Most primitive kangaroo ancestor rediscovered after 30 years in obscurity

A handful of tiny teeth have led scientists to identify the most distant ancestor of today’s kangaroos. The fossils were found in the desert heart of Australia, and then hidden away, and almost forgotten in a museum collection for over three decades. The findings are published in the Journal of Vertebrate Paleontology.

Kangaroos are icons of Australia’s unique living fauna. However, their earliest ancestry is shrouded in mystery. At the beginning of the 1980’s, a few enigmatic molar teeth were excavated by palaeontologists hunting for fossils around a dry salt lake in northern South Australia. The rare specimens were recognised as an ancient kangaroo ancestor, but had to wait for over 30 years before modern computer-based analyses could confirm the significance of the discovery.

Originally dubbed Palaeopotorous priscus, Latin for ‘[very] ancient’, ‘ancient rat-kangaroo’, by the now eminent Australian palaeontologists Prof. Tim Flannery (University of Melbourne) and Dr Tom Rich (Museums Victoria), the importance of these remains was suggested in their first unveiling to science.

“The teeth of Palaeopotorous were initially described in 1986. Even then they were stated as representing possibly the most primitive relative of the entire modern kangaroo radiation. Yet, nobody ever evaluated this claim, and despite being occasionally mentioned in the scientific literature, they were never again examined in detail,” said Dr Wendy den Boer, who studied the fossils as part of her recently awarded PhD from Uppsala University in Sweden.

“The name Palaeopotorous was established using a single molar tooth, although, eleven other anatomically very similar teeth were recovered during the expedition. None of these fossils were found in association, so it is still unclear whether we are dealing with one, or more species,” said Dr Benjamin Kear, Dr den Boer’s PhD supervisor and co-author on the published article. “This uncertainly means that we have had to use a complex series of analyses to assess its morphological similarity and evolutionary relationships relative to other members of the kangaroo family tree.”

“Our results showed that Palaeopotorous was most similar to living rat-kangaroos, as well as some other extinct kangaroo relatives. Using information from fossils, and the DNA of living species, we were able to further determine that at around 24 million years old, Palaeopotorous is not just primitive, but likely represents the most distant forerunner of all known kangaroos, rat-kangaroos and their more ancient ancestors,” said Dr den Boer.

“Palaeopotorous was about the size of a small rabbit, and probably did not hop, but would have bounded on all four legs. Nevertheless, a few bones found at the same site in central Australia indicate that the earliest kangaroos already possessed some key adaptations for hopping gaits,” said Dr Kear.

Palaeopotorous lived at a time when central Australia was much wetter than it is today. Its fossils were buried in clay deposits left by a river, but these earliest kangaroo ancestors would have foraged amongst vegetation growing nearby and along the banks. The teeth of Palaeopotorous were washed into the river after death, along with the remains of many other ancient marsupials.

The dinosaur menu, as revealed by calcium

By studying calcium in fossil remains in deposits in Morocco and Niger, researchers have been able to reconstruct the food chains of the past, thus explaining how so many predators could coexist in the dinosaurs’ time. This study, conducted by the Laboratoire de géologie de Lyon: Terre, planètes et environnement (CNRS/ENS de Lyon/Claude Bernard Lyon 1 University), in partnership with the Centre for Research on Palaeobiodiversity and Palaeoenvironments (CNRS/French National Museum of Natural History/Sorbonne University), is published on April 11, 2018 in the Proceedings of the Royal Society of London B.

A hundred million years ago, in North Africa, terrestrial ecosystems were dominated by large predators — giant theropod dinosaurs, large crocodiles — with comparatively few herbivores. How were so many carnivores able to coexist?

To understand this, French researchers have studied fossils in the Gadoufaoua deposits in Niger (dating from 120 million years ago) and the Kem Kem Beds in Morocco (dating from 100 million years ago). These two sites are characterized by an overabundance of predators compared to the herbivorous dinosaurs found in the locality. More specifically, the researchers measured the proportions of different calcium isotopes(1) in the fossilized remains (tooth enamel and fish scales).

Among vertebrates, calcium is almost exclusively derived from food. By comparing the isotopic composition of potential prey (fish, herbivores) with that of the carnivores’ teeth, it is thus possible to retrace the diet of those carnivores.

The data obtained show similar food preferences at the two deposits: some large carnivorous dinosaurs (abelisaurids and carcharodontosaurids) preferred to hunt terrestrial prey such as herbivorous dinosaurs, while others (the spinosaurids) were piscivorous (fish-eating).(2) The giant crocodile-like Sarcosuchus had a diet somewhere in between, made up of both terrestrial and aquatic prey. Thus, the different predators avoided competition by subtly sharing food resources.

Some exceptional fossils, presenting traces of feeding marks and stomach content, had already provided clues about the diet of dinosaurs. Yet such evidence remains rare. The advantage of the calcium isotope method is that it produces a global panorama of feeding habits at the ecosystem scale. It thus opens avenues for further study of the food chains of the past.

Rare Scottish dinosaur prints give key insight into era lost in time

Dozens of giant footprints discovered on a Scottish island are helping shed light on an important period in dinosaur evolution.

The tracks were made some 170 million years ago, in a muddy, shallow lagoon in what is now the north-east coast of the Isle of Skye.

Most of the prints were made by long-necked sauropods — which stood up to two metres tall — and by similarly sized theropods, which were the older cousins of Tyrannosaurus rex.

The find is globally important as it is rare evidence of the Middle Jurassic period, from which few fossil sites have been found around the world.

Researchers measured, photographed and analysed about 50 footprints in a tidal area at Brothers’ Point — Rubha nam Brathairean — a dramatic headland on Skye’s Trotternish peninsula.

The footprints were difficult to study owing to tidal conditions, the impact of weathering and changes to the landscape. In spite of this, scientists identified two trackways in addition to many isolated foot prints.

Researchers used drone photographs to make a map of the site. Additional images were collected using a paired set of cameras and tailored software to help model the prints.

Analysis of the clearest prints — including the overall shape of the track outline, the shape and orientation of the toes, and the presence of claws — enabled scientists to ascribe them to sauropods and theropods.

The study, carried out by the University of Edinburgh, Staffin Museum and Chinese Academy of Sciences, was published in the Scottish Journal of Geology. It was supported by a grant from the National Geographic Society, and subsidiary funding from the Association of Women Geologists, Derek and Maureen Moss, Edinburgh Zoo and Edinburgh Geological Society.

Paige dePolo, who led the study, conducted the research while an inaugural student in the University’s Research Master’s degree programme in palaeontology and geobiology.

Ms dePolo said: “This tracksite is the second discovery of sauropod footprints on Skye. It was found in rocks that were slightly older than those previously found at Duntulm on the island and demonstrates the presence of sauropods in this part of the world through a longer timescale than previously known. This site is a useful building block for us to continue fleshing out a picture of what dinosaurs were like on Skye in the Middle Jurassic.”

Dr Steve Brusatte of the University of Edinburgh’s School of GeoSciences, who led the field team, said: “The more we look on the Isle of Skye, the more dinosaur footprints we find. This new site records two different types of dinosaurs — long-necked cousins of Brontosaurus and sharp-toothed cousins of T. rex — hanging around a shallow lagoon, back when Scotland was much warmer and dinosaurs were beginning their march to global dominance.”

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‘Rainbow’ dinosaur had iridescent feathers like a hummingbird

Scientists discovered a dinosaur fossil with feathers so well-preserved that they were able to see the feathers’ microscopic color-bearing structures. By comparing the shapes of those feather structures with the structures in modern bird feathers, they’re able to infer that the new dino, Caihong juji (‘rainbow with the big crest’) had iridescent rainbow feathers like a hummingbird.

Birds are the last remaining dinosaurs. They’re also some of the most vibrantly colored animals on Earth. A new study in Nature Communications reveals that iridescent feathers go way back — a newly discovered species of dinosaur from 161 million years ago had rainbow coloring.

Caihong juji was tiny, about the size of a duck, with a bony crest on its head and long, ribbon-like feathers. And, based on analysis of its fossilized feathers, the feathers on its head, wings, and tail were probably iridescent, with colors that shimmered and shifted in the light. Its name reflects its appearance — in Mandarin, it means, “rainbow with the big crest.” The new species, which was first discovered by a farmer in northeastern China, was described by an international team of scientists led by Dongyu Hu, a professor in the College of Paleontology at the Shenyang Normal University in China.

“When you look at the fossil record, you normally only see hard parts like bone, but every once in a while, soft parts like feathers are preserved, and you get a glimpse into the past,” says Chad Eliason, a postdoctoral researcher at The Field Museum and one of the study’s authors. Eliason, who began work on the project as a postdoctoral fellow at the University of Texas at Austin, added, “The preservation of this dinosaur is incredible, we were really excited when we realized the level of detail we were able to see on the feathers.”

When the scientists examined the feathers under powerful microscopes, they could see the imprints of melanosomes, the parts of cells that contain pigment. For the most part, the pigment that was once present was long gone, but the physical structure of the melanosomes remained. As it turns out, that was enough for scientists to be able to tell what color the feathers were.

That’s because color isn’t only determined by pigment, but by the structure of the melanosomes containing that pigment. Differently shaped melanosomes reflect light in different colors. “Hummingbirds have bright, iridescent feathers, but if you took a hummingbird feather and smashed it into tiny pieces, you’d only see black dust. The pigment in the feathers is black, but the shapes of the melanosomes that produce that pigment are what make the colors in hummingbird feathers that we see,” explains Eliason.

The scientists were able to match the shapes of the pancake-shaped melanosomes in Caihong with the shapes of melanosomes in birds alive today. By finding birds with similarly shaped melanosomes, they were able to determine what kinds of colors Caihong may have flashed. The best matches: hummingbirds.

Colorful plumage is used in modern birds to attract mates — the rainbow feathers of Caihong might be a prehistoric version of a peacock’s iridescent tail. Caihong is the oldest known example of platelet-shaped melanosomes typically found in bright iridescent feathers.

It’s also the earliest known animal with asymmetrical feathers — a feature used by modern birds to steer when flying. Caihong couldn’t fly, though — its feathers were probably primarily used to attract mates and keep warm. While modern birds’ asymmetrical feathers are on their wingtips, Caihong’s were on its tail. “The tail feathers are asymmetrical but wing feathers not, a bizarre feature previously unknown among dinosaurs including birds,” said co-author Xing Xu of the Chinese Academy of Science. “This suggests that controlling [flight] might have been first evolved with tail feathers during some kind of aerial locomotion.”

But while Caihong’s feathers were a first, it had other traits associated with much earlier species of dinosaurs, including the bony crest on its head. “This combination of traits is rather unusual,” says co-author Julia Clarke of the University of Texas at Austin. “It has a velociraptor-type skull on the body of this very avian, fully feathered, fluffy kind of form.”

This combination of old and new traits, says Eliason, is evidence of mosaic evolution, the concept of different traits evolving independently from each other. “This discovery gives us insight into the tempo of how fast these features were evolving,” he adds.

For Eliason, the study also illuminates the value of big data. “To find the color of Caihong’s feathers, we compared its melanosomes with a growing database of thousands of measurements of melanosomes found in modern birds,” he says. It’s also broadened his own research interests.

“I came out of the project with a whole different set of questions that I wanted answers to — when I open up a drawer full of birds in the Field Museum’s collections, now I want to know when those iridescent feathers first developed, and how.”

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Synchrotron sheds light on the amphibious lifestyle of a new raptorial dinosaur

An exceptionally well-preserved dinosaur skeleton from Mongolia unites an unexpected combination of features that defines a new group of semi-aquatic predators related to Velociraptor. Detailed 3D synchrotron analysis allowed an international team of researchers to present the bizarre 75 million-year-old predator, named Halszkaraptor escuilliei, in Nature. The study not only describes a new genus and species of bird-like dinosaur that lived during the Campanian stage of the Cretaceous in Mongolia but also sheds light on an unexpected amphibious lifestyle for raptorial dinosaurs.

Theropods encompass all carnivorous dinosaurs, including the largest land-living predators in the history of life on Earth, such as Tyrannosaurus, and iconic agile hunters like Velociraptor. During 160 million years of the Mesozoic Era, theropods became the dominant predators on all continents, yet never conquered aquatic environments. Although some theropods reportedly incorporated fish in their diet, proposed indications for aquatic locomotion associated with exclusively aquatic lifestyles remain controversial.

A swan-necked and flipper-forelimbed new dinosaur species that combines an unexpected mix of features now demonstrates that some bird-like dinosaurs did adopt a semi-aquatic lifestyle. The fossil, nicknamed “Halszka” for Halszkaraptor escuilliei, was found at Ukhaa Tolgod. This locality in southern Mongolia has been known by palaeontologists for decades and is often targeted by poachers. “Illicit fossil trade presents a great challenge to modern palaeontology and accounts for a dramatic loss of Mongolian scientific heritage,” says Pascal Godefroit of the Royal Belgian Institute of Natural Sciences in Brussels. “Illegally exported from Mongolia, Halszka resided in private collections around the world before it was acquired in 2015 and offered to palaeontologists for study and to prepare its return to Mongolia.”

Although several important groups of predatory dinosaurs have been discovered in Mongolia, Halszka does not belong to any of them, having a number of strange features that are mostly absent among dinosaurs, but are shared by reptilian and avian groups with aquatic or semiaquatic ecologies. “The first time I examined the specimen, I even questioned whether it was a genuine fossil” says Andrea Cau of the Geological Museum Capellini in Bologna. Although Halszka is unique in many ways, certain parts of the skeleton, including the sickle-shaped “killer claws” on its feet, are shared with well-known dinosaurs such as Velociraptor. “This unexpected mix of traits makes it difficult to place Halszka within traditional classifications,” Cau remarks.

In order to ascertain the integrity of the fossil, the specimen was visualised and reconstructed in three dimensions using synchrotron multi-resolution X-ray microtomography. “This technique is currently the most powerful and sensitive method to image internal details without damaging invaluable fossils. The ESRF has become the worldwide leader for high quality X-ray imaging of such precious specimens,” notes Paul Tafforeau of the ESRF. “We had to mobilise an ESRF team of palaeontologists to study the complete anatomy of Halzka. So far, it’s the specimen for which the greatest number of experiments were made on a single fossil,” adds Tafforeau.

“Our first goal was to demonstrate that this bizarre and unexpected fossil is indeed a genuine animal: multi-resolution scanning confirmed that the skeleton is not a composite assembled from parts of different dinosaurs,” explains Dennis Voeten of the ESRF. “We implemented new methods for the acquisition and optimisation of tomographic scan data, which not only confirmed the integrity of the specimen, but also revealed additional palaeontological information,” Vincent Fernandez of the ESRF clarifies.

The synchrotron was even able to reveal, in astonishing detail, those parts of the skeleton that have remained deep within the rock ever since the dinosaur got buried. “Our analysis demonstrated that numerous teeth, which are not visible externally, are still preserved inside the mouth,” says Vincent Beyrand of the ESRF. “We also identified a neurovascular mesh inside its snout that resembles those of modern crocodiles to a remarkable degree. These aspects suggest that Halszka was an aquatic predator.”

The ESRF data revealed that the fossil represents a new genus and species of amphibious dinosaur that walked on two legs on land, with postural adaptations similar to short-tailed birds (like ducks), but used its flipper-like forelimbs to manoeuvre in water (like penguins and other aquatic birds), relying on its long neck for foraging and ambush hunting.

This new species was named Halszkaraptor escuilliei. Its generic name honours the late palaeontologist Halszka Osmólska. “This important genus is named in recognition of Halszka’s contribution to the study of Mongolian dinosaurs from the Gobi,” comments Rinchen Barsbold of the Mongolian Academy of Sciences. “The specific name refers to François Escuillié and thereby acknowledges his role in the first recognition and in the return of this specimen to Mongolia,” adds Khishigjav Tsogtbaatar of the Institute of Paleontology and Geology in Ulaanbaatar.

Halszkaraptor is not the only strange dinosaur recovered from the Gobi. Several previously described enigmatic Mongolian theropods were closely related to the new species, the study found. United in a new group, named Halszkaraptorinae, “is an unexpected subfamily of dromaeosaurs — the group colloquially known as raptors. This bizarre subfamily appears to have evolved a lifestyle different from all other predatory dinosaurs,” says Philip Currie of the University of Alberta.

“When we look beyond fossil dinosaurs, we find most of Halszkaraptor’s unusual features among aquatic reptiles and swimming birds,” concludes lead author Andrea Cau. “The peculiar morphology of Halszkaraptor fits best with that of an amphibious predator that was adapted to a combined terrestrial and aquatic ecology: a peculiar lifestyle that was previously unreported in these dinosaurs. Thanks to synchrotron tomography, we now demonstrate that raptorial dinosaurs not only ran and flew, but also swam!”

Early avian evolution: The Archaeopteryx that wasn‘t

Paleontologists at Ludwig-Maximilians-Universitaet (LMU) in Munich correct a case of misinterpretation: The first fossil “Archaeopteryx” to be discovered is actually a predatory dinosaur belonging to the anchiornithid family, which was previously known only from finds made in China.

Even 150 million years after its first appearance on our planet, Archaeopteryx is still good for surprises. The so-called Urvogel has attained an iconic status well beyond the world of paleontology, and it is one of the most famous fossils ever recovered. In all, a dozen fossil specimens have been assigned to the genus. Archaeopteryx remains the oldest known bird fossil, not only documenting the evolutionary transition from reptiles to birds, but also confirming that modern birds are the direct descendants of carnivorous dinosaurs. LMU paleontologist Oliver Rauhut and Christian Foth from the Staatliches Museum für Naturkunde in Stuttgart have re-examined the so-called Haarlem specimen of Archaeopteryx, which is kept in Teylers Museum in that Dutch city and has gone down in history as the first member of this genus to be discovered.

In the journal BMC Evolutionary Biology, Foth and Rauhut now report that this fossil differs in several important respects from the other known representatives of the genus Archaeopteryx. In fact, their taxonomic analysis displaces it from its alleged perch on the phylogenetic tree: “The Haarlem specimen is not a member of the Archaeopteryx clade,” says Rauhut, a paleontologist in the Department of Earth and Environmental Sciences at LMU who is also affiliated with the Bavarian State Collections for Paleontology and Geology in Munich.

Instead, the two scientists assign the fossil to a group of bird-like maniraptoran dinosaurs known as anchiornithids, which were first identified only a few years ago based on material found in China. These rather small dinosaurs possessed feathers on all four limbs, and they predate the appearance of Archaeopteryx. “The Haarlem fossil is the first member of this group found outside China. And together with Archaeopteryx, it is only the second species of bird-like dinosaur from the Jurassic discovered outside eastern Asia. This makes it even more of a rarity than the true specimens of Archaeopteryx,” Rauhut says.

Made in China

The Haarlem specimen was found about 10 km to the northeast of the closest Archaeopteryx locality known (Schamhaupten) a full four years before the discovery of the skeleton that would introduce the Urvogel to the scientific world in 1861. Schamhaupten was once part of the so-called Solnhofen archipelago in the Altmühl Valley in southern Bavaria, the area from which all known specimens of the genus Archaeopteryx originated. Its taxonomic reassignment therefore provides new insights into the evolution of the bird-like dinosaurs in the Middle to Late Jurassic. “Our biogeographical analysis demonstrates that the group of dinosaurs that gave rise to birds originated in East Asia — all of the oldest finds have been made in China. As they expanded westward, they also reached the Solnhofen archipelago,” says Christian Foth. Thus, the fossil hitherto incorrectly assigned to the genus Archaeopteryx must have been one of the first members of the group to arrive in Europe.

Around 150 million years ago, the area known today as the Altmühl Valley was dotted with the coral and sponge reefs and lagoons of the Solnhofen archipelago, and the open sea lay to the West and South. The Haarlem fossil was originally recovered from what was then the eastern end of the archipelago, quite close to the mainland. Unlike Archaeopteryx, anchiornithids were unable to fly, and might not have been able to reach areas further offshore. On the other hand, all true fossils of Archaeopteryx found so far were recovered from the lithographic limestone strata further to the west, closer to the open sea. Based on the new findings, Rauhut argues that other known Archaeopteryx fossils may need reassessment: “Not every bird-like fossil that turns up in the fine-grained limestones around Solnhofen need necessarily be a specimen of Archaeopteryx,” he points out.

The authors of the new study have proposed that the Haarlem specimen be assigned to a new genus, for which they suggest the name Ostromia — in honor of the American paleontologist John Ostrom, who first identified the fossil as a theropod dinosaur.

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Feathered dinosaurs were even fluffier than we thought

A University of Bristol-led study has revealed new details about dinosaur feathers and enabled scientists to further refine what is potentially the most accurate depiction of any dinosaur species to date.

Birds are the direct descendants of a group of feathered, carnivorous dinosaurs that, along with true birds, are referred to as paravians — examples of which include the infamous Velociraptor.

Researchers examined, at high resolution, an exceptionally-preserved fossil of the crow-sized paravian dinosaur Anchiornis — comparing its fossilised feathers to those of other dinosaurs and extinct birds.

The feathers around the body of Anchiornis, known as contour feathers, revealed a newly-described, extinct, primitive feather form consisting of a short quill with long, independent, flexible barbs erupting from the quill at low angles to form two vanes and a forked feather shape.

The observations were made possible by decay processes that separated some of these feathers from the body prior to burial and fossilisation, making their structure easier to interpret.

Such feathers would have given Anchiornis a fluffy appearance relative to the streamlined bodies of modern flying birds, whose feathers have tightly-zipped vanes forming continuous surfaces. Anchiornis’s unzipped feathers might have affected the animal’s ability to control its temperature and repel water, possibly being less effective than the vanes of most modern feathers. This shaggy plumage would also have increased drag when Anchiornis glided.

Additionally, the feathers on the wing of Anchiornis lack the aerodynamic, asymmetrical vanes of modern flight feathers, and the new research shows that these vanes were also not tightly-zipped compared to modern flight feathers. This would have hindered the feather’s ability to form a lift surface. To compensate, paravians like Anchiornis packed multiple rows of long feathers into the wing, unlike modern birds, where most of the wing surface is formed by just one row of feathers.

Furthermore, Anchiornis and other paravians had four wings, with long feathers on the legs in addition to the arms, as well as elongated feathers forming a fringe around the tail. This increase in surface-area likely allowed for gliding before the evolution of powered flight.

To assist in reconstructing the updated look of Anchiornis, scientific illustrator Rebecca Gelernter worked with Evan Saitta and Dr Jakob Vinther, from the University of Bristol’s School of Earth Sciences and School of Biological Sciences, to draw the animal as it was in life.

The new piece represents a radical shift in dinosaur depictions and incorporates previous research.

The color patterns for Anchiornis are known from fossilised pigment studies, the outline of the flesh of the animal has been constructed by examining fossils under laser fluorescence, and previous work has described the multi-tiered layering of the wing feathers.

Evan Saitta said: “The novel aspects of the wing and contour feathers, as well as fully-feathered hands and feet, are added to the depiction.

“Most provocatively, Anchiornis is presented in this artwork climbing in the manner of hoatzin chicks, the only living bird whose juveniles retain a relic of their dinosaurian past, a functional claw.

“This contrasts much previous art that places paravians perched on top of branches like modern birds.

“However, such perching is unlikely given the lack of a reversed toe as in modern perching birds and climbing is consistent with the well-developed arms and claws in paravians.

“Overall, our study provides some new insight into the appearance of dinosaurs, their behavior and physiology, and the evolution of feathers, birds, and powered flight.”

Rebecca Gelernter added: “Paleoart is a weird blend of strict anatomical drawing, wildlife art, and speculative biology. The goal is to depict extinct animals and plants as accurately as possible given the available data and knowledge of the subject’s closest living relatives.

“As a result of this study and other recent work, this is now possible to an unprecedented degree for Anchiornis. It’s easy to see it as a living animal with complex behaviours, not just a flattened fossil.

“It’s really exciting to be able to work with the scientists at the forefront of these discoveries, and to show others what we believe these fluffy, toothy almost-birds looked like as they went about their Jurassic business.”

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Bryozoans: Fossil fills missing evolutionary link

Lurking in oceans, rivers and lakes around the world are tiny, ancient animals known to few people. Bryozoans, tiny marine creatures that live in colonies, are “living fossils” — their lineage goes back to the time when multi-celled life was a newfangled concept. But until now, scientists were missing evidence of one important breakthrough that helped the bryozoans survive 500 million years as the world changed around them.

Today, the diverse group of bryozoans that dominate modern seas build a great range of structures, from fans to sheets to weird, brain-like blobs. But for the first 50 or 60 million years of their existence, they could only grow like blankets over whatever surface they happened upon.

Scientists recently announced the discovery of that missing evolutionary link — the first known member of the modern bryozoans to grow up into a structure. Called Jablonskipora kidwellae, it is named after UChicago geophysical scientists David Jablonski and Susan Kidwell.

Both are prominent scholars in their fields: Jablonski in origins, extinctions and other forces shaping biodiversity across time and space in marine invertebrates; Kidwell in the study of how fossils are preserved and the reliability of paleobiologic data, especially for detecting recent, human-driven changes to ecosystems. They also happen to be married.

“We were absolutely thrilled. What a treat and an honor, to have this little guy named after us,” said Jablonski, the William R. Kenan Jr. Distinguished Service Professor of Geophysical Sciences.

“I never expected to have a fossil named after me,” said Kidwell, the William Rainey Harper Professor in Geophysical Sciences, “and here it’s one that is an evolutionary breakthrough. We’re still smiling about it.”

Jablonskipora kidwellae lived about 105 million years ago, latching on to rocks and other hard surfaces in shallow seas — a bit like corals, though they’re not related. The fossils came from southwest England, along cliffs near Devon, originally collected in 1903 and analyzed by co-discoverers Paul Taylor and Silviu Martha from London’s Natural History Museum.

Bryozoans never figured out a symbiotic partnership with photosynthetic bacteria, as coral did, so their evolution took a different turn. Each one in a colony is genetically identical, but they have specialized roles, like ants or bees. Their shelly apartment complexes house thousands of the creatures, which have soft bodies with tiny tentacles to catch nutrients.

Growing upright was an evolutionary hack for Jablonskipora kidwellae, the two professors said: building bigger colonies extending upward from just a tiny attachment site was a good evolutionary move, allowing it to tap the water flowing above the sea floor — both for food and to scatter its offspring further. “This is a huge competitive advantage for them,” Jablonski said, “but it required some evolutionary organization to create a vertical structure.” Kidwell added: “This is the next level of cooperation among these individuals within the colony.”

They expressed a fondness for the creature, which they said was, like other bryozoans, “small and slow, but fierce.” Bryozoan fossils are sometimes found having bulldozed right over neighboring colonies in an intense battle for growing space. In a manner of speaking: this all would have taken place in extremely slow motion.

“They’re pretty fabulous little animals,” Kidwell said.

Jablonski and Kidwell have been friends with Taylor, one of the discoverers, since they spent summers on various research at the London Natural History Museum in the 1980s, but they said his news took them both completely by surprise. Jablonski had previously co-authored one paper with Taylor; Kidwell is currently collaborating with him on a study of bryozoan skeletal debris in modern sediments from the Channel Islands off Los Angeles.

It is the second honor of the year for both Kidwell and Jablonski: In April she received the Moore Medal from the Society for Sedimentary Geology, and in October he received the Paleontological Society Medal, that society’s highest honor.

Jablonski had one previous species named after him — a tiny clam — but Jablonskiporawill now be a genus in addition to a species.

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Colorado River’s connection with the ocean was a punctuated affair

The Colorado River’s initial trip to the ocean didn’t come easy, but its story has emerged from layers of sediment preserved within tectonically active stretches of the waterway’s lower reaches.

A scientific team, led by geologist Rebecca Dorsey of the University of Oregon, theorizes that the river’s route off the Colorado Plateau was influenced by a combination of tectonic deformation and changing sea levels that produced a series of stops and starts between roughly 6.3 and 4.8 million years ago.

Dorsey’s team lays out its case in an invited-research paper in the journal Sedimentary Geology. The team’s interpretation challenges long-held conventional thinking that once a river connects to the ocean it’s a done deal.

“The birth of the Colorado River was more punctuated and filled with more uneven behavior than we expected,” Dorsey said. “We’ve been trying to figure this out for years. This study is a major synthesis of regional stratigraphy, sedimentology and micropaleontology. By integrating these different datasets we are able to identify the different processes that controlled the birth and early evolution of this iconic river system.”

The region covered in the research stretches from the southern Bouse Formation, near present-day Blythe, California, to the western Salton Trough north of where the river now trickles into the Gulf of California. The Bouse Formation and deposits in the Salton Trough have similar ages and span both sides of the San Andreas Fault, providing important clues to the river’s origins.

Last year, in the journal Geology, a project led by graduate student Brennan O’Connell, a co-author on the new study, concluded that laminated sediments found in exposed rock along the river near Blythe were deposited by tidal currents 5.5 million years ago. The Gulf of California, it was argued, extended into the region, but the age of the deposits and tectonic and sea level changes at work during that time were not well understood.

Analyses by Kristin McDougall, a micropaleontologist with the U.S. Geological Survey and co-author on the new paper, helped the team better pinpoint the timing of the limestone deposits to about 6 million years ago, when tiny marine organisms lived in the water and were deposited at the same time.

About 5.4 million years ago, conditions changed. Global sea level was falling but instead of bay water levels declining, as would be expected, the water depth increased due to tectonic subsidence of the crust, the researchers discovered.

The basal carbonate material left by marine organisms was then inundated by fresh water as the river swept down into lower elevations, bringing with it clay and sand from mountain terrain, they found.

“The bay filled up with river sediment as the sediment migrated toward the ocean,” Dorsey said. “As more sediment came in, transport processes caused the delta front to move down the valley, transforming the marine bay into a delta and then the earliest through-flowing Colorado River.”

The river had arrived in the gulf, but only temporarily. A tug-of-war lasting for 200,000 to 300,000 years began some 5.1 million years ago, when the river stopped delivering sediments from upstream. The delta retreated and seawater returned to the lower Colorado River valley for a short time. The evidence is in the stratigraphy and fossils. Researchers found that clay and sand from the river became mixed with and then covered by marine sediment.

Something, Dorsey said, apparently was happening upstream, trapping river sediment. A good bet, the researchers think, is tectonic activity, perhaps earthquakes along a fault zone in the river’s northern basin that created subsidence in the riverbed or deep lakes along the river’s path.

At roughly 4.8 million years ago, the river resumed depositing massive amounts of sediment back into the Salton Trough and began rebuilding the delta. Today’s view of the delta, however, reflects human-made modern disturbances to the river’s sediment discharge and flow of water reaching the gulf.

To meet agricultural demands for irrigation and drinking water for human consumption, Hoover Dam was constructed on the river to form Lake Mead during the 1930s. In 1956-1966, Glen Canyon Dam was built, forming Lake Powell.

“If we could go back to 1900 before the dams that trap the sediment and water, we would see that the delta area was full of channels, islands, sand bars and moving sediment. It was a very diverse, dynamic and rich delta system. But humanmade dams are trapping sediment today, eerily similar to what happened roughly 5 million years ago,” Dorsey said.

The bottom line of the research, she said, is that no single process controlled the Colorado River’s initial route to the sea. “Different processes interacted in a surprisingly complicated sequence of events that led to the final integration of that river out to the ocean,” she said.

The research, Dorsey said, provides insights that help scientists understand how such systems change through time. The Colorado River is an excellent natural laboratory, she said, because sedimentary deposits that formed prior to and during river initiation are well exposed throughout the lower river valley.

“This research,” Dorsey said, “is very relevant to today because we have global sea level rising, climate is warming, coastlines are being inundated and submerged, and the supply of river sediment exerts a critical control on the fate of deltas where they meet the ocean. Documenting the complex interaction of these processes in the past helps us understand what is happening today.”

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World’s longest sauropod dinosaur trackway brought to light

In 2009, the world’s largest dinosaur tracks were discovered in the French village of Plagne, in the Jura Mountains. Since then, a series of excavations at the site has uncovered other tracks, sprawling over more than 150 meters. They form the longest sauropod trackway ever to be found. Having compiled and analyzed the collected data, which is published in Geobios, scientists from the Laboratoire de Géologie de Lyon (CNRS / ENS de Lyon / Claude Bernard Lyon 1 University), the Laboratoire Magmas et Volcans (CNRS / Université Clermont Auvergne / Université Jean Monnet / IRD), and the Pterosaur Beach Museum conclude these tracks were left 150 million years ago by a dinosaur at least 35 m long and weighing no less than 35 t.

In 2009, when sauropod tracks were discovered in the French village of Plagne — near Lyon — the news went round the world. After two members of the Oyonnax Naturalists’ Society spotted them, scientists from the Paléoenvironnements et Paléobiosphère research unit (CNRS / Claude Bernard Lyon 1 University) confirmed these tracks were the longest in the world. Between 2010 and 2012, researchers from the Laboratoire de Géologie de Lyon supervised digs at the site, a meadow covering three hectares. Their work unearthed many more dinosaur footprints and trackways. It turns out the prints found in 2009 are part of a 110-step trackway that extends over 155 m — a world record for sauropods, which were the largest of the dinosaurs.

Dating of the limestone layers reveals that the trackway was formed 150 million years ago, during the Early Tithonian Age of the Jurassic Period. At that time, the Plagne site lay on a vast carbonate platform bathed in a warm, shallow sea. The presence of large dinosaurs indicates the region must have been studded with many islands that offered enough vegetation to sustain the animals. Land bridges emerged when the sea level lowered, connecting the islands and allowing the giant vertebrates to migrate from dry land in the Rhenish Massif.

Additional excavations conducted as late as 2015 enabled closer study of the tracks. Those left by the sauropod’s feet span 94 to 103 cm and the total length can reach up to 3 meters when including the mud ring displaced by each step. The footprints reveal five elliptical toe marks, while the handprints are characterized by five circular finger marks arranged in an arc. Biometric analyses suggest the dinosaur was at least 35 m long, weighted between 35 and 40 t, had an average stride of 2.80 m, and traveled at a speed of 4 km/h. It has been assigned to a new ichnospecies1: Brontopodus plagnensis. Other dinosaur trackways can be found at the Plagne site, including a series of 18 tracks extending over 38 m, left by a carnivore of the ichnogenus Megalosauripus. The researchers have since covered these tracks to protect them from the elements. But many more remain to be found and studied in Plagne.

1 The prefix ichno- indicates that a taxon (e.g., a genus or species) has been defined on the basis of tracks or other marks left behind, rather than anatomical remains like bones.

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