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Re: Ornithomimid bone study shows individual variations in growth marks (free pdf)

Ben Creisler

The paper is now out in final form (earlier version was MS form), and
in open access:


Blog posting:


On Thu, Dec 4, 2014 at 11:40 AM, Ben Creisler <bcreisler@gmail.com> wrote:
> Ben Creisler
> bcreisler@gmail.com
> A recent paper in open access, not yet mentioned:
> Thomas M Cullen, David C Evans, Michael J Ryan, Philip J Currie and
> Yoshitsugu Kobayashi (2014)
> Osteohistological variation in growth marks and osteocyte lacunar
> density in a theropod dinosaur (Coelurosauria: Ornithomimidae).
> BMC Evolutionary Biology 2014, 14:231
> doi:10.1186/s12862-014-0231-y
> http://www.biomedcentral.com/1471-2148/14/231/abstract
> Abstract (provisional)
> Background.
> Osteohistological examinations of fossil vertebrates have utilized a
> number of proxies, such as counts and spacing of lines of arrested
> growth (LAGs) and osteocyte lacunar densities (OLD), in order to make
> inferences related to skeletochronology and mass-specific growth
> rates. However, many of these studies rely on samplings of isolated
> bones from single individuals. These analyses do not take individual
> variation into account, and as a result may lead to misleading
> inferences of the physiology of extinct organisms. This study uses a
> multi-element, multi-individual sampling of ornithomimid dinosaurs to
> test the amount of individual variation in the aforementioned
> osteohistological indicators. Based on these results we also assess
> the conclusions of previous studies that tested paleohistological
> hypotheses using isolated elements.
> Results.
> LAG number was found to be consistent within the hind limb bones of
> each individual, with the exception of the fibula, which preserves one
> additional LAG. Considerable differences in LAG spacing were found
> between elements of the sampled individuals, with larger variation
> found in elements of the foot compared with the femur, fibula, and
> tibia. Osteocyte lacunar density ranged between 29000 and 42000
> osteocyte lacunae per mm3, and was found to vary more between hind
> limb bones of an individual and within bones, than between the average
> values of individuals.
> Conclusions.
> The variation between hind limb elements in LAG number and LAG spacing
> suggests that direct comparisons of these elements may be misleading,
> and that LAG spacing is not a reliable proxy for mass-specific growth
> rates of an individual. Sampling of multiple bones should be performed
> as an internal check of model-based LAG retro-calculation and growth
> equations. The observation that osteocyte lacunar density varies more
> between individual bone elements than between average individual
> values suggests that the choice of sampled element can greatly
> influence the result, and care should be taken to not bias
> interpretations of the physiology of fossil tetrapods.