Dinosaurian growth patterns and rapid avian growth rates

Did dinosaurs grow in a manner similar to extant reptiles, mammals or birds , or were they unique(1)? Are rapid avian growth rates an innovation unique to birds, or were they inherited from dinosaurian precursors(2)? We quanti fied growth rates for a group of dinosaurs spanning the phylogenetic and si ze diversity for the clade and used regression analysis to characterize the results. Here we show that dinosaurs exhibited sigmoidal growth curves sim ilar to those of other vertebrates, but had unique growth rates with respec t to body mass. All dinosaurs grew at accelerated rates relative to the pri mitive condition seen in extant reptiles. Small dinosaurs grew at moderatel y rapid rates, similar to those of marsupials, but large species attained r ates comparable to those of eutherian mammals and precocial birds. Growth i n giant sauropods was similar to that of whales of comparable size. Non-avi an dinosaurs did not attain rates like those of altricial birds. Avian grow th rates were attained in a stepwise fashion after birds diverged from ther opod ancestors in the Jurassic period.