A rebbachisaurid-mimicking titanosaur and evidence of a Late Cretaceous faunal disturbance event in South-West Gondwana

FILIPPI, LEONARDO S.; JUÁREZ VALIERI, RUBÉN D.; GALLINA, PABLO A.; MÉNDEZ, ARIEL H.; GIANECHINI, FEDERICO A.; GARRIDO, ALBERTO C.

CRETACEOUS RESEARCH (PRINT)

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 2023 vol. 154

0195-6671

The evolution of ecosystems during the late Mesozoic on the southern landmasses is complex and stillpoorly known. Starting from a single vicariant LaurasianeGondwanan scenario, the paleobiogeographicand biostratigraphic models have become more complex, including vicariant, dispersal, and local extinctions as major drivers of changes in the Cretaceous ecosystems during the isolation and posteriorfragmentation of Gondwana. However, the direct effects of replacement and the adaptive evolution ofterrestrial vertebrates to fill vacant ecological niches after disruptive ecological events have been poorlydiscussed. Here, we provide a preliminary description of a nearly complete new titanosaurian sauropodfrom the Upper Cretaceous of Patagonia, Inawentu oslatus gen. et. sp. nov., that shows remarkableconvergent anatomical traits with rebbachisaurid sauropods. A phylogenetic analysis recovers it within anot previously recovered titanosaurian subclade, named Clade A, which would be endemic to the UpperCretaceous of South America. The convergent evolution between rebbachisaurids and Clade A membersis interpreted as the result of the same ecological niche exploitation. The biostratigraphic scenario duringthe Late Cretaceous of South America leads to interpret rapid speciation of the titanosaurs because offilling the empty ecological niche left by the extinction of the rebbachisaurids, an idea concordant with aregional disturbance event of the ecosystems in this continent between 90 and 85 Ma.