First population analysis in Hadrosauroid dinosaurs (Ornithopoda: Iguanodontia: Hadrosauroidea)

Abstract

The study of biological population densities through direct measurements is one of the pillars of modern ecology; however, it does not apply to extinct fauna without modern extant representatives, as is the case with non-avian, plant-eating dinosaurs such as the Hadrosauroidea. On the other hand, mathematical models of population dynamics have also been used to estimate population density without the need for direct measurements. These models, however, require knowledge of population shift rates that are typically obtained through diverse observations. This presents a certain limitation for the use of such models when applied to extinct populations. Still, through the use of ecological analogies, it is possible to estimate population dynamics in extinct faunas. This work, utilizing a differential equation-based population dynamics model, estimates the population density of six species and two specimens of hadrosauroids recorded in Mexican territory, employing ungulate mammals as ecological analogues. The results show that individuals with low body mass, such as Huehuecanahutlus tiquichensis, had a higher average density of 0,69 individuals per square kilometer. For hadrosauroids with higher body mass, such as Magnapaulia laticaudus and the specimen PASAC-1, their population density would be around 0.13 to 0.17 individuals per square kilometer. The inference shows the possible existence of temporal shifts in population density. Maximum and minimum ranges were found due to scenarios of high food productivity or alimentary stress. The former infers a negative correlation between a higher body mass/lesser population density.