Nearly 17 million years ago, a relative of the modern giraffes that roamed northern China had a thick, squat neck and thick skull — perfect for fighting rival males in headbutt fights.
The newly discovered giraffe relative, a now-extinct species named Discokeryx xiezhi, also had a bony, disk-like shield on the top of its skull that was covered with a protective layer of keratin — the same type of tissue found in the horns of head butters such as bulls and rams. The disk resembled a sort of squat helmet that sat on the animal’s head, scientists reported in a new analysis of several D. xiezhi Fossils, published June 2 in the journal Science (opens in new tab).
D. xiezhi They likely clapped their “helmets” together during fights for mates, just as modern male giraffes fight for females by violently slamming their necks, using a fighting style known as “necking,” the researchers concluded.
“[The researchers] have provided clear evidence that the Diskeryx Fossil is wonderfully adapted to violent head collisions,” said Robert Simmons, a volunteer research fellow at the University of Cape Town’s FitzPatrick Institute of African Ornithology, who was not involved in the study. This trait must be sexually selected, “since head-to-head collisions are closely associated with male-male fighting,” Simmons told Live Science in an email.
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In other words, it was probably intense competition for partners D. xiezhi to develop his thick neck and built-in helmet. Simmons and other scientists have also hypothesized that the modern giraffe was tricked into developing its long neck and ossicone, or the bony protrusions that protrude from its head, through sexual competition. This idea is known as the “necks-for-sex” hypothesis.
Built for headbutts
The researchers uncovered the newly described D. xiezhi Fossils in the Junggar Basin, a large sediment-filled depression in the Xinjiang region of northwest China. One specimen contained a complete braincase – the part of the skull that houses it Brain – and the first four vertebrae of the animal’s spine.
These spinal bones, known as cervical vertebrae, are quite massive “because they were used with the skull for headbutts,” said study author Jin Meng, a vertebrate paleontologist and senior curator of fossil mammals at the American Museum of Natural History. Each neck bone “is very sturdy in terms of cross-section, very thick, so it can take that kind of impact,” he told Live Science.
Two of the D. xiezhi copies included teeth with “relatively tall crowns” suitable for eating grasses, the researchers reported. Based on the shape of the teeth and the isotopes – element variants with different numbers of neutrons – in its enamel, the team concluded that the creature was likely a grazer, changing its habitat depending on the season.
Based on the sizes of all the fossils, the team believes so D. xiezhi stood about the size of a modern sheep and had a similarly long neck to other land mammals of comparable size, Meng told Live Science. And based on analysis of the fossilized bones and teeth, the team determined that this stocky, extinct animal, while related to the towering giraffes of today, is not a direct ancestor of living giraffes.
“It’s a different branch of the giraffe family tree,” Meng said.
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The team then compared the bones to those of living giraffes and their extinct relatives. In this group they identified 14 different types of “headgear”, including the ossicon of modern giraffes and the helmets of D. xiezhi, for example. Alongside this wide variety of headgear, they noted a range of head and neck shapes, and in particular they noted that the animals’ uppermost vertebrae varied dramatically in length and thickness.
As well as D. xiezhi appears to be built for headbutting and modern giraffes for teasing, all of these giraffe relatives may have partially evolved their unique headgear and necks to suit their specific fighting styles, the team wrote in the study. This is consistent with the necks-for-sex hypothesis for modern giraffes, which suggests that at some point in evolutionary history, males with long, sinewy necks became dominant in fights over females. Over time, their reproductive success led the species to develop longer and longer necks.
Simmons and Lue Scheepers, a zoologist at the Etosha Ecological Institute in Namibia, first proposed the necks-for-sex idea as co-authors of an article published in the journal in 1996 The American naturalist (opens in new tab). At the time, their hypothesis contradicted the established notion of how giraffe necks evolved. Charles Darwin famously suggested that giraffes evolved long necks due to competition for food; Being ridiculously large allowed the animals to eat foliage that was inaccessible to other animals. Even today, debate continues as to whether giraffe necks evolved primarily due to competition for subsistence or for sex National Geographic (opens in new tab).
But in all likelihood, giraffes’ extreme necks were likely shaped to some degree by both evolutionary pressures, Simmons told Live Science.
“At present, it is not easy to distinguish the ‘eating competition’ hypothesis from the ‘neck for sex’ idea,” Simmons said. “It is very likely that both played a role in the development of the magnificent animals we see today.” The discovery of the short-necked creature D. xiezhi doesn’t settle the neck-versus-sex debate, but in the future, the discovery of older giraffe fossils could help clarify how modern giraffes got to look the way they do, he said.
Originally published on Live Science.
https://www.livescience.com/extinct-giraffe-relative-fossils Short-necked giraffe relative discovered in China. It used its helmet head to bash rivals.