An international team of paleontologists has studied the structure of the invertebrate fossil trilobite Valliserops, finding an unusual trident on its head. Researchers believe it is the oldest evidence of sexual selection, in which the "weapon" was used by animals to fight in "jousting tournaments" about 400 million years ago.
Scientists from the University of Bloomsburg in Pennsylvania and the UK Natural History Museum have tested the theory that the trident-like bony protuberance on the heads of male trilobites of the genus Walliserops may have served to obtain food, ward off predators or pierce prey. Because of the peculiarities of the long and rigid trident, neither hypothesis has been confirmed.
But because analysis of the fossils showed that the growth spur was resource-intensive and was found in sexually mature males, scientists have speculated that the spur was used to compete for mates.
We now believe that it was used for jousting between males striving for dominance. The evolution of sexually motivated competition in animals is hundreds of millions of years older than we thought.
Scientists investigated the behavior of a particular species of rhinoceros beetle, which is anatomically similar to trilobites, and found that the beetles use their horn to pick up and flip their rival during a fight for a female. Based on all the data, the research team believes that trilobites used their trident for the same purpose.
"Although fossil life habits are difficult to prove, the consilience of morphology, teratology, and biometric data all point to the same interpretation, making it one of the more robust examples of paleoecological speculation," Professor Fortey added.
If this theory is further confirmed, it may be the earliest example of combat behavior to win over females.