# Thousands of dinosaur skeletons, but just two dozen complete tails

By Ed Yong | September 3, 2012 11:37 am

Look up any dinosaur, and chances are you will soon come across an estimate for how long it was. And chances are that estimate is wrong. That’s because, as Dave Hone from University College Dublin points out, our knowledge of dinosaur tails is woefully inadequate.

After searching through papers, museum collections, photos, and the minds of his colleagues, Hone found that among the thousands of dinosaur specimens that have been found, there are “barely two dozen complete tails”. These range from animals like Spinosaurus, where virtually no tail fragments have been found, to others where skeletons are missing an unknown number of vertebrae from the tips. Even in complete skeletons, Hone’s research showed that closely related species, and even individuals, can vary greatly in the length and number of bones in their tails.

This matters since tails are factored into estimates of the animals’ lengths, and lengths are often used to estimate mass. As I wrote in my Nature piece on Hone’s work, “If tails are telling tall tales, other important measures could be inaccurate.” Head over there for the rest of the story.

Image by Ballista

1. David Hobby

“This matters since tails are factored into estimates of the animals’ lengths, and lengths are often used to estimate mass.” Some dinosaurs’ tails look pretty thin, so I was hoping that a better system was used for mass estimates. The linked article does mention that “Instead, they take the animal’s length to be the distance between the tip of its head to its anus — the “snout–vent length”.” Not that I have any idea what standard practice is.

2. TW

Something tells me there might be a math formula that could project the maximum number of missing bones based on the ones you have since every vertebrae down the length shrinks by a consistent ratio at least for the tapering tail ones. How many dinos had stub tails. I bet a manx t-rex would be cute though.

3. “Some dinosaurs’ tails look pretty thin, so I was hoping that a better system was used for mass estimates.”

Yep, the tails themselves might not add a huge amount of mass, but many mass estimates are done by taking the mass of one individual and then scaling that up/down to another. So the tail, by affecting length, could screw with mass in that way.

4. Does this bias in bone recovery tell us that the tail was the most delicious part of the dinosaur?

5. Michael Cook

“Does this bias in bone recovery tell us that the tail was the most delicious part of the dinosaur?

No, it tells us that dinosaurs are like some modern day lizards and lose their tail as a distraction for predators.

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