DINOSAURIAN LIFE HISTORY STRATEGIES, GROWTH RATES, AND CHARACTER EVOLUTION :

NEW INSIGHTS GARNERED FROM BONE HISTOLOGY AND DEVELOPMENTAL MASS EXTRAPOLATION

CURRY ROGERS, K., Science Museum of Minnesota, 120 W. Kellogg Blvd., St. Paul, MN 55102; ERICKSON, G. M., Biological Sciences, Florida State University, Conradi Bldg., Tallahassee, FL 32306; NORELL, M. A., American Museum of Natural History,
New York, New York 10024-5192

Comparisons of whole-body growth rates and life history strategies among extant vertebrates are typically achieved through the comparison of regressions of exponential stage growth standardized to body mass. In order to compare whole-body patterns between Dinosauria and extant taxa, similar quantified data are necessary. The recent merging of traditional bone histological analysis with scaling principles in a method termed Developmental Mass Extrapolation (DME) has provided the requisite tools and data to assess how dinosaurs really grew.

An analysis of dinosaurs spanning the phylogenetic and size diversity of the clade revealed that sigmoidal equations accurately describe the growth data for six diverse dinosaur taxa. The onset of somatic maturity occurred between the ages of three and 13 years, with values positively correlated with increased body size. The regression equation for Dinosauria indicates that while all dinosaurs grew at rates more rapid than those of extant reptiles, they exhibit rates below, equivalent to, or above the rates of extant mammals and did not attain the extremely rapid rates attained by modern altricial birds. Birds clearly attained a portion of their elevated growth rates from their dinosaurian precursors, but how and when they surpassed the rates of non-avian relatives has remained obscured. Our data indicate that small, non-avian maniraptoran dinosaurs were two to seven times slower growing than extant precocial birds, and that extremely rapid avian growth rates may have evolved only after the origin of Avialae.