Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Old skull bone rediscovered

Although clearly discernible in the embryo, shortly afterwards it fuses with other bones beyond recognition. Consequently, researchers have often missed it.
Now, however, paleontologists from the University of Zurich have rediscovered it: the “os interparietale”, a skull bone also referred to as the interparietal. Using imaging methods, they were able to detect its presence in all mammals – including humans, which is new as it was previously believed to have been lost in the course of evolution.

The mammalian skull, including that of people, is composed of about 20 bones. Fish, reptile and bird skulls, however, have considerably more. After all, when mammals evolved from reptile-like vertebrates 320 million years ago, the skull’s structure became simplified during its development and the number of skull bones decreased.

Some bones were lost in the lineage leading to mammals in the course of evolution, especially a number of skull roof bones. The skull’s interparietal, which is one of the skull roof bones, particularly puzzled researchers: on the one hand, it seems to have survived, such as in humans, carnivores and ungulates (especially horses); on the other hand, it is not found in all mammals.

Together with a colleague from the University of Tübingen, Marcelo Sánchez, a professor of paleontology at the University of Zurich, and post-doctoral student Daisuke Koyabu have now detected the presence of the interparietal after all: Studying fossils and embryos of over 300 species of vertebrate, they were able to identify the bone in all of them. They used non-invasive micro-CT imaging to analyze rare embryos of different species from museum collections. “The interparietal was clearly discernible in specimens from the embryonic period as the skull bones were fused less strongly here,” explains Sánchez. At the same time, he sees the fact that the bone is only clearly and easily discernible in the embryonic period as the reason why previous researchers failed to recognize it: “It would seem that many anatomists have overlooked the presence of the interparietal in numerous mammalian lineages as the bone becomes fused to other skull bones during growth and is unrecognizable in adult individuals.”

Same skull bone in fish and humans

Another result that also refutes previous assumptions concerns the origin of the bone. As Koyabu reports: “Whilst it was previously assumed that the mammalian interparietal was composed of two elements, we discovered that it develops from four elements: a medial and a lateral pair.”

The tabular bones of our reptile-like ancestors and fish correspond to the lateral interparietal bones, which were overlooked until now. According to the new results, however, they have survived in mammalian lineages after all.

The results also explain the mixed evolutionary tissue origin of the interparietal complex, which had been identified in mice but could not be confirmed by conventional anatomical tests: Genetic studies have revealed that the lateral bone pair develops from the mesoderm, but the medial pair from the neural crest cells.

This present study provides a conclusive explanation for the hitherto inexplicable mixed tissue origin of the interparietal complex: It stems from the evolutionary fusion of the os interparietale to the tabular bones in mammalian lineages.

The study also yields insights into us people, as Sánchez concludes: “The evidence of the continuation of fish bones in mammals provides new insights into the origins of our own anatomy.” These anatomical discoveries were made possible thanks to a microtomographic imaging, the museum collections of rare animal embryos and the interdisciplinary collaboration between paleontology and embryology.

Daisuke Koyabu, Wolfgang Maier, and Marcelo Sánchez-Villagra. Paleontological and developmental evidence resolve the homology and dual embryonic origin of a mammalian skull bone, the interparietal. Proceedings of the National Academy of Sciences PNAS. August 14, 2012. doi:10.1073/pnas.1208693109

Prof. Marcelo Sánchez-Villagra
Paleontological Institute and Museum
University of Zurich
Tel.: +41 (0)44 634 23 42

Beat Müller | Universität Zürich
Further information:

More articles from Earth Sciences:

nachricht Receding glaciers in Bolivia leave communities at risk
20.10.2016 | European Geosciences Union

nachricht UM researchers study vast carbon residue of ocean life
19.10.2016 | University of Miami Rosenstiel School of Marine & Atmospheric Science

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Innovative technique for shaping light could solve bandwidth crunch

20.10.2016 | Physics and Astronomy

Finding the lightest superdeformed triaxial atomic nucleus

20.10.2016 | Physics and Astronomy

NASA's MAVEN mission observes ups and downs of water escape from Mars

20.10.2016 | Physics and Astronomy

More VideoLinks >>>