Tag Archives: #plateosaurus

Dinosaur Species: ‘Everyone’s Unique (Paleontology)

Paleontologists from the Universities of Bonn and Liverpool examined 14 skulls of Plateosaurus trossingensis

“Everyone’s unique” is a popular maxim. All people are equal, but there are of course individual differences. This was no different with dinosaurs. A study by researchers at the University of Bonn and the Dinosaur Museum Frick in Switzerland has now revealed that the variability of Plateosaurus trossingensis was much greater than previously assumed. The paleontologists examined a total of 14 complete skulls of this species, eight of which they described for the first time. The results have now been published in the scientific journal “Acta Palaeontologica Polonica”.

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.

Photo of a skull of Plateosaurus trossingensis (top) and a reconstruction of the skull with the different bones highlighted in colour (bottom). © Jens Lallensack

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.

Photo (top) and 3D model (bottom, top view) of a Plateosaurus trossingensis skull deformed by loading during fossilization. © Jens Lallensack

“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.

Funding:

The study was funded by the German Research Foundation (DFG). The project received financial support for the excavation and preparation from the municipality of Frick and the Canton of Aargau (Swisslos Fund) of Switzerland.

Featured image: The complete fossil of a Plateosaurus trossingensis, on loan from the Frick Dinosaur Museum, on display at the Zoological Research Museum Alexander Koenig (ZFMK) in Bonn. © Volker Lannert/Uni Bonn


Publication: Lallensack, J.N., Teschner, E.M., Pabst, B., and Sander, P.M.: New skulls of the basal sauropodomorph Plateosaurus trossingensis from Frick, Switzerland: Is there more than one species? Acta Palaeontologica Polonica, DOI:  https://doi.org/10.4202/app.00804.2020;  http://app.pan.pl/article/item/app008042020.html


Provided by University of Bonn

Baby Dinosaurs Were ‘Little Adults’ (Paleontology)

Paleontologists describe skeleton of a juvenile Plateosaurus for the first time.

Long neck, small head and a live weight of several tons – with this description you could have tracked down the Plateosaurus in Central Europe about 220 million years ago. Paleontologists at the University of Bonn (Germany) have now described for the first time an almost complete skeleton of a juvenile Plateosaurus and discovered that it looked very similar to its parents even at a young age. The fact that Plateosaurus showed a largely fully developed morphology at an early age could have important implications for how the young animals lived and moved around. The young Plateosaurus, nicknamed “Fabian”, was discovered in 2015 at the Frick fossil site in Switzerland and is exhibited in the local dinosaur museum. The study was published in the journal “Acta Palaeontologica Polonica”.

Mounted skeleton of Plateosaurus “Fabian” in the Sauriermuseum Frick, with the 20 inch (50 cm) long thigh bone (femur) of a larger Plateosaur as size comparison. © Sauriermuseum Frick, Switzerland.

In order to study the appearance of dinosaurs more closely, researchers today rely on a large number of skeletons in so-called bone beds, which are places where the animals sank into the mud in large numbers during their lifetime. However, juvenile animals had hardly been found in these until now. Researchers described fossils of still juvenile plateosaurs for the first time just a few years ago, but these were already almost as large as the adults. One possible reason: “The smaller individuals probably did not sink into the mud quite as easily and are therefore underrepresented at the bone beds,” suspects study leader Prof. Martin Sander of the University of Bonn.

He and his team used comparative anatomy to examine the new skeleton, which was immediately remarkable because of its small size. “Based on the length of the vertebrae, we estimate the total length of the individual to be about 7.5 feet (2.3 meters), with a weight of about 90 to 130 lbs. (40 to 60 kilograms),” explains Darius Nau, who was allowed to examine the find for his bachelor’s thesis. For comparison: Adult Plateosaurus specimens reached body lengths of 16 to 33 feet (five to ten meters) and could weigh more than four tons. Because of its small size alone, it was obvious to assume that “Fabian” was a juvenile animal. This assumption was confirmed by the fact that the bone sutures of the spinal column had not yet closed. Background: Similar to skull sutures in human babies, bone sutures only fuse over the course of life.

Leg bones of “Fabian” next to those of XL, the largest plateosaurus skeleton discovered in Frick. ©Sauriermuseum Frick, Switzerland.

Young and old resembled each other anatomically and in their body proportions

Researchers found that the young dinosaur resembled its older relatives both in anatomical details, such as the pattern of the laminae on the vertebrae (bony lamellae connecting parts of the vertebrae, which are important anatomical features in many dinosaurs), and in the rough proportions of its body. “The hands and neck of the juveniles may be a little longer, the arm bones a little shorter and slimmer. But overall, the variations are relatively small compared to the variation within the species overall and also compared to other dinosaur species,” stresses Nau. The juveniles of the related Mussaurus for instance were still quadrupeds after hatching, but the adults were bipeds.

“The fact that the Plateosaurus juvenile already looked so similar to the adults is all the more remarkable considering that they were ten times heavier,” emphasizes paleontologist Dr. Jens Lallensack from the University of Bonn. It is however conceivable that the morphological development differed greatly from animal to animal, depending on the climatic conditions or the availability of food. Such differences are still seen in reptiles today.

The well-known descendants of Plateosaurus, the sauropods, are the subject of a current exhibition at the Zoological Research Museum Alexander Koenig in Bonn. The largest Plateosaurus skeleton ever found can be seen there.

References: Darius Nau, Jens N. Lallensack, Ursina Bachmann, P. Martin Sander: Postcranial Osteology of the First Early-Stage Juvenile Skeleton of Plateosaurus trossingensis (Norian, Frick, Switzerland). Acta Palaeontologica Polonica; DOI: 10.4202/app.00757.2020 http://app.pan.pl/article/item/app007572020.html

Provided by University of Bonn