‘Cthulhu’ fossil reconstruction reveals monstrous relative of modern sea cucumbers

An exceptionally-preserved fossil from Herefordshire in the UK has given new insights into the early evolution of sea cucumbers, the group that includes the sea pig and its relatives, according to a new article published today in the journal Proceedings of the Royal Society B.

Palaeontologists from the UK and USA created an accurate 3D computer reconstruction of the 430 million-year-old fossil which allowed them to identify it as a species new to science. They named the animal Sollasina cthulhu due to its resemblance to monsters from the fictional Cthulhu universe created by author H.P. Lovecraft.

Although the fossil is just 3 cm wide, its many long tentacles would have made it appear quite monstrous to other small sea creatures alive at the time. It is thought that these tentacles, or ‘tube feet’, were used to capture food and crawl over the seafloor.

Like other fossils from Herefordshire, Sollasina cthulhu was studied using a method that involved grinding it away, layer-by-layer, with a photograph taken at each stage. This produced hundreds of slice images, which were digitally reconstructed as a ‘virtual fossil’.

This 3D reconstruction allowed palaeontologists to visualise an internal ring, which they interpreted as part of the water vascular system — the system of fluid-filled canals used for feeding and movement in living sea cucumbers and their relatives.

Lead author, Dr Imran Rahman, Deputy Head of Research at Oxford University Museum of Natural History said:

Sollasina belongs to an extinct group called the ophiocistioids, and this new material provides the first information on the group’s internal structures. This includes an inner ring-like form that has never been described in the group before. We interpret this as the first evidence of the soft parts of the water vascular system in ophiocistioids.”

The new fossil was incorporated into a computerized analysis of the evolutionary relationships of fossil sea cucumbers and sea urchins. The results showed that Sollasina and its relatives are most closely related to sea cucumbers, rather than sea urchins, shedding new light on the evolutionary history of the group.

Co-author Dr Jeffrey Thompson, Royal Society Newton International Fellow at University College London, said:

“We carried out a number of analyses to work out whether Sollasina was more closely related to sea cucumbers or sea urchins. To our surprise, the results suggest it was an ancient sea cucumber. This helps us understand the changes that occurred during the early evolution of the group, which ultimately gave rise to the slug-like forms we see today.”

The fossil was described by an international team of researchers from Oxford University Museum of Natural History, University of Southern California, Yale University, University of Leicester, and Imperial College London. It represents one of many important finds recovered from the Herefordshire fossil site in the UK, which is famous for preserving both the soft as well as the hard parts of fossils.

The fossil slices and 3D reconstruction are housed at Oxford University Museum of Natural History.


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First-confirmed occurrence of a lambeosaurine dinosaur found on Alaska’s North Slope

Paleontologists from Hokkaido University in Japan, in cooperation with paleontologists from the Perot Museum of Nature and Science in Dallas, Texas, have discovered the first-confirmed occurrence of a lambeosaurine (crested ‘duck-billed’ dinosaur) from the Arctic — part of the skull of a lambeosaurine dinosaur from the Liscomb Bonebed (71-68 Ma) found on Alaska’s North Slope. The bonebed was previously known to be rich in hadrosaurine hadrosaurids (non-crested ‘duck-billed’ dinosaurs).

The discovery proves for the first time that lambeosaurines inhabited the Arctic during the Late Cretaceous. In addition, the numeric abundance of hadrosaurine fossils compared to the lambeosaurine fossils in the marine-influenced environment of the Liscomb Bonebed suggests the possibility that hadrosaurines and lambeosaurines had different habitat preferences.

The paleontologists’ findings were published today in Scientific Reports, an open-access, multi-disciplinary journal from Nature Research dedicated to constructive, inclusive and rigorous peer review. The paper — entitled “The first definite lambeosaurine bone from the Liscomb Bonebed of the Upper Cretaceous Prince Creek Formation, Alaska, United States” — is co-authored by Yoshitsugu Kobayashi, Ph.D., and Ryuji Takasaki, of Hokkaido University, in cooperation with Anthony R. Fiorillo, Ph.D., of the Perot Museum of Nature and Science. Other authors are Ronald Tykoski, Ph.D. of the Perot Museum and Paul McCarthy, Ph.D., of the University of Alaska.

“This new discovery illustrates the geographic link between lambeosaurines of North America and the Far East,” said Takasaki. “Hopefully, further work in Alaska will reveal how closely the dinosaurs of Asia and North America are connected.”

The newly discovered fossil, which is housed in the collections of the Perot Museum of Nature and Science, is a supraoccipital, one of the bones that forms the braincase. The new supraoccipital differs from those of hadrosaurines by the presence of large supraoccipital bosses and it’s short, front-to-back length. Since these features are commonly seen in other members of Lambeosaurinae, the newly discovered supraoccipital was assigned to that group.

“This first definitive evidence of a crested hadrosaur in the Cretaceous Arctic tells us that we still have much to learn about the biodiversity and the biologically productive environments of the ancient north, and that the story these fossils tell us is continually evolving,” adds Dr. Fiorillo.

Background. The Arctic is an extreme environment that is low in temperature, lacks sunlight during winters, and has seasonally limited food resources. Though it was warmer during the Late Cretaceous, the Arctic was surely one of the most challenging places to live for large vertebrates at the time. The Prince Creek Formation on the North Slope of Alaska is a world-famous rock unit for studying dinosaurs of the ancient Arctic. Because the dinosaurs found there lived in the ancient Arctic, rather than tropical or sub-tropical conditions, these dinosaurs challenge much of what we think we know about dinosaurs. The Liscomb Bonebed (71-68 Ma), which was deposited near the ancient Arctic shoreline, is especially rich in dinosaur bones, with more than 6,000 bones collected from it thus far.

More than 99% of dinosaur fossils known from the Liscomb Bonebed are hadrosaurs, a group of large, duck-billed herbivorous dinosaurs who lived during the Late Cretaceous and were found throughout much of the northern hemisphere. All of the hadrosaur fossils from the Liscomb Bonebed were long considered to belong to a hadrosaurine duck-billed dinosaur called Edmontosaurus. Up until now, all of the hadrosaurids known from across the Arctic, including those from the Liscomb Bonebed, were considered to belong to crest-less hadrosaurines.

The discovery of a fossil from a lambeosaurine hadrosaurid in the Liscomb Bonebed is historically important for Japanese paleontologists. The first “Japanese” dinosaur, Nipponosaurus, is a lambeosaurine hadrosaur. Based on the new discovery, Hokkaido University and the Perot Museum together used this discovery to further investigate the ecology of the Arctic hadrosaurids.

Significance

1. The first Arctic lambeosaurine: The new discovery indicates Arctic inhabitance and adaptation of lambeosaurines for the first time. In addition, the fossil’s morphological similarities to the same bone in the skull of southern Canadian lambeosaurines suggest faunal interactions between the Arctic and the mid-latitudes.

2. Implication on habitat preferences: While the Liscomb Bonebed is known for numerous hadrosaurine fossils, the newly discovered bone represents the only definite lambeosaurine fossil from the site. The same trend is also known in mid-latitude localities of North America and eastern Asia, which were also deposited in near-shore environments. On the other hand, more lambeosaurine fossils are found in deposits laid down in inland environments. Therefore, we hypothesize that lambeosaurines favored inland environments, while hadrosaurines preferred coastal environments, a trend likely to have been independent of latitude. Different habitat preferences might have been a strategy to avoid excessive competition between the two groups of ‘duck-billed’ dinosaurs.

Future plans

Although the new discovery reveals Arctic inhabitance by lambeosaurines, more specific taxonomic status and potential functional adaptations to the severe Arctic environment remain unknown due to incompleteness of the specimen. Additional excavation and further research will help answer these questions.


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Journal Reference:

  1. Ryuji Takasaki, Anthony R. Fiorillo, Yoshitsugu Kobayashi, Ronald S. Tykoski, Paul J. McCarthy. The First Definite Lambeosaurine Bone From the Liscomb Bonebed of the Upper Cretaceous Prince Creek Formation, Alaska, United StatesScientific Reports, March 29, 2019; DOI: 10.1038/s41598-019-41325-8

Mystery shrouding oldest animal fossils solved

Scientists from The Australian National University (ANU) have discovered that 558 million-year-old Dickinsonia fossils do not reveal all of the features of the earliest known animals, which potentially had mouths and guts.

ANU PhD scholar Ilya Bobrovskiy, lead author of the study, said the study shows that simple physical properties of sediments can explain Dickinsonia’s preservation, and implies that what can be seen today may not be what these creatures actually looked like.

“These soft-bodied creatures that lived 558 million years ago on the seafloor could, in principle, have had mouths and guts — organs that many palaeontologists argue emerged during the Cambrian period tens of millions of years later,” said Mr Bobrovskiy from the ANU Research School of Earth Sciences.

“Our discovery about Dickinsonia — and many other Ediacaran fossils — opens up new possibilities as to what they actually looked like.”

Ediacara biota were strange creatures that lived on the seafloor 571 to 541 million years ago. They grew up to two metres long and include the earliest known animals as well as colonies of bacteria.

The fact that Dickinsonia and other Ediacara biota fossils were preserved at all in the geological record has been a big mystery — until now.

The team, which includes scientists from Russian institutions, discovered how Ediacara biota fossils were preserved, despite the macroorganisms not having skeletons or shells.

“As the organisms decayed, softer sediment from below gradually flowed into the forming void, creating a cast,” Mr Bobrovskiy said.

“Now we know that what we are looking at is an impression of a soft organic skeleton that may have been anywhere within Dickinsonia’s body. What we’re seeing could be a part of Dickinsonia’s bottom, the inside of its body or part of its back.”

Mr Bobrovskiy said Dickinsonia had different types of tissues and must have been a true animal, a Eumetazoa, the lineages eventually leading to humans.

Co-researcher and RSES colleague Associate Professor Jochen Brocks said the team used a melting cast of a Death Star made of ice to show the physical properties of sediments that enabled the soft-bodied Ediacara biota to be preserved.

“This process of fossilisation could tell us more about what Ediacara biota were and how they lived,” he said.

“These fossils comprise our best window into earliest animal evolution and are the key to understanding our own deep origins.”


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Journal Reference:

  1. Ilya Bobrovskiy, Anna Krasnova, Andrey Ivantsov, Ekaterina Luzhnaya, Jochen J. Brocks. Simple sediment rheology explains the Ediacara biota preservationNature Ecology & Evolution, 2019; DOI: 10.1038/s41559-019-0820-7

Paleontologists report world’s biggest Tyrannosaurus rex

University of Alberta paleontologists have just reported the world’s biggest Tyrannosaurus rex and the largest dinosaur skeleton ever found in Canada. The 13-metre-long T. rex, nicknamed “Scotty,” lived in prehistoric Saskatchewan 66 million years ago.

“This is the rex of rexes,” said Scott Persons, lead author of the study and postdoctoral researcher in the Department of Biological Sciences. “There is considerable size variability among Tyrannosaurus. Some individuals were lankier than others and some were more robust. Scotty exemplifies the robust. Take careful measurements of its legs, hips, and even shoulder, and Scotty comes out a bit heftier than other T. rex specimens.”

Scotty, nicknamed for a celebratory bottle of scotch the night it was discovered, has leg bones suggesting a living weight of more than 8,800 kg, making it bigger than all other carnivorous dinosaurs. The scientific work on Scotty has been a correspondingly massive project.

The skeleton was first discovered in 1991, when paleontologists including T. rex expert and UAlberta professor Phil Currie were called in on the project. But the hard sandstone that encased the bones took more than a decade to remove — only now have scientists been able to study Scotty fully-assembled and realize how unique a dinosaur it is.

It is not just Scotty’s size and weight that set it apart. The Canadian mega rex also lays claim to seniority.

“Scotty is the oldest T. rex known,” Persons explains. “By which I mean, it would have had the most candles on its last birthday cake. You can get an idea of how old a dinosaur is by cutting into its bones and studying its growth patterns. Scotty is all old growth.”

But age is relative, and T. rexes grew fast and died young. Scotty was estimated to have only been in its early 30s when it died.

“By Tyrannosaurus standards, it had an unusually long life. And it was a violent one,” Persons said. “Riddled across the skeleton are pathologies — spots where scarred bone records large injuries.”

Among Scotty’s injures are broken ribs, an infected jaw, and what may be a bite from another T. rex on its tail — battle scars from a long life.

“I think there will always be bigger discoveries to be made,” said Persons “But as of right now, this particular Tyrannosaurus is the largest terrestrial predator known to science.”

A new exhibit featuring the skeleton of Scotty is set to open at the Royal Saskatchewan Museum in May 2019.


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Dinosaurs were thriving before asteroid strike that wiped them out

Dinosaurs were unaffected by long-term climate changes and flourished before their sudden demise by asteroid strike.

Scientists largely agree that an asteroid impact, possibly coupled with intense volcanic activity, wiped out the dinosaurs at the end of the Cretaceous period 66 million years ago.

However, there is debate about whether dinosaurs were flourishing before this, or whether they had been in decline due to long-term changes in climate over millions of years.

Previously, researchers used the fossil record and some mathematical predictions to suggest dinosaurs may have already been in decline, with the number and diversity of species falling before the asteroid impact.

Now, in a new analysis that models the changing environment and dinosaur species distribution in North America, researchers from Imperial College London, University College London and University of Bristol have shown that dinosaurs were likely not in decline before the meteorite.

Lead researcher Alessandro Chiarenza, a PhD student in the Department of Earth Science and Engineering at Imperial, said: “Dinosaurs were likely not doomed to extinction until the end of the Cretaceous, when the asteroid hit, declaring the end of their reign and leaving the planet to animals like mammals, lizards and a minor group of surviving dinosaurs: birds.

“The results of our study suggest that dinosaurs as a whole were adaptable animals, capable of coping with the environmental changes and climatic fluctuations that happened during the last few million years of the Late Cretaceous. Climate change over prolonged time scales did not cause a long-term decline of dinosaurs through the last stages of this period.”

The study, published today in Nature Communications, shows how the changing conditions for fossilisation means previous analyses have underestimated the number of species at the end of the Cretaceous.

The team focused their study on North America, where many Late Cretaceous dinosaurs are preserved, such as Tyrannosaurus rex and Triceratops. During this period, the continent was split in two by a large inland sea.

In the western half there was a steady supply of sediment from the newly forming Rocky Mountains, which created perfect conditions for fossilising dinosaurs once they died. The eastern half of the continent was instead characterised by conditions far less suitable for fossilisation.

This means that far more dinosaur fossils are found in the western half, and it is this fossil record that is often used to suggest dinosaurs were in decline for the few million years before the asteroid strike.

Co-author Dr Philip Mannion, from University College London, commented: “Most of what we know about Late Cretaceous North American dinosaurs comes from an area smaller than one-third of the present-day continent, and yet we know that dinosaurs roamed all across North America, from Alaska to New Jersey and down to Mexico.”

Instead of using this known record exclusively, the team employed ‘ecological niche modelling’. This approach models which environmental conditions, such as temperature and rainfall, each species needs to survive.

The team then mapped where these conditions would occur both across the continent and over time. This allowed them to create a picture of where groups of dinosaur species could survive as conditions changed, rather than just where their fossils had been found.

The team found habitats that could support a range of dinosaur groups were actually more widespread at the end of the Cretaceous, but that these were in areas less likely to preserve fossils.

Furthermore, these potentially dinosaur-rich areas were smaller wherever they occurred, again reducing the likelihood of finding a fossil from each of these areas.


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500-million-year old worm ‘superhighway’ discovered in Canada

Prehistoric worms populated the sea bed 500 million years ago — evidence that life was active in an environment thought uninhabitable until now, research by the University of Saskatchewan (USask) shows.

The sea bed in the deep ocean during the Cambrian period was thought to have been inhospitable to animal life because it lacked enough oxygen to sustain it.

But research published in the scientific journal Geology reveals the existence of fossilized worm tunnels dating back to the Cambrian period — 270 million years before the evolution of dinosaurs.

The discovery, by USask professor Brian Pratt, suggests that animal life in the sediment at that time was more widespread than previously thought.

The worm tunnels — borrows where worms lived and munched through the sediment — are invisible to the naked eye. But Pratt “had a hunch” and sliced the rocks and scanned them to see whether they revealed signs of ancient life.

The rocks came from an area in the remote Mackenzie Mountains of the Northwest Territories in Canada which Pratt found 35 years ago.

Pratt then digitally enhanced images of the rock surfaces so he could examine them more closely. Only then did the hidden ‘superhighway’ of burrows made by several different sizes and types of prehistoric worm emerge in the rock.

Some were barely a millimetre in size and others as large as a finger. The smaller ones were probably made by simple polychaetes — or bristle worms — but one of the large forms was a predator that attacked unsuspecting arthropods and surface-dwelling worms.

Pratt said he was “surprised” by the unexpected discovery.

“For the first time, we saw evidence of large populations of worms living in the sediment — which was thought to be barren,” he said. “There were cryptic worm tunnels — burrows — in the mud on the continental shelf 500 million years ago, and more animals reworking, or bioturbating, the sea bed than anyone ever thought.”

Pratt, a geologist and paleontologist and Fellow of the Geological Society of America, found the tunnels in sedimentary rocks that are similar to the Burgess Shale, a famous fossil-bearing deposit in the Canadian Rockies.

The discovery may prompt a rethink of the level of oxygenation in ancient oceans and continental shelves.

The Cambrian period saw an explosion of life on Earth in the oceans and the development of multi-cellular organisms including prehistoric worms, clams, snails and ancestors of crabs and lobsters. Previously the seas had been inhabited by simple, single-celled microbes and algae.

It has always been assumed that the creatures in the Burgess Shale — known for the richness of its fossils — had been preserved so immaculately because the lack of oxygen at the bottom of the sea stopped decay, and because no animals lived in the mud to eat the carcasses.

Pratt’s discovery, with co-author Julien Kimmig, now of the University of Kansas, shows there was enough oxygen to sustain various kinds of worms in the sea bed.

“Serendipity is a common aspect to my kind of research,” Pratt said. “I found these unusual rocks quite by accident all those years ago. On a hunch I prepared a bunch of samples and when I enhanced the images I was genuinely surprised by what I found,” he said.

“This has a lot of implications which will now need to be investigated, not just in Cambrian shales but in younger rocks as well. People should try the same technique to see if it reveals signs of life in their samples.”

The research was funded by the Natural Sciences and Engineering Research Council of Canada.


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Amoebae diversified at least 750 million years ago, far earlier than expected

Brazilian researchers have reconstructed the evolutionary history of amoebae and demonstrated that at the end of the Precambrian period, at least 750 million years ago, life on Earth was much more diverse than suggested by classic theory.

The study, which was supported by São Paulo Research Foundation — FAPESP, revealed eight new ancestral lineages of Thecamoebae, the largest group in Amoebozoa. Thecamoebians are known as testates because of their hard outer carapace or shell.

Interpretations of the evolution of Earth’s atmosphere and climate change are also affected by the discovery that amoebae are more diverse than previously thought.

In this study, published in the journal Current Biology, researchers affiliated with the University of São Paulo’s Bioscience Institute (IB-USP) in Brazil, in partnership with colleagues at the Mississippi State University in the United States, used innovative techniques to reconstruct the phylogenetic (evolutionary) tree of Thecamoeba, which belongs to the order Arcellinida.

The new phylogenetic tree was created using mathematical algorithms and the transcriptomes of 19 arcellinids found in nature today. The researchers also established the morphology and composition of the hypothetical ancestors of this group of amoebae and compared them with the fossil record.

The results showed that at least 750 million years ago, ancestors of the thecamoebians were already evolving. This finding indicates that the late Precambrian was more diverse than previously thought.

“We reached our conclusions using a combination of two major scientific areas — paleontology and phylogenetic systematics, the field within biology that reconstructs evolutionary history and studies the patterns of relationships among organisms. In this way, we were able to untangle one of the knots in evolutionary theory about life on the planet,” said Daniel Lahr, a professor at IB-USP and lead author of the article.

Reclassification of Amoebozoa

The researchers completely dismantled the previous classification of thecamoebians. “We succeeded in developing a robust structure and for the first time, discovered eight deep lineages [from 750 million years ago] of arcellinids about which nothing was known,” Lahr told.

The old thecamoebian classification was based on shell composition. “They were divided into agglutinate and organic. However, from our molecular reconstruction, we discovered that the classification is actually determined by shell shape rather than composition,” Lahr said.

The old classification, he added, had been questioned for several years, but more evidence was needed to demolish it. Previous genetic research has shown that the classification was unsustainable, but not enough data were available to justify a new classification.

“The scientific community suspected that the arcellinid testate amoebae had emerged and evolved sufficiently to diversify some 750 million years ago. We’ve now succeeded in demonstrating this hypothesis,” he said.

Past and future

According to Lahr, the study presents a different view of how microorganisms evolved on the planet. The late Precambrian was considered a period of low biotic diversity, with only a few species of bacteria and some protists.

“It was in this period 800 million years ago that the oceans became oxygenated. For a long time, oxygenation was assumed to have led to diversification of the eukaryotes, unicellular and multicellular organisms in which the cell’s nucleus is isolated by a membrane, culminating in the diversification of macroorganisms millions of years later in the Cambrian,” Lahr said.

The study published in Current Biology, he added, focuses on a detail of this question. “We show that diversification apparently already existed in the Precambrian and that it probably occurred at the same time as ocean oxygenation. What’s more, geophysicists are discovering that this process was slow and may have lasted 100 million years or so,” he said.

However, scientists do not know what pressure triggered this oxygenation. “Regardless of the cause, oxygenation eventually led to more niches, the eukaryotes diversified, and there was more competition for niches. One way to resolve the competition was for some lineages to become larger and hence multicellular,” Lahr said.

The study has also contributed to a better understanding of today’s climate change. “We began to understand in more depth how this microbial life affected the planet in several ways,” Lahr said. “The climate changed in fundamental ways during the period, which saw the occurrence of the Sturtian glaciation some 717 million years ago. This was one of the largest glaciation events ever.”

According to Lahr, these changes may have had biological origins. “By increasing the resolution of how life evolved in the very remote past, we can understand a little better how life affects the planet’s climate and even its geology. That will help us understand the climate changes we’re currently experiencing,” he said.

In rock

In addition to the discovery of greater diversity in the Precambrian, the study also innovates by reconstructing the morphology of the ancestors of thecamoebians to establish that the vase-shaped microfossils (VSMs) found in various parts of the world already existed in the Precambrian and even in the major ice ages that occurred during this era.

VSMs are presumed to be fossils of testate amoebae. They are unicellular and eukaryotic and have an external skeleton. Significant diversity of VSMs has been documented for the Neoproterozoic Era, which spanned between 1 billion and 541 million years ago, and was the terminal era of the Precambrian.

“The study constitutes a very different vision of how microorganisms evolved on the planet. Although the fossils do not contain genetic information, it is possible to obtain morphological and compositional information and to verify whether they are organic or silica-based. So it’s possible to compare their shape and chemical composition, which in this case are especially well preserved, with those of current thecamoebians reconstituted by big data,” said Luana Morais, a postdoctoral researcher with a scholarship from FAPESP and coauthor of the article.

Innovative techniques

In addition to the lack of DNA-containing fossils, the researchers faced another obstacle in reconstructing the phylogenetic tree: thecamoebians cannot be cultured in the laboratory, and genetic sequencing by conventional means is therefore ruled out.

The solution to this problem was to use the single-cell transcriptome technique to analyze phylogenetics (instead of gene expression, its normal application). “We sequenced whole transcriptomes of arcellinid amoebae using live samples,” Lahr explained. “This yielded several thousand genes and some 100,000 amino acid sites, or 100,000 datapoints giving us the phylogenetic tree, which had never been seen before.”

The researchers used transcriptome-based methodology to capture all messenger RNAs from each individual cell and convert them into a sequenceable complementary DNA library.

“Our research drew fundamentally on single-cell transcriptomics, in which our lab is one of the worldwide pioneers,” Lahr said. “It’s a revolutionary technique in this field because it enables us to find a single [unicellular] amoeba, isolate and clean it, and perform all the laboratory procedures to sequence the whole transcriptome.”

In this study, the researchers selected 250 genes to construct the phylogenetic tree. “It’s no good looking at only one cell when you’re studying gene expression, because the resolution will be insufficient,” Lahr said. “In an evolutionary study, however, this doesn’t matter. You need to obtain the sequence, not the number of times a gene is expressed. So it’s possible to use this technique, which was originally developed for tumor cells, and adapt it, with the advantage that an amoeba cell is much larger than a tumor cell.”

Before the technique was developed, only organisms grown in the laboratory could be sequenced. “It extends the range of my research in this field by enabling me to obtain genetic information from organisms I’ve only found once. It’s estimated that only 1% or less of all biodiversity is cultivable,” Lahr said.


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New species of tiny tyrannosaur foreshadows rise of T. rex

A newly discovered, diminutive — by T. rexstandards — relative of the tyrant king of dinosaurs reveals crucial new information about when and how T. rex came to rule the North American roost.

Meet Moros intrepidus, a small tyrannosaur who lived about 96 million years ago in the lush, deltaic environment of what is now Utah during the Cretaceous period. The tyrannosaur, whose name means “harbinger of doom,” is the oldest Cretaceous tyrannosaur species yet discovered in North America, narrowing a 70-million-year gap in the fossil record of tyrant dinosaurs on the continent.

“With a lethal combination of bone-crunching bite forces, stereoscopic vision, rapid growth rates, and colossal size, tyrant dinosaurs reigned uncontested for 15 million years leading up to the end-Cretaceous extinction — but it wasn’t always that way,” says Lindsay Zanno, paleontologist at North Carolina State University, head of paleontology at the North Carolina Museum of Sciences and lead author of a paper describing the research. “Early in their evolution, tyrannosaurs hunted in the shadows of archaic lineages such as allosaurs that were already established at the top of the food chain.”

Medium-sized, primitive tyrannosaurs have been found in North America dating from the Jurassic (around 150 million years ago). By the Cretaceous — around 81 million years ago — North American tyrannosaurs had become the enormous, iconic apex predators we know and love. The fossil record between these time periods has been a blank slate, preventing scientists from piecing together the story behind the ascent of tyrannosaurs in North America. “When and how quickly tyrannosaurs went from wallflower to prom king has been vexing paleontologists for a long time,” says Zanno. “The only way to attack this problem was to get out there and find more data on these rare animals.”

That’s exactly what Zanno and her team did. A decade spent hunting for dinosaur remains within rocks deposited at the dawn of the Late Cretaceous finally yielded teeth and a hind limb from the new tyrannosaur. In fact, the lower leg bones of Moros were discovered in the same area where Zanno had previously found Siats meekerorum, a giant meat-eating carcharodontosaur that lived during the same period. Moros is tiny by comparison — standing only three or four feet tall at the hip, about the size of a modern mule deer. Zanno estimates that the Moros was over seven years old when it died, and that it was nearly full-grown.

But don’t let the size fool you. “Moros was lightweight and exceptionally fast,” Zanno says. “These adaptations, together with advanced sensory capabilities, are the mark of a formidable predator. It could easily have run down prey, while avoiding confrontation with the top predators of the day.

“Although the earliest Cretaceous tyrannosaurs were small, their predatory specializations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the Late Cretaceous,” Zanno says. “We now know it took them less than 15 million years to rise to power.”

The bones of Moros also revealed the origin of T. rex’s lineage on the North American continent. When the scientists placed Moroswithin the family tree of tyrannosaurs they discovered that its closest relatives were from Asia. “T. rex and its famous contemporaries such as Triceratops may be among our most beloved cultural icons, but we owe their existence to their intrepid ancestors who migrated here from Asia at least 30 million years prior,” Zanno says. “Moros signals the establishment of the iconic Late Cretaceous ecosystems of North America.”

The research appears in Communications Biology, and was supported in part by Canyonlands Natural History Association. Lecturer Terry Gates, postdoctoral research scholar Aurore Canoville and graduate student Haviv Avrahami from NC State, as well as the Field Museum’s Peter Makovicky and Ryan Tucker from Stellenbosch University, contributed to the work.


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Half-a-billion-year-old weird wonder worm finally gets its place in the tree of life

Amiskwia was originally described by the famous palaeontologist Charles Doolittle Walcott (1850-1927) in 1911 who compared it to the modern arrow worms (chaetognaths) — a group of ocean-dwelling worms that are fierce predators, equipped with an array of spines on their head for grasping small prey.

Such organisms are found world-wide at sites like the famous Burgess Shale in the Canadian Rockies, where their soft bodies are preserved intact.

The strange anatomies exhibited by these animals led the American palaeontologist Stephen Jay Gould (1941-2002) to speculate that these organisms represented extinct body plans that are no longer seen today and that if we were to wind back the clocks to the Cambrian, more than 500-million-years-ago, and re-run the tape of life, then perhaps the animals alive today would look very different.

More than 50 years after Doolittle Walcott came up with his theory about Amiskwia, scientists investigated its affinities and rejected his interpretation as they could not find evidence of the canonical grasping spines.

Instead, they suggested it could be a ribbon worm, or its own distinct lineage only distantly related to anything that resembles it today.

When Dr Jakob Vinther from the University of Bristol’s Schools of Earth Sciences and Biological Sciences and Luke Parry, now at Yale University, studied specimens of Amiskwia, kept at the Smithsonian Institution they found something that had been missed before.

Dr Vinther said: “I coated the specimen with ammonium chloride smoke to make the relief of the fossil stand out and then I could see that in the head was a pair of robust elements.”

Interpreting these structures as a set of jaws, their resemblance led him to think of a group of animals, called gnathiferans, which include rotifers, gnathostomulids and micrognathozoans. These animals are microscopic worms, with a distinctive internal jaw apparatus.

The scientists realised that Amiskwia suddenly had a jaw of a gnathiferan, but a body of an arrow worm.

Dr Vinther said: “The bizarre combination of anatomy seemed altogether alien back in 2012.

“Some people have proposed that there could be a relationship between arrow worms and gnathiferans based on their shared possession of a jaw apparatus, both made of a substance called chitin.

“However, there was little other evidence to suggest a relationship, such as evidence from phylogenetic analyses of DNA.”

Luke Parry added: “It altogether seemed like heresy to propose that gnathiferans and arrow worms may be related back then so we held off publishing our intriguing results out of fear of criticism from our peers.

“However, new DNA studies have since emerged that found arrow worms to be more and more closely affiliated to the Gnathifera in the Tree of Life.

“In particular, some researchers found that arrow worms share a duplication of the important Hox genes with a gnathiferan, the rotifers. We suddenly felt no more in a deadlock situation.”

Now the authors have published their findings in the journal Current Biology. The study follows a new phylogenetic study, which finds robust support for arrow worms forming an evolutionary group with gnathiferans.

Luke Parry said: “We were excited to see that these researchers found a relationship between arrow worms and rotifers.

“Our phylogenetic analysis, based on anatomical features, strongly suggest a relationship between these two groups of animals as well.”

The researchers find that Amiskwia is a stem lineage to arrow worms that possess the jaw apparatus seen in gnathiferan worms.

This jaw evolved into the fearsome grasping spines in living arrow worms, which now is an important link in the marine food chain. Small crustacean larvae have evolved long protective spines to protect themselves from being swallowed by arrow worms.


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Marsupial lived among Arctic dinosaurs

A research team has discovered a previously unknown species of marsupial that lived in Alaska’s Arctic during the era of dinosaurs, adding a vivid new detail to a complex ancient landscape.

The thumb-sized animal, named Unnuakomys hutchisoni, lived in the Arctic about 69 million years ago during the late Cretaceous Period. Its discovery, led by scientists from the University of Colorado and University of Alaska Fairbanks, is outlined in an article published in the Journal of Systematic Palaeontology.

The discovery adds to the picture of an environment that scientists say was surprisingly diverse. The tiny animal, which is the northernmost marsupial ever discovered, lived among a unique variety of dinosaurs, plants and other animals.

Alaska’s North Slope, which was at about 80 degrees north latitude when U. hutchisoni lived there, was once thought to be a barren environment during the late Cretaceous. That perception has gradually changed since dinosaurs were discovered along the Colville River in the 1980s, with new evidence showing the region was home to a diverse collection of unique species that didn’t exist anywhere else.

Finding a new marsupial species in the far north adds a new layer to that evolving view, said Patrick Druckenmiller, the director of the University of Alaska Museum of the North.

“Northern Alaska was not only inhabited by a wide variety of dinosaurs, but in fact we’re finding there were also new species of mammals that helped to fill out the ecology,” said Druckenmiller, who has studied dinosaurs in the region for more than a decade. “With every new species, we paint a new picture of this ancient polar landscape.”

Marsupials are a type of mammal that carries underdeveloped offspring in a pouch. Kangaroos and koalas are the best-known modern marsupials. Ancient relatives were much smaller during the late Cretaceous, Druckenmiller said. Unnuakomys hutchisoniwas probably more like a tiny opossum, feeding on insects and plants while surviving in darkness for as many as four months each winter.

The research team, whose project was funded with a National Science Foundation grant, identified the new marsupial using a painstaking process. With the help of numerous graduate and undergraduate students, they collected, washed and screened ancient river sediment collected on the North Slope and then carefully inspected it under a microscope. Over many years, they were able to locate numerous fossilized teeth roughly the size of a grain of sand.

“I liken it to searching for proverbial needles in haystacks — more rocks than fossils,” said Florida State University paleobiologist Gregory Erickson, who contributed to the paper.

Jaelyn Eberle, curator of fossil vertebrates at the University of Colorado Museum of Natural History, led the effort to examine those teeth and a few tiny jawbones. Their analysis revealed a new species and genus of marsupial.

Mammal teeth have unique cusps that differ from species to species, making them a bit like fingerprints for long-dead organisms, said Eberle, the lead author of the study.

“If I were to go down to the Denver Zoo and crank open the mouth of a lion and look in — which I don’t recommend — I could tell you its genus and probably its species based only on its cheek teeth,” Eberle said.

The name Unnuakomys hutchisoni combines the Iñupiaq word for “night” and the Greek word “mys” for mouse, a reference to the dark winters the animal endured, and a tribute to J. Howard Hutchison, a paleontologist who discovered the fossil-rich site where its teeth were eventually found.

Other co-authors of the Journal of Systematic Palaeontology paper include William Clemens, of the University of California, Berkeley; Paul McCarthy, of UAF; and Anthony Fiorillo, of the Perot Museum of Nature and Science.


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