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Tyrannosaur Ageing in Biology Letters



http://www.journals.royalsoc.ac.uk/(dlfjyyzgh30yyd55hmenb455)/app/home/contribution.asp?referrer=parent&backto=issue,29,30;journal,2,11;linkingpublicationresults,1:110824,1

Biology Letters
ISSN: 1744-9561 (Paper) 1744-957X (Online)
Issue: Volume 3, Number 2 / April 22, 2007
Pages: 214 - 217

Tyrannosaur ageing
Robert E. Ricklefs
Department of Biology, University of Missouri-St Louis, St Louis, MO
63121-4499, USA

Abstract:
Rate of ageing in tyrannosaurs was calculated from parameters of
Weibull functions fitted to survival curves based on the estimated
ages at death of fossilized remains. Although tyrannosaurs are more
closely related to birds than to mammals, they apparently aged at
rates similar to mammals of comparable size. Rate of growth in body
mass of tyrannosaurs was similar to that of large mammals, and their
rates of ageing were consistent with the estimated extrinsic
mortality, which is strongly correlated with the rate of ageing across
birds and mammals. Thus, tyrannosaurs appear to have had life
histories resembling present-day large terrestrial mammals. Rate of
ageing in warm-blooded vertebrates appears to be adjusted in response
to extrinsic mortality and potential lifespan, independently of both
physiological and developmental rates. However, individuals in species
with the slowest rates of ageing suffer the highest proportion of
ageing-related mortality, hence potentially strong selection to
further postpone senescence. Thus, the longest observed lifespans in
birds, tyrannosaurs and mammals might be close to the maximum
possible.

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Michael D. Barton Bozeman, MT MSU Bozeman, History-SETS Major darwinsbulldog@gmail.com