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Re: Maiasaura population biology and life history synthesis

Press release:


On Thu, Oct 1, 2015 at 8:02 AM, Ben Creisler <bcreisler@gmail.com> wrote:
> Ben Creisler
> bcreisler@gmail.com
> A new online paper:
> Holly N. Woodward, Elizabeth A. Freedman Fowler, James O. Farlow and
> John R. Horner (2015)
> Maiasaura, a model organism for extinct vertebrate population biology:
> a large sample statistical assessment of growth dynamics and
> survivorship.
> Paleobiology  (advance online publication)
> DOI: http://dx.doi.org/10.1017/pab.2015.19
> http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9985365&fulltextType=RA&fileId=S0094837315000196
> Fossil bone microanalyses reveal the ontogenetic histories of extinct
> tetrapods, but incomplete fossil records often result in small sample
> sets lacking statistical strength. In contrast, a histological sample
> of 50 tibiae of the hadrosaurid dinosaur Maiasaura peeblesorum allows
> predictions of annual growth and ecological interpretations based on
> more histologic data than any previous large sample study. Tibia
> length correlates well (R2>0.9) with diaphyseal circumference,
> cortical area, and bone wall thickness, thereby allowing longitudinal
> predictions of annual body size increases based on growth mark
> circumference measurements. With an avian level apposition rate of
> 86.4 μm/day, Maiasaura achieved over half of asymptotic tibia
> diaphyseal circumference within its first year. Mortality rate for the
> first year was 89.9% but a seven year period of peak performance
> followed, when survivorship (mean mortality rate=12.7%) was highest.
> During the third year of life, Maiasaura attained 36% (x=1260 kg) of
> asymptotic body mass, growth rate was decelerating (18.2 μm/day),
> cortical vascular orientation changed, and mortality rate briefly
> increased. These transitions may indicate onset of sexual maturity and
> corresponding reallocation of resources to reproduction. Skeletal
> maturity and senescence occurred after 8 years, at which point the
> mean mortality rate increased to 44.4%. Compared with Alligator, an
> extant relative, Maiasaura exhibits rapid cortical increase early in
> ontogeny, while Alligator cortical growth is much lower and protracted
> throughout ontogeny. Our life history synthesis of Maiasaura utilizes
> the largest histological sample size for any extinct tetrapod species
> thus far, demonstrating how large sample microanalyses strengthen
> paleobiological interpretations.