Clues to How Plants Evolved to Cope With Cold
Dec. 22, 2013 — Researchers have found new clues to how plants evolved to withstand wintry weather. In a study to appear in the December 22 issue of the journal Nature, the team constructed an evolutionary tree of more than 32,000 species of flowering plants — the largest time-scaled evolutionary tree to date. By combining their tree with freezing exposure records and leaf and stem data for thousands of species, the researchers were able to reconstruct how plants evolved to cope with cold as they spread across the globe. The results suggest that many plants acquired characteristics that helped them thrive in colder climates — such as dying back to the roots in winter — long before they first encountered freezing.
Fossil evidence and reconstructions of past climatic conditions suggest that early flowering plants lived in warm tropical environments, explained co-author Jeremy Beaulieu at the National Institute for Mathematical & Biological Synthesis (NIMBioS) at the University of Tennessee.
As plants spread to higher latitudes and elevations, they evolved in ways that helped them deal with cold conditions. Plants that live in the tundra, such as Arctic cinquefoil and three-toothed saxifrage, can withstand winter temperatures below minus 15 degrees Celsius.
Unlike animals, most plants can’t move to escape the cold or generate heat to keep them warm. It’s not so much the cold but the ice that poses problems for plants. For instance, freezing and thawing cause air bubbles to form in the plant’s internal water transport system.
“Think about the air bubbles you see suspended in the ice cubes,” said co-author Amy Zanne of the George Washington University. “If enough of these air bubbles come together as water thaws they can block the flow of water from the roots to the leaves and kill the plant.”
The researchers identified three traits that help plants get around these problems.
Some plants, such as hickories and oaks, avoid freezing damage by dropping their leaves before the winter chill sets in — effectively shutting off the flow of water between roots and leaves — and growing new leaves and water transport cells when warmer weather returns.
Other plants, such as birches and poplars, also protect themselves by having narrower water transport cells, which makes the parts of the plant that deliver water less susceptible to blockage during freezing and thawing.
Still others die back to the ground in winter and re-sprout from their roots, or start growing as new plants from seeds when conditions are right.
To compile the plant trait data for their study, the researchers spent hundreds of hours scouring and merging multiple large plant databases containing tens of thousands of species, largely with the support of the National Evolutionary Synthesis Center in North Carolina and Macquarie University in Australia.
When they mapped their collected leaf and stem data onto their evolutionary tree for flowering plants, they found that many plants were well equipped for icy climates even before cold conditions hit.
Plants that die back to the ground in winter, for example, acquired the ability to die and come back when conditions improve long before they first experienced freezing. Similarly, species with narrow water transport cells acquired a finer circulatory system well before they confronted cold climates.
“This suggests that some other environmental pressure — possibly drought — caused these plants to evolve this way, and it happened to work really well for freezing tolerance too,” said Zanne.
The only exceptions were plants that shed and replace their leaves seasonally — these plant groups didn’t gain the ability to drop their leaves during winter until after they encountered freezing, Beaulieu added.
As a next step, the researchers plan to use their evolutionary tree to find out how plants evolved to withstand other environmental stresses in addition to freezing, such as drought and heat.
New Evidence for Warm-Blooded Dinosaurs
July 17, 2013 — University of Adelaide research has shown new evidence that dinosaurs were warm-blooded like birds and mammals, not cold-blooded like reptiles as commonly believed.
In a paper published in PLoS ONE, Professor Roger Seymour of the University’s School of Earth and Environmental Sciences, argues that cold-blooded dinosaurs would not have had the required muscular power to prey on other animals and dominate over mammals as they did throughout the Mesozoic period.
“Much can be learned about dinosaurs from fossils but the question of whether dinosaurs were warm-blooded or cold-blooded is still hotly debated among scientists,” says Professor Seymour.
“Some point out that a large saltwater crocodile can achieve a body temperature above 30°C by basking in the sun, and it can maintain the high temperature overnight simply by being large and slow to change temperature.
“They say that large, cold-blooded dinosaurs could have done the same and enjoyed a warm body temperature without the need to generate the heat in their own cells through burning food energy like warm-blooded animals.”
In his paper, Professor Seymour asks how much muscular power could be produced by a crocodile-like dinosaur compared to a mammal-like dinosaur of the same size.
Saltwater crocodiles reach over a tonne in weight and, being about 50% muscle, have a reputation for being extremely powerful animals.
But drawing from blood and muscle lactate measurements collected by his collaborators at Monash University, University of California and Wildlife Management International in the Northern Territory, Professor Seymour shows that a 200 kg crocodile can produce only about 14% of the muscular power of a mammal at peak exercise, and this fraction seems to decrease at larger body sizes.
“The results further show that cold-blooded crocodiles lack not only the absolute power for exercise, but also the endurance, that are evident in warm-blooded mammals,” says Professor Seymour.
“So, despite the impression that saltwater crocodiles are extremely powerful animals, a crocodile-like dinosaur could not compete well against a mammal-like dinosaur of the same size.
“Dinosaurs dominated over mammals in terrestrial ecosystems throughout the Mesozoic. To do that they must have had more muscular power and greater endurance than a crocodile-like physiology would have allowed.”
His latest evidence adds to that of earlier work he did on blood flow to leg bones which concluded that the dinosaurs were possibly even more active than mammals.
Big-Nosed, Long-Horned Dinosaur Discovered in Utah: Dinosaur in Same Family as Triceratops
July 17, 2013 — A remarkable new species of horned dinosaur has been unearthed in Grand Staircase-Escalante National Monument, southern Utah. The huge plant-eater inhabited Laramidia, a landmass formed when a shallow sea flooded the central region of North America, isolating western and eastern portions for millions of years during the Late Cretaceous Period. The newly discovered dinosaur, belonging to the same family as the famous Triceratops, was announced today in the British scientific journal, Proceedings of the Royal Society B.
The study, funded in large part by the Bureau of Land Management and the National Science Foundation, was led by Scott Sampson, when he was the Chief Curator at the Natural History Museum of Utah at the University of Utah. Sampson is now the Vice President of Research and Collections at the Denver Museum of Nature & Science. Additional authors include Eric Lund (Ohio University; previously a University of Utah graduate student), Mark Loewen (Natural History Museum of Utah and Dept. of Geology and Geophysics, University of Utah), Andrew Farke (Raymond Alf Museum), and Katherine Clayton (Natural History Museum of Utah).
Horned dinosaurs, or “ceratopsids,” were a group of big-bodied, four-footed herbivores that lived during the Late Cretaceous Period. As epitomized by Triceratops, most members of this group have huge skulls bearing a single horn over the nose, one horn over each eye, and an elongate, bony frill at the rear. The newly discovered species, Nasutoceratops titusi, possesses several unique features, including an oversized nose relative to other members of the family, and exceptionally long, curving, forward-oriented horns over the eyes. The bony frill, rather than possessing elaborate ornamentations such as hooks or spikes, is relatively unadorned, with a simple, scalloped margin. Nasutoceratops translates as “big-nose horned face,” and the second part of the name honors Alan Titus, Monument Paleontologist at Grand Staircase-Escalante National Monument, for his years of research collaboration.
For reasons that have remained obscure, all ceratopsids have greatly enlarged nose regions at the front of the face. Nasutoceratops stands out from its relatives, however, in taking this nose expansion to an even greater extreme. Scott Sampson, the study’s lead author, stated, “The jumbo-sized schnoz of Nasutoceratops likely had nothing to do with a heightened sense of smell — since olfactory receptors occur further back in the head, adjacent to the brain — and the function of this bizarre feature remains uncertain.”
Paleontologists have long speculated about the function of horns and frills on horned dinosaurs. Ideas have ranged from predator defense and controlling body temperature to recognizing members of the same species. Yet the dominant hypothesis today focuses on competing for mates — that is, intimidating members of the same sex and attracting members of the opposite sex. Peacock tails and deer antlers are modern examples. In keeping with this view, Mark Loewen, a co-author of the study claimed that, “The amazing horns of Nasutoceratops were most likely used as visual signals of dominance and, when that wasn’t enough, as weapons for combatting rivals.”
A Treasure Trove of Dinosaurs on the Lost Continent of Laramidia
Nasutoceratops was discovered in Grand Staircase-Escalante National Monument (GSENM), which encompasses 1.9 million acres of high desert terrain in south-central Utah. This vast and rugged region, part of the National Landscape Conservation System administered by the Bureau of Land Management, was the last major area in the lower 48 states to be formally mapped by cartographers. Today GSENM is the largest national monument in the United States. Sampson proclaimed that, “Grand Staircase-Escalante National Monument is the last great, largely unexplored dinosaur boneyard in the lower 48 states.”
For most of the Late Cretaceous, exceptionally high sea levels flooded the low-lying portions of several continents around the world. In North America, a warm, shallow sea called the Western Interior Seaway extended from the Arctic Ocean to the Gulf of Mexico, subdividing the continent into eastern and western landmasses, known as Appalachia and Laramidia, respectively. Whereas little is known of the plants and animals that lived on Appalachia, the rocks of Laramidia exposed in the Western Interior of North America have generated a plethora of dinosaur remains. Laramidia was less than one-third the size of present day North America, approximating the area of Australia.
Most known Laramidian dinosaurs were concentrated in a narrow belt of plains sandwiched between the seaway to the east and mountains to the west. Today, thanks to an abundant fossil record and more than a century of collecting by paleontologists, Laramidia is the best known major landmass for the entire Age of Dinosaurs, with dig sites spanning from Alaska to Mexico. Utah was located in the southern part of Laramidia, which has yielded far fewer dinosaur remains than the fossil-rich north. The world of dinosaurs was much warmer than the present day; Nasutoceratops lived in a subtropical swampy environment about 100 km from the seaway.
Beginning in the 1960’s, paleontologists began to notice that the same major groups of dinosaurs seemed to be present all over this Late Cretaceous landmass, but different species of these groups occurred in the north (for example, Alberta and Montana) than in the south (New Mexico and Texas). This finding of “dinosaur provincialism” was very puzzling, given the giant body sizes of many of the dinosaurs together with the diminutive dimensions of Laramidia. Currently, there are five giant (rhino-to-elephant-sized) mammals on the entire continent of Africa. Seventy-six million years ago, there may have been more than two dozen giant dinosaurs living on a landmass about one-quarter that size. Co-author Mark Loewen noted that, “We’re still working to figure out how so many different kinds of giant animals managed to co-exist on such a small landmass?” The new fossils from GSENM are helping us explore the range of possible answers, and even rule out some alternatives.
During the past dozen years, crews from the Natural History Museum of Utah, the Denver Museum of Nature & Science and several other partner institutions (e.g., the Utah Geologic Survey, the Raymond Alf Museum of Paleontology, and the Bureau of Land Management) have unearthed a new assemblage of more than a dozen dinosaurs in GSENM. In addition to Nasutoceratops, the collection includes a variety of other plant-eating dinosaurs — among them duck-billed hadrosaurs, armored ankylosaurs, dome-headed pachycephalosaurs, and two other horned dinosaurs, Utahceratops and Kosmoceratops — together with carnivorous dinosaurs great and small, from “raptor-like” predators to a mega-sized tyrannosaur named Teratophoneus. Amongst the other fossil discoveries are fossil plants, insect traces, clams, fishes, amphibians, lizards, turtles, crocodiles, and mammals. Together, this diverse bounty of fossils is offering one of the most comprehensive glimpses into a Mesozoic ecosystem. Remarkably, virtually all of the identifiable dinosaur remains found in GSENM belong to new species, providing strong support for the dinosaur provincialism hypothesis.
Andrew Farke, a study co-author, noted that, “Nasutoceratops is one of a recent landslide of ceratopsid discoveries, which together have established these giant plant-eaters as the most diverse dinosaur group on Laramidia.”
Eric Lund, another co-author as well as the discoverer of the new species, stated that, “Nasutoceratops is a wondrous example of just how much more we have to learn about with world of dinosaurs. Many more exciting fossils await discovery in Grand Staircase-Escalante National Monument.”
Tooth Is ‘Smoking Gun’ Evidence That Tyrannosaurus Rex Was Hunter, Killer
July 16, 2013 — Tyrannosaurus rex has long been popular with kids and moviemakers as the most notorious, vicious killing machine to roam the planet during the age of the dinosaurs.
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So, it may come as a shock that for more than a century some paleontologists have argued that T. rex was a scavenger, not a true predator — more like a vulture than a lion. Indeed, a lack of definitive fossil proof of predation in the famous theropod has stirred controversy among scientists — until now.
“T. rex is the monster of our dreams,” said David Burnham, preparator of vertebrate paleontology at the Biodiversity Institute at the University of Kansas. “But ever since it was discovered in Montana and named in the early 1900s, there’s been a debate about whether these large carnivores were scavengers or predators. Most people assume they were predators, but the scientific evidence for predation has been really elusive. Yes, we’ve found lots of dinosaur skeletons with tooth marks that had been chewed up by something. But what did that really prove? Yes, these large carnivores fed on other dinosaurs — but did they eat them while they were alive or dead? That’s where the debate came in. Where was the evidence for hunt and kill?”
Now, Burnham is part of a team that has unearthed “smoking gun” physical proof that T. rex was indeed a predator, hunter and killer. In the Hell Creek Formation of South Dakota, Burnham and colleagues discovered the crown of a T. rex tooth lodged in the fossilized spine of a plant-eating hadrosaur that seems to have survived the attack. The team describes the find in the current issue of the Proceedings of the National Academy of Sciences.
Burnham’s KU co-authors are Bruce Rothschild and the late Larry Martin, along with former KU student Robert DePalma II of The Palm Beach Museum of Natural History and Peter Larson of the Black Hills Institute of Geological Research.
“Robert DePalma was a student here at KU doing his master’s thesis in the Hell Creek formation,” said Burnham. “He found a specimen that represents the tail of one of these hadrosaurs. It had a distorted-looking bone growth. He came to me and said, ‘What do you think is causing this?’ So we cleaned it and could see a tooth embedded in one of these duck-billed dinosaur vertebrae. Then we went to Lawrence Memorial Hospital and used a CT machine to scan the bones — and we saw all of the tooth.”
Previous evidence for predation included T. rex fossil discoveries with preserved stomach contents that included the bones of a young ceratopsian (e.g., Triceratops or one of its kin). However, there was no evidence to conclude whether the ceratopsian was alive or dead when the T. rex made a snack of it.
By contrast, Burnham said the tooth was definitive evidence of hunting, after carefully measuring its length and the size of its serrations to ensure that it came from the mouth of a T. rex.
“Lo and behold, the tooth plotted out just exactly with T. rex — the only known large theropod from the Hell Creek formation,” he said. “We knew we had a T. rex tooth in the tail of a hadrosaur. Better yet, we knew the hadrosaur got away because the bone had begun to heal. Quite possibly it was being pursued by the T. rex when it was bitten. It was going in the right direction — away. The hadrosaur escaped by some stroke of luck. The better luck is finding this fossil with the preserved evidence.”
Because T. rex regularly shed its teeth, the predator went away hungry, but otherwise no worse for the encounter. It would have grown a new tooth to replace the one left behind in the hadrosaur’s tail. This could have been a typical example of T. rex’s hunting efforts, even if it didn’t result in a meal.
“To make an analogy to modern animals, when lions go attack a herd of herbivores, they go after the sick and the slow,” Burnham said. “Most of the time, hadrosaurs traveled in packs. This hadrosaur may have been a little slower, or this T. rex may have been a little faster — at least fast enough to almost catch a duck-billed dinosaur.”
This concrete proof of T. rex’s predation continues a long relationship between KU paleontologists and the theropod, which lived in North America during the Late Cretaceous, some 65 million years ago. KU graduate Barnum Brown discovered the first documented remains of the dinosaur in Wyoming in 1900.
High Diversity of Flying Reptiles in England 110 Million Years Ago
June 12, 2013 — Brazilian paleontologists Taissa Rodrigues, of the Federal University of Espirito Santo, and Alexander W. A. Kellner, of the National Museum of the Federal University of Rio de Janeiro, have just presented the most extensive review yet available of toothed pterosaurs from the Cretaceous of England. The study features detailed taxonomic information, diagnoses and photographs of 30 species and was published in the open access journal ZooKeys.
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Pterosaurs from the Cretaceous of England were first described by British naturalists Richard Owen and Harry Seeley in the 19th century, when little was known about the diversity of the group, resulting in the description of dozens of species, all based on very fragmentary remains, represented mostly by the tips of the snouts of these animals. However, more recent findings of pterosaur fossils have challenged views on their diversity.
Results show that these pterosaurs had a remarkable diversity in their appearances. Some species had head crests of different sizes and shapes, while others had none. Most had large teeth at the tip of their snouts and were fish eaters, but others had smaller teeth, suggesting different feeding preferences. The paleontologists were able to identify fourteen different species, belonging to at least five different genera, showing a greater diversity than previously thought.
Most of these fossils were found in a deposit known as the Cambridge Greensand, located in the eastern part of the country. This unit, one of the most important for the study of flying reptiles, records a past marine environment where the bones that were already fossilized and buried, were eroded, exposed to weathering, and then buried again. Cycles of erosion and burial must have taken place during several years. Due to this peculiarity, the pterosaur assemblage from this deposit probably presents temporal mixing of faunas, thus explaining the high diversity found.
Another find was that these English flying reptiles turned out to be closely related to species unearthed in northeastern Brazil and eastern China. According to Dr. Rodrigues, ‘This is very interesting, especially because the continents had already drifted apart. If these animals were migratory, we would expect to find the same species in all these deposits.’ Instead, the scientists have discovered that England, Brazil and China all had their own species and genera.
Analysis of fossils from other continents showed that this group of pterosaurs was already widespread in the whole planet 110 million years ago, and must have been important faunistic elements at this time of the Cretaceous period, being early bird competitors, before they went extinct a few million years later.
X-Rays Reveal New Picture of ‘Dinobird’ Plumage Patterns
June 11, 2013 — The first complete chemical analysis of feathers from Archaeopteryx, a famous fossil linking dinosaurs and birds, reveals that the feathers of this early bird were patterned – light in colour, with a dark edge and tip to the feather - rather than all black, as previously thought.
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The findings came from X-ray experiments undertaken by a team from the University of Manchester, working with colleagues at the US Department of Energy’s (DOE) SLAC National Accelerator Laboratory. The scientists were able to find chemical traces of the original ‘dinobird’ and dilute traces of plumage pigments in the 150 million-year-old fossil.
“This is a big leap forward in our understanding of the evolution of plumage and also the preservation of feathers,” said Dr Phil Manning, a palaeontologist at The University of Manchester and lead author of the report in the June 13 issue of the Journal of Analytical Atomic Spectrometry (Royal Society of Chemistry).
Only 11 specimens of Archaeopteryx have been found, the first one consisting of a single feather. Until a few years ago, researchers thought minerals would have replaced all the bones and tissues of the original animal during fossilisation, leaving no chemical traces behind, but two recently developed methods have turned up more information about the dinobird and its plumage.
The first is the discovery of melanosomes – microscopic ‘biological paint pot’ structures in which pigment was once made, but are still visible in some rare fossil feathers. A team led by researchers at Brown University announced last year that an analysis of melanosomes in the single Archaeopteryx feather indicated it was black. They identified the feather as a covert – a type of feather that covers the primary and secondary wing feathers – and said its heavy pigmentation may have strengthened it against the wear and tear of flight, as it does in modern birds.
However, that study examined melanosomes from just a few locations in the fossilised feather, explained SLAC’s Dr Uwe Bergmann: “It’s actually quite a beautiful paper,” he said, “but they took just tiny samples of the feather, not the whole thing.”
The second is a method that Drs Bergmann, Manning and Roy Wogelius have developed for rapidly scanning entire fossils and analysing their chemistry with an X-ray beam at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) in the USA.
Over the past three years, the team used this method to discover chemical traces locked in the dinobird’s bones, feathers and in the surrounding rock, as well as pigments from the fossilised feathers of two specimens of another species of early bird. This allowed the team to recreate the plumage pattern of an extinct bird for the very first time.
In the latest study, the team scanned the entire fossil of the first Archaeopteryx feather with the SSRL X-ray beam. They found trace-metals that have been shown to be associated with pigment and organic sulphur compounds that could only have come from the animal’s original feathers.
“The fact that these compounds have been preserved in-place for 150 million years is extraordinary,” said Dr Manning said. “Together, these chemical traces show that the feather was light in colour with areas of darker pigment along one edge and on the tip.
“Scans of a second fossilised Archaeopteryx, known as the Berlin counterpart, also show that the trace-metal inventory supported the same plumage pigmentation pattern.”
Co-author Dr Roy Wogelius, also based in Manchester’s School of Earth, Atmospheric and Environmental Sciences, said: “This work refines our understanding of pigment patterning in perhaps the most important known fossil. Our technique shows that complex patterns were present even at the very earliest steps in the evolution of birds.”
The team’s results show that the chemical analysis provided by synchrotron X-ray sources, such as SSRL, is crucial when studying the fossil remains of such pivotal species. The plumage patterns can begin to help scientists review their possible role in the courtship, reproduction and evolution of birds and possibly shed new light on their health, eating habits and environment.
Dr Manning added: “It is remarkable that x-rays brighter than a million suns can shed new light on our understanding of the processes that have locked elements in place for such vast periods of time. Ultimately, this research might help inform scientists on the mechanisms acting during long-term burial, from animal remains to hazardous waste. The fossil record has potential to provide the experimental hindsight required in such studies.”
The research team included scientists from The University of Manchester (UK); SLAC (USA); the Black Hills Institute of Geological Research in South Dakota (USA); and the Museum für Naturkunde in Berlin (Germany), which provided the stunning Archaeopteryx fossils for analysis.
Fossil Saved from Mule Track Revolutionizes Understanding of Ancient Dolphin-Like Marine Reptile
May 14, 2013 — An international team of scientists have revealed a new species of ichthyosaur (a dolphin-like marine reptile from the age of dinosaurs) from Iraq, which revolutionises our understanding of the evolution and extinction of these ancient marine reptiles.
The results, produced by a collaboration of researchers from universities and museums in Belgium and the UK and published today (May 15) in Biology Letters, contradict previous theories that suggest the ichthyosaurs of the Cretaceous period (the span of time between 145 and 66 million years ago) were the last survivors of a group on the decline.
Ichthyosaurs are marine reptiles known from hundreds of fossils from the time of the dinosaurs. “They ranged in size from less than one to over 20 metres in length. All gave birth to live young at sea, and some were fast-swimming, deep-diving animals with enormous eyeballs and a so-called warm-blooded physiology,” says lead author Dr Valentin Fischer of the University of Liege in Belgium.
Until recently, it was thought that ichthyosaurs declined gradually in diversity through multiple extinction events during the Jurassic period. These successive events were thought to have killed off all ichthyosaurs except those strongly adapted for fast-swimming life in the open ocean. Due to this pattern, it has been assumed that ichthyosaurs were constantly and rapidly evolving to be ever-faster open-water swimmers; seemingly, there was no ‘stasis’ in their long evolutionary history.
However, an entirely new ichthyosaur from the Kurdistan region of Iraq substantially alters this view of the group. The specimen concerned was found during the 1950s by British petroleum geologists. “The fossil — a well-preserved partial skeleton that consists of much of the front half of the animal — wasn’t exactly being treated with the respect it deserves. Preserved within a large, flat slab of rock, it was being used as a stepping stone on a mule track,” says co-author Darren Naish of the University of Southampton. “Luckily, the geologists realized its potential importance and took it back to the UK, where it remains today,” adds Dr Naish, who is based at the National Oceanography Centre, Southampton.
Study of the specimen began during the 1970s with ichthyosaur expert Robert Appleby, then of University College, Cardiff. “Robert Appleby recognised that the specimen was significant, but unfortunately died before resolving the precise age of the fossil, which he realised was critical,” says Jeff Liston of National Museums Scotland and manager of the research project. “So continuation of the study fell to a new generation of researchers.”
In the new study (which properly includes Appleby as an author), researchers name it Malawania anachronus, which means ‘out of time swimmer’. Despite being Cretaceous in age, Malawania represents the last-known member of a kind of ichthyosaur long believed to have gone extinct during the Early Jurassic, more than 66 million years earlier. Remarkably, this kind of archaic ichthyosaur appears characterised by an evolutionary stasis: they seem not to have changed much between the Early Jurassic and the Cretaceous, a very rare feat in the evolution of marine reptiles.
“Malawania’s discovery is similar to that of the coelacanth in the 1930s: it represents an animal that seems ‘out of time’ for its age. This ‘living fossil’ of its time demonstrates the existence of a lineage that we had never even imagined. Maybe the existence of such Jurassic-style ichthyosaurs in the Cretaceous has been missed because they always lived in the Middle-East, a region that has previously yielded only a single, very fragmentary ichthyosaur fossil,” adds Dr Fischer.
Thanks to both their study of microscopic spores and pollen preserved on the same slab as Malawania, and to their several analyses of the ichthyosaur family tree, Fischer and his colleagues retraced the evolutionary history of Cretaceous ichthyosaurs. In fact, the team was able to show that numerous ichthyosaur groups that appeared during the Triassic and Jurassic ichthyosaur survived into the Cretaceous. It means that the supposed end of Jurassic extinction event did not ever occur for ichthyosaurs, a fact that makes their fossil record quite different from that of other marine reptile groups.
When viewed together with the discovery of another ichthyosaur by the same team in 2012 and named Acamptonectes densus, the discovery of Malawania constitutes a ‘revolution’ in how we imagine ichthyosaur evolution and extinction. It now seems that ichthyosaurs were still important and diverse during the early part of the Cretaceous. The final extinction of the ichthyosaurs — an event that occurred about 95 million years ago (long before the major meteorite-driven extinction event that ended the Cretaceous) — is now even more confusing than previously assumed.
Mum and Dad Dinosaurs Shared the Work
May 15, 2013 — A study into the brooding behaviour of birds has revealed their dinosaur ancestors shared the load when it came to incubation of eggs.
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Research into the incubation behaviour of birds suggests the type of parental care carried out by their long extinct ancestors.
The study aimed to test the hypothesis that data from extant birds could be used to predict the incubation behaviour of Theropods, the group of carnivorous dinosaurs from which birds descended.
The paper, out today in Biology Letters, was co-authored by Dr Charles Deeming and Dr Marcello Ruta from the University of Lincoln’s School of Life Sciences and Dr Geoff Birchard from George Mason University, Virginia.
By taking into account factors known to affect egg and clutch size in living bird species, the authors — who started their investigation last summer at the University of Lincoln’s Riseholme campus — found that shared incubation was the ancestral incubation behaviour. Previously it had been claimed that only male Theropod dinosaurs incubated the eggs.
Dr Deeming said: “In 2009 a study in the journal Science suggested that it was males of the small carnivorous dinosaurs Troodon and Oviraptor that incubated their eggs. Irrespective of whether you accept the idea of Theropod dinosaurs sitting on eggs like birds or not, the analysis raised some concerns that we wanted to address. We decided to repeat the study with a larger data set and a better understanding of bird biology because other palaeontologists were starting to use the original results in Science in order to predict the incubation behaviour of other dinosaur species. Our analysis of the relationship between female body mass and clutch mass was interesting in its own right but also showed that it was not possible to conclude anything about incubation in extinct distant relatives of the birds.”
Palaeobiologist Dr Ruta was involved in mapping the parental behaviour in modern birds on to an evolutionary tree.
Dr Ruta said: “As always in any study involving fossils, knowledge of extant organisms helps us make inferences about fossils. Fossils have a unique role in shaping our knowledge of the Tree of Life and the dynamics of evolutionary processes. However, as is the case with our study, data from living organisms may augment and refine the potential of fossil studies and may shift existing notions of the biology and behaviour of long extinct creatures.”
Dr Birchard added: “The previous study was carried out to infer the type of parental care in dinosaurs that are closely related to birds. That study proposed that paternal care was present in these dinosaurs and this form of care was the ancestral condition for birds. Our new analysis based on three times as many species as in the previous study indicates that parental care cannot be inferred from simple analyses of the relationship of body size to shape, anatomy, physiologyand behaviour. Such analyses ought to take into account factors such as shared evolutionary history and maturity at hatching. However, our data does suggest that the dinosaurs used in the previous study were likely to be quite mature at birth.”
The project has helped in understanding the factors affecting the evolution of incubation in birds. More importantly it is hoped that the new analysis will assist palaeontologists in their interpretation of future finds of dinosaur reproduction in the fossil record.
Earliest Archaeological Evidence of Human Ancestors Hunting and Scavenging
May 10, 2013 — A recent Baylor University research study has shed new light on the diet and food acquisition strategies of some the earliest human ancestors in Africa.
Beginning around two million years ago, early stone tool-making humans, known scientifically as Oldowan hominin, started to exhibit a number of physiological and ecological adaptations that required greater daily energy expenditures, including an increase in brain and body size, heavier investment in their offspring and significant home-range expansion. Demonstrating how these early humans acquired the extra energy they needed to sustain these shifts has been the subject of much debate among researchers.
A recent study led by Joseph Ferraro, Ph.D., assistant professor of anthropology at Baylor, offers new insight in this debate with a wealth of archaeological evidence from the two million-year-old site of Kanjera South (KJS), Kenya. The study’s findings were recently published in PLOS One.
“Considered in total, this study provides important early archaeological evidence for meat eating, hunting and scavenging behaviors -cornerstone adaptations that likely facilitated brain expansion in human evolution, movement of hominins out of Africa and into Eurasia, as well as important shifts in our social behavior, anatomy and physiology,” Ferraro said.
Located on the shores of Lake Victoria, KJS contains “three large, well-preserved, stratified” layers of animal remains. The research team worked at the site for more than a decade, recovering thousands of animal bones and rudimentary stone tools.
According to researchers, hominins at KJS met their new energy requirements through an increased reliance on meat eating. Specifically, the archaeological record at KJS shows that hominins acquired an abundance of nutritious animal remains through a combination of both hunting and scavenging behaviors. The KJS site is the earliest known archaeological evidence of these behaviors.
“Our study helps inform the ‘hunting vs. scavenging’ debate in Paleolithic archaeology. The record at KJS shows that it isn’t a case of either/or for Oldowan hominins two million years ago. Rather hominins at KJS were clearly doing both,” Ferraro said.
The fossil evidence for hominin hunting is particularly compelling. The record shows that Oldowan hominins acquired and butchered numerous small antelope carcasses. These animals are well represented at the site by most or all of their bones from the tops of their head to the tips of their hooves, indicating to researchers that they were transported to the site as whole carcasses.
Many of the bones also show evidence of cut marks made when hominins used simple stone tools to remove animal flesh. Some bones also bear evidence that hominins used fist-sized stones to break them open to acquire bone marrow.
In addition, modern studies in the Serengeti–an environment similar to KJS two million years ago–have also shown that predators completely devour antelopes of this size within minutes of their deaths. As a result, hominins could only have acquired these valuable remains on the savanna through active hunting.
The site also contains a large number of isolated heads of wildebeest-sized antelopes. In contrast to small antelope carcasses, the heads of these somewhat larger individuals are able to be consumed several days after death and could be scavenged, as even the largest African predators like lions and hyenas were unable to break them open to access their nutrient-rich brains.
“Tool-wielding hominins at KJS, on the other hand, could access this tissue and likely did so by scavenging these heads after the initial non-human hunters had consumed the rest of the carcass,” Ferraro said. “KJS hominins not only scavenged these head remains, they also transported them some distance to the archaeological site before breaking them open and consuming the brains. This is important because it provides the earliest archaeological evidence of this type of resource transport behavior in the human lineage.”
Other contributing authors to the study include: Thomas W. Plummer of Queens College & NYCEP; Briana L. Pobiner of the National Museum of Natural History, Smithsonian Institution; James S. Oliver of Illinois State Museum and Liverpool John Moores University; Laura C. Bishop of Liverpool John Moores University; David R. Braun of George Washington University; Peter W. Ditchfield of University of Oxford; John W. Seaman III , Katie M. Binetti and John W. Seaman Jr. of Baylor University; Fritz Hertel of California State University and Richard Potts of the National Museum of Natural History, Smithsonian Institution and National Museums of Kenya.
The research was supported by funding from the National Science Foundation, Leakey Foundation, Wenner-Gren Foundation, National Geographic Society, The Leverhulme Trust, University of California, Baylor University and the City University of New York. Additional logistical support was provided by the Smithsonian Institution’s Human Origins Program and the Peter Buck Fund for Human Origins Research, the British Institute of Eastern Africa and the National Museums of Kenya.
Four New Dinosaur Species Identified
May 8, 2013 — Just when dinosaur researchers thought they had a thorough knowledge of ankylosaurs, a family of squat, armour plated, plant eaters, along comes University of Alberta graduate student, Victoria Arbour.
Arbour visited dinosaur fossil collections from Alberta to the U.K. examining skull armour and comparing those head details with other features of the fossilized ankylosaur remains. She made a breakthrough that resurrected research done more than 70 years ago.
Arbour explains that between 1900 and 1930 researchers had determined that small variations in the skull armour and the tail clubs in some ankylosaurs constituted four individual species of the dinosaurs.
“In the 1970s the earlier work was discarded and those four species were lumped into one called species Euoplocephalus,” said Arbour.
“I examined many fossils and found I could group some fossils together because their skull armour corresponded with a particular shape of their tail club,” said Arbour.
Finding common features in fossils that come from the same geologic time is evidence that the original researchers were right says Arbour. “There were in fact four different species represented by what scientists previously thought was only one species, Euoplocephalus.”
The four species span a period of about 10 million years. Arbour’s research shows three of those ankylosaurs species lived at the same time in what is now Dinosaur Provincial Park in southern Alberta.
Arbour says this opens the door to new questions.
“How did these three species shared their habitat, how did they divide food resources and manage to survive?” said Arbour.
Arbour will also look into how slight differences in skull ornamentation and tail shape between the species influenced the animals’ long reign on Earth.
Arbour’s research was published May 8, in the journal PLOS ONE.