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Giant marine invertebrates

FAU researchers investigate which environmental factors influence the evolution of animals with giant proportions

Animals come in all different sizes – from huge whales to tiny crustaceans. Certain species stand out due to their extreme size – such as the giant squid, which can grow to up to 13 metres in length. Animals of such giant proportions appeared again and again over the past 500 million years. Together with colleagues from Germany, Switzerland, England and the USA, researchers at FAU have investigated whether the development of marine invertebrates is influenced by environmental factors across time and space.

A human being looks tiny in comparison with these reconstructions of gigantic marine invertebrates from the Palaeozoic Era. Arthropods: E) Nautiloid Endoceras giganteum, Upper Ordovician, USA, body length: approx. 9 metres; F) Nautiloid Endoceras giganteum, Upper Ordovician, USA, reconstructed body length: approx. 4.5 metres (based on an example from Harvard University's Museum of Comparative Zoology); G) Nautiloid Deiroceras hollardi, Lower Devonian, Morocco, reconstructed body length: 3 metres; J) Ammonite Carinoceras sp., Upper Devonian, USA max. body diameter: 50 centimetres. Cephalopods: H) Sea scorpion Jaekelopterus rhenaniae, Lower Devonian, Germany, reconstructed length: 2.5 metres (without chelicerae); I) Trilobite Hungioides bohemicus, Upper Ordovician, Portugal, length: 80–90 centimetres. (Image: Christian Klug, taken from Klug et al. 2014)

A human being looks tiny in comparison with these reconstructions of gigantic marine invertebrates from the Palaeozoic Era. Arthropods: E) Nautiloid Endoceras giganteum, Upper Ordovician, USA, body length: approx. 9 metres; F) Nautiloid Endoceras giganteum, Upper Ordovician, USA, reconstructed body length: approx. 4.5 metres (based on an example from Harvard University’s Museum of Comparative Zoology); G) Nautiloid Deiroceras hollardi, Lower Devonian, Morocco, reconstructed body length: 3 metres; J) Ammonite Carinoceras sp., Upper Devonian, USA max. body diameter: 50 centimetres. Cephalopods: H) Sea scorpion Jaekelopterus rhenaniae, Lower Devonian, Germany, reconstructed length: 2.5 metres (without chelicerae); I) Trilobite Hungioides bohemicus, Upper Ordovician, Portugal, length: 80–90 centimetres. (Image: Christian Klug, taken from Klug et al. 2014)

 

The Palaeozoic Era is the period of time between 500 million and 300 million years ago. Researchers have attributed several of the largest known arthropods and cephalopods to this era, such as 2.5 metre long sea scorpions and extinct arthropods with bodies up to 9 metres in length – distant relatives of today’s nautilus and squid. As part of their project, the international team of researchers investigated whether the appearance and prevalence of these gigantic marine arthropods and cephalopods in the Palaeozoic Era was dependent on temperature and/or oxygen conditions or on variations in sea level. However, their results did not support this hypothesis. ‘Optimal environmental conditions did not play a larger role for the appearance of gigantic marine life than for the diversity of marine organisms in general,’ concludes Dr. Kenneth De Baets from the Chair of Palaeoenviromental Studies at FAU.

Instead, the researchers were able to show that the invertebrate sea creatures took on gigantic proportions during two specific periods – the Ordovician Period and the Devonian Period. These were also both periods during which the number of different species increased significantly. Many new species evolved during these periods because animals from one species created different ecological niches, adapting themselves particularly well to certain environments. The development of new species led in turn to the development of new, complex ecosystems.

In addition, the researchers showed that, up to around 300 million years ago, giants within species or genera typically occurred at higher latitudes near the poles – similar to what is observed today. During the periods which followed, members of all of the groups studied moved to lower, equatorial latitudes. The researchers believe that possible causes of this migration could be simultaneous changes in oxygen concentration, the constellation of the continents and ocean temperatures.

*The researchers’ results have recently been published in the Wiley Online Library.

Further information:

Dr. Kenneth De Baets
Phone: +49 9131 8522906
kenneth.debaets@fau.de

 

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