This is the restoration of the head of Nasutoceratops Andrey Atuchin 
 
 For decades, researchers have tried to figure out why dinosaurs had such enormous bony frills and fearsome spikes on their heads. 
 
 They speculated that dinosaurs like the Triceratops — members of the ceratopsian or horned dinosaur family — had these distinctive traits for self-defense, or to ensure they didn't mate with a dinosaur from another species, among other possibilities. 
 
 But according to new research, the likeliest explanation is simpler and more universal: sexual selection. While the horns might look violent, their main purpose seems to have been for picking up mates. 
 
 A study newly published in the journal Proceedings of the Royal Society B explains that dinosaurs developed these burdensome traits as ways of showing off to potential partners — the same way modern animals such as peacocks do. 
 
 "This resolves a long-standing and hitherto untested hypothesis concerning the origin and function of ornamental traits in ceratopsian dinosaurs," Knapp said. "Many general discussions of ceratopsian ornaments in museum signage and popular literature often include examples of what they might have been for, but these tend to be rather speculative." 
 
 Understanding how the development of these traits can drive species change is important for understanding Earth's history, and also for investigating how modern creatures may evolve in a world where there's intense pressure to survive. 
 
 This is the Chasmosaurus skeleton in the Royal Tyrrell Museum of Paleontology. Royal Tyrrell Museum of Paleontology 
 
 Ruling out other explanations 
 
 There are more than 70 known species of ceratopsian dinosaurs, which the study explains have "exaggerated and often elaborate horns and frills, which vary considerably between species." 
 
 Many reasons for these features have been debated over time, but some seemingly likely options — including predator defense and temperature regulation — were ruled out by previous research, according to the new study. 
 
 One lingering explanation was that ceratopsian dinosaurs used these features to differentiate between species. Animals that mate with related but distinct species can produce offspring that tends to be sterile (like mules that come from horses and donkeys). That's obviously not a good evolutionary strategy, so paleontologists theorized that dinosaurs might use frills and horns as cues that something was or wasn't right. 
 
 To test that theory, the authors of the recent study analyzed 350 different traits from 46 ceratopsian species. If species differentiation was a major factor, species that lived in close proximity should have evolved physical features to distinguish themselves. 
 
 But the team found that this wasn't the case in the fossil record, which helps rule out that explanation. Plus, as we see in present-day animals, prominent differences aren't usually needed for a creature to know whether another animal is a member of its own species. 
 
 This is the Protoceratops in the Horniman Museum, London. Horniman Museum, London 
 
 Showing off 
 
 If the horns weren't for fighting or avoiding sterile offspring, the likeliest explanation is that these traits were mostly about impressing potential mates. 
 
 The evolutionary record shows that these features evolved relatively quickly, which often happens because of a sexual drive. 
 
 None of this means that horns and frills couldn't have been simultaneously used for another purpose as well — it's possible that some dinosaurs occasionally used them to fend off or intimidate predators. But the primary role of these huge and cumbersome traits was most likely ornamental. 
 
 That's remarkable when you consider that these features weren't easy to live with or maintain — dinosaurs would have used up a lot of energy to carry that additional weight. But good mates, it seems, were worth the extra effort. 
 
 "Modern computer models have suggested that sexual selection can promote rapid speciation, adaptation, and extinction," Andrew Knapp, lead study author and a researcher at Queen Mary University of London, said in a statement. "In our world of increasing pressure on the natural world, these predictions may have important consequences for conservation and the fate of living things everywhere." ||||| Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period. ||||| Image copyright Andrey Atuchin Image caption Artist's impression of two ceratopsian dinosaurs: Utahceratops gettyi (l) and Nasutoceratops titusi (r) 
 
 Dinosaurs like the Triceratops may have had horns and frills to attract a mate, a new study suggests. 
 
 Ceratopsian, or horned dinosaurs, were previously thought to have developed this ornamentation to distinguish between different species. 
 
 This has now been ruled out in a study published in a Royal Society journal. 
 
 Instead, the aggressive-looking armour may actually have evolved to signal an animal's suitability as a partner, known as socio-sexual selection. 
 
 "Individuals are advertising their quality or genetic make-up," explained Andrew Knapp, lead author of the research reported in Proceedings of the Royal Society B. 
 
 "We see that in peacocks too, with their tail feathers." 
 
 Putting on a show 
 
 Features that can differentiate between species are usually less elaborate than those distinguishing males and females. 
 
 To prevent mating with other species, only subtle indications are needed. When the goal is to repel, not attract, it is not worth putting in the extra evolutionary effort. 
 
 The study's original design was to determine whether the distinctive horns and frills of ceratopsian dinosaurs were for this inter-species purpose. 
 
 Image copyright Getty Images Image caption Frills and horns are common features in ceratopsian dinosaurs 
 
 Previous research had ruled out their use for predator defence and regulating body temperature. 
 
 "It is exciting that dinosaur fossils are being examined more and more exhaustively in order to further understand their palaeobiology," commented Dr Darla Zelenitsky, from the University of Calgary, Canada, who was not involved in the study. 
 
 Fossil records for all known ceratopsian species were analysed by location and time period. 
 
 "Some of these ornaments were also likely used at times for defence against predators or, to some extent, for recognition of members of different species, but these were apparently not the primary driver in their evolution," added Dr Zelenitsky, who teaches palaeobiology. 
 
 Further work will now be done to test whether socio-sexual selection is the motivating factor behind the evolution of these ornaments. 
 
 Mr Knapp points out that there is not a massive amount of evidence for species recognition even in living animals. Instead, there may be some more innate understanding at work. 
 
 Image copyright Royal Tyrrell Museum of Paleontology Image caption Chasmosaurus skeleton: some frills have holes to reduce weight 
 
 "Individuals within large herds such as reindeer don't have trouble distinguishing their siblings," the Queen Mary University of London, UK, researcher said. 
 
 Equal parenting 
 
 The study did find that male and female ceratopsian dinosaurs could not be distinguished from each other in the fossil record. If there were physical differences, they may have been very subtle. 
 
 "The fact that they both have these large ornaments is very interesting in itself. If it is sexual selection, that will tell us a lot about how these animals lived," added Mr Knapp. 
 
 Ceratopsians are egg-laying, and the female does not need to carry young to term in the way that mammals do. This could point to a different breeding system with more mate co-operation. 
 
 "Possibly they're both quite invested in raising their young, like we see in birds," said Mr Knapp. ||||| The elaborate frills and horns of a group of dinosaurs including Triceratops and Styracosaurus did not evolve to help species recognise each other, according to researchers at Queen Mary University of London. 
 
 It has been suggested that different species that live in the same location may evolve features in order to distinguish one another to help avoid problems such as hybridisation, where two individuals of different species produce infertile or unfit offspring. 
 
 To test this hypothesis the researchers examined patterns of diversity in the ornamentation of 46 species of ceratopsians, the horned dinosaurs, but found no difference between species that lived together and those that lived separately. 
 
 A previous research paper from Queen Mary found that the frill in one ceratopsian species, Protoceratops, may have evolved under sexual selection. These new findings appear to add evidence to this across the entire group. 
 
 The researchers also found evidence that ornamental traits seemed to evolve at a much faster rate than other traits. As these structures are costly to grow and maintain, this finding similarly points to a strong selective pressure on these traits. 
 
 The study was published in Proceedings of the Royal Society B. 
 
 Andrew Knapp, PhD candidate from the School of Biological and Chemical Sciences and lead author of the study, said: "This resolves a long-standing and hitherto untested hypothesis concerning the origin and function of ornamental traits in ceratopsian dinosaurs. Many general discussions of ceratopsian ornaments in museum signage and popular literature often include examples of what they might have been for, but these tend to be rather speculative. 
 
 "We have shown that species recognition, one of the commonest explanations, is unlikely to be responsible for the diversity or origin of ornamentation in this group." 
 
 The researchers believe the implications extend beyond the scope of ceratopsians and have consequences for the study of evolutionary theory over vast stretches of time. 
 
 The fossil record offers an opportunity to see evolution in action over much longer time periods than can be achieved with living organisms, but it is difficult to assign explanations to unusual features such as ceratopsian ornaments with the limited information that fossils provide. 
 
 The researchers have now largely ruled out one explanation, species recognition, and provided some evidence for another, sexual selection. 
 
 Mr Knapp said: "If sexual selection is indeed the driver of ornament evolution in ceratopsians, as we are increasingly confident it is, demonstrating it through different lines of evidence can provide a crucial window into tracing its effects over potentially huge timescales." 
 
 He added: "Modern computer models have suggested that sexual selection can promote rapid speciation, adaptation, and extinction. In our world of increasing pressure on the natural world, these predictions may have important consequences for conservation and the fate of living things everywhere." 
 
 To test these predictions the researchers hope to look at changes in the fossil record and gather further evidence to first identify sexual selection in a fossil group. 
 
 ### 
 
 The study was conducted in collaboration with the Raymond M. Alf Museum of Paleontology in California and Natural History Museum of Utah. It was funded by a Natural Environment Research Council (NERC) doctoral training partnerships (DTP) grant through the London DTP programme.
– The horns and frills of dinosaurs like Triceratops and Styracosaurus weren't for defending against predators, regulating body temperature, or even attaching fearsome battle helmets, according to a study published this week in Proceedings of the Royal Society B. Rather researchers found the defining features of ceratopsian dinosaurs were actually for attracting mates. "Individuals are advertising their quality or genetic make-up," researcher Andrew Knapp tells the BBC. "We see that in peacocks too, with their tail feathers." Business Insider reports there are over 70 species of ceratopsian dinosaurs, and their horns and frills vary widely. Researchers behind the recent study had set out to see if the purpose of the horns and frills was to let different species tell each other apart for mating purposes (previous research had ruled out temperature regulation and defense). After looking at 350 different traits from 46 ceratopsian species, researchers concluded that wasn't the case. In modern animals, features for species to differentiate between each other are typically subtler and more evolutionary work goes into features used to attract members of the same species. The relatively speedy evolution of horns and frills was also another clue as to their purpose. "Modern computer models have suggested that sexual selection can promote rapid speciation, adaptation, and extinction," Knapp says in a press release. As for both male and female ceratopsian dinosaurs having horns and frills, Knapp says it could "tell us a lot about how these animals lived." For example, they may have been co-parents when it came to raising their young. (The Sahara Desert revealed the "Holy Grail" of dinosaur discoveries.)