Growth and age of Allosaurus

[Guy Leahy <xrciseguy@sbcglobal.net>]

J Morphol. 2006 Mar;267(3):347-59.   

Sizing the Jurassic theropod dinosaur Allosaurus:
assessing growth strategy and evolution of ontogenetic
scaling of limbs.

Bybee PJ, Lee AH, Lamm ET.

Department of Earth Science, Utah Valley State
College, Orem, 84058-5999, USA.

Allosaurus is one of the most common Mesozoic theropod
dinosaurs. We present a histological analysis to
assess its growth strategy and ontogenetic limb bone
scaling. Based on an ontogenetic series of humeral,
ulnar, femoral, and tibial sections of fibrolamellar
bone, we estimate the ages of the largest individuals
in the sample to be between 13-19 years. Growth curve
reconstruction suggests that maximum growth occurred
at 15 years, when body mass increased 148 kg/year.
Based on larger bones of Allosaurus, we estimate an
upper age limit of between 22-28 years of age, which
is similar to preliminary data for other large
theropods. Both Model I and Model II regression
analyses suggest that relative to the length of the
femur, the lengths of the humerus, ulna, and tibia
increase in length more slowly than isometry predicts.
That pattern of limb scaling in Allosaurus is similar
to those in other large theropods such as the
tyrannosaurids. Phylogenetic optimization suggests
that large theropods independently evolved reduced
humeral, ulnar, and tibial lengths by a phyletic
reduction in longitudinal growth relative to the
femur.

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Guy Leahy