The question of whether the Late Jurassic dino-bird Archaeopteryx was an elaborately feathered ground dweller, a glider, or an active flyer has fascinated palaeontologists for decades. Valuable new information obtained with state-of-the-art synchrotron microtomography at the ESRF, the European Synchrotron (Grenoble, France), allowed an international team of scientists to answer this question in Nature Communications. The wing bones of Archaeopteryx were shaped for incidental active flight, but not for the advanced style of flying mastered by today's birds.

The Munich specimen of the transitional bird Archaeopteryx. It preserves a partial skull (top left), shoulder girdle and both  wings slightly raised up (most left to center left), the ribcage (center), and the pelvic girdle and both legs in a 'cycling' posture (right); all connected by the vertebral column from the neck (top left, under the skull) to the tip of the tail (most right). Imprints of its wing feathers are visible radiating from below the shoulder and vague imprints of the tail plumage can be recognized extending from the tip of the tail [Credit: ESRF/Pascal Goetgheluck]

Was Archaeopteryx capable of flying, and if so, how? Although it is common knowledge that modern-day birds descended from extinct dinosaurs, many questions on their early evolution and the development of avian flight remain unanswered. Traditional research methods have thus far been unable to answer the question whether Archaeopteryx flew or not. Using synchrotron microtomography at the ESRF's beamline ID19 to probe inside Archaeopteryx fossils, an international team of scientists from the ESRF, Palacký University, Czech Republic, CNRS and Sorbonne University, France, Uppsala University, Sweden, and Bürgermeister-Müller-Museum Solnhofen, Germany, shed new light on this earliest of birds.

Reconstructing extinct behaviour poses substantial challenges for palaeontologists, especially when it comes to enigmatic animals such as the famous Archaeopteryx from the Late Jurassic sediments of southeastern Germany that is considered the oldest potentially free-flying dinosaur. This well-preserved fossil taxon shows a mosaic anatomy that illustrates the close family relations between extinct raptorial dinosaurs and living dinosaurs: the birds. Most modern bird skeletons are highly specialised for powered flight, yet many of their characteristic adaptations in particularly the shoulder are absent in the Bavarian fossils of Archaeopteryx. Although its feathered wings resemble those of modern birds flying overhead every day, the primitive shoulder structure is incompatible with the modern avian wing beat cycle.

The Munich specimen of Archaeopteryx at beamline ID19 at the ESRF. The limestone plate was mounted on a rotating sample stage and the beam is here centered on the skull using lasers. The X-ray beam, coming from the right of the picture, travels through the sample and arrives at the detector (visible left) where a camera records the signal [Credit: ESRF/Pascal Goetgheluck]

"The cross-sectional architecture of limb bones is strongly influenced by evolutionary adaptation towards optimal strength at minimal mass, and functional adaptation to the forces experienced during life," explains Prof. Jorge Cubo of the Sorbonne University in Paris. "By statistically comparing the bones of living animals that engage in observable habits with those of cryptic fossils, it is possible to bring new information into an old discussion," says senior author Dr. Sophie Sanchez from Uppsala University, Sweden

Archaeopteryx skeletons are preserved in and on limestone slabs that reveal only part of their morphology. Since these fossils are among the most valuable in the world, invasive probing to reveal obscured or internal structures is therefore highly discouraged. "Fortunately, today it is no longer necessary to damage precious fossils," states Dr. Paul Tafforeau, beamline scientist at the ESRF. "The exceptional sensitivity of X-ray imaging techniques for investigating large specimens that is available at the ESRF offers harmless microscopic insight into fossil bones and allows virtual 3D reconstructions of extraordinary quality. Exciting upgrades are underway, including a substantial improvement of the properties of our synchrotron source and a brand new beamline designated for tomography. These developments promise to give even better results on much larger specimens in the future."

Dennis Voeten indicates the bone wall thickness of the 'Chicken Wing' specimen of Archaeopteryx on the top computer screen for comparison against the bone walls of a primitive pterosaur on the bottom screen. A three-dimensional model of the 'Chicken Wing' is held up, the referred bone cross section is that of the humerus, the uppermost arm bone visible most right on the 3-D-printed model [Credit: ESRF]

Scanning data unexpectedly revealed that the wing bones of Archaeopteryx, contrary to its shoulder girdle, shared important adaptations with those of modern flying birds. "We focused on the middle part of the arm bones because we knew those sections contain clear flight-related signals in birds," says Dr. Emmanuel de Margerie, CNRS, France. "We immediately noticed that the bone walls of Archaeopteryx were much thinner than those of earthbound dinosaurs but looked a lot like conventional bird bones," continues lead author Dennis Voeten of the ESRF. "Data analysis furthermore demonstrated that the bones of Archaeopteryx plot closest to those of birds like pheasants that occasionally use active flight to cross barriers or dodge predators, but not to those of gliding and soaring forms such as many birds of prey and some seabirds that are optimised for enduring flight."

"We know that the region around Solnhofen in southeastern Germany was a tropical archipelago, and such an environment appears highly suitable for island hopping or escape flight," remarks Dr. Martin Röper, Archaeopteryx curator and co-author of the report. "Archaeopteryx shared the Jurassic skies with primitive pterosaurs that would ultimately evolve into the gigantic pterosaurs of the Cretaceous. We found similar differences in wing bone geometry between primitive and advanced pterosaurs as those between actively flying and soaring birds," adds Vincent Beyrand of the ESRF.

Since Archaeopteryx represents the oldest known flying member of the avialan lineage that also includes modern birds, these findings not only illustrate aspects of the lifestyle of Archaeopteryx but also provide insight into the early evolution of dinosaurian flight. "Indeed, we now know that Archaeopteryx was already actively flying around 150 million years ago, which implies that active dinosaurian flight had evolved even earlier!" says Prof. Stanislav Bureš of Palacký University in Olomouc. "However, because Archaeopteryx lacked the pectoral adaptations to fly like modern birds, the way it achieved powered flight must also have been different. We will need to return to the fossils to answer the question on exactly how this Bavarian icon of evolution used its wings," concludes Voeten.

It is now clear that Archaeopteryx is a representative of the first wave of dinosaurian flight strategies that eventually went extinct, leaving only the modern avian flight stroke directly observable today.

Source: European Synchrotron Radiation Facility [March 13, 2018]

Fossils of six new species of pterosaurs - giant flying reptiles that flew over the heads of the dinosaurs - have been discovered by a research team led by the Milner Centre for Evolution at the University of Bath, revealing that this lineage was killed off in its prime. An analysis of the fossils, published in the open access journal PLOS Biology shows that, contrary to previous studies, there was still remarkable diversity among pterosaurs up to the point of their extinction.

Some of the Moroccan pterosaur fossils from the study. Top: the mandible (lower jaw) of Alcione elainus, a small pterosaur newly described in this paper. Bottom: part of the ulna (forearm bone) from a giant pterosaur, tentatively identified as Arambourgiania. Note the different scales - the mandible is less than 20 cm long, while the ulna is more than 40 cm long; Arambourgiania would have had a wingspan more than three times that of Alcione [Credit: pbio.2001663]

Pterosaurs - prehistoric reptiles popularly known as pterodactyls - were flying cousins of the dinosaurs. Soaring on skin wings supported by a single huge finger, they were the largest animals ever to take wing.

The pterosaurs were previously thought to be declining before the mass extinction at the end of the Cretaceous period, which was caused by an asteroid impact 66 million years ago. However, hundreds of new fossils from the end of the Cretaceous, discovered at sites in northern Morocco, show that the region supported seven species of pterosaur from three different families. It was thought that the rarity of pterosaur fossils from the end of the dinosaur era meant that they were slowly going extinct. But the new study shows that the data had been misleadingly skewed by the dearth of fossils and that the pterosaurs at this time were actually far more diverse than thought.

The new pterosaurs ranged in wingspan from a little over two meters to almost ten meters (from 6 to 30 feet) - almost three times bigger than the largest living bird - and weighed up to 200 kg (440 pounds). The fossils date to just over 66 million years ago, the very end of the Cretaceous period, making these pterosaurs among the last of their kind on Earth. As well as the diversity in size, the authors were also able to show that the species differed significantly in the shape and size of parts of their bodies (such as beak shape, neck length, and wing proportions), suggesting that they occupied distinct ecological niches.

Dr Nick Longrich, from the Milner Centre for Evolution and the Department of Biology & Biochemistry at the University of Bath, and the study's lead author, said: "To grow so large and still be able to fly, pterosaurs evolved incredibly lightweight skeletons, with the bones reduced to thin-walled, hollow tubes like the frame of a carbon-fiber racing bike.

"But unfortunately, that means these bones are fragile, and so almost none survive as fossils."

Longrich said he had always found pterosaurs fascinating, and as a university student had dreamed of studying them. Years later in Morocco, he would stumble across a single, small bone mixed in with fossil fish dug up from a phosphate mine. "It was like a light went off," he said. "I remembered back to the Illustrated Encyclopedia of Pterosaurs, a book I'd practically memorized as an undergraduate. And I thought 'that's a nyctosaur.'"

Nyctosaurs, a family of small pterosaurs, hadn't been proven to survive to the end of the Cretaceous. On a hunch, he looked for more pterosaurs, and found more species - including Tethydraco, a member of the pteranodontids, a family that had been thought to disappear fifteen million years earlier. In addition to the single species previously found in the area, six additional species turned up. "I believe there are many more species to find," he said.

Co-author of the study, Professor David Martill from the University of Portsmouth said: "Exciting discoveries are being made all the time, and sometimes, just the smallest of bones can radically change our perception of the history of life on Earth."

Dr Brian Andres, Research Associate at The University of Texas at Austin, also a co-author of the study, added: "The Moroccan fossils tell the last chapter of the pterosaurs' story - and they tell us pterosaurs dominated the skies over the land and sea, as they had for the previous 150 million years."

Moroccan paleontologist Professor Nour-Eddine Jalil from the Muséum national d'Histoire naturelle, France commented: "This is a fabulous discovery of pterosaurs from Morocco - they tell us their amazing diversity while we thought them in decline. "The Moroccan phosphates are an open window on a key moment in the history of the Earth, one that shortly preceded the global crisis that swept away, among others, dinosaurs and marine reptiles."

Source: Public Library of Science [March 13, 2018]

The tiny fossil of a prehistoric baby bird is helping scientists understand how early avians came into the world in the Age of Dinosaurs.

Artist impression of Enantiornithes [Credit: Raúl Martín]

The fossil, which dates back to the Mesozoic Era (250-65 million years ago), is a chick from a group of prehistoric birds called, Enantiornithes. Made up of a nearly complete skeleton, the specimen is amongst the smallest known Mesozoic avian fossils ever discovered.

It measures less than five centimetres -- smaller than the little finger on an average human hand -- and would have weighed just 10 grams or 0.3 ounces when it was alive. What makes this fossil so important and unique is the fact it died not long after its birth. This is a critical stage in a bird's skeletal formation. That means this bird's extremely short life has given researchers a rare chance to analyse the species' bone structure and development.

Studying and analysing ossification - the process of bone development - can explain a lot about a young bird's life the researchers say. It can help them understand everything from whether it could fly or if it needed to stay with its parents after hatching or could survive on its own.

Phosphorous mapping image and photo of fossil [Credit: Dr. Fabien Knoll]

The lead author of the study, Fabien Knoll, from The University of Manchester's Interdisciplinary Centre for Ancient Life (ICAL), School of Earth and Environmental Sciences, and the ARAID--Dinopolis in Spain explains: 'The evolutionary diversification of birds has resulted in a wide range of hatchling developmental strategies and important differences in their growth rates. By analysing bone development we can look at a whole host of evolutionary traits.'

With the fossil being so small the team used synchrotron radiation to picture the tiny specimen at a 'submicron' level, observing the bones' microstructures in extreme detail.

Knoll said: 'New technologies are offering palaeontologists unprecedented capacities to investigate provocative fossils. Here we made the most of state-of-the-art facilities worldwide including three different synchrotrons in France, the UK and the United States.'

Dr Fabien Knoll in lab [Credit: Dr. Fabien Knoll]

The researchers found the baby bird's sternum (breastplate bone) was still largely made of cartilage and had not yet developed into hard, solid bone when it died, meaning it wouldn't have been able to fly.

The patterns of ossification observed in this and the other few very young enantiornithine birds known to date also suggest that the developmental strategies of this particular group of ancient avians may have been more diverse than previously thought.

However, the team say that its lack of bone development doesn't necessarily mean the hatchling was over reliant on its parents for care and feeding, a trait known as being 'altricial'. Modern day species like love birds are highly dependent on their parents when born. Others, like chickens, are highly independent, which is known as 'precocial'. Although, this is not a black-and-white issue, but rather a spectrum, hence the difficulty in clarifying the developmental strategies of long gone bird species.

Luis Chiappe, from the LA Museum of Natural History and study's co-author added: 'This new discovery, together with others from around the world, allows us to peek into the world of ancient birds that lived during the age of dinosaurs. It is amazing to realise how many of the features we see among living birds had already been developed more than 100 million years ago.'

The findings are published in Nature Communications.

Source: University of Manchester [March 05, 2018]

Fossilized bones of two new species of tiny, flightless extinct birds have been discovered by Australasian scientists in 19 to 16-million-year-old sediments of an ancient lake on the South Island of New Zealand.

A tiny extinct rail (30-40g) is overshadowed by a regular duck  [Credit: Gavin Mouldey]

The two miniscule species—one barely larger than a sparrow—were members of the rail family, a group of birds common today in wetlands that includes swamphens, moorhens, coots and crakes. Their remains were unearthed near the town of St Bathans in Central Otago.

Many rail species can fly well and have dispersed to far-flung oceanic islands. However, flightlessness has evolved more times in this group of birds that in any other, especially on predator-free islands. The world's largest rails evolved in New Zealand, notably the flightless takahe and weka.

The study, led by scientists from Flinders University with colleagues from UNSW, Canterbury Museum and the Museum of New Zealand, is published in the Journal of Systematic Palaeontology.

Team member UNSW Professor Mike Archer, says: "This new discovery emphasizes the fact that New Zealand has long been one of the world's most extraordinary engines driving bird evolution.

"Charting how lineages like these rails have changed through time on an island that has been geographically isolated for more than 80 million years will test basic presumptions made about bird evolution in general," says Professor Archer of the of the PANGEA Research Centre in the School of Biological, Earth and Environmental Sciences.

Nineteen to 16 million years ago, a 5600 square kilometre megalake dominated the landscape of New Zealand's South Island. It was surrounded by a subtropical rainforest and plants typical of Australia and long lost from New Zealand, such as eucalypts, casuarinas, palms and cycads, were common there.

"Flightlessness in birds is often associated with an increase in size," says Ellen Mather, study lead author and Ph.D. student at Flinders University. "The weka, which is in the same family as our fossil birds and lives in New Zealand today, is about the size of a chicken. The Banded Rail, their closest flying relative, is about half that size."

The most common of the new fossil rails has been named Priscaweka parvales, meaning ancient weka with small wings. It was a mere one twentieth of the weight of a weka and was similar in size to the recently extinct Chatham rail Cabalus modestus.

Small flightless birds only exist in the absence of terrestrial mammalian predators, and New Zealand has long been recognised as the iconic example of a country with an avifauna which evolved in the absence of such predators.

When humans discovered New Zealand, the main islands had many flightless birds including giants within the nine species of moa, several kiwi, two huge geese, two adzebills, even some tiny wrens, and at least five flightless rails.

Team member, Dr. Paul Scofield, a Senior Curator at the Natural History at Canterbury Museum, says: "The new St Bathans' rails join a host of other fossil birds recovered from these deposits that show New Zealand has long been a land of birds. The discovery of these two miniscule flightless rails raises the question of 'Where did they come from?'"

The researchers suggest they had ancestors in Australia which flew across the 1500 km ocean to New Zealand in previous millennia. However, the new species are unlike any rail known elsewhere, so their exact origin or closest relatives remain a mystery.

Other than hints of large flightless moa ancestors, these rails are the first flightless birds to be described from this fauna. This is unexpected as the St Bathans Fauna contains small terrestrial mammals, which normally preclude evolution of small flightless species. The tiny flightless rails therefore strongly suggest that the mysterious mammals were not predators of small birds. Flightless birds have been a feature of the New Zealand avifauna for millions of years, much longer than previously thought. They are probably the oldest flightless rails known globally.

"The ongoing research into the fossil birds of New Zealand builds on that begun over 150 years ago. It continues to throw up revelations into the timing and origins of major groups of birds that characterize modern avifaunas" says Associate Professor Trevor Worthy of Flinders University.

Source: University of New South Wales [February 28, 2018]

Researchers from Ludwig-Maximilians-Universitaet (LMU) in Munich report the first description of the geologically oldest fossil securely attributable to the genus Archaeopteryx, and provide a new diagnostic key for differentiating bird-like dinosaurs from their closest relatives.

The geologically oldest, but most recently discovered specimen of Archaeopteryx [Credit: O. Rauhut, LMU Munich]

Some 150 million years ago in what is now Northern Bavaria, Archaeopteryx, the oldest bird species ever discovered, inhabited a subtropical environment characterized by reef islands and lagoons set in a shallow sea that was part of the primordial Mediterranean. All the specimens of Archaeopteryx so far recovered were found in the valley of the Altmühl River, in geological settings that represent this habitat—the Jurassic Solnhofen Archipelago. The latest find was made there in 2010, and this new specimen has now been analyzed by a team of researchers led by LMU paleontologist Oliver Rauhut, a professor in the Department of Earth and Environmental Sciences who is also affiliated with the Bavarian State Collections for Paleontology and Geology in Munich. Stratigraphic analysis of the find locality reveals that the fossil is the oldest known representative of the genus Archaeopteryx.

"Specimens of Archaeopteryx are now known from three distinct rock units, which together cover a period of approximately 1 million years," Rauhut explains. Notably, the oldest example exhibits features that were not observed in the other specimens. "Among other things, they reveal that Archaeopteryx was very similar to advanced predatory dinosaurs in many respects," says Rauhut. Moreover, in the new study, he and his colleagues provide a diagnosis that reliably distinguishes Archaeopteryx from its closest relatives, both non-avialan theropod dinosaurs and basal birds. This key will be very valuable, as a whole series of bird-like predatory dinosaurs has been described in recent years, mainly from China, which has greatly complicated the taxonomic classification of the group.

The new specimen is the 12th fossil to be attributed to the genus. However, in a study published in the online journal BMC Evolutionary Biology last year, Rauhut's group reported that the first of these to come to light—the so-called Haarlem specimen discovered in 1861—does not actually belong to the group. This result thus reduces the number of Archaeopteryx fossils to 11, although some doubts remain concerning the assignment of two of these. This underlines the necessity for a diagnosis to clearly identify Archaeopteryx.

Moreover, the investigation of the 11th specimen demonstrates that the known specimens span a remarkable range of anatomical variation. Potential explanations for the broad spectrum of variation extend from intraspecific developmental polymorphism to evolutionary differentiation, i.e., the possibility that the fossil material so far recovered represents more than one species. "The high degree of variation in the teeth is particularly striking—none of the specimens shows the same pattern of dentition as any other, which could reflect differences in diet," Rauhut says. "This is very reminiscent of the famous case of Darwin's finks on the Galapagos, which show remarkable variation in their beak shapes. It is even conceivable that this primeval bird genus might, in a similar fashion, have diversified into several specialized forms on the islands of the Solnhofener Archipelago. In that case, the Archaeopteryx fossils could represent a species flock, a Jurassic analog of Darwin's finches."

Source: Ludwig Maximilian University of Munich [January 26, 2018]