Plateosaurus lived during the Late Triassic, about 217 to 201 million years ago. “With well over 100 skeletons, some of them completely preserved, it is one of the best known dinosaurs,” says Dr. Jens Lallensack, who researched dinosaur biology at the University of Bonn and has been working at Liverpool John Moores University (UK) for several months. The herbivore had a small skull, a long neck and tail, powerful hind legs and strong grasping hands. The spectrum is considerable: Adult specimens ranged from a few to ten meters in length, weighing between about half a ton and four tons.

The first bones of Plateosaurus were found as early as 1834 near Nuremberg, making it the first dinosaur found in Germany, and one of the first ever. Between 1911 and 1938, excavations unearthed dozens of skeletons from dinosaur “graveyards” in Halberstadt (Saxony-Anhalt) and Trossingen (Baden-Württemberg). A third such cemetery was discovered in the 1960s in Frick, Switzerland. “It’s the only one where there are still digs every year,” Lallensack says. The material from Frick, which is described in detail for the first time, includes eight complete and seven fragmentary skulls excavated by Swiss paleontologist and dinosaur researcher Dr. Ben Pabst and his team.

Natural variation between individuals

Dinosaurs have been preserved for posterity mainly through bones. Paleontologists rely on anatomical details to distinguish different species. “A perpetual difficulty with this is that such anatomical differences can also occur within a species, as natural variation between individuals,” Lallensack reports. Researchers at the University of Bonn and the Dinosaur Museum Frick (Switzerland) have now been able to show that Plateosaurus anatomy was significantly more variable than previously thought — and the validity of some species needs to be re-examined. These findings were made possible by analyses of 14 complete and additional incomplete skulls of Plateosaurus. “Such a large number of early dinosaurs is unique,” says paleontologist Prof. Dr. Martin Sander of the University of Bonn.

Can all these fossils from Germany and Switzerland really be assigned to a single species? Answering this question has become all the more urgent since Martin Sander and Nicole Klein of the University of Bonn published in “Science” in 2005. According to this, Plateosaurus was probably already warm-blooded like today’s birds, but was able to adapt its growth to the environmental conditions — something that today can only be observed in cold-blooded animals. “This hypothesis is of great importance for our understanding of the evolution of warm-bloodedness,” reports Lallensack. However, until now the observed individually distinct growth patterns could alternatively be explained by the assumption that there was not only one, but several species present. The current study debunks this.

Bone deformations during fossilization

The researchers have now carefully documented the variations in skulls of different sizes. A significant portion of the differences can be attributed to bone deformation during fossilization deep below the Earth’s surface. Individual variations must be distinguished from this: The posterior branch of the zygomatic bone, which is sometimes bifurcated and sometimes not, appeared most striking to the researchers. A strongly sculptured bone bridge over the eye was also present only in some skulls. The relative size of the nasal opening also varies.

“It becomes apparent that each skull has a unique combination of features,” Lallensack notes, emphasizing the distinct individuality of these dinosaurs. The uniquely large number of skulls studied made it possible to show that the differences in characteristics were variations within a species and not different species. “Only if as many finds as possible are excavated and secured will we obtain the high quantities needed to prove species affiliation and answer fundamental questions of biology” says Sander.

WFS,World Fossil Society,Riffin T Sajeev,Russel T Sajeev

The international effort provides a scientific framework for understanding planetary habitability and for finding critical metal resources needed for a low-carbon future.

It reveals a planet in constant movement as land masses move around the Earth’s surface, for instance showing that Antarctica was once at the equator.

The video is based on new research published in the March 2021 edition of Earth-Science Reviews.

Co-author and academic leader of the University of Sydney EarthByte geosciences group, Professor Dietmar Müller, said: “Our team has created an entirely new model of Earth evolution over the last billion years.

Schematic comparison of evolution of plate tectonic modelling. (a) ‘Continental drift’/palaeogeographic type models and (b) full-plate models; (i)–(iv) identify separate plates. Palaeomagnetic data are the primary constraint of the movement of continents in both (a) and (b) however, the inclusion of geological data into the model in (b) preserves the relative type of motion between two continents (divergence, convergence or transform) and allows for the construction of plate boundaries.

“Our planet is unique in the way that it hosts life. But this is only possible because geological processes, like plate tectonics, provide a planetary life-support system.”

Lead author and creator of the video Dr Andrew Merdith began work on the project while a PhD student with Professor Müller in the School of Geosciences at the University of Sydney. He is now based at the University of Lyon in France.

Co-author, Dr Michael Tetley, who also completed his PhD at the University of Sydney, told Euronews: “For the first time a complete model of tectonics has been built, including all the boundaries”

“On a human timescale, things move in centimetres per year, but as we can see from the animation, the continents have been everywhere in time. A place like Antarctica that we see as a cold, icy inhospitable place today, actually was once quite a nice holiday destination at the equator.”

Co-author Dr Sabin Zahirovic from the University of Sydney, said: “Planet Earth is incredibly dynamic, with the surface composed of ‘plates’ that constantly jostle each other in a way unique among the known rocky planets. These plates move at the speed fingernails grow, but when a billion years is condensed into 40 seconds a mesmerising dance is revealed.

“Oceans open and close, continents disperse and periodically recombine to form immense supercontinents.”

Earth scientists from every continent have collected and published data, often from inaccessible and remote regions, that Dr Andrew Merdith and his collaborators have assimilated over the past four years to produce this billion-year model.

It will allow scientists to better understand how the interior of the Earth convects, chemically mixes and loses heat via seafloor spreading and volcanism. The model will help scientists understand how climate has changed, how ocean currents altered and how nutrients fluxed from the deep Earth to stimulate biological evolution.

Professor Müller said: “Simply put, this complete model will help explain how our home, Planet Earth, became habitable for complex creatures. Life on Earth would not exist without plate tectonics. With this new model, we are closer to understanding how this beautiful blue planet became our cradle.”

1. Andrew S. Merdith, Simon E. Williams, Alan S. Collins, Michael G. Tetley, Jacob A. Mulder, Morgan L. Blades, Alexander Young, Sheree E. Armistead, John Cannon, Sabin Zahirovic, R. Dietmar Müller. Extending full-plate tectonic models into deep time: Linking the Neoproterozoic and the Phanerozoic. Earth-Science Reviews, 2021; 214: 103477 DOI: 10.1016/j.earscirev.2020.103477

Cartilaginous fishes, which include sharks and rays, are one of the most successful vertebrate groups still alive today. Due to their life-long tooth replacement, teeth of cartilaginous fishes are among the most common fossil vertebrate finds. However, the low preservation potential of their cartilaginous skeletons prevents fossilization of completely preserved specimens in most cases. The extremely rare preservation of fossil cartilaginous fish skeletons is therefore linked to special conditions during fossilization and restricted to a few fossil-bearing localities only.

Asteracanthus ornatissimus Agassiz, 1837, PBP‐SOL‐8003, from the lower Tithonian of Solnhofen, Bavaria, Germany. A, photograph of dentition. B, interpretation. Abbreviations: LA, lower anterior teeth; LL, lower lateral teeth; LP, lower posterior teeth; S, lower symphyseal teeth; UA, upper anterior teeth; UL, upper lateral teeth; UP, upper posterior teeth; (l), left; (r), right. Scale bars represent 5 cm.

The Solnhofen limestones in Bavaria, Germany, which were formed during the Late Jurassic, about 150 million years ago, is such a rare occurrence. They are world-renowned for having produced skeletons of the small feathered dinosaur Archaeopteryx and have yielded numerous shark and ray skeletons, recovered during excavations over the past 150 years. A new study published in the journal Papers in Palaeontology and led by the paleontologist Sebastian Stumpf from the University of Vienna presents the largest fossil shark skeleton that has ever been discovered in the Solnhofen limestones. The specimen is represented by an almost completely preserved skeleton of the extinct hybodontiform shark Asteracanthus, the total length of which was two-and-a-half meters in life, which made it a giant among Jurassic sharks.

Hybodontiform sharks, which are the closest relatives of modern sharks and rays, first appeared during the latest Devonian, about 361 million years ago, and went extinct together with dinosaurs at the end of the Cretaceous, about 66 million years ago. They had two dorsal fins, each supported by a prominent fin spine. The body size of hybodontiform sharks ranged from a few centimeters to approximately three meters in maximum length, which consequently makes Asteracanthus one of the largest representatives of both its group and its time. In contrast, modern sharks and rays, which were already diverse during the Jurassic, only reached a body size of up to two meters in maximum length in very rare cases.

Asteracanthus was scientifically described more than 180 years ago by the Swiss-American naturalist Louis Agassiz on the basis of isolated fossil dorsal fin spines. However, articulated skeletal remains have never been found — until now. The dentition of the skeleton is exceptionally well-preserved and contains more than 150 teeth, each with a well-developed central cusp that is accompanied on both sides by several smaller cusplets. “This specialized type of dentition suggests that Asteracanthus was an active predator feeding on a wide range of prey animals. Asteracanthus was certainly not only one of the largest cartilaginous fishes of its time, but also one of the most impressive.” says Sebastian Stumpf.

1. Stumpf, S., López-Romero, F.A., Kindlimann, R., Lacombat, F., Pohl, B. & Kriwet, J. A unique hybodontiform skeleton provides novel insights into Mesozoic chondrichthyan life. Papers in Palaeontology, 2021 DOI: 10.1002/spp2.1350

In a study published in Nature Communications, the researchers show that an organic molecule often found in high-latitude ocean sediments, known as tetra-unsaturated alkenone (C37:4), is produced by one or more previously unknown species of ice-dwelling algae. As sea ice concentration ebbs and flows, so do the algae associated with it, as well as the molecules they leave behind.

“We’ve shown that this molecule is a strong proxy for sea ice concentration,” said Karen Wang, a Ph.D. student at Brown and lead author of the research. “Looking at the concentration of this molecule in sediments of different ages could allow us to reconstruct sea ice concentration through time.”

Other types of alkenone molecules have been used for years as proxies for sea surface temperature. At different temperatures, algae that live on the sea surface make differing amounts of alkenones known as C37:2 and C37:3. Scientists can use the ratios between those two molecules found in sea sediments to estimate past temperature. C37:4 — the focus of this new study — had been long considered a bit of problem for temperature measurements. It turns up in sediments taken from closer to the Arctic, throwing off the C37:2/C37:3 ratios.

“That was mostly what the C37:4 alkenone was known for — throwing off the temperature ratios,” said Yongsong Huang, principal investigator of the National Science Foundation-funded project and a professor in Brown’s Department of Earth, Environmental and Planetary Science. “Nobody knew where it came from, or whether it was useful for anything. People had some theories, but no one knew for sure.”

To figure it out, the researchers studied sediment and sea water samples containing C37:4 taken from icy spots around the Arctic. They used advanced DNA sequencing techniques to identify the organisms present in the samples. That work yielded previously unknown species of algae from the order Isochrysidales. The researchers then cultured those new species in the lab and showed that they were indeed the ones that produced an exceptionally high abundance of C37:4.

The next step was to see whether the molecules left behind by these ice-dwelling algae could be used as a reliable sea ice proxy. To do that, the researchers looked at concentrations of C37:4 in sediment cores from several spots in the Arctic Ocean near the present-day sea ice margins. In the recent past, sea ice in these spots is known to have been highly sensitive to regional temperature variation. That work found that the highest concentrations of C37:4 occurred when climate was coldest and ice was at its peak. The highest concentrations dated back to the Younger-Dryas, a period of very cold and icy conditions that occurred around 12,000 years ago. When climate was at its warmest and ice ebbed, C37:4 was sparse, the research found.

“The correlations we found with this new proxy were far stronger than other markers people use,” said Huang, a research fellow at the Institute at Brown for Environment and Society. “No correlation will be perfect because modeling sea ice is a messy process, but this is probably about as strong as you’re going to get.”

And this new proxy has some additional advantages over others, the researchers say. One other method for reconstructing sea ice involves looking for fossil remains of another kind of algae called diatoms. But that method becomes less reliable further back in time because fossil molecules can degrade. Molecules like C37:4 tend to be more robustly preserved, making them potentially better for reconstructions over deep time than other methods.

The researchers plan to further research these new algae species to better understand how they become embedded in sea ice, and how they produce this alkenone compound. The algae appear to live in brine bubbles and channels inside sea ice, but it may also bloom just after the ice melts. Understanding those dynamics will help the researchers to better calibrate C37:4 as a sea ice proxy.

Ultimately, the researchers hope that the new proxy will enable better understanding of sea ice dynamics through time. That information would improve models of past climate, which would make for better predictions of future climate change.

1. Karen Jiaxi Wang, Yongsong Huang, Markus Majaneva, Simon T. Belt, Sian Liao, Joseph Novak, Tyler R. Kartzinel, Timothy D. Herbert, Nora Richter, Patricia Cabedo-Sanz. Group 2i Isochrysidales produce characteristic alkenones reflecting sea ice distribution. Nature Communications, 2021; 12 (1) DOI: 10.1038/s41467-020-20187-z