'Juvenile T. rex' fossils are a distinct species of small tyrannosaur

A new analysis of fossils believed to be juveniles of T. rex now shows they were adults of a small tyrannosaur, with narrower jaws, longer legs, and bigger arms than T. rex. The species, Nanotyrannus lancensis, was first named decades ago but later reinterpreted as a young T. rex.

The first skull of Nanotyrannus was found in Montana in 1942, but for decades, paleontologists have gone back and forth on whether it was a separate species, or simply a juvenile of the much larger T. rex.

Dr Nick Longrich, from the Milner Centre for Evolution at the University of Bath (UK), and Dr Evan Saitta, from the University of Chicago (USA) re-analysed the fossils, looking at growth rings, the anatomy of Nanotyrannus, and a previously unrecognized fossil of a young T. rex.

Measuring the growth rings in Nanotyrannus bones, they showed that they became more closely packed towards the outside of the bone -- its growth was slowing. It suggests these animals were nearly full size; not fast-growing juveniles.

Modelling the growth of the fossils showed the animals would have reached a maximum of around 900-1500 kilograms and five metres -- about 15 per cent of the size of the giant T. rex, which grew to 8,000 kilograms and nine metres or more.

The researchers have published their findings in Fossil Studies.

"When I saw these results I was pretty blown away," said Longrich. "I didn't expect it to be quite so conclusive.

"If they were young T. rex they should be growing like crazy, putting on hundreds of kilograms a year, but we're not seeing that.

"We tried modeling the data in a lot of different ways and we kept getting low growth rates. This is looking like the end for the hypothesis that these animals are young T. rex."

Supporting the existence of distinct species, the researchers found no evidence of fossils combining features of both the Nanotyrannus and T. rex - which would exist if the one turned into the other. Every fossil they examined could be confidently identified as one species or the other.

Neither did the patterns of growth in other tyrannosaurs fit with the hypothesis that these were young T. rex.

Dr Longrich said: "If you look at juveniles of other tyrannosaurs, they show many of the distinctive features of the adults. A very young Tarbosaurus - a close relative of T. rex - shows distinctive features of the adults.

"In the same way that kittens look like cats and puppies look like dogs, the juveniles of different tyrannosaurs are distinctive. And Nanotyrannus just doesn't look anything like a T. rex.

"It could be growing in a way that's completely unlike any other tyrannosaur, or any other dinosaur- but it's more likely it's just not a T. rex."

But that raises a mystery -- if Nanotyrannus isn't a juvenile Tyrannosaurus, then why hasn't anyone ever found a young T. rex?

"That's always been one of the big questions. Well, it turns out we actually had found one," said Longrich. "But the fossil was collected years ago, stuck in a box of unidentified bones in a museum drawer, and then forgotten."

The research led Longrich and co-author Evan Saitta to a previous fossil discovery, stored in a museum in San Francisco which they identified as a juvenile Tyrannosaurus.

That young T. rex is represented by a skull bone -- the frontal bone -- with distinctive features that ally it with Tyrannosaurus, but which aren't seen in Nanotyrannus. It comes from a small animal, one with a skull about 45 cm long and a body length of around 5 metres.

Dr Longrich said: "Yes, it's just one specimen, and just one bone, but it only takes one. T. rex skull bones are very distinctive, nothing else looks like it. Young T. rex exist, they're just incredibly rare, like juveniles of most dinosaurs."

The researchers argue these findings are strong evidence that Nanotyrannus is a separate species, one not closely related to Tyrannosaurus. It was more lightly-built and long-limbed than its thick-set relative. It also had larger arms, unlike the famously short-armed T. rex.

"The arms are actually longer than those of T. rex. Even the biggest T. rex, has shorter arms and smaller claws than in these little Nanotyrannus. This was an animal where the arms were actually pretty formidable weapons. It's really just a completely different animal -- small, fast, agile.

"T. rex relied on size and strength, but this animal relied on speed."

The long arms and other features suggest it was only distantly related to T. rex - and may have sat outside the family Tyrannosauridae, which T. rex is part of, in its own family of predatory dinosaurs.

The new study is the latest in a series of publications on the problem, going back decades.

Longrich said: "Nanotyrannus is highly controversial in paleontology. Not long ago, it seemed like we'd finally settled this problem, and it was a young T. rex.

"I was very skeptical about Nanotyrannus myself until about six years ago when I took a close look at the fossils and was surprised to realise we'd gotten it wrong all these years."

The authors suggest that, given how difficult it is to tell dinosaurs apart based on their often-incomplete skeletons, we may be underestimating the diversity of dinosaurs, and other fossil species.

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Fossils tell tale of last primate to inhabit North America before humans

The story of Ekgmowechashala, the final primate to inhabit North America before Homo sapiens or Clovis people, reads like a spaghetti western: A grizzled and mysterious loner, against the odds, ekes out an existence on the American Plains.

Except this tale unfolded about 30 million years ago, just after the Eocene-Oligocene transition during which North America saw great cooling and drying, making the continent less hospitable to warmth-loving primates.

Today, paleontologists from the University of Kansas and the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing have published evidence in the Journal of Human Evolution shedding light on the long-standing saga of Ekgmowechashala, based on fossil teeth and jaws found in both Nebraska and China.

To do so, the researchers first had to reconstruct its family tree, a job helped by the discovery of an even more ancient Chinese "sister taxon" of Ekgmowechashala the team has named Palaeohodites (or "ancient wanderer"). The Chinese fossil discovery resolves the mystery of Ekgmowechashala's presence in North America, showing it was an immigrant rather than the product of local evolution.

"This project focuses on a very distinctive fossil primate known to paleontologists since the 1960s," said lead author Kathleen Rust, a doctoral candidate in paleontology at KU's Biodiversity Institute and Natural History Museum. "Due to its unique morphology and its representation only by dental remains, its place on the mammalian evolutionary tree has been a subject of contention and debate. There's been a prevailing consensus leaning towards its classification as a primate. But the timing and appearance of this primate in the North American fossil record are quite unusual. It appears suddenly in the fossil record of the Great Plains more than 4 million years after the extinction of all other North American primates, which occurred around 34 million years ago."

In the 1990s, Rust's doctoral adviser and co-author Chris Beard, KU Foundation Distinguished Professor and senior curator of vertebrate paleontology, collected fossils from the Nadu Formation in the Baise Basin in Guangxi, China, that closely resembled the Ekgmowechashala material known from North America. By that time, Ekgmowechashala was notoriously enigmatic among North American paleontologists.

"When we were working there, we had absolutely no idea that we would find an animal that was closely related to this bizarre primate from North America, but literally as soon as I picked up the jaw and saw it, I thought, 'Wow, this is it,'" Beard said. "It's not like it took a long time, and we had to undertake all kinds of detailed analysis -- we knew what it was. Here in KU's collection, we have some critical fossils, including what is still by far the best upper molar of Ekgmowechashala known from North America. That upper molar is so distinctive and looks quite similar to the one from China that we found that it kind of seals the deal."

Beard left it to Rust to conduct the morphological analysis that tied Ekgmowechashala and its cousin Palaeohodites from China in a phylogenetic tree to establish their evolutionary relationships.

In the course of the work, Rust was able to draw conclusions about how Ekgmowechashala came to be discovered in Nebraska, millions of years after its fellow primates died out in the continent's fossil record.

"We collected a substantial amount of morphological data to create an evolutionary tree using a phylogenetic reconstruction software and algorithm," Rust said. "This evolutionary tree suggests a close evolutionary relationship between North American Ekgmowechashala and Palaeohodites from China, which Chris and his colleagues discovered in the 1990s. The results from our analysis unequivocally supports this hypothesis."

The KU researchers said their discovery is not only exciting in terms of discovering a new primate species from late Eocene China -- but also in settling the origin story of Ekgmowechashala. Based on their investigation, Ekgmowechashala did not descend from an older North American primate that somehow survived the cooler and drier conditions that caused other North American primates to go extinct. Rather, its ancestors crossed over the Beringian region millions of years later, anticipating the route followed by the first Native Americans much later in time.

"Our analysis dispels the idea that Ekgmowechashala is a relic or survivor of earlier primates in North America," Rust said. "Instead, it was an immigrant species that evolved in Asia and migrated to North America during a surprisingly cool period, most likely via Beringia."

Species like Ekgmowechashala that show up suddenly in the fossil record long after their relatives have died off are referred to as "Lazarus taxa" after the biblical figure who was raised from the dead.

"The 'Lazarus effect' in paleontology is when we find evidence in the fossil record of animals apparently going extinct -- only to reappear after a long hiatus, seemingly out of nowhere," Beard said. "This is the grand pattern of evolution that we see in the fossil record of North American primates. The first primates came to North America about 56 million years ago at the beginning of the Eocene, and they flourished on this continent for more than 20 million years. But they went extinct when climate became cooler and drier near the Eocene-Oligocene boundary, about 34 million years ago. Several million years later Ekgmowechashala shows up like a drifting gunslinger in a Western movie, only to be a flash in the pan as far as the long trajectory of evolution is concerned. After Ekgmowechashala is gone for more than 25 million years, Clovis people come to North America, marking the third chapter of primates on this continent. Like Ekgmowechashala, humans in North America are a prime example of the Lazarus effect."

Rust and Beard were joined in the work by co-authors Xijun Ni of the Chinese Academy of Sciences, Beijing, and Kristen Tietjen, scientific illustrator with the KU Biodiversity Institute and Natural History Museum.

According to Rust, the tale of Ekgmowechashala is worth people's attention because it happened in an era of profound environmental and climatic changes, much like our own that's driven by human activity.

"It's crucial to comprehend how past biota reacted to such shifts," she said. "In such situations, organisms typically either adapt by retreating to more hospitable regions with available resources or face extinction. Around 34 million years ago, all of the primates in North America couldn't adapt and survive. North America lacked the necessary conditions for survival. This underscores the significance of accessible resources for our non-human primate relatives during times of drastic climatic change."

The study is also a part of a larger story that represents the earliest chapters of our own evolutionary journey that ultimately led to our own species, Rust said.

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Fruit, nectar, bugs and blood: How bat teeth and jaws evolved for a diverse dinnertime

They don't know it, but Darwin's finches changed the world. These closely related species -- native to the Galapagos Islands -- each sport a uniquely shaped beak that matches their preferred diet. Studying these birds helped Charles Darwin develop the theory of evolution by natural selection.

A group of bats has a similar -- and more expansive -- evolutionary story to tell. There are more than 200 species of noctilionoid bats, mostly in the American tropics. And despite being close relatives, their jaws evolved in wildly divergent shapes and sizes to exploit different food sources. A paper published Aug. 22 in Nature Communications shows those adaptations include dramatic, but also consistent, modifications to tooth number, size, shape and position. For example, bats with short snouts lack certain teeth, presumably due to a lack of space. Species with longer jaws have room for more teeth -- and, like humans, their total tooth complement is closer to what the ancestor of placental mammals had.

According to the research team behind this study, comparing noctilionoid species can reveal a lot about how mammalian faces evolved and developed, particularly jaws and teeth. And as a bonus, they can also answer some outstanding questions about how our own pearly whites form and grow.

"Bats have all four types of teeth -- incisors, canines, premolars and molars -- just like we do," said co-author Sharlene Santana, a University of Washington professor of biology and curator of mammals at the Burke Museum of Natural History & Culture. "And noctilionoid bats evolved a huge diversity of diets in as little as 25 million years, which is a very short amount of time for these adaptations to occur."

"There are noctilionoid species that have short faces like bulldogs with powerful jaws that can bite the tough exterior of the fruits that they eat. Other species have long snouts to help them drink nectar from flowers. How did this diversity evolve so quickly? What had to change in their jaws and teeth to make this possible?" said lead author Alexa Sadier, an incoming faculty member at the Institute of Evolutionary Science of Montpellier in France, who began this project as a postdoctoral researcher at the University California, Los Angeles.

Scientists don't know what triggered this frenzy of dietary adaptation in noctilionoid bats. But today different noctilionoid species feast on insects, fruit, nectar, fish and even blood -- since this group also includes the infamous vampire bats.

The team used CT scans and other methods to analyze the shapes and sizes of jaws, premolars and molars in more than 100 noctilionoid species. The bats included both museum specimens and a limited number of wild bats captured for study purposes. The researchers compared the relative sizes of teeth and other cranial features among species with different types of diets, and used mathematical modeling to determine how those differences are generated during development.

The team found that, in noctilionoid bats, certain "developmental rules" caused them to generate the right assortment of teeth to fit in their diet-formed grins. For example, bats with long jaws -- like nectar-feeders -- or intermediate jaws, like many insect-eaters, tended to have the usual complement of three premolars and three molars on each side of the jaw. But bats with short jaws, including most fruit-eating bats, tended to ditch the middle premolar or the back molar, if not both.

"When you have more space, you can have more teeth," said Sadier. "But for bats with a shorter space, even though they have a more powerful bite, you simply run out of room for all these teeth."

Having a shorter jaw may also explain why many short-faced bats also tended to have wider front molars.

"The first teeth to appear tend to grow bigger since there is not enough space for the next ones to emerge," said Sadier.

"This project is giving us the opportunity to actually test some of the assumptions that have been made about how tooth growth, shape and size are regulated in mammals," said Santana. "We know surprisingly little about how these very important structures develop!"

Many studies about mammalian tooth development were done in mice, which have only molars and heavily modified incisors. Scientists are not entirely sure if the genes and developmental patterns that control tooth development in mice also operate in mammals with more "ancestral" sets of chompers -- like bats and humans.

Sadier, Santana and their colleagues believe their project, which is ongoing, can start to answer these questions in bats -- along with many other outstanding questions about how evolution shapes mammalian features. They're expanding this study to include noctilionoid incisors and canines, and hope to uncover more of the genetic and developmental mechanisms that control tooth development in this diverse group of bats.

"We see such strong selective pressures in these bats: Shapes have to closely match their function," said Santana. "I think there are many more evolutionary secrets hidden in these species."

Read more at Science Daily

Jawbone may represent earliest presence of humans in Europe

For over a century, one of the earliest human fossils ever discovered in Spain has been long considered a Neanderthal. However, new analysis from an international research team, including scientists at Binghamton University, State University of New York, dismantles this century-long interpretation, demonstrating that this fossil is not a Neanderthal; rather, it may actually represent the earliest presence of Homo sapiens ever documented in Europe.

In 1887, a fossil mandible was discovered during quarrying activities in the town of Banyoles, Spain, and has been studied by different researchers over the past century. The Banyoles fossil likely dates to between approximately 45,000-65,000 years ago, at a time when Europe was occupied by Neanderthals, and most researchers have generally linked it to this species.

"The mandible has been studied throughout the past century and was long considered to be a Neanderthal based on its age and location, and the fact that it lacks one of the diagnostic features of Homo sapiens: a chin," said Binghamton University graduate student Brian Keeling.

The new study relied on virtual techniques, including CT scanning of the original fossil. This was used to virtually reconstruct missing parts of the fossil, and then to generate a 3D model to be analyzed on the computer.

The authors studied the expressions of distinct features on the mandible from Banyoles that are different between our own species, Homo sapiens, and the Neanderthals, our closest evolutionary cousins.

The authors applied a methodology known as "three-dimensional geometric morphometrics" that analyzes the geometric properties of the bone's shape. This makes it possible to directly compare the overall shape of Banyoles to Neanderthals and H. sapiens.

"Our results found something quite surprising -- Banyoles shared no distinct Neanderthal traits and did not overlap with Neanderthals in its overall shape," said Keeling.

While Banyoles seemed to fit better with Homo sapiens in both the expression of its individual features and its overall shape, many of these features are also shared with earlier human species, complicating an immediate assignment to Homo sapiens. In addition, Banyoles lacks a chin, one of the most characteristic features of Homo sapiens mandibles.

"We were confronted with results that were telling us Banyoles is not a Neanderthal, but the fact that it does not have a chin made us think twice about assigning it to Homo sapiens," said Rolf Quam, professor of anthropology at Binghamton University, State University of New York. "The presence of a chin has long been considered a hallmark of our own species."

Given this, reaching a scientific consensus on what species Banyoles represents is a challenge. The authors also compared Banyoles with an early Homo sapiens mandible from a site called Peştera cu Oase in Romania. Unlike Banyoles, this mandible shows a full chin along with some Neanderthal features, and an ancient DNA analysis has revealed this individual had a Neanderthal ancestor four to six generations ago. Since the Banyoles mandible shared no distinct features with Neanderthals, the researchers ruled out the possibility of mixture between Neanderthals and H. sapiens to explain its anatomy.

The authors point out that some of the earliest Homo sapiens fossils from Africa, predating Banyoles by more than 100,000 years, do show less pronounced chins than in living populations.

Thus, these scientists developed two possibilities for what the Banyoles mandible may represent: a member of a previously unknown population of Homo sapiens that coexisted with the Neanderthals; or a hybrid between a member of this Homo sapiens group and a non-Neanderthal unidentified human species. However, at the time of Banyoles, the only fossils recovered from Europe are Neanderthals, making this latter hypothesis less likely.

"If Banyoles is really a member of our species, this prehistoric human would represent the earliest H. sapiens ever documented in Europe," said Keeling.

Whichever species this mandible belongs to, Banyoles is clearly not a Neanderthal at a time when Neanderthals were believed to be the sole occupants of Europe.

The authors conclude that "the present situation makes Banyoles a prime candidate for ancient DNA or proteomic analyses, which may shed additional light on its taxonomic affinities."

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DNA sequence enhances understanding origins of jaws

Researchers at Uppsala University have discovered and characterised a DNA sequence found in jawed vertebrates, such as sharks and humans, but absent in jawless vertebrates, such as lampreys. This DNA is important for the shaping of the joint surfaces during embryo development.

The vast majority of vertebrate species living today, including humans, belong to the jawed vertebrate group. The development of articulating jaws during vertebrate evolution was one of the most significant evolutionary transitions from jawless to jawed vertebrates, taking place at least 423 million years ago. The lower and upper jaws were initially connected by the primary jaw joint. However, during the evolution of mammals this moved to the middle ear to enhance hearing and was replaced by the secondary jaw joint, which is how humans are constructed today.

The primary jaw joint is formed during embryonic development and has an active gene which contains sequence information for a specific protein -- transcription factor Nkx3.2. This protein has long been thought to have played a major role in the evolution of this jaw joint, but little was known before about how its gene activity is regulated in the jaw joint cells.

Typically, genes are activated with help from DNA sequences, known as enhancers, that do not contain gene sequence information. Furthermore, such 'regulatory' DNA can contribute to the activation of the gene only in a certain cell type and can be conserved among different animal species.

"We searched through the genome sequences of many different vertebrate species and only found the DNA sequence near the Nkx3.2 gene in jawed vertebrates -- not in jawless ones. When we injected these DNA sequences from jawed vertebrates into zebrafish embryos, they were all activated in the jaw joint cells. The fact that their ability to activate has been preserved for over 400 million years shows how important it is for jawed vertebrates," notes Tatjana Haitina, researcher at Uppsala University, who led the study.

"In experiments where we deleted the newly discovered DNA sequence from the zebrafish genome using the CRISPR/Cas9 technique, we saw that the early activation of the Nkx3.2 gene was reduced, which caused defects in the jaw joint shape. It turned out that these defects were later repaired, suggesting that there is additional regulatory DNA somewhere in the genome that controls the activation of the Nkx3.2 gene and is waiting to be discovered," adds Jake Leyhr, doctoral student student in the research team.

The researchers hope that their discovery is an important step towards eventually understanding the process behind the origins of vertebrate jaws.

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Fossils of giant sea lizard that ruled the oceans 66 million years ago discovered

Researchers have discovered a huge new mosasaur from Morocco, named Thalassotitan atrox, which filled the apex predator niche. With massive jaws and teeth like those of killer whales, Thalassotitan hunted other marine reptiles -- plesiosaurs, sea turtles, and other mosasaurs.

At the end of the Cretaceous period, 66 million years ago, sea monsters really existed. While dinosaurs flourished on land, the seas were ruled by the mosasaurs, giant marine reptiles.

Mosasaurs weren't dinosaurs, but enormous marine lizards growing up to 12 metres (40 feet) in length. They were distant relatives of modern iguanas and monitor lizards.

Mosasaurs looked like a Komodo dragon with flippers instead of legs, and a shark-like tail fin. Mosasaurs became larger and more specialised in the last 25 million years of the Cretaceous, taking niches once filled by marine reptiles like plesiosaurs and ichthyosaurs. Some evolved to eat small prey like fish and squid. Others crushed ammonites and clams. The new mosasaur, named Thalassotitan atrox, evolved to prey on all the other marine reptiles.

The remains of the new species were dug up in Morocco, about an hour outside Casablanca. Here, near the end of the Cretaceous, the Atlantic flooded northern Africa. Nutrient rich waters upwelling from the depths fed blooms of plankton. Those fed small fish, feeding larger fish, which fed mosasaurs and plesiosaurs -- and so on, with these marine reptiles becoming food for the giant, carnivorous Thalassotitan.

Thalassotitan, had an enormous skull measuring 1.4 metres (5 feet long), and grew to nearly 30 feet (9 metres) long, the size of a killer whale. While most mosasaurs had long jaws and slender teeth for catching fish, Thalassotitan had a short, wide muzzle and massive, conical teeth like those of an orca. These let it seize and rip apart huge prey. These adaptations suggest Thalassotitan was an apex predator, sitting at the top of the food chain. The giant mosasaur occupied the same ecological niche as today's killer whales and great white sharks.

Thalassotitan's teeth are often broken and worn, however eating fish wouldn't have produced this sort of tooth wear. Instead, this suggests that the giant mosasaur attacked other marine reptiles, chipping, breaking, and grinding its teeth as it bit into their bones and tore them apart. Some teeth are so heavily damaged they have been almost ground down to the root.

Fossilised remains of prey

Remarkably, possible remains of Thalassotitan's victims have been discovered. Fossils from the same beds show damage from acids, with teeth and bone eaten away. Fossils with this peculiar damage include large predatory fish, a sea turtle, a half-meter long plesiosaur head, and jaws and skulls of at least three different mosasaur species. They would have been digested in Thalassotitan's stomach before it spat out their bones.

"It's circumstantial evidence," said Dr Nick Longrich, Senior Lecturer from the Milner Centre for Evolution at the University of Bath and lead author on the study, published in Cretaceous Research.

"We can't say for certain which species of animal ate all these other mosasaurs. But we have the bones of marine reptiles killed and eaten by a large predator.

"And in the same location, we find Thalassotitan, a species that fits the profile of the killer -- it's a mosasaur specialised to prey on other marine reptiles. That's probably not a coincidence."

Thalassotitan was a threat to everything in the oceans -- including other Thalassotitan. The huge mosasaurs bear injuries sustained in violent combat with other mosasaurs, with injuries to their face and jaws sustained in fights. Other mosasaurs show similar injuries, but in Thalassotitan these wounds were exceptionally common, suggesting frequent, intense fights over feeding grounds or mates.

"Thalassotitan was an amazing, terrifying animal," said Dr Nick Longrich, who led the study. "Imagine a Komodo Dragon crossed with a great white shark crossed with a T. rex crossed with a killer whale."

The new mosasaur lived in the final million years of the Age of Dinosaurs, a contemporary of animals like T. rex and Triceratops. Along with recent discoveries of mosasaurs from Morocco, it suggests that mosasaurs weren't in decline before the asteroid impact that drove the Cretaceous mass extinction. Instead, they flourished.

Professor Nour-Eddine Jalil, a co-author on the paper from the Museum of Natural History in Paris, said: "The phosphate fossils of Morocco offer an unparalleled window on the paleobiodiversity at the end of Cretaceous.

"They tell us how life was rich and diversified just before the end of the 'dinosaur era', where animals had to specialise to have a place in their ecosystems. Thalassotitan completes the picture by taking on the role of the megapredator at the top of the food chain."

Read more at Science Daily

A large predator from the Pyrenees

A fossilized lower jaw has led an international team of palaeontologists, headed by Bastien Mennecart from the Natural History Museum Basel, to discover a new species of predator that once lived in Europe. These large predators belong to a group of carnivores colloquially known as "bear dogs." They could weigh around 320 kilograms, appeared 36 million years ago before becoming extinct around 7.5 million years ago.

Palaeontologist Bastien Mennecart and his research group precisely described the fossilized lower jaw of a carnivore and discovered that it must be a specimen from a new species. The jawbone comes from 12.8 to 12 million-year-old marine deposits that were examined in the small community of Sallespisse in the Pyrénées-Atlantiques department of south western France.

The teeth of time

The jawbone was striking because of its teeth. Unlike the familiar amphicyonidae specimens, this animal has a unique fourth lower premolar. This tooth is particularly important for determining species and genera. Correspondingly, the lower jaw examined probably represents a new genus. It is called Tartarocyon. This name comes from Tartaro, a large, powerful, one-eyed giant from Basque mythology. The legend of Tartaro is also known in Béarn, the region where the lower jaw was found. Floréal Solé, a specialist in carnivorous mammals, Jean-François Lesport and Antoine Heitz from the Natural History Museum Basel chose the name of the new genus.

Dog-like predator

The fossilized lower jaw can be classified as belonging to predators that resembled a cross between a bear and a large dog, known as "bear dogs." Their scientific name is "Amphicyonidae." They belong to a group of carnivores such as dogs, cats, bears, seals and badgers. These predators were a widespread part of the European fauna of the Miocene (23 to 5.3 million years ago). They were very species-rich and diverse, weighing between 9 kg and 320 kg. Tarataroyon is estimated at 200 kg. The last European Amphicyonidae disappeared during the late Miocene 7.5 million years ago.

Key contemporary witnesses

Discoveries of fossilized terrestrial vertebrates that lived on the northern edge of the Pyrenees 13 to 11 million years ago are very rare. The discovery and description of the lower jaw is even more significant. That is because it offers the opportunity to explore the development of European "bear dogs" against the background of known environmental events at this time.

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Jaws hold crucial knowledge on the fate of sharks

Jaws was the only word needed to give the iconic 1970's thriller about a great white with a preference for humans its eerie title. Though a strong and important player at the top of the foodchain, sharks face a range of enemies: overfishing, habitat loss, pollution and climate change and human fear resulting in the use of shark control programs in some locations.

The fear and fascination for sharks have made people collect shark jaws for decades. These collections of shark jaws from museums, national fishery institutes and personal collections, including modern samples from fishery institutes represent a great opportunity for scientists.

Using genomic data retrieved from historical tiger shark jaws, an international group of scientists including Professor Einar Eg from the Technical University of Denmark has found evidence of the disappearance of a local southeastern Australian population of tiger sharks. A disappearance associated with a documented local decline in abundance of tiger sharks, likely caused by the ongoing shark control program.

The international study Retrospective genomics highlights changes in genetic composition of tiger sharks (Galeocerdo cuvier) and potential loss of a south-eastern Australia population has just been published in the journal Scientific Reports

"Our study shows that tiger sharks can have local and genetically isolated populations at a restricted geographical scale -- such as the south Eastern Australian coast -- and that these local populations are vulnerable to direct exploitation and shark control programs," says Einar Eg.

Top predator controls the ecosystem balance

The study shows that there are still tiger sharks in the area. However, these individuals belong to an, apparently, more widespread population found across the east/north coast of Australia.

"When we, through genetic analysis, better understand the distribution and migration of shark populations and their responses to human activities over historical time, we are better able to design proper management plans and actions at the appropriate geographical scale. Not only for the benefit of sharks, but for marine ecosystems as a whole," says Einar Eg and explains:

"Sharks are top predators. They control the abundance of other species below them, and sick fish, in the food chain, ensuring species diversity. I.e. they are important for maintaining ecosystem balance. They are generally long lived and slow reproducers, so a healthy shark fauna signals a healthy ocean and ecosystem."

Genetic diversity is the fuel that drives future evolution

Before the new study, it was believed that tiger sharks did not display local population structure. Thus, genetic differences among tiger shark populations were only found at a basin wide scale, such as between tiger sharks in the Pacific and Atlantic oceans. Accordingly, tiger sharks were expected to display low vulnerability towards local depletion. Therefore management of the species at a large geographical scale was in focus.

"From our samples alone, it appears that the historical local population has been extirpated or significantly reduced. This means that management of the species also has to focus on regional processes and exploitation patterns in order to protect local populations and biodiversity of the species as a whole," says Einar Eg and points to the crucial aspects of genetic research:

"Genetic diversity within a species, is the fuel that drives future evolution and adaptation to the environment, e.g. climate change. Without historical genetic/genomic data, there is no way of assessing the loss of genetic diversity within a species."

Fear and facts -- are sharks moving North?

With regards to the shark control programs having an impact on shark numbers, the obvious question arises "How afraid should one actually be to go swimming in Australia or South Africa?"

"In 2021, there were 73 cases of unprovoked shark bites worldwide, with a total of 11 fatalities. Most attacks were related to surfing and board sports. In Australia, there were three fatalities and 1 in SA. So, the chance of being attacked and killed by a shark is almost non-existing. One should definitely be more afraid of driving in your car writing txt messages," says Einar Eg.

As climate change causes sea temperatures to rise, some researchers say that we may be looking into a future with large sharks entering Danish/European waters. However, Einar Eg stresses that though changed temperature conditions could allow for more large sharks occurring in Danish/European waters, many other factors determine the distribution of a species.

"The Mediterranean, for instance, is very suitable for large sharks, but we do not see large assemblages of white, tiger, mako sharks there. If they come, it is highly unlikely that this would result in any bather-shark conflicts. As an example, there were no reported shark bites in Europe for 2021," says Einar Eg.

A future for sharks

On a global scale, the tiger shark is near threatened. According to Professor Einar Eg that covers a significant species depletion in some areas, while they're doing ok in other regions of the world: "We need to shift tiger shark management conceptually from an exclusive species view to also include the local population aspect. I.e. saving global populations has to go through protection and proper management of local populations," says Einar Eg.

"Now, by having our temporal genetic data, we can study the genetic impact of anthropogenic pressure on marine species, enabling us to improve management in order to secure biodiversity."

How can genetic research continue and help improve shark control and hunting in favour of sharks?

"Genetic research can help to elucidate the proper biological units (genetic populations), which should be the target for fisheries management, conservation and biodiversity protection," says Einar Eg and concludes:

"Studies like ours can illustrate the likely consequences of local over-exploitation in relation to shark control and make us realize what we can lose by not paying attention to the distribution of genetic variation within a species."

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New fossil birds discovered near China’s Great Wall – one had a movable, sensitive 'chin'

Approximately 80 miles from the westernmost reach of China's Great Wall, paleontologists found relics of an even more ancient world. Over the last two decades, teams of researchers unearthed more than 100 specimens of fossil birds that lived approximately 120 million years ago, during the time of the dinosaurs. However, many of these fossils have proved difficult to identify: they're incomplete and sometimes badly crushed. In a new paper published in the Journal of Systematics and Evolution, researchers examined six of these fossils and identified two new species. And as a fun side note, one of those new species had a movable bony appendage at the tip of its lower jaw that may have helped the bird root for food.

"It was a long, painstaking process teasing out what these things were," says Jingmai O'Connor, the study's lead author and the associate curator of vertebrate paleontology at Chicago's Field Museum. "But these new specimens include two new species that increase our knowledge of Cretaceous bird faunas, and we found combinations of dental features that we've never seen in any other dinosaurs."

"These fossils come from a site in China that has produced fossils of birds that are pretty darned close to modern birds, but all the bird fossils described thus far haven't had skulls preserved with the bodies," says co-author Jerry Harris of Utah Tech University. "These new skull specimens help fill in that gap in our knowledge of the birds from this site and of bird evolution as a whole."

All birds are dinosaurs, but not all dinosaurs are birds; a small group of dinosaurs evolved into birds that coexisted with other dinosaurs for 90 million years. Modern birds are the descendants of the group of birds that survived the extinction that killed the rest of the dinosaurs, but many prehistoric birds went extinct then too. O'Connor's work focuses on studying different groups of early birds to figure out why some survived while others went extinct.

The fossil site in northwestern China, called Changma, is an important place for researchers like O'Connor studying bird evolution. It's the second-richest Mesozoic (time of the dinosaurs) fossil bird site in the world, but more than half of the fossils found there belong to the same species, Gansus yumenensis.Determining which fossils are Gansus and which ones aren't is tricky; the six specimens that O'Connor and her colleagues examined in this study are primarily just skulls and necks, parts not preserved in known specimens of Gansus. The fossils were also somewhat smushed by their time deep in the Earth, which made analyzing them difficult.

"The Changma site is a special place," says study co-author Matt Lamanna of Pittsburgh's Carnegie Museum of Natural History. "The fossil-bearing rocks there tend to split into thin sheets along ancient bedding planes. So, when you're digging, it's like you're literally turning back the pages of history, layer by layer uncovering animals and plants that haven't seen the light of day in roughly 120 million years."

"Because the specimens were pretty flattened, CT-scanning them and fully segmenting them could take years and might not even give you that much information, because these thin bones are flattened into almost the same plane, and then it just becomes almost impossible to figure out where the boundaries of these bones are," says O'Connor. "So we had to kind of work with what was exposed." Through painstaking work, the researchers were able to identify key features in the birds' jaws that showed that two of the six specimens were unknown to science.

The new species (or, more accurately, new genera -- genus is a step above species in the order scientists use to name organisms) are called Meemannavis ductrix and Brevidentavis zhangi. Meemannavis is named for Meemann Chang, a Chinese paleontologist who became the first woman to lead the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing. The name Brevidentavis means "short-toothed bird." Like Gansus, both Meemannavis and Brevidentavis are ornithuromorph birds -- the group that contains modern birds. Like today's birds, Meemannavis was toothless. Brevidentavis, on the other hand, had small, peg-like teeth packed close together in its mouth. Along with those teeth came another strange feature.

"Brevidentavis is an ornithuromorph bird with teeth, and in ornithuromorphs with teeth, there's a little bone at the front of the jaw called the predentary, where its chin would be if birds had chins," explains O'Connor. In a previous study on the predentary in another fossil bird, the authors figured out, by CT-scanning the bone and staining it with chemicals, that the predentary bone underwent stress and also found a kind of cartilage that only forms when there's movement.

"In this earlier study, we were able to tell that the predentary was capable of being moved, and that it would have been innervated -- Brevidentavis wouldn't just have been able to move its predentary, it would have been able to feel through it," says O'Connor. "It could have helped them detect prey. We can hypothesize that these toothed birds had little beaks with some kind of movable pincer at the tip of their jaws in front of the teeth."

Brevidentavis isn't the first fossil bird discovered with a predentary that might have been used in this way, but its existence, along with Meemannavis, helps round out our understanding of the diversity of prehistoric birds, especially in the Changma region.

The study also helps shed light on the most common bird from the site, Gansus, since at least four of the other specimens examined probably belong to this species. "Gansus is the first known true Mesozoic bird in the world, as Archaeopteryx is more dinosaur-like, and now we know what its skull looks like after about 40 years," notes Hai-Lu You of the IVPP.

"These amazing fossils are like a lockpick allowing us to open the door to greater knowledge of the evolutionary history of the skull in close relatives of living birds," says Tom Stidham, a co-author from the IVPP. "At a time when giant dinosaurs still roamed the land, these birds were the products of evolution experimenting with different lifestyles in the water, in the air, and on land, and with different diets as we can see in some species having or lacking teeth. Very few fossils of this geological age provide the level of anatomical detail that we can see in these ancient bird skulls."

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New muscle layer discovered on the jaw

Human anatomy still has a few surprises in store for us: researchers at the University of Basel have discovered a previously overlooked section of our jaw muscles and described this layer in detail for the first time.

The masseter muscle is the most prominent of the jaw muscles. If you place your fingers on the back of your cheeks and press your teeth together, you'll feel the muscle tighten. Anatomy textbooks generally describe the masseter as consisting of one superficial and one deep part.

Now, researchers led by Dr. Szilvia Mezey from the Department of Biomedicine at the University of Basel and Professor Jens Christoph Türp from the University Center for Dental Medicine Basel (UZB) have described the structure of the masseter muscle as consisting of an additional third, even deeper layer. In the scientific journal Annals of Anatomy, they propose that this layer be given the name Musculus masseter pars coronidea -- in other words, the coronoid section of the masseter -- because the newly described layer of muscle is attached to the muscular (or "coronoid") process of the lower jaw.

The anatomical study was based on detailed examination of formalin-fixed jaw musculature, computer tomographic scans and the analysis of stained tissue sections from deceased individuals who had donated their bodies to science. This was in addition to MRI data from a living person.

As if a new animal species had been discovered

"This deep section of the masseter muscle is clearly distinguishable from the two other layers in terms of its course and function," explains Mezey. The arrangement of the muscle fibers, she says, suggests that this layer is involved in the stabilization of the lower jaw. It also appears to be the only part of the masseter that can pull the lower jaw backwards -- that is, toward the ear.

A look at historical anatomy studies and textbooks reveals that the structure of the masseter muscle has already raised questions in the past. In a previous edition of Gray's Anatomy, from the year 1995, the editors also describe the masseter muscle as having three layers, although the cited studies were based on the jaw musculature of other species and partly contradicted one another.

Other individual studies from the early 2000s also reported three layers, but they divided the superficial section of the masseter into two layers and agreed with standard works in their description of the deeper section.

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Theropod dinosaur jaws became stronger as they evolved

Theropod dinosaurs evolved more robust jaws through time allowing them to consume tougher food, a new study reveals.

Researchers used digital modelling and computer simulation to uncover a common trend of jaw strengthening in theropods -- expanding the rear jaw portion in all groups, as well as evolving an upturned jaw in carnivores and a downturned jaw in herbivores.

Publishing their findings today in Current Biology, scientistsrevealed that biomechanical analysis showed these form changes made jaws mechanically more stable when biting -- minimising the chance of bone fracture.

The international team, led by scientists at the University of Birmingham, created digital models of more than 40 lower jaws from five different theropod dinosaur groups, including typical carnivores like Tyrannosaurus and Velociraptor, and lesser-known herbivores like ornithomimosaurs, therizinosaurs and oviraptorosaurs.

Fion Waisum Ma, PhD researcher at the University of Birmingham, who led the study, said: "Although theropod dinosaurs are always depicted as fearsome predators in popular culture, they are in fact very diverse in terms of diets. It is interesting to observe the jaws becoming structurally stronger over time, in both carnivores and herbivores. This gives them the capacity to exploit a wider range of food items.

"Theropod dinosaurs underwent extreme dietary changes during their evolutionary history of 165 million years. They started off as carnivores, later on evolved into more specialised carnivores, omnivores and herbivores. Studying how their feeding mechanics changed is key to understanding the dietary transitions in other vertebrate animals too."

For example, in carnivores like tyrannosauroids, an early form like Guanlong had a relatively slender and straight jaw. But later forms such as Tarbosaurus and Tyrannosaurus evolved deeper jaws with the front portion bending upward, which increase jaw strength.

Having a strengthened jaw is especially important to herbivorous theropods, as their jaws experience considerable stress from repetitive plant cropping. Herbivores like Erlikosaurus and Caudipteryx have extremely downward-bending jaws that could help dissipate such stress.

Dr Stephan Lautenschlager, Senior Lecturer at the University of Birmingham and senior author of the study, said: "It is fascinating to see how theropod dinosaurs had evolved different strategies to increase jaw stability depending on their diet. This was achieved through bone remodelling -- a mechanism where bone is deposited in regions of the jaw that experience high stresses during feeding."

The researchers studied the feeding mechanics of tyrannosaurids through growth and observed that the deeper and more upturned jaws of adult theropods, such as Tyrannosaurus and Tarbosaurus, are structurally stronger compared to those of their juvenile forms.

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Mammals’ noses come from reptiles’ jaws

New examinations of skeletons and animal embryos have allowed researchers to discover how mammals developed protruding, flexible noses. This study contributes to uncovering the origin of mammals' strong sense of smell and creates the potential for new animal models, like chickens or frogs, that are often used in lab experiments to investigate facial development disorders such as cleft palate.

The traditional scientific understanding of facial evolution is that both mammalian and reptilian jaws develop in almost the same way. Even though mammals have a unique nose, the evolution of this structure has remained unknown.

"Existing fossils of four-legged animals, both reptilian and mammalian ancestors, have the same number of upper jaw bones. It's very easy to think that the bones are the same, but now we can study embryos and track cellular development to study these bones in much greater detail," explained postdoctoral researcher Hiroki Higashiyama, who studies evolutionary development at the University of Tokyo Graduate School of Medicine. The research, recently published in Proceedings of the National Academy of Sciences, is the first to examine the evolution of facial structure using cellular studies comparing multiple embryos of multiple species.

Higashiyama and his colleagues in the laboratory of Professor Hiroki Kurihara designed experiments to track facial development in embryos of different species, including birds (chickens), reptiles (geckos) and mammals (mice). They focused on a group of cells known as the facial prominences in embryos that produce the physical structures of the face. Researchers stained the cells to track them as they moved and grew. A group of cells called the frontonasal prominence forms the jaw tip in reptiles, but becomes the protruding nose in mammals. Mammals' jaw tips form instead from a separate group of cells called the maxillary prominence.

Using this new perspective from their cellular experiments, researchers then examined fossil specimens.

As species' ancestors accumulated more physical and genetic differences, the bone at the tip of reptiles' upper jaw, the premaxilla, became smaller and migrated upwards and the bone that was behind it, the septomaxilla, became larger and moved forwards to become mammals' jaw tip. Researchers say that the facial bones of egg-laying mammals, like the Australian platypus and echidna, provide additional living examples of transitional bone structures from the evolutionarily older reptile model to the more recently evolved mammalian structure.

This separation of the nose and jaw gives mammals their unique ability to "sniff," using muscles to flare the nostrils and deeply inhale odors from the environment.

"This finding is a key innovation in the evolution of our and other mammals' motile nose, which contributes to mammals' highly sensitive sense of smell," said Higashiyama.

Distinguishing and recognizing so many odors may have also helped mammals develop larger, more complex brains than earlier ancestor species.

The recent research has provided physical evidence of the evolutionary shift in premaxilla and septomaxilla arrangement, but separate studies will be needed to identify the genetic causes.

"Now we know the composition of facial prominences and embryonic development in multiple species, so we can compare facial development disorders in chickens or frogs to humans. We have mainly just improved textbook knowledge for now, but in the future, these animal models will be a practical application of our studies," said Higashiyama.

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