Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

First fruitful, then futile: ammonites or the boon and bane of many offspring

23.04.2012
Ammonites changed their reproductive strategy from initially few and large offspring to numerous and small hatchlings. Thanks to their many offspring, they survived three mass extinctions, a research team headed by paleontologists from the University of Zurich has discovered.

For 300 million years, they were the ultimate survivors. They successfully negotiated three mass extinctions, only to die out eventually at the end of the Cretaceous along with the dinosaurs: Ammonoids, or ammonites as they are also known, were marine cephalopods believed to be related to today’s squid and nautiloids. Ammonoids changed their reproductive strategy early on in the course of evolution.


These marcasite-coated ammonites were discovered during the redevolpment of the railway station in Bielefeld, Germany. Picture: Paul Marx / PIXELIO

However, what was once a successful initial strategy may well have proved to be a fatal boomerang at the end of the Cretaceous, as an international team of researchers headed by paleontologists from the University of Zurich demonstrate in a study recently published in the science journal Evolution.

Embryos already had coiled shells
At the beginning of their evolution, ammonoids had straighter shells, which, like other mollusks, they began to coil during the Devonian Period. The precise reason behind this change is unknown. The selection pressure in favor of more tightly coiled shells is believed to have sprung from the ammonoids’ natural predators. As the scientists have now discovered, the shell change also affected the ammonoid embryos. “In the oldest ammonoids, the embryonic shells were considerably bigger and coiled less tightly than in later forms,” explains Kenneth De Baets, a paleontologist at the University of Zurich, summing up the latest findings.
Smaller hatchlings, more offspring
There were two more evolutionary trends that coincided with the increasingly more tightly coiled shells: The size of the embryonic shells shrank increasingly over time – the hatchlings became smaller and smaller. In parallel, the shell size of fully grown animals increased and, on the whole, the animals became increasingly bigger. Based on this, the researchers deduced that the number of offspring in ammonoids rocketed during the Devonian Period. This is confirmed by discoveries of substantial clusters of fossilized embryonic shells at the end of the Devonian Period and more recent deposits.

“The large number of offspring could have been the key to the rapid proliferation of the ammonoids in the aftermath of each mass extinction,” De Baets suspects. His hypothesis is supported by the fact that precisely the groups with smaller, loosely coiled embryonic shells and proportionately fewer offspring died out in certain Devonian extinction events. Nevertheless, the once successful reproductive strategy of many offspring appears to have turned against them at the end of the Cretaceous Period: The ammonoids died out. Only nautiloids have survived until today: They are characterized by large young and a small number of offspring. Exactly how this circumstance had a positive impact upon the survival of the nautiloids is unknown. All that is clear, according to De Baets, is that nautiloids are extremely vulnerable with their reproductive strategy nowadays in view of overfishing.

Further reading:
Kenneth De Baets, Christian Klug, Dieter Korn, Neil H. Landmann. Early evolutionary trends in ammonoid embryonic development. Evolution, International Journal of Organic Evolution. February 14, 2012. doi: 10.1111/j.1558-5646.2011.01567.x
Contact:
Dr. Kenneth de Baets
Paleontological Institute and Museum
University of Zurich
Tel.: +41 44 634 23 47
Email: kenneth.debaeats@pim.uzh.ch

Nathalie Huber | Universität Zürich
Further information:
http://www.uzh.ch

More articles from Earth Sciences:

nachricht New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New technology for mass-production of complex molded composite components

23.01.2017 | Process Engineering

Quantum optical sensor for the first time tested in space – with a laser system from Berlin

23.01.2017 | Physics and Astronomy

The interactome of infected neural cells reveals new therapeutic targets for Zika

23.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>