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Tenontosaurus Growth and Osteohistology

From: Ben Creisler

New in PLoS ONE:

Werning, S, (2012)
The Ontogenetic Osteohistology of Tenontosaurus tilletti.
PLoS ONE 7(3): e33539.

Tenontosaurus tilletti is an ornithopod dinosaur known from the Early
Cretaceous (Aptian-Albian) Cloverly and Antlers formations of the
Western United States. It is represented by a large number of
specimens spanning a number of ontogenetic stages, and these specimens
have been collected across a wide geographic range (from central
Montana to southern Oklahoma). Here I describe the long bone histology
of T. tilletti and discuss histological variation at the individual,
ontogenetic and geographic levels. The ontogenetic pattern of bone
histology in T. tilletti is similar to that of other dinosaurs,
reflecting extremely rapid growth early in life, and sustained rapid
growth through sub-adult ontogeny. But unlike other iguanodontians,
this dinosaur shows an extended multi-year period of slow growth as
skeletal maturity approached. Evidence of termination of growth (e.g.,
an external fundamental system) is observed in only the largest
individuals, although other histological signals in only slightly
smaller specimens suggest a substantial slowing of growth later in
life. Histological differences in the amount of remodeling and the
number of lines of arrested growth varied among elements within
individuals, but bone histology was conservative across sampled
individuals of the species, despite known paleoenvironmental
differences between the Antlers and Cloverly formations. The bone
histology of T. tilletti indicates a much slower growth trajectory
than observed for other iguanodontians (e.g., hadrosaurids),
suggesting that those taxa reached much larger sizes than
Tenontosaurus in a shorter time.