Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna.

摘要: In the wake of end-Permian mass extinction, Early Triassic (~251.9 to 247 million years ago) is portrayed as an environmentally unstable interval characterized by several biotic crises and heavily depauperate marine benthic ecosystems. We describe a new fossil assemblage—the Paris Biota—from earliest Spathian (middle Olenekian, ~250.6 Bear Lake area, southeastern Idaho, USA. This highly diversified assemblage documents remarkably complex ecosystem including at least seven phyla 20 distinct metazoan orders, along with algae. Most unexpectedly, it combines early Paleozoic middle Mesozoic taxa previously unknown from strata, among which are primitive Cambrian-Ordovician leptomitid sponges (a 200–million year Lazarus taxon) gladius-bearing coleoid cephalopods, poorly documented group before Jurassic (~50 after Triassic). Additionally, crinoid ophiuroid specimens show derived anatomical characters that were thought have evolved much later. Unlike previous works suggested sluggish postcrisis recovery low diversity for organisms, unexpected composition this exceptional points toward rapid post-Permian diversification these clades. Overall, illustrates phylogenetically diverse, functionally complex, trophically multileveled ecosystem, primary producers up top predators potential scavengers. Hence, Biota highlights key evolutionary position ecosystems in transition Modern fauna dawn era.