SHARED ADAPTIVE RESPONSES AMONG EPIFAUNAL INVERTEBRATES IN THE LATE TRIASSIC: A SYMPTOM OF INCREASED PREDATION OR ENVIRONMENTAL UPHEAVAL? (Invited Presentation)

Obligate sessile and epifaunal animals are among those that are most likely to have been impacted by amplified seafloor predation in the Early Mesozoic, and an impressive array of adaptations appear during this interval among shelly invertebrates, particularly in the Late Triassic (235-199 Ma). Seafloor predators specialized for shell-crushing are inferred to have become more abundant in shallow marine environments based on taxonomic radiations among key durophage taxa including neopterygians, chondrosteans, chondrichthyans, and marine reptiles. Determining direct relationships between marine vertebrates and potential shelly invertebrate prey is limited by the differential preservation potential of these groups in shallow marine environments, and many possible environmental forcers must be considered as morphological drivers.

Morphological and behavioral adaptations appeared among stationary epifauna in the Late Triassic, but specific adaptations were not global and were constrained by biological limitations of the older assemblages. The regional differences between three distinct oceanic regions are reviewed in the context of their invertebrate assemblages, sedimentological settings, and ichthyolith record from the same sedimentary deposits, which provides stronger evidence for predator-prey interactions. Distinct latitudinal differences in diversity are observed for both vertebrates and invertebrates in the Late Triassic, but sessile epifauna that persisted during this interval tended to exhibit morphological features that would have been beneficial in interactions with demersal shell-crushing predators.