Supplementary file 3_Paleoecological dynamics of the Jurassic-Cretaceous transition: insights from the Vaca Muerta Formation marine biota.docx

The results reveal a complex, vertically stratified pelagic realm that remained functionally stable for over nine million years. The vertebrate assemblage is abundant and taxonomically diverse, including top predators and more specialized forms. Actinopterygian fishes, particularly, displayed a wide range of body shapes, locomotor modes, and feeding strategies, spanning pelagic to demersal/benthic habitats and encompassing suspension-feeding, invertivorous, microphagous, piscivorous, and durophagous forms.

Mesopredatory marine reptiles’ morphological disparity suggests strict niche partitioning despite preying upon similar food sources. Ammonite communities tracked a shallowing-upward trend, shifting from early Tithonian streamlined, demersal active swimmers into heavily sculptured planktonic drifters mechanically adapted to storm-dominated environments. Conversely, the benthic realm dynamics remained decoupled from the water column and were strictly regulated by oxygenation, water energy, and substrate consistency variations.

Benthic invertebrate ecosystems shifted from highly impoverished, opportunistic, or pseudoplanktic communities during the early Tithonian into highly diversified, multi-tiered assemblages punctuated by extensive oyster biostromes as oxygenation improved by the late Berriasian, before a final shallowing trend led to a major ecological reorganization at the Intravalanginian Discontinuity. Direct and indirect evidence on biotic interactions reveal a highly interconnected, complex trophic network, spanning microplanktonic producers to hypercarnivorous reptile apex predators.

Ultimately, these findings highlight the coordinated eco-spatial and trophic mechanisms of Gondwanan ecosystems and establish the Neuquén Basin as a critical window into global marine dynamics during the Jurassic–Cretaceous transition.</p>