Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Four-legged fish an evolutionary mistake

02.09.2005


The ”four-legged fish” Ichthyostega is not the ”missing link” between marine and land animals, but rather one of several short-lived ”experiments”. This is what scientists from Uppsala and Cambridge universities maintain in an article in the latest issue of the scientific journal Nature.



The ”four-legged fish” Ichthyostega lived in Greenland during the Devon Period, some 355 million years ago, and is one of the very oldest land vertebrates. Since it was discovered back in the 1930s, and nearly the entire skeleton has been preserved, it quickly acquired iconic status as the ”missing link” between fish and land animals. Now a Swedish-British research team is presenting a new reconstruction of this classic animal that paints a radically different picture of its body shape and life style.

It isn´t easy to interpret the fossil of Ichthyostega. Even though almost the whole skeleton is represented, there is no single fossil that shows the whole animal. Instead it is necessary to assemble a puzzle from information found in several different fossils. This was first done in the 1950s by Professor Erik Jarvik at the Museum of Natural History in Stockholm, who reconstructed the animal with a crocodile-like body standing on four sturdy legs, with a large torso and a simple backbone made up of identical vertebrae. However, for the last five years a research team from Uppsala and Cambridge has been piecing together another interpretation.


- We discovered that the vertebrae are not at all identical, but differ depending on where in the body they were located. Moreover, the torso is differently shaped than Jarvik thought, and the hind legs look more like the flippers of a seal, says Professor Per Ahlberg of Uppsala University.

The new reconstruction assigns Ichthyostega a backbone that resembles that of a mammal-surprising for such an early land animal. This means that Ichthyostega had an unusual pattern of locomotion. Both fish and primitive now-living land animals, such as salamanders and lizards, move by slithering their bodies sideways. This also seems to be the case for Acanthostega, the other (and more primitive) four-legged fish from Greenland in the Devon Period. But Ichthyostega‚s large torso, with ribs that overlap like roofing tiles, made its upper body completely stiff, and the hind quarters seem rather to be adapted to flexing vertically, as in mammals.

- Ichthyostega probably moved rather clumsily on land by lifting its upper body and ”walking” on its front legs while simultaneously floundering along on its hind flippers. Its also possible that it combined with this a vertical bending of the spine to slide forward something like a giant inchworm, says Per Ahlberg, who maintains that Ichthyostega is not the ”missing link” but rather one of several short-lived evolutionary experiments with various bodily shapes and patterns of locomotion during the transitional period from marine to land life.

Anneli Waara | alfa
Further information:
http://www.uu.se
http://www.nature.com

More articles from Life Sciences:

nachricht The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie

nachricht Party discipline for jumping genes
22.09.2017 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

Hope to discover sure signs of life on Mars? New research says look for the element vanadium

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>