It’s a mystery that has persisted for tens of millions of years: why did some dinosaurs have such long necks?
Now, a team of U.K. researchers have put forth a theory, saying long-necked dinosaurs relied mainly on mostly hollow neck bones and a series of evolutionary traits that are no longer present in modern animals.
Examining a number of fossil specimens, researchers discovered that the 100-foot-plus sauropods — just one of a number of species of long-necked dinosaurs – possessed a number of distinct traits that allowed them to support their long necks.
Researchers say the long necks served an evolutionary purpose. The necks, which evolved repeatedly, imposed a high structural and metabolic cost, but provide evolutionary advantages including an increased browsing range. They also probably played some role in mate attraction, researchers noted in the paper. Moreover, the muscles, tendons and ligaments were positioned in such a way around their spine that a huge support was offered to them for maximizing leverage. The alignment likely made neck movements more efficient.
“They were really stupidly, absurdly oversized,” said lead researcher Michael Taylor, a vertebrate paleontologist at the University of Bristol in England. “In our feeble, modern world, we’re used to thinking of elephants as big, but sauropods reached ten times the size elephants do. They were the size of walking whales.”
The discovery was made by examining the osteology of sauropod necks more closely, comparing their cervical anatomy with that of their nearest extant relatives, the birds and crocodilians, and discussing unusual features of sauropods’ cervical vertebrae.
The research team says various anatomical features enabled the extreme elongation, including: an absolutely large body size and quadrupedal stance providing a stable platform for a long neck; a small, light head that did not orally process food; cervical vertebrae that were both numerous and individually elongate; an efficient air-sac-based respiratory system; and a distinctive cervical architecture.
According to researchers, the lack of similar traits have limited neck length in modern animals. For example, the largest extinct land-living mammal of all time was the rhino-like Paraceratherium, with a record neck of eight feet long. Among living animals, adult bull giraffes have the longest necks, capable of reaching about eight feet long.
The study was published in the journal PeerJ.
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