An ornithomimid theropod dinosaur from the Upper Cretaceous (Turonian) Bissekty Formation of
Uzbekistan is one of the basal members of Ornithomimidae. Here we present a description of ontogenetic
changes in the long-bone histology of this taxon and distinguish four distinct histological stages. Analysis
of a growth series of femora demonstrates early histological maturation during ontogeny in the Bissekty
ornithomimid, expressed by the progressive formation of Haversian bone, endosteal bone deposition, and
changing of composition of primary bone tissue from fibrolamellar complex to parallel-fibered bone with
only a small amount of woven bone. The long-bone histology of the Bissekty ornithomimid is similar to that
of the basal ornithomimid Archaeornithomimus asiaticus and differs from those of derived ornithomimids
in early histological maturation, the absence of laminar and plexiform vascularization of the primary cortex,
and the presence of little or no woven bone in medium-sized and large individuals. These
