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

作者：Brayard, Arnaud^*; Krumenacker, L. J.; Botting, Joseph P.; Jenks, James F.; Bylund, Kevin G.; Fara, Emmanuel; Vennin, Emmanuelle; Olivier, Nicolas; Goudemand, Nicolas; Saucede, Thomas; Charbonnier, Sylvain; Romano, Carlo; Doguzhaeva, Larisa; Ben Thuy; Hautmann, Michael; Stephen, Daniel A.; Thomazo, Christophe; Escarguel, Gilles

来源：Science Advances, 2017, 3(2): e1602159.

DOI：10.1126/sciadv.1602159

• PERMIAN MASS-EXTINCTION
• HIGH-RESOLUTION BIOCHRONOLOGY
• NORTHERN INDIAN MARGIN
• U-PB AGES
• BIOTIC RECOVERY
• THAYNES FORMATION
• SOUTH CHINA
• EXCEPTIONAL PRESERVATION
• AMMONOID BIOCHRONOZONES
• COLEOID CEPHALOPODS

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

• 出版日期2017-2
• 单位中国科学院南京地质古生物研究所