Mass extinction typically conjures up a picture of a meteor falling to Earth and decimating the dinosaurs along with everything else. However, this is not exactly what happened. Different groups of living beings were affected differently by the various mass extinctions that have occurred during the planet’s history.

Consider mammals, a class of vertebrates that already existed during the dinosaur era and survived the mass extinction event in which almost all the dinosaurs were wiped out 66 million years ago, marking the end of the Cretaceous Period.

Four lineages of mammals were contemporaries of the giant reptiles. All four survived. Some were worse hit than others. In a study published in the journal Biology Letters, biologists Tiago Bosisio Quental of the University of São Paulo (USP) and Mathias Pires of the University of Campinas (UNICAMP), both from Brazil, set out to understand how the different groups of mammals made it through the end-Cretaceous mass extinction. Their research was supported by São Paulo Research Foundation — FAPESP.

“When people talk about a mass extinction, it’s assumed that they’re referring to a single extinction event of exceptional magnitude during which a large number of species became extinct in a relatively short time,” Pires said.

Another way of looking at mass extinctions consists of observing the number of species in the fossil record. It can be inferred that a mass extinction occurred in a given geological period when the total number of species that disappeared from the fossil record was much higher than the number of new species that emerged.

“In other words, the extinction rate — the speed at which species are lost — surpasses the speciation rate — the speed at which species are created. This makes the diversification rate negative, since the diversification rate is given by the difference between the extinction and speciation rates,” Pires said.

Five great mass extinctions have been identified in the fossil record in the last 500 million years (as well as many others on a smaller scale). They occurred for various reasons, such as magma spills lasting thousands or millions of years and releasing billions of tons of greenhouse gases that poisoned the atmosphere and blocked out the sun’s rays.

This is what caused the worst of all mass extinctions, in which over 90% of species vanished. It happened 252 million years ago, marking the boundary between the Permian and Triassic Periods (and between the Paleozoic and Mesozoic Eras).

Mass extinctions have also been caused by huge greenhouse effects due to the release of billions of tons of carbon gas (CO2) trapped under the seabed. One such episode is believed to have occurred at the end of the Triassic some 201 million years ago, killing 80% of all species.

The reverse has also happened, with billions of tons of CO2 being sequestered from the atmosphere and causing temperatures to crash and ice to cover the planet. This was the case 444 million years ago at the end of the Ordovician, when 86% of life forms disappeared.

The mass extinction that occurred 66 million years ago is known as the K-Pg event. The acronym refers to the end of the Cretaceous (Kreide in German) and the onset of the Paleogene (Pg).

On a larger time scale, the K-Pg event marks the boundary between the Mesozoic, the era dominated by dinosaurs, and the Cenozoic, the era extending from 66 million years ago to the present day during which mammals have been one of the dominant groups on the planet.

The K-Pg event was caused by a combination of two factors: devastating magma spills in what is now India and the impact of a comet or asteroid with a diameter of 10 km on the Yucatán peninsula in Mexico.

“All these mass extinction episodes are heterogeneous. They occurred for different reasons and unfolded in different ways. Their impact on life forms was not absolute but relative. Some groups suffered more, others less. Some disappeared, while others took advantage of the new environmental conditions after the catastrophe to diversify rapidly,” Pires said.

In the new study that was supported by FAPESP, the researchers set out to investigate how the different lineages of mammals that existed at the end of the Cretaceous succeeded in emerging from the biotic bottleneck represented by the K-Pg event. Daniele Silvestro of the University of Gothenburg (Sweden) and Brian Rankin of the University of California Berkeley (USA) also participated in the study.

The great class of mammals emerged in the Triassic at least 220 million years ago. This is the age of the oldest known fossil. At the end of the Cretaceous, mammalian species were highly diversified. There were the Eutheria or placental mammals, the clade to which Homo sapiens belongs, as do all primates, rodents, bats, cetaceans, and ungulates, among others.

In addition, there were Metatheria or marsupials, the clade to which today’s opossums, kangaroos, and koalas belong. They shared the planet with monotremes (egg-laying mammals) and multituberculates (an extinct taxon of rodent-like mammals named for the specific shape of their teeth, which had multiple tubercles).

The study by Pires and Quental stresses that mammals were particularly hard hit by the mass extinction in the Cretaceous. This does not mean that all four groups suffered equally. The mass extinction was more severe for some than for others.

During the Cretaceous, between 145 million and 66 million years ago, the multituberculates were the dominant and most diversified group of mammals. We know this because multituberculates are the vast majority in the fossil record prior to the K-Pg event. Fossils of placentals and marsupials are less numerous but also plentiful.

Monotremes are the exception. Today, they are few and far between. Indeed, they are comprised of just two families: one includes the duck-billed platypus while the other regards echidnas. Monotremes are also rare in the fossil record both before and after the Cretaceous, suggesting that the group has always been relatively marginal among mammals. For this reason, the researchers did not include monotremes in their study.

Given the knowledge that there were multituberculates, placentals, and marsupials, which group of mammals was most severely affected by the K-Pg event? Which had the most surviving genera? Which displayed the largest increase in diversity (or highest speciation rate) in the millions of years that followed the biotic bottleneck? Which group failed to recover from the cataclysm?

The only way to find answers to these questions is by analyzing the fossil record in a specific region of the planet to try to ensure that all groups of mammals were affected more or less to the same extent by the catastrophe 66 million years ago and in that region.

Quental and Pires chose North America as the focus for their study. One hundred and fifty years of continuous paleontological prospecting in the region have created a detailed picture of mammalian diversity before, during and after the K-Pg event.

“North America has a fossil record of sufficient quality for this kind of study. Other studies have been conducted to analyze how mammals as a whole survived the Cretaceous extinction, but as far we know, this is one of the first studies to analyze the dynamics of diversification in the different groups of mammals,” Quental said.

Distinct diversification patterns

The scientists used a dataset containing 188 recent fossil assemblages from the Cretaceous and Paleocene (spanning from 69.9 million to 55 million years ago) located in the western interior of North America.

“The North American mammal fossil record has the richest and most extensively studied assemblages near the K-Pg event. Fossil occurrences are relatively well resolved, minimizing taxonomic uncertainty. This dataset includes information on nearly 290 genera of mammals, including multituberculates, eutherians, and metatherians,” Quental said.

Several advanced statistical methods were used to estimate origination, extinction and diversification patterns before, during and after the K-Pg event. The results showed that the three groups emerged very differently from the mass extinction.

The origination rate for Methateria (marsupials), for example, remained approximately constant throughout the studied interval. However, a clear peak in extinction was identified during the K-Pg, generating a pulse of negative net diversification. After the K-Pg, the extinction rate gradually diminished, but negative net diversification persisted for more than 2 million years until approximately 64 million years ago.

Multituberculates were diversifying toward the end of the Cretaceous prior to the K-Pg boundary, showing high origination rates and relatively low extinction rates. Near the K-Pg boundary, the extinction rate remained low, but a drop in origination reduced the diversification of multituberculates to near zero. In other words, during the K-Pg, the diversification rate was in balance, as roughly the same number of genera were being created and becoming extinct.

According to the study, after the K-Pg boundary, the extinction rate for multituberculates continued to fall; however, the decrease in multituberculates’ origination rate was even sharper, hence leading to negative diversification. Thus, the number of genera continued to diminish throughout the rest of the period analyzed, until 55 million years ago. The decline appears to have persisted for a long time, given that the multituberculates steadily disappear from the world fossil record. The clade ends approximately 35 million years ago.

Scientists believe the reason for the disappearance of the multituberculates may have been growing competition with rodents, a new eutherian lineage that originated shortly after the K-Pg in the Paleogene.

Eutherians (placentals) display high origination and high extinction near the K-Pg, resulting in high diversity turnover. Originations were higher than extinctions, except between 66 million and 64 million years ago.

Not long after this, there was a second origination pulse accompanied by a drop in the extinction rate, evidencing a short burst in diversification. Around 62 million years ago origination decreased and diversification remained around zero, suggesting diversity equilibrium.

“We found three diversification patterns among the mammalian groups. Metatheria (marsupials) conformed to the classic mass extinction response, with several temporally clustered extinctions leading to a sharp drop in diversification,” Quental said.

Multituberculates underwent a reduction in diversity, with a decrease in diversification and subsequent diversity loss driven by declining origination rates rather than extinction. In other words, their diversity diminished because the creation of new species took a long time.

“Among eutherians there was a more complex rise-and-fall pattern due to rapid fluctuations in the speciation rate during and just after the K-Pg, while the extinction rate rose but not enough to cause negative diversification for long,” Quental said.

According to Pires, the study shows that the K-Pg mass extinction was ecologically selective among mammalian lineages. “Extinctions were concentrated among the specialized carnivorous metatherians and insectivorous eutherians, whereas more generalized eutherians and multituberculates survived and maintained higher diversity,” he said.

Although the results suggest eutherians suffered substantial losses at the K-Pg boundary, these losses were offset by increased origination. Diversification may have occurred among the survivors as other groups of eutherians came to North America from other continents.

“The dietary plasticity of multituberculates may have enabled some species to persist, explaining the low extinction rates. The ecological and taxonomic diversity of multituberculates increased during the late Cretaceous. However, our analysis shows that the multituberculates failed to offset extinction losses because they created less and less diversity, unlike the eutherians, whose losses were offset by high origination rates,” Pires said.

In their conclusion, the authors note that when clades are assessed individually, mass extinction events may be seen as shifts in extinction, in origination, or in both regimes.

“This means that studies of macroevolutionary phenomena focusing on broad taxonomic groups may miss a much richer macroevolutionary history, which can be perceived only at finer taxonomic scales,” Pires said.

Reference:
Mathias M. Pires, Brian D. Rankin, Daniele Silvestro, Tiago B. Quental. Diversification dynamics of mammalian clades during the K–Pg mass extinction. Biology Letters, 2018; 14 (9): 20180458 DOI: 10.1098/rsbl.2018.0458

Note: The above post is reprinted from materials provided by Fundação de Amparo à Pesquisa do Estado de São Paulo.

Early Jurassic predatory dinosaurs are very rare, and mostly small in size. Saltriovenator zanellai, a new genus and species described in the peer-reviewed journal PeerJ — the Journal of Life and Environmental Sciences by Italian paleontologists, is the oldest known ceratosaurian, and the world’s largest (one ton) predatory dinosaur from the Lower Jurassic (Sinemurian, ~198 Mya).

This unique specimen, which also represents the first Jurassic dinosaur from Italy, was accidentally discovered in 1996 by a fossil amateur within a quarry near Saltrio, some 80 km N-E of Milan. Many bones of Saltriovenator bear feeding marks by marine invertebrates, which represent the first case on dinosaurian remains and indicate that the dinosaur carcass floated in a marine basin and then sunk, remaining on the sea bottom for quite a long time before burial.

Although fragmentary, “Saltriovenator shows a mosaic of ancestral and advanced anatomical features, respectively seen in the four-fingered dilophosaurids and ceratosaurians, and the three-fingered tetanuran theropods, such as allosaurids,” says first author Cristiano Dal Sasso, of the Natural History Museum of Milan, who reassembled and studied the fossil for several years.

“Paleohistological analysis indicates that Saltriovenator was a still growing subadult individual, therefore its estimated size is all the more remarkable, in the context of the Early Jurassic period,” says co-author Simone Maganuco.

“The evolutionary ‘arms race’ between stockier predatory and giant herbivorous dinosaurs, involving progressively larger species, had already begun 200 million of years ago.”

The evolution of the hand of birds from their dinosaurian ancestors is still hotly debated. “The grasping hand of Saltriovenator fills a key gap in the theropod evolutionary tree: predatory dinosaurs progressively lost the pinky and ring fingers, and acquired the three-fingered hand which is the precursor of the avian wing,” remarks co-author Andrea Cau.

Reference:
Cristiano Dal Sasso, Simone Maganuco, Andrea Cau. The oldest ceratosaurian (Dinosauria: Theropoda), from the Lower Jurassic of Italy, sheds light on the evolution of the three-fingered hand of birds. PeerJ, 2018; 6: e5976 DOI: 10.7717/peerj.5976

Note: The above post is reprinted from materials provided by PeerJ.

Being a gigantic dinosaur presented some challenges, such as overheating in the Cretaceous sun and frying your brain. Researchers from Ohio University and NYITCOM at Arkansas State show in a new article in PLOS ONE that the heavily armored, club-tailed ankylosaurs had a built-in air conditioner in their snouts.

“The huge bodies that we see in most dinosaurs must have gotten really hot in warm Mesozoic climates,” said Jason Bourke, Assistant Professor at the New York Institute of Technology College of Osteopathic Medicine at Arkansas State and lead author of the study. “Brains don’t like that, so we wanted to see if there were ways to protect the brain from cooking. It turns out the nose may be the key.”

Bourke and the team used CT scanning and a powerful engineering approach called computational fluid dynamics to simulate how air moved through the nasal passages of two different ankylosaur species, the hippo-sized Panoplosaurus and larger rhino-sized Euoplocephalus, to test how well ankylosaur noses transferred heat from the body to the inhaled air.

“A decade ago, my colleague Ryan Ridgely and I published the discovery that ankylosaurs had insanely long nasal passages coiled up in their snouts,” said study co-author Lawrence Witmer, professor at the Ohio University Heritage College of Osteopathic Medicine. “These convoluted airways looked like a kid’s ‘crazy-straw!’ It was completely unexpected and cried out for explanation. I was thrilled when Jason took up the problem as part of his doctoral research in our lab.”

“This project is an excellent example of how advances in CT scanning, 3-D reconstruction, imaging, and computational fluid dynamics modeling can be used in biological research to test long-standing hypotheses,” said Kathy Dickson, a program officer at the National Science Foundation that funded the research. “From these new images and models, fossils can provide further insight into extinct organisms like the ankylosaur — in this case, offering an explanation of how unusual features actually function physiologically.”

Smell may be a primary function of the nose, but noses are also heat exchangers, making sure that air is warmed and humidified before it reaches our delicate lungs. To accomplish this effective air conditioning, birds and mammals, including humans, rely on thin curls of bone and cartilage within their nasal cavities called turbinates, which increase the surface area, allowing for air to come into contact with more of the nasal walls. “Ankylosaurs didn’t have turbinates, but instead made their noses very long and twisty,” said Bourke.

When the researchers compared their findings to data from living animals, they discovered that the dinosaurs’ noses were just as efficient at warming and cooling respired air. “This was a case of nature finding a different solution to the same problem,” said Bourke.

Just how long were these nasal passages? In Panoplosaurus, they were a bit longer than the skull itself and in Euoplocephalus they were almost twice as long as the skull, which is why they’re coiled up in the snout. To see if nasal passage length was the reason for this efficiency, Bourke ran alternative models with shorter, simpler nasal passages that ran directly from the nostril to the throat, as in most other animals. The results clearly showed that nose length was indeed the key to their air-conditioning ability. “When we stuck a short, simple nose in their snouts, heat-transfer rates dropped over 50 percent in both dinosaurs. They were less efficient and didn’t work very well,” said Bourke.

Another line of evidence that these noses were air conditioners that helped cool the brain came from analyses of blood flow.

“When we reconstructed the blood vessels, based on bony grooves and canals, we found a rich blood supply running right next to these convoluted nasal passages,” said Ruger Porter, lecturer at the Ohio University Heritage College of Osteopathic Medicine and one of the study’s co-authors. “Hot blood from the body core would travel through these blood vessels and transfer their heat to the incoming air. Simultaneously, evaporation of moisture in the long nasal passages cooled the venous blood destined for the brain.”

So why the need for such effective heat exchangers? The large bodies of Panoplosaurus and Euoplocephalus were really good at retaining heat, which is good for staying warm, but bad when the animals need to cool off. This heat-shedding problem would have put them at risk of overheating even on cloudy days. In the absence of some protective mechanism, the delicate neural tissue of the brain could be damaged by the hot blood from the body core.

“Sure, their brains were almost comically small,” Bourke said. “But they’re still their brains and needed protection.”

The complicated nasal airways of these dinosaurs were acting as radiators to cool down the brain with a constant flow of cooled venous blood, allowing them to keep a cool head at all times. This natural engineering feat also may have allowed the evolution of the great sizes of so many dinosaurs.

“When we look at the nasal cavity and airway in dinosaurs, we find that the most elaborate noses are found in the large dinosaur species, which suggests that the physiological stresses of large body size may have spurred some of these anatomical novelties to help regulate brain temperatures,” Witmer said.

The next step for the researchers is to examine other dinosaurs to determine when this nasal enlargement happened.

“We know that large dinosaurs had these crazy airways, but at exactly what size did this happen?” Bourke said. “Was this elaboration gradual as body size increased, or is there a threshold size where a run-of-the-mill nose can no longer do the job? We just don’t know yet.”

The research was funded by National Science Foundation (NSF) grants to Witmer (part of the Visible Interactive Dinosaur Project) and an NSF fellowship to Bourke, as well as by the Ohio University Heritage College of Osteopathic Medicine.

Reference:
Jason M. Bourke, Wm. Ruger Porter, Lawrence M. Witmer. Convoluted nasal passages function as efficient heat exchangers in ankylosaurs (Dinosauria: Ornithischia: Thyreophora). PLOS ONE, 2018; 13 (12): e0207381 DOI: 10.1371/journal.pone.0207381

Note: The above post is reprinted from materials provided by Ohio University.

Spectacular flying reptiles armed with long teeth and claws which once dominated the skies have been rediscovered, thanks to a palaeontology student’s PhD research.

Dr Michael O’Sullivan, at the University of Portsmouth, has uncovered evidence of well armed and substantial flying reptiles from historically important, but overlooked, British Jurassic fossils.

He’s also found a new species of pterosaur with a wingspan of two metres — as large as a modern mute swan, and a giant in its time.

Some 200 fossils of flying reptiles — pterosaurs — have been collected over the last two centuries from the Stonesfield Slate, but their significance has been long neglected by palaeontologists, probably because they are mere fragments.

Closer inspection has revealed evidence of multiple pterosaur lineages in the UK’s Jurassic past, including some unexpectedly large and formidably armed species.

The research is Published in Acta Palaeontologica Polonica where it is highlighted as ‘editor’s choice’.

Dr O’Sullivan, in the University’s School of Earth and Environmental Sciences, said: “It’s large fangs would have meshed together to form a toothy cage, from which little could escape once Klobiodon had gotten a hold of it.

“The excellent marine reptiles and ammonites of the UK’s Jurassic heritage are widely known, but we celebrate our Jurassic flying reptiles far less.

“The Stonesfield pterosaurs are rarely pretty or spectacular, but they capture a time in flying reptile evolution which is poorly represented globally. They have an important role to play in not only understanding the UK’s natural history, but help us understand the bigger global picture as well.”

He has named the new species Klobiodon rochei.

The generic name means ‘cage tooth’, in reference to its huge, fang-like teeth — up to 26mm long at a time when few pterosaurs had any teeth — and the species name honours comic book artist Nick Roche in recognition of the role popular media has in how extinct animals are portrayed.

Only the lower jaw of Klobiodon is known, but it has a unique dental configuration that allows it to be distinguished from other pterosaurs. It was likely a gull or tern-like creature — a coastal flier that caught fish and squid using its enormous teeth, swallowing them whole.

Much of Dr O’Sullivan’s research has involved untangling the messy science associated with these neglected specimens.

He said: “Klobiodon has been known to us for centuries, archived in a museum drawer and seen by dozens or hundreds of scientists, but it’s significance has been overlooked because it’s been confused with another species since the 1800s.”

Klobiodon and the other Stonesfield pterosaurs lived alongside one of the most famous and important dinosaurs in the world, the predatory Megalosaurus, the first dinosaur ever named. But as global sea levels were higher, and the world was much warmer, their Jurassic Britain was a series of large tropical islands.

Dr O’Sullivan was examining the Stonesfield pterosaur collections held in museums across the UK for his PhD studies when he found evidence of three distinct types of pterosaur, some of which are the oldest of their kind, as well as evidence of a new pterosaur species.

Stonesfield Slate, where the new pterosaur fossils were found, is a rich source of Jurassic fossils about 10 miles northwest of Oxford. It is where, in 1824, Britain’s first discovered dinosaur, the Megalosaurus, was found.

The quantity and quality of such fossils from the area might be why these fragments have until now been overlooked.

Reference:
Michael O’Sullivan, David Martill. Pterosauria of the Great Oolite Group (Middle Jurassic, Bathonian) of Oxfordshire and Gloucestershire, England.. Acta Palaeontologica Polonica, 2018; 63 DOI: 10.4202/app.00490.2018

Note: The above post is reprinted from materials provided by University of Portsmouth.

More than 85 well-preserved dinosaur footprints — made by at least seven different species — have been uncovered in East Sussex, representing the most diverse and detailed collection of these trace fossils from the Cretaceous Period found in the UK to date.

The footprints were identified by University of Cambridge researchers between 2014 and 2018, following periods of coastal erosion along the cliffs near Hastings. Many of the footprints — which range in size from less than 2 cm to over 60 cm across — are so well-preserved that fine detail of skin, scales and claws is easily visible.

The footprints date from the Lower Cretaceous epoch, between 145 and 100 million years ago, with prints from herbivores including Iguanodon, Ankylosaurus, a species of stegosaur, and possible examples from the sauropod group (which included Diplodocus and Brontosaurus); as well as meat-eating theropods. The results are reported in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

Over the past 160 years, there have been sporadic reports of fossilised dinosaur footprints along the Sussex coast, but no new major discoveries have been described for the past quarter century and the earlier findings were far less varied and detailed than those described in the current research.

The area around Hastings is one of the richest in the UK for dinosaur fossils, including the first known Iguanodon in 1825, and the first confirmed example of fossilised dinosaur brain tissue in 2016. However, trace fossils such as footprints, which can help scientists learn more about the composition of dinosaur communities, are less common in the area.

“Whole body fossils of dinosaurs are incredibly rare,” said Anthony Shillito, a PhD student in Cambridge’s Department of Earth Sciences and the paper’s first author. “Usually you only get small pieces, which don’t tell you a lot about how that dinosaur may have lived. A collection of footprints like this helps you fill in some of the gaps and infer things about which dinosaurs were living in the same place at the same time.”

The footprints described in the current study, which Shillito co-authored with Dr Neil Davies, were uncovered during the past four winters, when strong storms and storm surges led to periods of collapse of the sandstone and mudstone cliffs.

In the Cretaceous Period, the area where the footprints were found was likely near a water source, and in addition to the footprints, a number of fossilised plants and invertebrates were also found.

“To preserve footprints, you need the right type of environment,” said Davies. “The ground needs to be ‘sticky’ enough so that the footprint leaves a mark, but not so wet that it gets washed away. You need that balance in order to capture and preserve them.”

“As well as the large abundance and diversity of these prints, we also see absolutely incredible detail,” said Shillito. “You can clearly see the texture of the skin and scales, as well as four-toed claw marks, which are extremely rare.

“You can get some idea about which dinosaurs made them from the shape of the footprints — comparing them with what we know about dinosaur feet from other fossils lets you identify the important similarities. When you also look at footprints from other locations you can start to piece together which species were the key players.”

As part of his research, Shillito is studying how dinosaurs may have affected the flows of rivers. In modern times, large animals such as hippopotamuses or cows can create small channels, diverting some of the river’s flow.

“Given the sheer size of many dinosaurs, it’s highly likely that they affected rivers in a similar way, but it’s difficult to find a ‘smoking gun’, since most footprints would have just washed away,” said Shillito. “However, we do see some smaller-scale evidence of their impact; in some of the deeper footprints you can see thickets of plants that were growing. We also found evidence of footprints along the banks of river channels, so it’s possible that dinosaurs played a role in creating those channels.”

It’s likely that there are many more dinosaur footprints hidden within the eroding sandstone cliffs of East Sussex, but the construction of sea defences in the area to slow or prevent the process of coastal erosion may mean that they remained locked within the rock.

The research was funded by the Natural Environment Research Council (NERC).

Reference:
Anthony P. Shillito, Neil S. Davies. Dinosaur-landscape interactions at a diverse Early Cretaceous tracksite (Lee Ness Sandstone, Ashdown Formation, southern England). Palaeogeography, Palaeoclimatology, Palaeoecology, 2019; 514: 593 DOI: 10.1016/j.palaeo.2018.11.018

Note: The above post is reprinted from materials provided by University of Cambridge. The original story is licensed under a Creative Commons License.

Palentologists are announcing a new dinosaur discovery in the southwest United States. Crittendenceratops krzyzanowskii is a new ceratopsid (horned) dinosaur from 73-million-year-old (Late Cretaceous) rocks in southern Arizona. It is one of the few dinosaurs named from Arizona.

Crittendenceratops krzyzanowskii was named by Sebastian Dalman, John-Paul Hodnett, Asher Lichtig and Spencer Lucas, Ph.D, in an article recently published in the New Mexico Museum of Natural History & Science Bulletin.

Dalman and Lichtig are Research Associates of the New Mexico Museum of Natural History & Science (NMMNHS), Lucas is a curator at NMMNHS, and Hodnett is a paleontologist employed by the Maryland-National Capital Parks Commission.

The name Crittendenceratops is for the Fort Crittenden Formation (the rock formation that yielded the dinosaur fossils) and Greek ceratops, which means horned face. The species name krzyzanowskii is for the late Stan Krzyzanowski, a NMMNHS Research Associate who discovered the bones of the new dinosaur.

Crittendenceratops belongs to a group of horned dinosaurs called the centrosaurs, and can be distinguished from other centrosaurs by the unique shape of the bones in its frill (head shield). Crittendenceratrops was about 11 feet long and weighed an estimated three-quarters of a ton. Like other ceratopsids, Crittendenceratops was a plant eater.

The rocks that yielded the bones were deposited along the margins of a large lake that was present in an area southeast of Tucson, Arizona during the Late Cretaceous.

Reference:
A New Ceratopsid Dinosaur (Centrosaurinae: Nasutoceratopsini) From The Fort Crittenden Formation, Upper Cretaceous (Campanian) Of Arizona. www.researchgate.net/publicati … CAMPANIAN_OF_ARIZONA

Note: The above post is reprinted from materials provided by New Mexico Museum of Natural History & Science.

An international team of palaeontologists, which includes the University of Bristol, has discovered that the flying reptiles, pterosaurs, actually had four kinds of feathers, and these are shared with dinosaurs — pushing back the origin of feathers by some 70 million years.

Pterosaurs are the flying reptiles that lived side by side with dinosaurs, 230 to 66 million years ago. It has long been known that pterosaurs had some sort of furry covering often called ‘pycnofibres’, and it was presumed that it was fundamentally different to feathers of dinosaurs and birds.

In a new work published today in the journal Nature Ecology & Evolution, a team from Nanjing, Bristol, Cork, Beijing, Dublin, and Hong Kong show that pterosaurs had at least four types of feathers:

• simple filaments (‘hairs’)
• bundles of filaments,
• filaments with a tuft halfway down
• down feathers.

These four types are now also known from two major groups of dinosaurs — the ornithischians, which were plant-eaters, and the theropods, which include the ancestors of birds.

Baoyu Jiang of Nanjing University, who led the research, said: “We went to Inner Mongolia to do fieldwork in the Daohugou Formation.

“We already knew that the sites had produced excellent specimens of pterosaurs with their pycnofibres preserved and I was sure we could learn more by careful study.”

Zixiao Yang, also of Nanjing University, has studied the Daohugou localities and the pterosaurs as part of his PhD work. He said: “This was a fantastic opportunity to work on some amazing fossils.

“I was able to explore every corner of the specimens using high-powered microscopes, and we found many examples of all four feathers.”

Maria McNamara of University College Cork, added: “Some critics have suggested that actually there is only one simple type of pycnofibre, but our studies show the different feather types are real.

“We focused on clear areas where the feathers did not overlap and where we could see their structure clearly. They even show fine details of melanosomes, which may have given the fluffy feathers a ginger colour.”

Professor Mike Benton from the University of Bristol’s School of Earth Sciences, said: “We ran some evolutionary analyses and they showed clearly that the pterosaur pycnofibres are feathers, just like those seen in modern birds and across various dinosaur groups.

“Despite careful searching, we couldn’t find any anatomical evidence that the four pycnofibre types are in any way different from the feathers of birds and dinosaurs. Therefore, because they are the same, they must share an evolutionary origin, and that was about 250 million years ago, long before the origin of birds.”

Birds have two types of advanced feathers used in flight and for body smoothing, the contour feathers with a hollow quill and barbs down both sides.

These are found only in birds and the theropod dinosaurs close to bird origins. But the other feather types of modern birds include monofilaments and down feathers, and these are seen much more widely across dinosaurs and pterosaurs.

The armoured dinosaurs and the giant sauropods probably did not have feathers, but they were likely suppressed, meaning they were prevented from growing, at least in the adults, just as hair is suppressed in whales, elephants, and hippos. Pigs are a classic example, where the piglets are covered with hair like little puppies, and then, as they grow, the hair growth is suppressed.

Professor Benton added: “This discovery has amazing implications for our understanding of the origin of feathers, but also for a major time of revolution of life on land.

“When feathers arose, about 250 million years ago, life was recovering from the devasting end-Permian mass extinction.

“Independent evidence shows that land vertebrates, including the ancestors of mammals and dinosaurs, had switched gait from sprawling to upright, had acquired different degrees of warm-bloodedness, and were generally living life at a faster pace.

“The mammal ancestors by then had hair, so likely the pterosaurs, dinosaurs and relatives had also acquired feathers to help insulate them.

“The hunt for feathers in fossils is heating up and finding their functions in such early forms is imperative. It can rewrite our understanding of a major revolution in life on Earth during the Triassic, and also our understanding of the genomic regulation of feathers, scales, and hairs in the skin.”

Reference:
Zixiao Yang, Baoyu Jiang, Maria E. McNamara, Stuart L. Kearns, Michael Pittman, Thomas G. Kaye, Patrick J. Orr, Xing Xu, Michael J. Benton. Pterosaur integumentary structures with complex feather-like branching. Nature Ecology & Evolution, 2018; 3 (1): 24 DOI: 10.1038/s41559-018-0728-7

Note: The above post is reprinted from materials provided by University of Bristol.

Iridescence is responsible for some of the most striking visual displays in the animal kingdom. Now, thanks to a new study of feathers from almost 100 modern bird species, scientists have gained new insights into how this colour diversity evolved.

Iridescence refers to the phenomena where colour changes when an object is viewed from different angles. Birds produce this varying coloration in their feathers by using nanoscale arrays of melanin-filled organelles (melanosomes) layered with keratin. In this form of structural colouration, the shapes of melanosomes together with the thickness of keratin layers determine what colour is produced.

While melanosome morphology has previously been used to predict colour in fossil animals, melanosome variation in iridescent feathers has not been analysed on as large a scale until this study.

As reported in the journal Evolution, a team of University of Bristol researchers used scanning electron microscopy to quantify melanosome extracts from the feathers of 97 species of modern birds with iridescent plumage, taken from the collections of the Zoological Museum of Copenhagen.

The study showed that iridescent feathers contain the most varied melanosome morphologies of all types of bird coloration sampled to date. Unlike black, grey and brown feathers that always contain solid melanosomes, iridescent feathers can contain melanosomes that are hollow and/or flattened.

“We found that melanosomes in modern iridescent feathers are more diverse in shape than those found in grey, black or brown feathers combined (that also contain melanosomes),” said lead author Klara Nordén, who conducted the study during her undergraduate years at Bristol’s School of Earth Sciences. “It is already known that structural coloration is responsible for 70 per cent of the colour variability in birds. These two facts might be coupled — birds evolved varied forms of melanosomes to achieve ever greater diversity in colour.

“I wanted to find out if we could improve current predictive models for fossil colour based on melanosome morphology by including all types of melanosomes found in iridescent feathers.”

Dr Jakob Vinther, co-author of the study and a leading researcher in the field of paleocolour at Bristol’s School of Biological Sciences, had already collected the perfect fossil samples to test the new model on.

“We had sampled Scaniacypselus, related to modern tree swifts, and Primotrogon, ancestor to modern trogons. These groups are iridescent today and have flat and hollow melanosomes. Did their 48-million-year-old ancestors from Germany also have iridescent plumage?”

Interestingly, the model predicted that Primotrogon probably was iridescent, but it used solid rather than hollow melanosomes, unlike its modern descendants.

“This demonstrates how we now have the tools to map out the evolution of iridescence in fossil lineages,” said Klara, who is now a PhD student at Princeton University. “It opens the door to many new discoveries of dazzling displays in fossil birds and other dinosaurs.”

The current study focused on mapping out how melanosomes vary in iridescent feathers. Further avenues of research might examine why birds utilise such diversity of melanosome types in iridescent feathers. These insights could ultimately enhance our understanding of why fossil birds or dinosaurs might have used such morphologies, revealing something about their behaviour.

Reference:
Klara K. Nordén, Jaeike Faber, Frane Babarović, Thomas L. Stubbs, Tara Selly, James D. Schiffbauer, Petra Peharec Štefanić, Gerald Mayr, Fiann M. Smithwick, Jakob Vinther. Melanosome diversity and convergence in the evolution of iridescent avian feathers-Implications for paleocolor reconstruction. Evolution, 2018; DOI: 10.1111/evo.13641

Note: The above post is reprinted from materials provided by University of Bristol.