For many years scientists have pondered the mystery of why the giraffe evolved such a long neck. To be sure, they aren't the only long-necked creature to have evolved, look at flamingos for instance, but why the giraffe has one has long perplexed scientists with most siding with Darwin who posited it could be the result of allowing those with longer necks to reach food that those with shorter necks couldn't.
But now a recent discovery is challenging that hypothesis. The fossilized remains of an early giraffoid is pointing to another possibility.
Researchers in northwestern China unearthed the cranium along with some cervical vertebrae from a creature that lived during the Early Miocene between 17 and 16.9 mya that they named Discokeryx xiezhi, and discovered that they exhibited tell-tale signs of adaptations for head-butting behavior like we see in modern rams and musk-oxen.
The cranium itself was thick-boned and possessed a disc-shaped large ossicone in the middle of its head, whereas the vertebrae were very stout, with a thickened centra, and have the most complex joints between head and neck and between cervical vertebrae of any mammal known to date.
All of this drew attention to the mating behavior of modern giraffes where the males compete against one another by "necking," or swinging their necks and heads against one another delivering powerful blows. With the giraffe's head bristling with ossicones, they could do substantial damage if they were swung into flesh. The point being, the giraffes with the longest neck is at an advantage in such fights for mates and the new discovery indicates that they evolved out of the original head-butting behavior of their ancestors.
This isn't the first time that researchers have theorized that sexual selection was the driving force behind the lengthening of necks (see Winning by a Neck: Sexual Selection in the Evolution of Giraffe from 1996 for one instance), but the discovery is probably the first concrete physical evidence in support of it.
The abstract from the paper, Sexual selection promotes giraffoid head-neck evolution and ecological adaptation can be read below:
One observation... Am I the only one that thinks that Discokeryx looks like they're wearing bowlers?
But now a recent discovery is challenging that hypothesis. The fossilized remains of an early giraffoid is pointing to another possibility.
Researchers in northwestern China unearthed the cranium along with some cervical vertebrae from a creature that lived during the Early Miocene between 17 and 16.9 mya that they named Discokeryx xiezhi, and discovered that they exhibited tell-tale signs of adaptations for head-butting behavior like we see in modern rams and musk-oxen.
The cranium itself was thick-boned and possessed a disc-shaped large ossicone in the middle of its head, whereas the vertebrae were very stout, with a thickened centra, and have the most complex joints between head and neck and between cervical vertebrae of any mammal known to date.
All of this drew attention to the mating behavior of modern giraffes where the males compete against one another by "necking," or swinging their necks and heads against one another delivering powerful blows. With the giraffe's head bristling with ossicones, they could do substantial damage if they were swung into flesh. The point being, the giraffes with the longest neck is at an advantage in such fights for mates and the new discovery indicates that they evolved out of the original head-butting behavior of their ancestors.
This isn't the first time that researchers have theorized that sexual selection was the driving force behind the lengthening of necks (see Winning by a Neck: Sexual Selection in the Evolution of Giraffe from 1996 for one instance), but the discovery is probably the first concrete physical evidence in support of it.
The abstract from the paper, Sexual selection promotes giraffoid head-neck evolution and ecological adaptation can be read below:
Abstract
The long neck of the giraffe has been held as a classic example of adaptive evolution since Darwin’s time. Here we report on an unusual fossil giraffoid, Discokeryx xiezhi, from the early Miocene, which has an unusual disk-shaped headgear and the most complicated head-neck joints in known mammals. The distinctive morphology and our finite element analyses indicate an adaptation for fierce head-butting behavior. Tooth enamel isotope data suggest that D. xiezhi occupied a niche different from that of other herbivores, comparable to the characteristic high-level browsing niche of modern giraffes. The study shows that giraffoids exhibit a higher headgear diversity than other ruminants and that living in specific ecological niches may have fostered various intraspecific combat behaviors that resulted in extreme head-neck morphologies in different giraffoid lineages.
The long neck of the giraffe has been held as a classic example of adaptive evolution since Darwin’s time. Here we report on an unusual fossil giraffoid, Discokeryx xiezhi, from the early Miocene, which has an unusual disk-shaped headgear and the most complicated head-neck joints in known mammals. The distinctive morphology and our finite element analyses indicate an adaptation for fierce head-butting behavior. Tooth enamel isotope data suggest that D. xiezhi occupied a niche different from that of other herbivores, comparable to the characteristic high-level browsing niche of modern giraffes. The study shows that giraffoids exhibit a higher headgear diversity than other ruminants and that living in specific ecological niches may have fostered various intraspecific combat behaviors that resulted in extreme head-neck morphologies in different giraffoid lineages.
One observation... Am I the only one that thinks that Discokeryx looks like they're wearing bowlers?
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