Dinosaurs grew as fast as your average living mammal, according to a new
research article. The article is a re-analysis of a widely publicized
2014 Science paper on dinosaur metabolism and growth that concluded
dinosaurs were neither ectothermic nor endothermic -- terms popularly
simplified as 'cold-blooded' and 'warm-blooded' -- but instead occupied
an intermediate category.
"The study that I re-analyzed was remarkable for its breadth -- the
authors compiled an unprecedented dataset on growth and metabolism from
studies of hundreds of living animals," said Dr. D'Emic, a Research
Instructor in the Department of Anatomical Sciences as Stony Brook, when
referring to "Evidence for mesothermy in dinosaurs."
"Upon re-analysis, it was apparent that dinosaurs weren't just
somewhat like living mammals in their physiology -- they fit right
within our understanding of what it means to be a 'warm-blooded'
mammal," he said.
Dr. D'Emic specializes in bone microanatomy, or the study of the
structure of bone on scales that are just a fraction of the width of a
human hair. Based on his knowledge of how dinosaurs grew, Dr. D'Emic
re-analyzed that study, which led him to the strikingly different
conclusion that dinosaurs were more like mammals than reptiles in their
growth and metabolism.
Dr. D'Emic re-analyzed the study from two aspects. First, the
original study had scaled yearly growth rates to daily ones in order to
standardize comparisons.
"This is problematic," Dr. D'Emic explains, "because many animals do
not grow continuously throughout the year, generally slowing or pausing
growth during colder, drier, or otherwise more stressful seasons.
"Therefore, the previous study underestimated dinosaur growth rates
by failing to account for their uneven growth. Like most animals,
dinosaurs slowed or paused their growth annually, as shown by rings in
their bones analogous to tree rings," he explained.
He added that the growth rates were especially underestimated for
larger animals and animals that live in very stressful or seasonal
environments -- both of which characterize dinosaurs.
The second aspect of the re-analysis with the original study takes
into account that dinosaurs should be statistically analyzed within the
same group as living birds, which are also warm-blooded, because birds
are descendants of Mesozoic dinosaurs.
"Separating what we commonly think of as 'dinosaurs' from birds in a
statistical analysis is generally inappropriate, because birds are
dinosaurs -- they're just the dinosaurs that haven't gone extinct."
He explained that re-analyzing the data with birds as dinosaurs lends
more support that dinosaurs were 'warm-blooded,' not occupants of a
special, intermediate metabolic category.
According to Holly Woodward, Assistant Professor in the Center for
Health Sciences at Oklahoma State University, Dr. D'Emic's re-analysis
is crucial to building research on the metabolism and development of
dinosaurs.
"D'Emic's study reveals how important access to the data behind
published results is for hypothesis testing and advancing our
understanding of dinosaur growth dynamics," said Woodward.
Dr. D'Emic hopes that his study will also spur new research into
when, why, and how pauses or slowdowns in growth are recorded in bones,
which may have implications in the development of other species and in
the study of bone diseases such as osteoporosis.
This story is taken from Science Daily
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