Stranger than friction: A force initiating life

As the potter works the spinning wheel, the friction between their hands and the soft clay helps them shape it into all kinds of forms and creations. In a fascinating parallel, sea squirt oocytes (immature egg cells) harness friction within various compartments in their interior to undergo developmental changes after conception. A study from the Heisenberg group at the Institute of Science and Technology Austria (ISTA), published in Nature Physics, now describes how this works.

The sea is full of fascinating life forms. From algae and colorful fish to marine snails and sea squirts, a completely different world reveals itself underwater.

Sea squirts or ascidians in particular are very unusual: after a free-moving larvae stage, the larva settles down, attaches to solid surfaces like rocks or corals, and develops tubes (siphons), their defining feature.

Although they look like rubbery blobs as adults, they are the most closely related invertebrate relatives to humans.

Especially at the larval stages, sea squirts are surprisingly similar to us.

Therefore, ascidians are often used as model organisms to study the early embryonic development of vertebrates to which humans belong.

"While ascidians exhibit the basic developmental and morphological features of vertebrates, they also have the cellular and genomic simplicity typical of invertebrates," explains Carl-Philipp Heisenberg, Professor at the Institute of Science and Technology Austria (ISTA). "Especially the ascidian larva is an ideal model for understanding early vertebrate development."

His research group's latest work, published in Nature Physics, now gives new insights into their development.

The findings suggest that upon fertilization of ascidian oocytes, friction forces play a crucial role in reshaping and reorganizing their insides, heralding the next steps in their developmental cascade.

Decoding oocyte transformation

Oocytes are female germ cells involved in reproduction. After successful fertilization with male sperm, animal oocytes typically undergo cytoplasmic reorganization, altering their cellular contents and components.

This process establishes the blueprint for the embryo's subsequent development.

In ascidians, for instance, this reshuffling leads to the formation of a bell-like protrusion -- a little bump or nose shape -- known as the contraction pole (CP), where essential materials gather that facilitate the embryo's maturation.

The underlying mechanism driving this process, however, has been unknown.

A group of scientists from ISTA, Université de Paris Cité, CNRS, King's College London, and Sorbonne Université set out to decipher that mystery.

For this endeavor, the Heisenberg group imported adult ascidians from the Roscoff Marine Station in France.

Almost all sea squirts are hermaphrodites, as they produce both male and female germ cells.

"In the lab, we keep them in saltwater tanks in a species-appropriate manner to obtain eggs and sperm for studying their early embryonic development," says Silvia Caballero-Mancebo, the first author of this study and previous PhD student in the Heisenberg lab.

The scientists microscopically analyzed fertilized ascidian oocytes and realized that they were following very reproducible changes in cell shape leading up to the formation of the contraction pole.

The researchers' first investigation focused on the actomyosin (cell) cortex -- a dynamic structure found beneath the cell membrane in animal cells.

Composed of actin filaments and motor proteins, it generally acts as a driver for shape changes in cells.

"We uncovered that when cells are fertilized, increased tension in the actomyosin cortex causes it to contract, leading to its movement (flow), resulting in the initial changes of the cell's shape," Caballero-Mancebo continues.

The actomyosin flows, however, stopped during the expansion of the contraction pole, suggesting that there are additional players responsible for the bump.

Friction forces impact cell reshaping

The scientists took a closer look at other cellular components that might play a role in the expansion of the contraction pole.

In doing so, they came across the myoplasm, a layer composed of intracellular organelles and molecules (related forms of which are found in many vertebrate and invertebrate eggs), positioned in the lower region of the ascidian egg cell.

"This specific layer behaves like a stretchy solid -- it changes its shape along with the oocyte during fertilization," Caballero-Mancebo explains.

During the actomyosin cortex flow, the myoplasm folds and forms many buckles due to the friction forces established between the two components.

As actomyosin movement stops, the friction forces also disappear.

"This cessation eventually leads to the expansion of the contraction pole as the multiple myoplasm buckles resolve into the well-defined bell-like-shaped bump," Caballero-Mancebo adds.

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Which came first: The reptile or the egg?

The earliest reptiles, birds and mammals may have borne live young, researchers from Nanjing University and University of Bristol have revealed.

Until now, the hard-shelled egg was thought to be the key to the success of the amniotes -- a group of vertebrates that undergo embryonic or fetal development within an amnion, a protective membrane inside the egg.

However, a fresh study of 51 fossil species and 29 living species which could be categorised as oviparous (laying hard or soft-shelled eggs) or viviparous (giving birth to live young) suggests otherwise.

The findings, published today in Nature Ecology & Evolution, show that all the great evolutionary branches of Amniota, namely Mammalia, Lepidosauria (lizards and relatives), and Archosauria (dinosaurs, crocodilians, birds) reveal viviparity and extended embryo retention in their ancestors.

Extended embryo retention (EER) is when the young are retained by the mother for a varying amount of time, likely depending on when conditions are best for survival.

While the hard-shelled egg has often been seen as one of the greatest innovations in evolution, this research implies it was EER that gave this particular group of animals the ultimate protection.

Professor Michael Benton from the Bristol's School of Earth Sciences explained: "Before the amniotes, the first tetrapods to evolve limbs from fishy fins were broadly amphibious in habits. They had to live in or near water to feed and breed, as in modern amphibians such as frogs and salamanders.

"When the amniotes came on the scene 320 million years ago, they were able to break away from the water by evolving waterproof skin and other ways to control water loss. But the amniotic egg was the key. It was said to be a 'private pond' in which the developing reptile was protected from drying out in the warm climates and enabled the Amniota to move away from the waterside and dominate terrestrial ecosystems."

Project Leader Professor Baoyu Jiang added: "This standard view has been challenged. Biologists had noticed many lizards and snakes display flexible reproductive strategy across oviparity and viviparity.

"Sometimes, closely related species show both behaviours, and it turns out that live-bearing lizards can flip back to laying eggs much more easily than had been assumed."

"Also, when we look at fossils, we find that many of them were live-bearers, including the Mesozoic marine reptiles like ichthyosaurs and plesiosaurs," said Dr Armin Elsler. "Other fossils, including a choristodere from the Cretaceous of China, described here, show the to-and-fro between oviparity and viviparity happened in other groups, not just in lizards."

Dr Joseph Keating explained: "EER is widespread among vertebrates today, where the developing young are retained by the mother for a lesser or greater span of time.

"EER is common and variable in lizards and snakes today. Their young can be released, either inside an egg or as little wrigglers, at different developmental stages, and there appears to be ecological advantages of EER, perhaps allowing the mothers to release their young when temperatures are warm enough and food supplies are rich."

Professor Benton concluded: "Our work, and that of many others in recent years, has consigned the classic 'reptile egg' model of the textbooks to the wastebasket.

"The first amniotes had evolved extended embryo retention rather than a hard-shelled egg to protect the developing embryo for a lesser or greater amount of time inside the mother, so birth could be delayed until environments become favourable.

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Researchers uncover 92 fossil nests belonging to some of India's largest dinosaurs

The discovery of more than 250 fossilized eggs reveals intimate details about the lives of titanosaurs in the Indian subcontinent, according to a study published January 18, 2022 in the open-access journal PLOS ONE by Harsha Dhiman of the University of Delhi, New Delhi and colleagues.

The Lameta Formation, located in the Narmada Valley of central India, is well-known for fossils of dinosaur skeletons and eggs of the Late Cretaceous Period. Recent work in the area uncovered 92 nesting sites containing a total of 256 fossil eggs belonging to titanosaurs, which were among the largest dinosaurs to have ever lived. Detailed examination of these nests has allowed Dhiman and colleagues to make inferences about the life habits of these dinosaurs.

The authors identified six different egg-species (oospecies), suggesting a higher diversity of titanosaurs than is represented by skeletal remains from this region. Based on the layout of the nests, the team inferred that these dinosaurs buried their eggs in shallow pits like modern-day crocodiles. Certain pathologies found in the eggs, such as a rare case of an "egg-in-egg," indicate that titanosaur sauropods had a reproductive physiology that parallels that of birds and possibly laid their eggs in a sequential manner as seen in modern birds. The presence of many nests in the same area suggests these dinosaurs exhibited colonial nesting behavior like many modern birds. But the close spacing of the nests left little room for adult dinosaurs, supporting the idea that adults left the hatchlings (newborns) to fend for themselves.

Details of dinosaur reproductive habits can be difficult to determine. These fossil nests provide a wealth of data about some of the largest dinosaurs in history, and they come from a time shortly before the age of dinosaurs came to an end. The insights gleaned from this study contribute significantly to paleontologists' understanding of how dinosaurs lived and evolved.

Harsha Dhiman, lead author of the research, adds: "Our research has revealed the presence of an extensive hatchery of titanosaur sauropod dinosaurs in the study area and offers new insights into the conditions of nest preservation and reproductive strategies of titanosaur sauropod dinosaurs just before they went extinct."

Guntupalli V.R. Prasad, co-author and leader of the research team, adds: "Together with dinosaur nests from Jabalpur in the upper Narmada valley in the east and those from Balasinor in the west, the new nesting sites from Dhar District in Madhya Pradesh (Central India), covering an east-west stretch of about 1000 km, constitute one of the largest dinosaur hatcheries in the world."

From Science Daily

Nits on ancient mummies shed light on South American ancestry

Human DNA can be extracted from the 'cement' head lice used to glue their eggs to hairs thousands of years ago, scientists have found, which could provide an important new window into the past.

In a new study, scientists for the first time recovered DNA from cement on hairs taken from mummified remains that date back 1,500-2,000 years. This is possible because skin cells from the scalp become encased in the cement produced by female lice as they attach eggs, known as nits, to the hair.

Analysis of this newly-recovered ancient DNA -- which was of better quality than that recovered through other methods -- has revealed clues about pre-Columbian human migration patterns within South America. This method could allow many more unique samples to be studied from human remains where bone and tooth samples are unavailable.

The research was led by the University of Reading, working in collaboration with the National University of San Juan, Argentina; Bangor University, Wales; the Oxford University Museum of Natural History; and the University of Copenhagen, Denmark. It is published in the journal Molecular Biology and Evolution.

Dr Alejandra Perotti, Associate Professor in Invertebrate Biology at the University of Reading, who led the research, said: "Like the fictional story of mosquitos encased in amber in the film Jurassic Park, carrying the DNA of the dinosaur host, we have shown that our genetic information can be preserved by the sticky substance produced by headlice on our hair. In addition to genetics, lice biology can provide valuable clues about how people lived and died thousands of years ago.

"Demand for DNA samples from ancient human remains has grown in recent years as we seek to understand migration and diversity in ancient human populations. Headlice have accompanied humans throughout their entire existence, so this new method could open the door to a goldmine of information about our ancestors, while preserving unique specimens."

Until now, ancient DNA has preferably been extracted from dense bone from the skull or from inside teeth, as these provide the best quality samples. However, skull and teeth remains are not always available, as it can be unethical or against cultural beliefs to take samples from indigenous early remains, and due to the severe damage destructive sampling causes to the specimens which compromise future scientific analysis.

Recovering DNA from the cement delivered by lice is therefore a solution to the problem, especially as nits are commonly found on the hair and clothes of well preserved and mummified humans.

The research team extracted DNA from nit cement of specimens collected from a number of mummified remains from Argentina. The mummies were of people who 1,500-2,000 years ago reached the Andes mountains of the San Juan province, Central West Argentina. The team also studied ancient nits on human hair used in a textile from Chile and nits from a shrunken head originating from the ancient Jivaroan people of Amazonian Ecuador.

The samples used for DNA studies of nit cement were found to contain the same concentration of DNA as a tooth, double that of bone remains, and four times that recovered from blood inside far more recent lice specimens.

Dr Mikkel Winther Pedersen from the GLOBE institute at the University of Copenhagen, and first author, said: "The high amount of DNA yield from these nit cements really came as a surprise to us and it was striking to me that such small amounts could still give us all this information about who these people were, and how the lice related to other lice species but also giving us hints to possible viral diseases.

"There is a hunt out for alternative sources of ancient human DNA and nit cement might be one of those alternatives. I believe that future studies are needed before we really unravel this potential."

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Exquisitely preserved embryo found inside fossilized dinosaur egg

A 72 to 66-million-year-old embryo found inside a fossilised dinosaur egg sheds new light on the link between the behaviour of modern birds and dinosaurs, according to a new study.

The embryo, dubbed 'Baby Yingliang', was discovered in the Late Cretaceous rocks of Ganzhou, southern China and belongs to a toothless theropod dinosaur, or oviraptorosaur. Among the most complete dinosaur embryos ever found, the fossil suggests that these dinosaurs developed bird-like postures close to hatching.

Scientists found the posture of 'Baby Yingliang' unique among known dinosaur embryos -- its head lies below the body, with the feet on either side and the back curled along the blunt end of the egg. Previously unrecognised in dinosaurs, this posture is similar to that of modern bird embryos.

In modern birds, such postures are related to 'tucking' -- a behaviour controlled by the central nervous system and critical for hatching success. After studying egg and embryo, researchers believe that such pre-hatching behaviour, previously considered unique to birds, may have originated among non-avian theropods.

Led by scientists from the University of Birmingham and China University of Geosciences (Beijing), the research team from institutions in China, UK and Canada today published its findings in iScience.

The embryo is articulated in its life position without much disruption from fossilisation. Estimated to be 27 cm long from head to tail, the creature lies inside a 17-cm-long elongatoolithid egg. The specimen is housed in Yingliang Stone Nature History Museum.

Fion Waisum Ma, joint first author and PhD researcher at the University of Birmingham, said: "Dinosaur embryos are some of the rarest fossils and most of them are incomplete with the bones dislocated. We are very excited about the discovery of 'Baby Yingliang' -- it is preserved in a great condition and helps us answer a lot of questions about dinosaur growth and reproduction with it.

"It is interesting to see this dinosaur embryo and a chicken embryo pose in a similar way inside the egg, which possibly indicates similar prehatching behaviours."

'Baby Yingliang' was identified as an oviraptorosaur based on its deep, toothless skull. Oviraptorosaurs are a group of feathered theropod dinosaurs, closely related to modern-day birds, known from the Cretaceous of Asia and North America. Their variable beak shapes and body sizes are likely to have allowed them to adopt a wide range of diets, including herbivory, omnivory and carnivory.

Birds are known to develop a series of tucking postures, in which they bend their body and bring their head under their wing, soon before hatching. Embryos that fail to attain such postures have a higher chance of death due to unsuccessful hatching.

By comparing 'Baby Yingliang' with the embryos of other theropods, long-necked sauropod dinosaurs and birds, the team proposed that tucking behaviour, which was considered unique to birds, first evolved in theropod dinosaurs many tens or hundreds of millions of years ago. Additional discoveries of embryo fossils would be invaluable to further test this hypothesis.

Professor Lida Xing from China University of Geosciences (Beijing), joint first author of the study, said: "This dinosaur embryo was acquired by the director of Yingliang Group, Mr Liang Liu, as suspected egg fossils around the 2000. During the construction of Yingliang Stone Nature History Museum in 2010s, museum staff sorted through the storage and discovered the specimens.

"These specimens were identified as dinosaur egg fossils. Fossil preparation was conducted and eventually unveiled the embryo hidden inside the egg. This is how 'Baby Yingliang' was brought to light."

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Go (over) easy on the eggs: 'Egg-cess' consumption linked to diabetes

 Scrambled, poached or boiled, eggs are a popular breakfast food the world over. Yet the health benefits of the humble egg might not be all they're cracked up to be as new research from the University of South Australia shows that excess egg consumption can increase your risk of diabetes.

Conducted in partnership with the China Medical University, and Qatar University, the longitudinal study (1991 to 2009) is the first to assess egg consumption in a large sample of Chinese adults.

It found that people who regularly consumed one or more eggs per day (equivalent to 50 grams) increased their risk of diabetes by 60 per cent.

With the prevalence of diabetes in China now exceeding 11 per cent -- above that of the global average of 8.5 per cent -- diabetes has become a serious public health concern.

The economic impact of diabetes is also significant, accounting for 10 per cent of global health expenditure (USD $760 billion). In China, diabetes-related costs have exceeded USD $109 billion.

Epidemiologist and public health expert, UniSA's Dr Ming Li, says the rise of diabetes is a growing concern, especially in China where changes to the traditional Chinese diet are impacting health.

"Diet is a known and modifiable factor that contributes to the onset Type 2 diabetes, so understanding the range of dietary factors that might impact the growing prevalence of the disease is important," Dr Li says.

"Over the past few decades China has undergone a substantial nutritional transition that's seen many people move away from a traditional diet comprising grains and vegetables, to a more processed diet that includes greater amounts of meat, snacks and energy-dense food.

"At the same time, egg consumption has also been steadily increasing; from 1991 to 2009, the number of people eating eggs in China nearly doubled*.

"While the association between eating eggs and diabetes is often debated, this study has aimed to assess people's long-term egg consumption of eggs and their risk of developing diabetes, as determined by fasting blood glucose.

"What we discovered was that higher long-term egg consumption (greater than 38 grams per day) increased the risk of diabetes among Chinese adults by approximately 25 per cent.

"Furthermore, adults who regularly ate a lot of eggs (over 50 grams, or equivalent to one egg, per day) had an increased risk of diabetes by 60 per cent."

The effect was also more pronounced in women than in men.

Dr Li says that while these results suggest that higher egg consumption is positively associated with the risk of diabetes in Chinese adults, more research is needed to explore causal relationships.

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First dinosaur eggs were soft like a turtle's

Soft turtle eggshells

New research suggests that the first dinosaurs laid soft-shelled eggs -- a finding that contradicts established thought. The study, led by the American Museum of Natural History and Yale University and published today in the journal Nature, applied a suite of sophisticated geochemical methods to analyze the eggs of two vastly different non-avian dinosaurs and found that they resembled those of turtles in their microstructure, composition, and mechanical properties. The research also suggests that hard-shelled eggs evolved at least three times independently in the dinosaur family tree.

"The assumption has always been that the ancestral dinosaur egg was hard-shelled," said lead author Mark Norell, chair and Macaulay Curator in the Museum's Division of Paleontology. "Over the last 20 years, we've found dinosaur eggs around the world. But for the most part, they only represent three groups -- theropod dinosaurs, which includes modern birds, advanced hadrosaurs like the duck-bill dinosaurs, and advanced sauropods, the long-necked dinosaurs. At the same time, we've found thousands of skeletal remains of ceratopsian dinosaurs, but almost none of their eggs. So why weren't their eggs preserved? My guess -- and what we ended up proving through this study -- is that they were soft-shelled."

Amniotes -- the group that includes birds, mammals, and reptiles -- produce eggs with an inner membrane or "amnion" that helps to prevent the embryo from drying out. Some amniotes, such as many turtles, lizards, and snakes, lay soft-shelled eggs, whereas others, such as birds, lay eggs with hard, heavily calcified shells. The evolution of these calcified eggs, which offer increased protection against environmental stress, represents a milestone in the history of the amniotes, as it likely contributed to reproductive success and so the spread and diversification of this group. Soft-shelled eggs rarely preserve in the fossil record, which makes it difficult to study the transition from soft to hard shells. Because modern crocodilians and birds, which are living dinosaur, lay hard-shelled eggs, this eggshell type has been inferred for all non-avian dinosaurs.

The researchers studied embryo-containing fossil eggs belonging to two species of dinosaur: Protoceratops, a sheep-sized plant-eating dinosaur that lived in what is now Mongolia between about 75 and 71 million years ago, and Mussaurus, a long-necked, plant-eating dinosaur that grew to 20 feet in length and lived between 227 and 208.5 million years ago in what is now Argentina. The exceptionally preserved Protoceratops specimen includes a clutch of at least 12 eggs and embryos, six of which preserve nearly complete skeletons. Associated with most of these embryos -- which have their backbones and limbs flexed -- consistent with the position the animals would assume while growing inside of the egg -- is a diffuse black-and-white egg-shaped halo that obscures some of the skeleton. In contrast, two potentially hatched Protoceratops newborns in the specimen are largely free of the mineral halos. When they took a closer look at these halos with a petrographic microscope and chemically characterized the egg samples with high-resolution in situ Raman microspectroscopy, the researchers found chemically altered residues of the proteinaceous eggshell membrane that makes up the innermost eggshell layer of all modern archosaur eggshells. The same was true for the Mussaurus specimen. And when they compared the molecular biomineralization signature of the dinosaur eggs with eggshell data from other animals, including lizards, crocodiles, birds, and turtles, they determined that the Protoceratops and Mussaurus eggs were indeed non-biomineralized -- and, therefore, leathery and soft.

"It's an exceptional claim, so we need exceptional data," said study author and Yale graduate student Jasmina Wiemann. "We had to come up with a brand-new proxy to be sure that what we were seeing was how the eggs were in life, and not just a result of some strange fossilization effect. We now have a new method that can be applied to all other sorts of questions, as well as unambiguous evidence that complements the morphological and histological case for soft-shelled eggs in these animals."

With data on the chemical composition and mechanical properties of eggshells from 112 other extinct and living relatives, the researchers then constructed a "supertree" to track the evolution of the eggshell structure and properties through time, finding that hard-shelled, calcified eggs evolved independently at least three times in dinosaurs, and probably developed from an ancestrally soft-shelled type.

"From an evolutionary perspective, this makes much more sense than previous hypotheses, since we've known for a while that the ancestral egg of all amniotes was soft," said study author and Yale graduate student Matteo Fabbri. "From our study, we can also now say that the earliest archosaurs -- the group that includes dinosaurs, crocodiles, and pterosaurs -- had soft eggs. Up to this point, people just got stuck using the extant archosaurs -- crocodiles and birds -- to understand dinosaurs."

Because soft eggshells are more sensitive to water loss and offer little protection against mechanical stressors, such as a brooding parent, the researchers propose that they were probably buried in moist soil or sand and then incubated with heat from decomposing plant matter, similar to some reptile eggs today.

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Archaeologists on a 5,000-year-old egg hunt

Ostrich with eggs

An international team of specialists, led by the University of Bristol, is closer to cracking a 5,000-year-old mystery surrounding the ancient trade and production of decorated ostrich eggs.

Long before Fabergé, ornate ostrich eggs were highly prized by the elites of Mediterranean civilisations during the Bronze and Iron Ages, but to date little has been known about the complex supply chain behind these luxury goods.

Examining ostrich eggs from the British Museum's collection, the team, led by Bristol's Dr Tamar Hodos, were able to reveal secrets about their origin and how and where they were made. Using state-of-the-art scanning electron microscopy, Dr Caroline Cartwright, Senior Scientist at the British Museum was able to investigate the eggs' chemical makeup to pinpoint their origins and study minute marks that reveal how they were made.

In the study, published today in the journal Antiquity, the researchers describe for the first time the surprisingly complex system behind ostrich egg production. This includes evidence about where the ostrich eggs were sourced, if the ostriches were captive or wild, and how the manufacture methods can be related to techniques and materials used by artisans in specific areas.

"The entire system of decorated ostrich egg production was much more complicated than we had imagined! We also found evidence to suggest the ancient world was much more interconnected than previously thought," said Dr Hodos, Reader in Mediterranean Archaeology in Bristol's School of Arts.

"Mediterranean ostriches were indigenous to the eastern Mediterranean and North Africa. Using a variety of isotopic indicators, we were able to distinguish eggs laid in different climatic zones (cooler, wetter and hotter, drier). What was most surprising to us was that eggs from both zones were found at sites in the other zone, suggestive of more extensive trade routes."

Dr Hodos and colleagues believe eggs were taken from wild birds' nests despite evidence of ostriches being kept in captivity during this period. This was no ordinary egg-hunt -- ostriches can be extremely dangerous so there was a tremendous risk involved in taking eggs from wild birds.

"We also found eggs require time to dry before the shell can be carved and therefore require safe storage. This has economic implications, since storage necessitates a long-term investment and this, combined with the risk involved, would add to an egg's luxury value," said Dr Hodos.

The study is part of an ongoing research project into ancient luxury goods, Globalising Luxuries.

Dr Hodos explains: "We are assessing not only how ancient luxuries were produced but also how they were used by different peoples. These questions are incredibly important for our own society today, in which the same object may have different social or symbolic meanings for different groups. Such knowledge and understanding helps foster tolerance and mutual respect in a multi-cultural society. If we can understand these mechanisms in the past, for which we have long-term outcomes in terms of social development, we can use this knowledge to better inform our own society in a number of ways."

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Synchrotron X-ray sheds light on some of the world's oldest dinosaur eggs

Dinosaur egg concept

An international team of scientists led by the University of the Witwatersrand in South Africa, has been able to reconstruct, in the smallest details, the skulls of some of the world's oldest known dinosaur embryos in 3D, using powerful and non-destructive synchrotron techniques at the ESRF, the European Synchrotron in France. They found that the skulls develop in the same order as those of today's crocodiles, chickens, turtles and lizards. The findings are published today in Scientific Reports.

University of the Witwatersrand scientists publish 3D reconstructions of the ~2cm-long skulls of some of the world's oldest dinosaur embryos in an article in Scientific Reports. The embryos, found in 1976 in Golden Gate Highlands National Park (Free State Province, South Africa) belong to South Africa's iconic dinosaur Massospondylus carinatus, a 5-meter long herbivore that nested in the Free State region 200 million years ago.

The scientific usefulness of the embryos was previously limited by their extremely fragile nature and tiny size. In 2015, scientists Kimi Chapelle and Jonah Choiniere, from the University of Witwatersrand, brought them to the European Synchrotron (ESRF) in Grenoble, France for scanning. At the ESRF, an 844 metre-ring of electrons travelling at the speed of light emits high-powered X-ray beams that can be used to non-destructively scan matter, including fossils. The embryos were scanned at an unprecedented level of detail -- at the resolution of an individual bone cell. With these data in hand, and after nearly 3 years of data processing at Wits' laboratory, the team was able to reconstruct a 3D model of the baby dinosaur skull. "No lab CT scanner in the world can generate these kinds of data," said Vincent Fernandez, one of the co-authors and scientist at the Natural History Museum in London (UK). "Only with a huge facility like the ESRF can we unlock the hidden potential of our most exciting fossils. This research is a great example of a global collaboration between Europe and the South African National Research Foundation," he adds.

Up until now, it was believed that the embryos in those eggs had died just before hatching. However, during the study, lead author Chapelle noticed similarities with the developing embryos of living dinosaur relatives (crocodiles, chickens, turtles, and lizards). By comparing which bones of the skull were present at different stages of their embryonic development, Chapelle and co-authors can now show that the Massospondylus embryos were actually much younger than previously thought and were only at 60% through their incubation period.

The team also found that each embryo had two types of teeth preserved in its developing jaws. One set was made up of very simple triangular teeth that would have been resorbed or shed before hatching, just like geckos and crocodiles today. The second set were very similar to those of adults, and would be the ones that the embryos hatched with. "I was really surprised to find that these embryos not only had teeth, but had two types of teeth. The teeth are so tiny; they range from 0.4 to 0.7mm wide. That's smaller than the tip of a toothpick!," explains Chapelle.

The conclusion of this research is that dinosaurs developed in the egg just like their reptilian relatives, whose embryonic developmental pattern hasn't changed in 200 million years. "It's incredible that in more than 250 million years of reptile evolution, the way the skull develops in the egg remains more or less the same. Goes to show -- you don't mess with a good thing!," concludes Jonah Choiniere, professor at the University of Witwatersrand and also co-author of the study.

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