Adaptations to Large Body Size in Dinosaurs

“

This study was a great addition to the line of work accomplished by all of the authors, each of which having made significant contributions to either dinosaur biomechanics or work on metaplasia. For me personally, this was a great project as an undergraduate to get started on research and to develop skills in writing, data collection, and statistical testing. As discussed in the paper, these vertebral projections are one of many adaptations observed in Dinosauria related to the stiffening of the spine. Notable examples relevant to the previous work of the authors are the ossified tendons seen in duck-billed hadrosaur dinosaurs (see Organ, 2006 in the Resources section) and the bifurcated neural spines in the long-necked sauropod dinosaurs (see Woodruff, 2016 in the Resources section). For the dinosaur enthusiasts, you may have thought of a couple exceptions in theropod dinosaurs that are large-bodied but did not possess these vertebral projections, such as Spinosaurus and Deinocheirus. The reason for this exception is another adaptation for spinal support entirely, and that is their long neural spines. The long neural spines could have aided in distributing stress evenly, like a cantilever bridge, throughout their spine. Many of these adaptations, including the vertebral projections described here and the ossified tendons of hadrosaur dinosaurs, were formed through the process of metaplasia. As detailed in the paper and in the summary above, the process of metaplasia does not produce bone but mineralizes existing tissue. This paper follows a line of work, lead by coauthor John (Jack) Horner, on understanding the cellular process of metaplasia and its prevalence throughout Dinosauria (see Horner et al. 2016 in the Resources section). This study also follows a line of work, conducted by the Montana State Macroevolution Lab (PI: Chris Organ), on the use of phylogenetic comparative methods in studying the evolution of dinosaur biomechanics. Phylogenetic comparative methods (PCM) is an approach that utilizes comparative data sets to statistically test evolutionary hypotheses using evolutionary (or phylogenetic) trees. This study specifically required the use of PCM to account for the non-independent shared ancestry of each species when conducting the phylogenetic t-test. As a graduate student in this lab, I have discovered that PCM is a great tool for connecting disciplines. The work conducted by this lab ranges from genetics to paleontology and anthropology. For more information on active work in the Montana State Macroevolution Lab, check out the link to our lab website in the Resources section.

”