Life Through the Ages

Palaeontologists look back on past geological eras and reconstruct evolution, but their work also looks to the future: It can show us what ecosystems untouched by humans looked like and develop suggestions for how to manage them in future.

Feb. 1, 2016

How did the form of animals evolve? How did their skeletal structures and adaptations emerge? How can the development of vertebrates be reconstructed? These are some of the questions that Jürgen Kriwet and his Evolutionary Morphology Research Group study. The researchers move back and forth between the present day and the past millions of years. In order to understand the evolution of life and the different adaptations of species, they also have to study organisms living today.

Hear, hear!

The inner ear allows us to hear – but it also contains the organ responsible for balance. Its anatomy varies between species depending on how they move. Cathrin Pfaff from Kriwet’s Group was able to demonstrate this in a study on squirrels in 2015. Gliding species have thinner semicircular canals than ground-dwelling species. The researchers are now planning to examine whether marsupials, birds and cartilaginous fish also exhibit a correlation between anatomy and locomotion mode. Pfaff explains that the goal is “to compare data from modern species with those from fossils”. This will allow them to determine how long-extinct species moved. According to Jürgen Kriwet, the reconstruction of the inner ear over millions of years has already been successfully completed for cats. The starting point was a Pseudaelurus fossil – one of the oldest cats in the world.

What causes functional traits to develop? What causes genetically and epigenetically determined adaptations? Our research on the inner ear has shown that this is an organ where we can make distinctions.”

Jürgen Kriwet, Professor of Palaeobiology with Special Emphasis on Vertebrate Palaeontology

A micro-CT at the Department and modern image analysis methods give researchers insights that would have been impossible to gain only a few years ago. Additionally, they can now make 3-D images and reconstruct the morphology of different body parts at an extremely high resolution without physically damaging the samples. Using special staining methods, even muscles, soft tissue and the nerve cells can be made visible. The micro-CT is also useful for the second key research area of the palaeobiologists: understanding processes of developmental biology in an evolutionary context.

Evolution and individual development

“Ontogeny recapitulates phylogeny.” In 1866, Ernst Haeckel postulated this biogenetic rule, according to which the prenatal development of an individual repeats the evolutionary history of its species in a very short time. This was long a controversial position. “Today we know that there is a clear connection,” says Jürgen Kriwet. His team studies these connections, entering uncharted waters: Kriwet’s Group is currently studying the individual development of shark embryos. For example, they want to understand how their jaws develop and compare them to fossil records.

Very little is known about the evolution and adaptation of teeth or the differences between species. “Cartilaginous fish are the oldest jaw-bearing vertebrates still living today. Based on them, we can try to find out what things look like at the base of the vertebrate family tree,” says Jürgen Kriwet. He and his team are cooperating with international institutions, including the Natural History Museum in London, the Okinawa Churaumi Aquarium and British and Japanese researchers. In 2015, Kriwet and Pfaff were able to show from the analysis of fossilised rays and sharks that their jaw teeth are not directly evolved from their external skin denticles – disproving an earlier hypothesis.

The state of the environment then and now

Essentially, the Viennese palaeobiologists have already succeeded in describing part of the evolutionary history of vertebrates. The Research Group Palaeoecosystems, led by the Head of the Department, Petra Heinz, on the other hand, focuses on reconstructing marine ecosystems from past eras.

The fascinating thing about palaeobiology is the connection between life on Earth today and life on Earth in past ages. And sometimes it can even help us think about the life that will come.”

Petra Heinz, Professor of Palaeoecosystems

Marine habitats are also one of the areas of research of Martin Zuschin’s Research Group Environmental Palaeontology: The researchers use palaeontological methods to study environmental changes in marine ecosystems in order to evaluate the current state. Their research is centred on the Persian Gulf and the Northern Adriatic. Environmental palaeontologist Zuschin specialises in shell-bearing invertebrates such as bivalves (mussels) and gastropods (snails), whose dead shells are dated with radiometric and other methods.

“By comparing living and dated dead fauna, e.g. in terms of size, distribution and diversity, we can draw conclusions on environmental conditions and their change over long periods of time,” says Zuschin.

By using palaeontological methods, we can gain insight into environmental conditions decades or centuries ago. That allows us to better assess the current situation and make predictions for future changes.”

Martin Zuschin, Professor of Palaeontology

In 2015, postdoc Paolo Albano studied the impact of oil rigs on the environment in the Persian Gulf (Arabian Gulf) by analysing molluscs and their remains on the sea bed. He was able to show that oil rigs have considerably less impact on the marine environment during normal operation than is usually assumed.

In the Northern Adriatic

In the Northern Adriatic, the researchers went even deeper to understand the condition of the ecosystem and its changes. In addition to analysing the top layer of the sea bed, they also took core samples. In areas with very little sedimentation, a 1.5-metre core sample was enough to depict the entire Holocene – the last approx. 10,000 years. In contrast, core samples taken in areas with a very high degree of sedimentation, such as the Po Delta, cover just about 100 years.

During their dives and underwater expeditions, the researchers studied sedimentation and pollution in seven different locations and compared the current biodiversity with the faunal development of subfossil mussels, snails, etc. One of their findings was that the communities of species are different now than they used to be. Many changes occurred as a result of rising sea levels during the Holocene, but researchers also identified anthropogenic changes in environmental conditions as causes. Their research forms the basis for potential rehabilitation measures: We now have indications of what a “healthy” Northern Adriatic looked like. An important finding of their studies is that fishing by pulling dragnets across the ocean floor, as has been done in the Northern Adriatic for decades, is currently the largest danger for the ecosystem. Without trawling, there would be the potential for self-regulation.

Migration on the ocean floor

In another study, doctoral candidate Rafal Nawrot was able to show how the migration of fauna from the Red Sea via the Suez Canal to the Mediterranean works and why large bivalves are particularly successful. “This study shows what has been happening in the last decades and allows us to predict how the fauna will develop in future,” says Zuschin. Although palaeobiology often looks to the past, it can also help develop plans for the future.