On the Traces of the Proto-Dinosaur

Orobates pabsti lived 300 million years ago. Using a 3D model of its skeleton, the Humboldt Labor demonstrates what cutting-edge modern research looks like. Researchers reconstructed how the proto-dinosaur moved around.

With its yellow backbone, red head and two blue feet the model of Orobates pabsti, unlike the pale dinosaur skeletons in museums, shines brightly in several colours. There is a reason for that. Reminiscent of a reptile, the model that will be on show in the Humboldt Labor typifies how scientists work, says John Nyakatura, Junior Professor of Morphology (Zoology) and the History of Forms at the Humboldt-Universität. “The assembled skeleton exemplifies our approach to reconstruction and shows that we are transparent in dealing with uncertainties,” says the biologist who, together with the Swiss EPFL Biorobotics Laboratory in Lausanne, investigated how the dinosaur moved around.

The nearly 300-million-year-old Orobates pabsti fossil was found in the Thuringian forest. Starting with the surviving fossilised bones, research scientists sought to find out what the proto-dinosaur’s complete skeleton looked like – in order to discover how it moved around.

Uncertainty is made visible

In the reconstructed 3D model the colour red stands for parts that were constructed on the basis of the CT scan of the fossil, Nyakatura explains. The scans were necessary because in such an old fossil the bones can no longer be separated from the surrounding rock matrix. The blue parts of the model stand for mirror images of the red. “That,” he says, “is a trick palaeontologists are fond of using.” The skeleton of a vertebrate can be assumed to be more or less symmetrical in shape.

The yellow parts of the model are, in contrast, slightly uncertain. They are based not on hard data but on what scientists consider on the basis of different clues to be plausible.

A mixture of certain and less certain data is usual in assembling skeletons, Nyakatura says. And that is no less true of dinosaur models in natural history museums. “In the vast majority of cases only fragments of skeletons have survived; they are almost never really complete.” As a rule, however, there is no transparency about how which parts were reconstructed. The teacher and curator Wilhelm Pabst discovered fossilised tracks of the proto-dinosaur near Gotha in the early years of the twentieth century. The fossil discovered in 1996 was named Orobates pabsti after him. “In terms of evolutionary biology Orobates pabsti is an interesting case because it marks the transition from an amphibious vertebrate to forms that have adapted totally to life on land,” Nyakatura explains.

Reconstruction provides clues about the evolution of vertebrates

Amphibians lay eggs from which tadpoles are hatched in water. Young hatched from the eggs of amniotes, in contrast, can live directly on land. “They no longer need to swim in a pond; they have their own private pond inside the egg,” Nyakatura says. Orobates pabsti marks this transition. It is the most closely related known fossil relative of the last common ancestor of all surviving amniotes today. His research enables inferences to be drawn about the origin of the larger group of amniotes, which includes, for instance, lizards and snakes, birds and mammals – in other words humans too.

We don’t know how Orobates pabsti reproduced, he says, but analysing its movements might provide clues. What distances might it have covered? Was it still limited to open waters?

Starting with the model of the skeleton and using track slabs attempts made to reconstruct its movements. A special feature of the project was that many different disciplines and technologies were involved, including palaeontology, zoology, biomechanics, biologically inspired robotics, 3D computer animation – and research scientists from Jena, Lausanne, Hamburg and London.

One approach was to develop a robot to test the reconstructed movements of Orobates pabsti in genuine physical conditions. This OroBOT was exhibited in 2016 together with the fossil and the 3D model in an exhibition at the Veterinary Anatomy Theatre of the Humboldt-Universität in Berlin and in the Phyletic Museum in Jena.

Models play a key role in science

The 3D skeleton shows that models can be much more informative than the original for purposes of demonstration and didactics, partly because the reconstruction maps the research process exactly, says Dr. Gorch Pieken, curator of the exhibition in the Humboldt Lab.

The model has a special place n the exhibition. One of 38 selected exhibits, it will hang on a pantograph in the exhibition hall. Next to it will be the proto-dinosaur’s fossilised footprints. One reason why Orobates is so exciting, Nyakatura says, is that scientists sought to set methodical research standards. Different approaches were adopted to try and limit options until the most plausible form of mobility emerged. Rather than dogmatically propound a theory the aim was to make it clear what scientists know and where uncertainties exist. The Orobates skeleton illustrates this approach, which includes disclosure of all data as part of an open science approach. “We hope this kind of research will increasingly become standard,” Nyakatura says.