(ORDO NEWS) — Ammonites were cephalopods that dominated the seas of the Paleozoic and Mesozoic eras, sometimes reaching impressive sizes.
To understand how these animals with a variety of spiral shells swam, scientists created underwater ammonite robots and evaluated their hydrodynamic properties.
It is not always easy for paleontologists to understand how this or that ancient creature looked, ate or moved, because all they have is a limited set of fossils. Therefore, the way of life of extinct animals sometimes has to be greatly revised and refined.
Sometimes reconstructions are used for this purpose – models that reproduce the morphology of ancient organisms, such as robots.
This is the approach taken by the authors of a new publication in the journal Scientific Reports , who used 3D printing to create floating robots that mimic both the shape of the ammonite shell and their swimming style.
Inside each there is a small electric motor that creates jet thrust, thanks to which such a robot is capable of independent movement.
With the help of these bionic (that is, imitating living) devices, researchers were able to identify the connection between the movement of animals and the structure of their shells.
In total, over 10 thousand species of ammonites are known : they dominated the seas for hundreds of millions of years, throughout the Paleozoic and the entire Mesozoic, but completely disappeared shortly after the extinction of the dinosaurs.
Ammonites are named after the ancient Egyptian god of the air, Amon, who was often depicted with ram’s horns – it is them that many ancient shells resemble.
They could have a different shape and even be asymmetrical, but, as a rule, they grew in a spiral, forming new chambers outside of the existing ones.
The mollusk itself now and then “moved” to new compartments, and the old ones could be filled with gas in order to regulate its buoyancy.
Scientists were interested in how differences in the shape of the ammonite shell affected its movement in the water. Their diversity was described using a triangular morphological space, each point in which depicts a specific mollusk, and each of the axes represents a specific shell parameter.
Thus, extremes appeared in the corners – shells with the most pronounced features. Thus, the model called serpenticon has narrow chambers with a wide shell, the spherocon is almost spherical in shape and a few wide chambers, while the oxycon is something in between and combines their features.
During the testing of ammonite robots in water, it turned out once again that not everything in evolution is simple and unambiguous.
“We expected that each specific form would be associated with various beneficial properties and changes,” admits David Peterman (David Peterman) from the University of Utah (USA), one of the authors.
Evolution gave them. A special way of transportation after they rose from the seabed thanks to a shell with many chambers filled with gas. These animals resemble strong submarines, sailing due to the streams of water they throw out.
With such a design, maneuverability inevitably suffers, and in this respect, ammonites are far from modern cephalopods without a shell like octopuses, cuttlefish , and even more so squid.
As a result, the researchers revealed a peculiar exchange between the stability of the ammonite shell structure and its maneuverability: by building one, the mollusk inevitably loses the other.
The main conclusion fits well with the evolutionary doctrine: there is no and cannot be an ideal shell, and the range of available forms is adapted to certain conditions and solving specific problems.
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