Evolutionary Dynamics of Tyrannosauroid Dinosaurs

Abstract

This study explores the evolutionary dynamics of tyrannosauroid dinosaurs, a successful clade of basal coelurosaur theropods. This is accomplished by estimating rates of evolution using the Claddis R package. Morphological diversity was measured from discrete character data and estimates of evolutionary tempo on current phylogenetic hypotheses of tyrannosauroid relationships. In this work it is shown the process to obtain the set of necessary documents to obtain the results with the script to finally calculated it with R. In this set of previous documents are included a matrix character, that gather a series of different characters associated with the different taxa into the clade. It is also added a temporary range of each taxon and a consensus phylogenetic tree made by phylogenetic analysis under parsimony. All of them obtained through different software (Mesquite, TNT and R) and necessaries to run the script to obtain the seek resultants rates. Evolutionary rates were estimated for different anatomical regions of the tyrannosauroid skeleton, including the skull and mandible, the post cranial body and the whole-body. These phylogenetic trees include the rate calculation, the mode and tempo of changes produced in each node, to perceive possible acceleration or deacceleration of morphological evolution on the different branches of this clade. To help with the conclusions and discussions of the study it is assessed a relationship between tyrannosauroid evolution and the body mass of their potential prey, ceratopsians and ornithopods through time. The results indicate that the mandible was a driver of the increasing mass of the skull in tyrannosauroids, accompanied by an increase of the size of the posterior region of the skeleton and the reduction of the forelimbs. An important conclusion of this study is that the increasing skull size facilitates a greater bite force. The relationship between tyrannosauroids body mass and that of their potential preys indicates that is boosting, which could be a case of arms race, being a potential cause of this mandible adaptation, which is supported by different studies