How to weigh a dinosaur

Date:
September 1, 2020
Source:
Royal Ontario Museum
Summary:
A new study looks at dinosaur body mass estimation techniques
revealing different approaches still yield strikingly similar
results.



FULL STORY ==========================================================================
How do you weigh a long-extinct dinosaur? A couple of ways, as it turns
out, neither of which involve actual weighing -- but according to a new
study, different approaches still yield strikingly similar results.


==========================================================================
New research published September 1 in the journal Biological Reviews
involved a review of dinosaur body mass estimation techniques carried
out over more than a century.

The findings should give us some confidence that we are building
an accurate picture of these prehistoric animals, says study leader
Dr. Nicola's Campione - - particularly our knowledge of the more massive dinosaurs that have no correlates in the modern world.

"Body size, in particular body mass, determines almost at all aspects of
an animal's life, including their diet, reproduction, and locomotion,"
said Dr.

Campione, a member of the University of New England's Palaeoscience
Research Centre.

"If we know that we have a good estimate of a dinosaur's body mass, then
we have a firm foundation from which to study and understand their life retrospectively." Estimating the mass of a dinosaur like the emblematic Tyrannosaurus rex is no small feat -- it is a creature that took its
last breath some 66 million years ago and, for the most part, only its
bones remain today. It is a challenge that has taxed the ingenuity of palaeobiologists for more than a century. Scientific estimates of the
mass of the biggest land predator of all time have differed substantially, ranging from about three tonnes to over 18 tonnes.



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The research team led by Dr. Campione compiled and reviewed an extensive database of dinosaur body mass estimates reaching back to 1905, to
assess whether different approaches for calculating dinosaur mass were clarifying or complicating the science.

Although a range of different methods to estimating body mass have
been tried over the years, they all come down to two fundamental
approaches. Scientists have either measured and scaled bones in living
animals, such as the circumference of the arm (humerus) and leg (femur)
bones, and compared them to dinosaurs; or they have calculated the volume
of three-dimensional reconstructions that approximate what the animal
may have looked like in real life. Debate over which method is 'better'
has raged in the literature.

The researchers found that once scaling and reconstruction methods are
compared en masse, most estimates agree. Apparent differences are the exception, not the rule.

"In fact, the two approaches are more complementary than antagonistic,"
Dr.

Campione said.

The bone scaling method, which relies on relationships obtained directly
from living animals of known body mass, provides a measure of accuracy,
but often of low precision; whereas reconstructions that consider the
whole skeleton provide precision, but of unknown accuracy. This is
because reconstructions depend on our own subjective ideas about what
extinct animals looked like, which have changed appreciably over time.

"There will always be uncertainty around our understanding of long-extinct animals, and their weight is always going to be a source of it," said
Dr. David Evans, Temerty Chair of Vertebrate Palaeontology at the Royal
Ontario Museum in Toronto, senior author on the new paper. "Our new study suggests we are getting better at weighing dinosaurs, and it paves the
way for more realistic dinosaur body mass estimation in the future."
The researchers recommend that future work seeking to estimate the sizes
of Mesozoic dinosaurs, and other extinct animals, need to better-integrate
the scaling and reconstruction approaches to reap their benefits.

Drs. Campione and Evans suggest that an adult T. rex would have weighed approximately seven tonnes -- an estimate that is consistent across reconstruction and limb bone scaling approaches alike. But the research emphasizes the inaccuracy of such single values and the importance of incorporating uncertainty in mass estimates, not least because dinosaurs,
like humans, did not come in one neat package. Such uncertainties suggest
an average minimum weight of five tonnes and a maximum average weight
of 10 tonnes for the 'king' of dinosaurs.

"It is only through the combined use of these methods and through
understanding their limits and uncertainties that we can begin to reveal
the lives of these, and other, long-extinct animals," Dr Campione said.


========================================================================== Story Source: Materials provided by Royal_Ontario_Museum. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Nicola's E. Campione, David C. Evans. The accuracy and precision
of body
mass estimation in non‐avian dinosaurs. Biological Reviews,
2020; DOI: 10.1111/brv.12638 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200901112207.htm

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