Biogeographical network analysis of the Late Triassic dinosaurs and new insights on their geodispersal routes

Dinosaurian paleobiogeography has remained a compelling domain of interest in the field of vertebrate paleontology over the past few decades, though there has been little/no work with respect to the Late Triassic dinosaurian remains from India. This study investigates the probable centers of origin of the early dinosaurs that included various lineages such as Sauropodomorpha, Herrerasauria and Theropoda through the Late Triassic period using a phylogeny-based network analysis with especial emphasis on the Indian dinosaurs including the new skeletal elements recovered from the late Carnian to early/ middle Norian Tiki Formation of India. Our phylogenetic study positions Tawa as sister taxa to other late diverging herrerasaurids near the base of Herrerasauria, supports the placement of Coelophysis near the base of Neotheropoda and proposes alternative placements for a few sauropodomorphs. Networks of the Late Triassic dinosaurs including the contemporary sauropodomorphs and Herrerasauria exhibit nearly identical topologies with strong interconnectivity. Based on the network analysis, we propose South American origin for the Late Triassic Dinosauria with two primary dispersal trajectories leading to the Laurasian and Eastern Gondwanan landmasses simultaneously. We propose a new model that showed a closer faunal relationship between the South African and European provinces suggesting intercontinental faunal exchange and paleomigration particularly during the later stages of sauropodomorph evolution. Community detection algorithms revealed that the Late Triassic dinosaurian assemblage of India showed a stronger affinity with that of the South American fauna. Therefore, this study highlights the importance of phylogeny-based network analysis in the deduction of origination center and dispersal routes of the fossil animals.