First Reported Cases of Biomechanically Adaptive Bone Modeling in Non-Avian Dinosaurs

Abstract

Predator confrontation or predator evasion frequently produces bone fractures in potential prey in the wild. Although there are reports of healed bone injuries and pathologies in non-avian dinosaurs, no previously published instances of biomechanically adaptive bone modeling exist. Two tibiae from an ontogenetic sample of fifty specimens of the herbivorous dinosaur Maiasaura peeblesorum (Ornithopoda: Hadrosaurinae) exhibit exostoses. We show that these outgrowths are cases of biomechanically adaptive periosteal bone modeling resulting from overstrain on the tibia after a fibula fracture. Histological and biomechanical results are congruent with predictions derived from this hypothesis. Histologically, the outgrowths are constituted by radial fibrolamellar periosteal bone tissue formed at very high growth rates, as expected in a process of rapid strain equilibration response. These outgrowths show greater compactness at the periphery, where tensile and compressive biomechanical constraints are higher. Moreover, these outgrowths increase the maximum bending strength in the direction of the stresses derived from locomotion. They are located on the antero-lateral side of the tibia, as expected in a presumably bipedal one year old individual, and in the posterior position of the tibia, as expected in a presumably quadrupedal individual at least four years of age. These results reinforce myological evidence suggesting that Maiasaura underwent an ontogenetic shift from the primitive ornithischian bipedal condition when young to a derived quadrupedal posture when older.

The bone microstructure of polar “hypsilophodontid” dinosaurs from Victoria, Australia

“…Within the woven pathologic tissue of the posterolateral side there are three “bands” of less vascularized tissue (Fig. 5g ) formed by a decrease in vascular canal diameter, with longitudinal rather than radial vascularity, very similar in appearance to the cortical outgrowths described in Maiasaura tibiae 30 (Fig. 5h ).…”

Maiasaura (Dinosauria: Hadrosauridae) Tibia Osteohistology Reveals Non-annual Cortical Vascular Rings in Young of the Year

“…There may have been an LVC on this crack, as larger tibiae with more than one LAG sometimes have an LVC just before the first LAG. LVCs were only found beyond the first LAG in a pathologic tibia [T42; see Cubo et al (2015) for discussion of pathology] with at least four LAGs (Figure 2). In this particular tibia, at least four diffuse LVCs were found throughout the cortex.…”

Peer Review #2 of "Cancellous bone and theropod dinosaur locomotion. Part I—an examination of cancellous bone architecture in the hindlimb bones of theropods (v0.1)"

“…A further line of osteological evidence that has been frequently investigated is the cross-sectional geometry of the mid-shaft of limb bones (e.g., Alexander 1985;Alexander 1989;Alexander 1991;Christiansen 1997;Christiansen 1998;Cubo et al 2015;Fariña et al 1997;Farke & Alicea 2009;Farlow et al 1995;Heinrich et al 1993;Lovejoy et al 2002;Mazzetta et al 1998;Wilson & Carrano 1999). The implicit assumption of such enquiry is that the manner in which cortical bone is distributed around a diaphyseal cross-section is related to the magnitude and direction of bending and torsional stresses it experiences (Biewener 1992;Brassey et al 2013;Wainwright et al 1976).…”