‘Squishier Joints’ Allowed Dinosaurs to Grow To Gigantic Size, Study


Large, plant-eating dinosaurs including sauropods, were able to grow to their enormous size because they had softer, 'squishier' joints than land mammals.

Diplodocus (54 meter long) and Apatosaurus, the gigantic species of sauropods, weighed more than 30 tons. On the other hand, an extinct rhino-like herbivore, considered to be one of the largest known land mammals, only grew to approximately one-third of that size.

A team of scientists from the Richard Stockton College of New Jersey claims that extra layers of cartilage connecting dinosaurs' bones enabled their skeletons to bear more weight and not crumble down under the pressure of too much weight.

The team arrived at the conclusion after studying the width of the thigh and arm bones in mammals, dinosaurs and their descendants - modern day reptiles and birds.

The researchers found that as mammals grow larger; their bones become more rounded at the ends. However, bones in dinosaurs, reptiles and birds tend to grow wider with flatter ends as the animals grow in size.

When the mammalian bones grow rounder at the edges, cartilage stretches out in a tight and thin layer across the surface. The tight fit thus enables even distribution of weight. On the other hand, dinosaur joints have many more layers of cartilage, making their joints squishier.

Squishier joints not only allow even distribution of weight but are also able to withstand more pressure.

"I would have expected a similar pattern in both groups as they got bigger, but you see opposite patterns. More than just evenly distributing the pressure, the joint itself may be deforming a little - it's actually squishier, increasing the force it can sustain," Bonnan told Fox News.

The finding has been published in PLOS ONE.

However, not all academicians are happy with the finding

"Mammal and dinosaur sizes do overlap, so it's not clear that there's a direct mechanical explanation for the differences in the patterns of cartilage that they see," said Richard Blob, a professor at Clemson University in S.C. who studies evolutionary biology and biomechanics.

 "The hypothesis about how dinosaurs were able to get so large so much more often than mammals did, and relating that to these differences in bone growth is intriguing," Russell Main, a researcher at Purdue University in West Lafayette, Ind. who studies musculoskeletal biology, said.

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