insightLMU - uni-muenchen.deinsightLMU / Issue 3, 2012 After the new find, a juvenile 70 cm long, had been fully exposed, Rauhut irradiated it with UV light. This enabled him to visualize

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Rauhut himself specializes in the evolu-tion of Mesozoic vertebrates, and is Curator of Dinosaurs, Amphibia and Fishes at the Bavarian State Collections for Paleontology and Geology. His goal is to understand the forces that drive evolution and, in particular, the factors responsible for the great success of the dinosaurs. Part of the answer, he believes, lies in their astonishing adaptability. So he studies how the distal elements of the forelimb changed in form over millions of years. This involves comparing dozens of skeletal fragments with each other – a painstaking and demanding task. And one always needs more fossils, new finds documenting related species from all continents. Particularly in the Southern hemisphere, much remains unexplored – in Argentina, for example, Rauhut’s favorite hunting ground.

Searching for traces of dinosaurs

And that’s why, in January 2009, the re-searchers spent 10 hours of every day for three weeks in the scorching sum-mer heat, striding slowly across the bare landscapes of the province of Chabut, wearing broad-brimmed hats to protect them from the merciless sun, noting geo-logical features, find-spots, areas for fu-ture examination. It looked like a stroll or a hike, but it demands incessant attention to detail – and it is back-breaking work.

The 30-member search party advances in a line, intently examining the ground ahead of them. Each a few meters apart from the next, they steadily climb the slope. On this clear January day in 2009, the River Chubut is visible below them, but all attention is focused on the stony ground, with its sparse cover of low bushes. Here in mountains of Patagonia, they are searching for traces of much older organisms. And today, they are finders. “When Diego called out, I knew immediately that we had turned up something special,” says Oliver Rauhut. Set against the sandy grey soil was the dark outline of the arched skull of a large dinosaur. An untrained eye would have missed it completely.

Rauhut, paleontologist and dinosaur specialist at LMU Munich, admits that there was an element of luck involved. “I had passed only 30 meters from the spot on the previous day. If it hadn’t been for Diego, we could not now describe the oldest abelisaurid, from a family of predatory dinosaurs that later became typical for the Southern hemisphere. Our specimen is 170 million years old. On the following day, I was able to return the favor, when found a primordial crocodile.” Diego Pol, Rauhut‘s Argen-tinian partner, who studies archaic reptiles, has a particular penchant for crocodiles.

The Patagonian puzzle

Oliver Rauhut is a rare bird. As a dinosaur expert, he visits the most remote areas on Earth to look for fossils, hoping to work out what made his favorite animals so successful for so long.

Paleontology

by Hubert Filser

insightLMUinsightLMU / Issue 3, 2012Research

During our conversation in his office at the State Collections, Rauhut brings out the geological maps of the region. “These maps are not always exact, the ones the oil companies use are usually more accurate,” he says. Regions in which faults cut through ancient rocks are particularly fossil-rich, and the maps show their locations and course. In such areas, tectonic shifts between the plates that make up the Earth’s crust can bring rocks that are 150 mil-lion years old back to the surface. This has happened in the mountains of Pata-gonia. The more precise the chart, the easier it is to pinpoint promising forma-tions. The rest is a matter of hard slogg-ing in the landscape, keeping one’s eyes peeled for vestiges of a long-lost past.

“My special interest centers on the vertebrate fauna of the Jurassic Period,” Rauhut says. This lasted from 200 to 145 million years ago. “In the Jurassic, all those groups of animals that survived the mass extinction that occurred at the end of the Triassic underwent an adaptive radiation and experienced their greatest expansion.” This holds particularly for the dinosaurs. “At the beginning of the Jurassic, there were six groups of them, at most; by the end of the periods the dinosaur fauna was incredibly diverse.”

Sciurumimus albersdoerferi - a baby dinosaur fossil from a quarry in the area around Painten in Lower Bavaria

Source: Helmut Tischlinger/dpa

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The year after the expedition described above, in the spring of 2010, the re-search team recovered the skull, which confirmed that the find was significant. Just how significant became clear as the work progressed. Rauhut and his team had not only found the almost complete skeleton of an abelisaurid, it turned out to be 40 million years older than any previously known specimen. Rauhut and Pol named it Eoabelisaurus mefi. The Greek prefix in the genus name means “dawn”. As Rauhut points out, “Finds like this from the Jurassic are extremely rare.” The exposed and fragile skeletal elements of the ancient carnivore then had to be embedded in plaster, and a heavy-duty crane lifted the whole bulky package onto a truck.

Some 170 million years ago, abelisaurs roamed the southern regions of what had been the supercontinent of Pangea. “Abelisaurs were previously known only from the Cretaceous, at which time the group was highly diverse and widely dis-tributed,” says Rauhut. “However, noth-ing was known about their early evolu-tion. Our new find shows that the history of the abelisaurids began at least 40 mil-lion years earlier than we thought.”

At that time in Earth’s history, all the continental blocks were still fused together. Rauhut suspects that a mass extinction of dinosaurs had taken place a few million years before. This may have been caused by an increase in volcanic activity associated with the gradual fragmentation of Pangea, which would ultimately lead to the separation of Africa and South America. The accom-panying climate changes transformed the habitats available, and an extensive desert in Central Pangaea may have re-stricted the spread of abelisaurids, which reached lengths of up to 10 me-ters, northwards. Interestingly, their

contemporaries in the south included other predatory dinosaurs such as mega-losaurs, which were distributed globally in Pangean times, and are known to have been present on what are now the Eurasian and North American land-masses.

Adding new pieces to the puzzle of dinosaur evolution

With the complete break-up of Pangea, dinosaur evolution in South America began anew, as it were. “One can learn a great deal about ecological conditions, selective pressures and evolutionary experiments from the study of dino-saurs.” For instance, the abelisaurid Rauhut found in Patagonia, like the tyrannosaurids of the Northern hemis-phere, has very short forelimbs. Further-more, the new specimen reveals that the reduction of forelimb length began at the distal end. “In Eoabelisaurus, the upper arm is of normal length, the lower arm is rather stocky, and the hand is already very short. This species had tiny finger bones and claws.” So the speci-men adds a new piece to the puzzle of dinosaur evolution.

Every year 30 – 40 new species come to light, and its discoverer can assign a scientific name to each new find. About 800 species of dinosaurs have now been described. Rauhut’s description of “his” new dinosaur fills 86 printed pages. The species name “mefi” was chosen in honor of the Museo Egidio Feruglio (MEF) in the province of Chubut, which provided logistical support for the ex-cavation. Upon completion of his studies in Berlin and Bristol, Oliver Rauhut started his career as an independent researcher at the MEF. There he had access to all the fossils that had been found in the province of Chubut – a real paradise for a paleontologist. Indeed,

his daughter was born in Patagonia, in the city of Trelew. He even has photos of her at the age of 10 months, sitting happily on a dinosaur skeleton and cleaning the bones with two brushes.

Oliver Rauhut has retained this sense of child-like fascination. As a boy, he devoured books on dinosaurs from an early age. His parents gave him his first one at the tender age of 4. “And I was immediately hooked,” he says, with a grin. Many of the pictures in those books would now need to modified, but that is a situation that he himself has helped to bring about. The second important article he published in 2012 will also have an impact on the popular image of dinosaurs. This was a study of a feathered dinosaur that lived about 150 million years ago, during the Jurassic. The specimen is one of the best pre-served predatory dinosaurs ever found in Europe. “The feathers appear to have been firmly anchored in the skin, form-ing a dense plumage,” he says.

Virtually all the feathered predatory dinosaurs discovered up to now have been found in China. “But all dinosaurs probably had the genetic potential for the formation of feathers. We may well have to revise the dominant notion of the dinosaur as a giant reptile covered with leathery scales.” Although it cannot yet be ruled out that mature dinosaurs shed their filamentous plumage and replaced them with scales, it is equally possible that dinosaurs retained their feathers lifelong. Rauhut argues that body plumage would have been of adaptive use in the regulation of body tempera-ture. Indeed, recent findings published by others have suggested, in contrast to the generally accepted view, that dino-saurs were probably endothermic, using metabolic energy to maintain a constant body temperature.

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six meters long and may have weighed up to a ton. But this very young indi-vidual, with its large eyes and sharp incisor teeth, probably fed mainly on insects and small rodents. As Rauhut explains, the lifestyles of carnivorous dinosaurs underwent quite drastic changes as they matured. “Based on the state of development of its jaws and teeth, this one was probably no more than 5 months old.” This is yet another example of what one can infer from careful anatomical studies.

Inspired by his scientific publications, artists often send him drawings illus-trating their impressions of what his finds might have looked like when alive. Rauhut has just received another one. It shows a bushy-tailed creature on a rock on a rainswept shore. The animal is on the look-out for something to eat. “The tail was probably less flexible than is shown here,” says Rauhut. Neverthe-less, he does not regard these visualiza-tions merely as playful speculations. “I find them stimulating because they help one to sharpen one’s own ideas,” he says.

For the objective is to comprehend the big picture, the progress of evolution. “I am interested in how this diversifica-tion of species, this extension of the morphological spectrum, in the Jurassic occurred, and what initiated it,” says Rauhut. And each new piece of the puzzle may be important.”

Research

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After the new find, a juvenile 70 cm long, had been fully exposed, Rauhut irradiated it with UV light. This enabled him to visualize the smallest preserved parts of the body, revealing not only the tiniest bones, but also traces of skin, muscle and the thin feathers, because they fluoresce under the ultraviolet radiation. However, it was not possible to discern whether or not the shafts of the feathers, which are only about 0.2 mm thick, were hollow, as they are in modern birds. Rauhut now plans to examine the specimen with synchrotron radiation at the Institut Laue-Langevin in Grenoble, in the hope that it may yield further in-sights into the structure of the skull and other anatomical details.

With a bit of luck, the researchers might even detect traces of pigment in the feathers. “This would give us an idea of how colorful the plumage was, and we would then have to consider whether dinosaurs had color vision,” says Rauhut. Obviously, these two issues are con-nected. Species that display colored markings are very likely to be able to perceive and recognize color patterns.

Such markings might even throw some light the animal’s behavior. “But the best thing is that we now have a complete megalosaur fossil from the Jurassic. Only if one has complete specimens can one hope to reconstruct evolutionary pro-cesses. And we want to provide as true and correct an account as possible of the phylogeny of our fossils.”

The slab that contained this fossil from a quarry in the area around Painten in Lower Bavaria was an incidental find. A well-known collector made the valuable specimen available for study. In his honor, the baby dinosaur was named Sciurumimus albersdoerferi, for its “squirrel-like” form. When fully grown, this carnivore would have been perhaps

Source: Stephan Rumpf/SZ Photo/picture alliance

PD Dr. Oliver Rauhutis a Privatdozent at the Chair of Paleontology and Geobiology at LMU, and became a Curator at the Bavarian State Collections for Paleontology and Geology. Born in 1969, Rauhut studied Geology and Paleontology at the Free University of Berlin and obtained his PhD at the University of Bristol (UK) in 2000. After working as a postdoctoral researcher at the Museo Paleontológico Egidio Feruglio in Trelew (Argentina), he took up a position at the Museum of Natural History in Berlin. Rauhut completed his Habilitation in 2007.

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Paleontologist Richard Butler has just returned from a fossil-hunting expedition in the Holy Cross Mountains of South-eastern Poland, where he studied rocks that are over 250 million years old. “We found some wonderful fossil trackways, dating from the very beginning of dinosaur evolution,” he says excitedly. At the onset of the Triassic Period, an early ancestor of the giants that would later become so dominant, a gracile creature about the size of a cat, with a long tail, lived in the area. It was a very agile, probably lived on insects and other invertebrates, and already possessed the typical three-toed dinosaur foot. “We now know that all dinosaurs are de-scended from a common ancestor,” Butler points out. Just before the Triassic began, the biosphere experienced the greatest mass extinction event the Earth has ever seen. Some 90% of all species were wiped out, and the larger ones were particularly badly hit. Suddenly there were lots of empty niches available for new species.

There are few regions in the world that offer such a window into deep time and the history of evolution as this range of moun-tains north of Krakow does. It is one of those places where enor-mous tectonic forces have brought ancient rocks that lay buried for millions of years back to the surface. And paleontologists like Richard Butler, who are interested in the origins of the di-nosaurs, flock to these localities, in South Africa and Argentina, European Russia, Poland, Germany and China. “Thanks to the traces left behind in these age-old rocks, we can follow how the earliest dinosaurs evolved and dispersed, and work out how and why they became such a dominant presence in the Earth’s ecosystems from about 230 million years ago,” Butler explains.

The rise of the dinosaurs began with a catastrophe, a disaster that was a huge stroke of luck for the dinosaur lineage, just as the meteorite impact that brought their reign to an end 65 million years ago was a lucky break for mammals and ulti-mately for our species. “Mass extinctions – unique, un-predictable and irreversible events – act as drivers of evolution. They initiated the era in which dinosaurs dominated the bio-sphere, and they terminated it,” says Butler. The 31-year-old paleontologist heads a junior research group, which is funded by a prestigious Emmy Noether Award from the German Re-search Foundation (DFG). The evocative title of the project is “The Dawn of the Dinosaurs.”

The world inhabited by the early dinosaurs was a challenging one, and they had to adapt to very difficult conditions. “And the biological attributes that were to make them so successful

were quite unique. They had very high growth rates, an effec-tive mode of locomotion, a very efficient respiratory system similar to that of birds, and many species developed complex social behaviors.” According to Butler, these features played a far more prominent role in their evolution than abiotic factors such as climate change, to which they adapted well. Indeed, at the peak of their diversity, there were probably thousands of dinosaur species.

“We tend to think of dinosaurs only as huge primeval monsters, but they were actually highly diverse,” says Butler. Even at the end of the Cretaceous, there were still hundreds of species, which varied widely in size, form and lifestyle. For more than 150 million years, dinosaurs were the dominant organisms on the planet. Butler is convinced that: “Nothing but a catastrophe of astounding dimensions could have brought their hegemony to an end.”

However, others have suggested that the dinosaurs were already in decline in the Late Cretaceous, and some would argue that their fall was inevitable. However, in his most recent paper, Butler has presented evidence that clearly conflicts with this view, and leads him to reject the thesis. He and his colleagues analyzed the morphological diversity of selected families at the end of the Cretaceous. The results indicated that only moder-ately large herbivores, such as the horned dinosaur Tricer tops with its imposing crest, or the hadrosaurs of North America were under pressure at that time. “Most families and species were flourishing before the arrival of the fatal projectile,” says Butler. His investigations demonstrate that among carnivorous dinosaurs such as the tyrannosaurids, or the smaller herbivores and the giant, long-neckyed sauropods, the range of diversity was stable or actually increasing. Without the meteorite impact at the end of the Cretaceous, the dinosaurs would still be here, and mammals would still be inconspicuous nocturnal creatures. “Had that catastrophe not intervened,” says Butler, “we very probably wouldn’t be here.” (Hubert Filser)

Dr. Richard Butler has led his own Junior Research Group at LMU’s GeoBio-Center since September 2011. The group is financed by the German Research Foundation (DFG) in the context of the Emmy Noether Program. Butler, born in 1981, studied at the University of Bris-tol, did his Ph.D. at Cambridge University and at the Natural History Museum in London, where he worked as researcher be-fore joining the Bavarian State Collections for Paleontology and Geology as a Humboldt Fellow in 2009.

Profiting from catastropheRichard Butler explores the rise and fall of the dinosaurs

The original article will appear in „Einsichten – das Forschungsmagazin No. 2, 2012“, LMU‘s German-language research magazine. Translation: Paul Hardy, Copyright: Ludwig-Maximilians-Universität München, 2012.

Source: LMU Munich