The macrovertebrate fauna of the uppermost Albian to lower Turonian Winton Formation supports interpretations of a relatively homogenous fluvial setting. However, little documentation exists of microvertebrate faunas despite their purported richness in association with larger dinosaur skeletons. An assemblage of lamniform shark teeth has been recovered from a site within the Winton Formation mixed with other microvertebrate remains from both marine and terrestrial organisms, raising questions of the palaeoenvironmental interpretation of this site and across nearby dinosaur-bearing localities on the same property—Belmont Station.
A lamniform commonly associated with marginal marine settings is Archaeolamna, known only from its type species throughout the Late Cretaceous. More recent taxonomic works into Cretaceous lamniforms have demonstrated a greater diversity across the period for many groups considered to have morphologically conservative tooth forms. The description of the type material for Archaeolamna denotes a subspecies from the Campanian of North America, which was limited to a general diagnosis.
This thesis primarily contributes to our understanding of the alpha diversity and palaeoenvironmental intricacies of the Winton Formation by providing the first systematic description of a microvertebrate assemblage. I document the first occurrences of lamniform sharks, elopiform fish, plesiosaurs, and testudines, and additional occurrence data from ceratodontid lungfishes and theropod dinosaurs. These occurrences represent the strongest marine signal for the Winton Formation, which has implications for fossil sites across Belmont Station. I therefore hypothesise a proximate spatiotemporal context to the underlying Mackunda Formation and support a lower stratigraphic position for the Belmont Station portion of the Winton Formation akin to the fossil sites at Isisford, Queensland, which lies in contrast to other fossil sites within the Winton region.
Secondarily, this thesis provides a detailed description of a new species of archaeolamnid from the Late Cretaceous – Archaeolamna judithensis comb. nov., from the lowermost upper Campanian Woodhawk Member of the Judith River Formation in Montana, United States of America. Through detailed description and elevation of this taxon, I demonstrate the requirement of an associated tooth set within a constrained deposit to establish species of fossil sharks, and the complementary use of morphometrics to distinguish shark species from similar tooth morphologies. Furthermore, through the establishment of two Campanian species of Archaeolamna, my work serves as a beginning to a broader taxonomic revision of archaeolamnids across the Cretaceous, which may give these sharks biostratigraphic utility as well as potential as palaeoshoreline markers from their preference for shallow to marginal marine settings.