Age-Old Secret That Hollywood Celebrities Try To Keep From You Has Been Uncovered

So, if not for hunting, what were these impressive sets of pointy teeth for? Defence against predators? Nope! These prehistoric characters used them to seduce the beauties!

Currently living species of sabre-toothed animals, such as the piscivorous walrus or the herbivorous deer-like muntiac, use their canines as a display apparatus, to seduce a mate, or to intimidate their kin. The large sabre-like canine therefore becomes a sexually selected trait.

However, the question now is whether sexual selection was an important phenomenon in mammalian ancestry?

In new research published in the journal, Plos One, the palaeontologists of the University of the Witwatersrand (Evolutionary Studies Institute (ESI) and School of Anatomical Sciences, Johannesburg, South Africa) and their colleagues from the European Synchrotron Radiation Facility (Grenoble, France), used CT and synchrotron radiation scanning to uncover this mystery.

The delicate skull of Choerosaurus dejageri in lateral and dorsal views, with its conspicuous cranial bosses.

Credit: Wits University

By using X-ray computerised micro-tomographic (microCT) scanning on the mysterious fossil therapsid Choerosaurus dejageri (Therocephalia, Eutheriodontia), a “mammal-like reptile” that lived 259 million years ago and belong to the lineage that gave birth to mammals, the scientists revealed that the Choerosaurus evolved his very peculiar ornamented face under sexual pressure.

“Choerosaurus is known by only one, delicate skull. It is unique since it is the only Eutheriodont to have two symmetrical bosses on its maxilla and mandible,” says Dr Julien Benoit, a postdoctoral fellow at the ESI at Wits and lead author of the study. “In this research, we address the possibility that these cranial bosses were either for intra-specific combat or for sexual display”.

The thorough CT scan survey revealed that these structures were not pathological, and comparisons with a synchrotron scan of the skull of the monstrous dinocephalian Moschops, also known as the head-butting therapsid, confirmed that the skull and cranial bosses of Choerosaurus were too weak for high energy combat. Additionally, the maxillary boss was richly innervated and highly vascular, which is not compatible for fighting but is more suitable for supporting a colourful and/or sensitive cornified pad, potentially involved in display behaviour.

Wits University’s Dr Julien Benoit with the skull of the herbivorous Dinocephalian, which used its teeth for sexual display

Lauren Mulligan/Wits University

“The cranial bosses of Choerosaurus are the first evidence of structures dedicated solely to intraspecific, sexual competition (either low energy fight and/or sexual display) in Eutheriodontia, the group directly ancestral to mammals,” says Benoit. “Whereas few studies have investigated sexual dimorphism and competition in early therapsids, this fossil shows that sexual competition and the associated complex, ritualised behaviour were indeed an important component of therapsid evolution at the very root of the therapsid clade, as far back in the past as 300 million years, hundreds of millions of years before mammals or the more advanced dinosaurs expressed these behaviours.”

Benoit says this finding expends the record of sexually selected traits in pre-mammalian therapsids and suggests that sexual selection may have played a more important role in the origin of mammals than previously thought.

“This reshape our understanding of our deep evolutionary root, particularly that of the canine which likely originated as a display organ.”