Diversification after mass extinction

March 1, 2019, Ludwig Maximilian University of Munich
Diversification after mass extinction
Fossil Fish E. diskosomus. Credit: A. López-Arbarello

A team led by LMU paleontologist Adriana López-Arbarello has identified three hitherto unknown fossil fish species in the Swiss Alps, which provide new insights into the diversification of the genus Eosemionotus.

Monte San Giorgio in the Swiss canton of Ticino is one of the most important known sources of marine fossils from the Middle Triassic Period (around 240 million years ago). The new and exquisitely preserved fossil fish specimens, which Dr. Adriana López-Arbarello (a member of the Institute of Paleontology and Geobiology and of the Geobiocenter at LMU) has been studying in collaboration with colleagues based in Switzerland were also discovered in these dolomites and limestones. As the researchers now report in the online journal Palaeontologia Electronica, the specimens represent three previously unknown of Eosemionotus, a of ray-finned fishes. "The largest episode of mass extinction in the history of the Earth took place about 250 million years ago," as López-Arbarello explains. "Our finds now provide further evidence that after this , the biosphere recovered relatively fast and went through a period of rapid diversification and the emergence of numerous new species during the Middle Triassic."

The first member of the genus Eosemionotus was discovered in the vicinity of Berlin in 1906, and was named E. vogeli. Almost a century later, in 2004, a second species was described from Monte San Giorgio as E. ceresiensis. Detailed anatomical studies of new material from this locality, carried out by López-Arbarello, have now enabled the recognition of three further species that can be assigned to same genus – E. diskosomus, E. sceltrichensis and E. minutus. All five species are small in size, but they can be clearly distinguished from each other on the basis of the relative proportions of their bodies, the position of the fins, the morphology of the skull, and the disposition of teeth and scales. "These differences indicate that each species was adapted to different ecological niches," López-Arbarello concludes.

These findings provide new insights into the evolution of the genus. "Our demonstrate that Eosemionotus is the oldest known member of an extinct family within the Order Semionotiformes. Although the Semionotiformes were a species-rich and highly diversified clade during the Mesozoic Era, the order died out in the Cretaceous. Only a few members of its sister group have survived down to the present day, and this ancient lineage is now represented by a single family, the gars," says López-Arbarello.

Explore further: Aftermath of a mass extinction

More information: Adriana López-Arbarello et al. Taxonomy and phylogeny of Eosemionotus Stolley, 1920 (Neopterygii: Ginglymodi) from the Middle Triassic of Europe, Palaeontologia Electronica (2019). DOI: 10.26879/904

Related Stories

Aftermath of a mass extinction

July 19, 2016

A new study of fossil fishes from Middle Triassic sediments on the shores of Lake Lugano provides new insights into the recovery of biodiversity following the great mass extinction event at the Permo-Triassic boundary 240 ...

Adaptive radiations in the Mesozoic

March 22, 2018

Bony fishes are the most diverse of all extant vertebrate groups. A comprehensive phylogenetic analysis of the group now provides new insights into its 250-million-year evolutionary history.

Discovery of two new species of primitive fishes

March 31, 2015

Working with an international team, paleontologists at the University of Zurich have discovered two new species of Saurichthys. The ~242 million year old predatory fishes were found in the fossil Lagerstätte Monte San Giorgio, ...

The Archaeopteryx that wasn't

December 4, 2017

Paleontologists at LMU correct a case of misinterpretation: The first fossil "Archaeopteryx" to be discovered is actually a predatory dinosaur belonging to the anchiornithid family, which was previously known only from finds ...

Recommended for you

Coffee-based colloids for direct solar absorption

March 22, 2019

Solar energy is one of the most promising resources to help reduce fossil fuel consumption and mitigate greenhouse gas emissions to power a sustainable future. Devices presently in use to convert solar energy into thermal ...

Paleontologists report world's biggest Tyrannosaurus rex

March 22, 2019

University of Alberta paleontologists have just reported the world's biggest Tyrannosaurus rex and the largest dinosaur skeleton ever found in Canada. The 13-metre-long T. rex, nicknamed "Scotty," lived in prehistoric Saskatchewan ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.