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Previously underestimated number of nautilids might have survived the mass extinction at the conclusion of the Triassic era.


Credit: KD Schroeder, Creative Commons Attribution-Share Alike 3.0 via Wikimedia

The end of the Triassic period, 201 million years ago, is considered one of the greatest mass extinction events in Earth’s history. It is believed that the main cause of this catastrophe for life and development was the extreme volcanoes in Siberia. This led to global climate disturbance and acidification of sea water.

Among marine organisms, ammonites and nautiluses were particularly affected. Hitherto it was assumed that only one genus of each of the two groups survived this period of crisis and that all subsequent diversification of species evolved from these two surviving lineages. This idea has now been revised due to the examination and re-evaluation of an unusual 185-million-year-old nautilid from the mid-early Jurassic period at Pahla near Donaueschingen, Germany.

The fossil has been in the collection of the Stuttgart Museum of Natural History since 1975. The marine fossils were researched by Dr. Günter Schweigert, a paleontologist at the museum and described in the journal Neues Jahrbuch für Geologie und Paläontologie as a new species, Germanonautilus warthi.

New and valuable insights into the evolution of nautiluses

Nautilids are generally much rarer than those of ammonites and many fossil species are known only from chance finds. This makes the discovery of Germanonautilus warthi even more valuable to experts. The fossil reviews the evolutionary scenario on the Triassic-Jurassic boundary from the 1950s, which dates back to the American paleontologist and Nautilus scholar Bernard Kummel (1919-1980).

“The specimen clearly belongs to Germanonautilus, a genus that was widespread around the world in the Triassic period. For 15 million years, there is no evidence for Germanonautilus, but the genus, along with other nautilids, must have survived the crisis at the boundary of the era.” somewhere Triassic-Jurassic,” says Dr. Guenter Schweigert. Therefore, the new species provides valuable new evidence for the evolution of nautilids.

The significance of the discovery was kept hidden for a long time

The responsible coordinator made the discovery in the 1970s during field work and classified the specimen in the collection. Since the fossil had not yet been prepared at the time, Germanonautilus warthi was thought to be a representative of Cenoceras, the genus to which nearly all nautiluses from the lower Jurassic period belong. Since Jurassic nautiluses have not been scientifically refined for decades, the significance of the find has remained hidden until now.

“Some features of the Germanonautilus nautilus also suggest that a completely successful family of younger Jurassic nautilids has its immediate roots in this genus, but the traditional assumption that all post-Triassic nautilids date back to Cenoceras has overshadowed this view,” says Dr. Günter Schweigert. The paleontologist is sure that the new findings can provide valuable clues for future studies on the evolution of marine animals in prehistoric and current times.

Unlike ammonites, nautiluses survive today, but are currently severely threatened by poaching and habitat destruction.

more information:
Günter Schweigert, First record of Germanonautilus Spath, 1927 (Cephalopoda: Nautiloidea) from the Lower Jurassic (Pliensbachian) period of southwestern Germany and its implications for the phylogeny of post-Triassic nautiluses, Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen (2023). DOI: 10.1127/njgpa/2023/1131

Provided by the Staatliches Museum für Naturkunde Stuttgart

the quote: More nautilids may have survived the mass extinction at the end of the Triassic period than previously thought (2023, May 25) Retrieved May 25, 2023 from https://phys.org/news/2023-05-nautilids- survived-mass-triassic-extinction.html

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