Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Prehistoric tusks point to earliest fossil evidence of differences between sexes


Image: R. Reisz

Findings point to complex social behaviour

The large tusks of an animal that roamed Earth before the dinosaurs may provide the earliest evidence yet of male-female distinctions in land animals that existed millions of years ago, say U of T scientists.

Robert Reisz, a biology professor at the University of Toronto at Mississauga, and his team have found convincing evidence of sexual dimorphism - different physical traits between the sexes of the same species - in their study of fossils from between 252 to 260 million years ago. They believe that the male Diictodon, a herbivorous barrel-shaped creature, had two large tusks extending down from the upper jaw. The tusks, Reisz says, were used as weapons, possibly for ritualistic or physical combat.

"Our findings give very clear evidence of complex social behaviour," Reisz says. "To see this kind of behaviour [physical combat] early in the history of the group that eventually gave rise to mammals is really quite startling."

Reisz’s study, which is featured on the cover of the January issue of the Proceedings of the Royal Society of London B, was based on detailed studies of nearly a hundred skeletons unearthed in South Africa over the last two decades.

Diictodon appeared during the Late Permian Period of the Paleozoic Era, at least 30 million years before dinosaurs existed. It was part of a group of animals described as mammal-like reptiles and was an evolutionary relative of the animals that evolved into mammals. Diictodon, which was covered in scales and measured about one metre in length, was a burrowing herbivore with a beaked skull and short tail.

In its investigation, the team was able to rule out other uses for the tusks, Reisz says. The tusks were not used for feeding because the females did not have them nor were they used for digging because the ends did not show signs of wear. It appears the tusks became longer, wider and thicker as the animals aged and extended well below the jaw line; those lost, possibly in combat, were never replaced, Reisz says. "All these factors are very strong indicators of armament."

Reisz says these findings go beyond the standard skeletal descriptions that accompany research on fossils. "This is a wonderful opportunity to study the biology of animals that lived so long ago. Rather than just simply looking at them and describing them, we can do more with their lifestyle, with their feeding habits, and with their general biology than just looking at their skeletons would suggest."

Along with Reisz, the study involved Corwin Sullivan, now a graduate student at Harvard University, and Dr. Roger M.H. Smith of the South African Museum in Cape Town, South Africa. The research was funded by the Natural Sciences and Engineering Council of Canada and by the American Museum of Natural History.

Nicolle Wahl is a news services officer with the department of public affairs.


U of T Public Affairs, ph: (416) 978-6974; email:

Nicolle Wahl | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München

nachricht Second research flight into zero gravity
21.10.2016 | Universität Zürich

All articles from Life 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

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>