Tempo and mode in Trilobite Evolutionary Faunas replacement from the Cordillera Oriental basin (Northwestern Argentina)

F.R. MEROI ARCERITO; HALPERN K.; D. BALSEIRO; B.G. WAISFELD

COMPTES RENDUS PALEVOL

ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

Año: 2017 vol. 16 p. 821 - 831

1631-0683

Major ecological transitions among evolutionary faunas is amatter of continuous debate.Our study analyses the timing and mode of replacement of Ibex I and IITrilobite Evolutionary Faunas (TEF) in Early Ordovician successions ofNorthwestern Argentina, with special emphasis on olenids and asaphids askey groups of the Ibex I and Ibex II faunas, respectively. We explorerichness by using the sample rarefaction method, and occupancy based on apresence-absence dataset. The late Tr2 represents an inflexion point inrichness and occupancy trajectories of asaphids and olenids. Whileolenids diminish their generic richness through time, asaphids became therichest family since the Tr3 predating the global trend recognized forthe expansion of the Ibex II Fauna. Asaphids gained diversity at theexpense of other trilobites, as well, their rise in diversity lags behindthe increase in occupancy suggesting a displacement scenario as theprobable mode of replacement between the Ibex I and II TEFs. Apparently,processes of replacement variate among regions across the globe,configuring a complex global mosaic of regional patterns.