development from several public natural history collections.

Although many specimens of adult coelacanths are available in natural history collections, earlier life stages such as fetuses are extremely rare. Scientists hence used state-of-the-art imaging techniques to visualize the internal anatomy of the specimens without damaging them. They notably digitalized a 5 cm-long fetus, the earliest developmental stage available for Latimeria, with synchrotron X-ray microtomography at the European Synchrotron (ESRF). Over the last two decades, the ESRF has developed unique expertise in designing non-invasive techniques widely used for evolutionary biology studies.

In addition, the researchers also imaged other stages with a powerful Magnetic Resonance Imaging (MRI) scanner at the Brain and Spine Institute (Paris, France), and a conventional X-ray micro-CTscan at the Muséum national d'Histoire naturelle (Paris, France). These data were used to generate detailed 3D models, which allowed scientists to describe how the form of the skull, the brain and the notochord (a tube extending below the brain and the spinal cord in the early stages of life) changes from a fetus to an adult.

They also observed how these structures are positioned relative to each other at each stage, and compared their observations with what is known about the formation of the skull in other vertebrates.

In contrast to most other vertebrates, where the notochord is replaced by the vertebral column early in embryonic development, the notochord expands considerably in Latimeria. The dramatic enlargement of the notochord likely influences the patterning of the braincase, and might underpin the formation of the intracranial joint. The brain might also be affected by the enlargement of the notochord, as relative size dramatically decreases during development.

These results illuminate for the first time the development of the living coelacanth skull and brain, and open up new avenues for research on the evolution of the vertebrate head.

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