Cladogenesis and early diversification of Titanosauria (Dinosauria, Sauropoda): Comparative osteology, phylogeny, and paleobiogeography.

Abstract

Titanosaurs are a diverse and widespread group of sauropod dinosaurs, comprising one-third of all known sauropod diversity. However, analyses focusing on their phylogenetic relationships generated divergent hypotheses, and their interrelations have not yet been fully elucidated. Although numerous phylogenetic proposals have been presented for Titanosauria in the last two decades, none of them included a comprehensive sampling of early-diverging forms, with most analyses being based on updated versions of the same datasets. This approach consequently biased previous attempts to retrieve the evolutionary history of the group, making it difficult to understand how and when the typical titanosaurian morphology evolved. This project aims to fill such gaps in our knowledge of titanosaurian phylogeny, focusing primarily on their origin and early diversification. We propose an evaluation of several early-diverging titanosaurian specimens, including a critical appraisal of the main phylogenies published in the past thirty years (1993-2023). Our purpose is to evaluate and select independent characters to compose a new, more inclusive dataset that encompasses a substantial diversity of basal titanosaurian forms and their closely related taxa. The resulting expanded dataset will provide not only a solid framework for the assessment of their lower-level relationships but also its biogeographic history.