EPIBETHIC TO ENDOBENTHIC TRANSITIONS

Replacement of the Paleozoic Fauna by the Modern Fauna was accompanied and followed by an overall infaunalization of the benthic fauna of shallow seas floored by unconsolidated sediment. By the beginning of the Cenozoic, sedentary epibenthos typically were absent or greatly reduced on shallow sedimentary sea floors, although they still commonly are abundant on rock substrata. Hypotheses to explain the transition from epibenthos-dominated Paleozoic benthic ecology to endobenthos-dominated Modern marine benthic ecology include amensalism (suppression of sedentary epibenthos by largely endobenthic bioturbators), higher concentration of nutrients in marine waters through time leading to higher accumulation of food resources within sediments, increased predation leading to refuge-seeking within sediments, and competitive displacement of the slow-growing, low-energy Paleozoic fauna by the more rapidly growing, higher-energy Modern Fauna.

The northern Adriatic is a silt- and fine sand-floored small epeiric sea in which some regions are characterized by abundant endobenthos with little epibenthos, while other regions have abundant sedentary epibenthos. Water masses, sediment accumulation rate, prevalence of bioturbators, types of predators, and sediment grain size vary across the region. Correlation of these environmental parameters with degree of infaunalization of local communities allows the various hypotheses about the change from Paleozoic to Modern benthic ecology to be tested in a Modern marine setting.