Turtle shells are unique in the animal kingdom. In order to be able to breathe in this inflexible casing, tortoises have a muscle sling which is attached to the shell to ventilate the lung.
A team of researchers including paleontologist Torsten Scheyer from the University of Zurich can now reveal that the turtle's ancestor Eunotosaurus africanus already breathed with the aid of such a sling – even though it did not yet have a solid shell. The muscle sling was thus the anatomical prerequisite for the development of the rigid turtle shell.
The present-day extinct ancestors of turtles had a flexible ribcage and breathed, like us, by alternately expanding and contracting the lungs and thorax. The development of a solid shell on the back and belly, however, rendered this kind of respiratory process impossible.
Today’s turtles breathe with the aid of a muscle sling attached to the shell, which contracts and relaxes to aerate the lungs. An international team of researchers from North American, African and European institutes and museums have now discovered the origin of this muscle sling:
in Eunotosaurus africanus, a fossil reptile which lived in South Africa during the Middle Permian around 260 million years ago, as the study just published in Nature Communications reveals.
Instead of a rigid plastron and shell like modern turtles, Eunotosaurus merely had extremely broad, partly overlapping T-shaped ribs. “However, these already heavily restricted the freedom of movement of the ribcage” explains Torsten Scheyer from the Paleontological Institute and Museum of the University of Zurich, who is involved in the study.
Judging by the internal and external bone structures of the ribs, Eunotosaurus evidently only had reduced back muscles, but already possessed a muscle sling that aided respiration. “The small fossil reptile thus provides the explanation as to how the vital adaptation of the breathing apparatus could come about in turtle evolution,” says the UZH paleontologist.
Muscle loop enables shell development
“Eunotosaurus constitutes a morphological link between the body plan of early reptiles and the highly modified body blueprint of the turtles that exist today,” explains Scheyer. The scientists studied the rib plates, so-called costals, of turtle shells and the ribs of various fossil and living vertebrate groups, including mammals, crocodiles and even dinosaurs.
Head of the study Tyler Lyson from the Smithsonian Institution in Washington D.C. and the Denver Museum of Nature and Science, Colorado, adds that, “Based on what we know today, solid shells did not appear in fossil stem turtles until 50 million years after Eunotosaurus.”
The study shows that the steady increase of rigidity of the body wall triggered a separation of the rib and abdominal respiratory muscle functions: The increasing broadening and hardening of the body caused the ribs to become less involved in the respiratory process while the muscles increasingly took over the role. “The ribs became thus free and later completely integrated in the turtle's shell,” says Scheyer.
Lyson, T. R., E. R. Schachner, J. Botha-Brink, T. M. Scheyer, M. Lambertz, G. S. Bever, B. Rubidge, and K. de Queiroz. Origin of the unique ventilatory apparatus of turtles. Nature Communications. November 7, 2014. 5:5211. doi: 10.1038/ncomms6211
Dr. Torsten M. Scheyer
University of Zurich
Paleontological Institute and Museum
Tel.: +41 44 634 23 22
University of Zurich
Tel.: +41 44 634 44 39
Bettina Jakob | Universität Zürich
Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH
Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute
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...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
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...
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...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences