The aulacopleurid trilobiteMaurotarionAlberti, 1969, in the Silurian-Devonian of Argentina: systematic, phylogenetic and paleobiogeographic significance

Abstract

Five new species ofMaurotarionAlberti, 1969 from the Silurian Lipeón Formation and Lower Devonian Talacasto Formation of Argentina are recognized. The comparisons with Bolivian and South African species support a Malvinokaffric clade based on librigenal synapomorphies, here erected asMaurotarion(Malvinotarion) new subgenus. The Malvinokaffric origin of the family would not be a migration from lower paleolatitudes but an Early Silurian stock of rare cosmopolitan ancestors which underwent a great Devonian radiation. Two lineages can be recognized within MalvinokaffricMaurotarion.The Silurian-Pragiandereimsilineage is a plesiomorphic one resembling Silurian representatives and involvesM.(Malvinotarion)dereimsi, M.(Malvinotarion)talacastoensenew species,M.(Malvinotarion?) new species A,M.(Malvinotarion?) new species B,M.(Malvinotarion) sp., and eventuallyM. (Malvinotarion?)cf.dereimsi.Theisaacsonilineage ranges from the Lower Pragian to Eifelian exhibiting a defined morphologic trend in the librigena. This lineage comprisesM.(Malvinotarion)isaacsoni, M.(Malvinotarion) sp. A from South Africa,M.(Malvinotarion)gauchonew species,M.(Malvinotarion)haudeinew species andM.(Malvinotarion)legrandi.A Lochkovian diversification probably took place yet an adequate assessment remains difficult. In contrast, a great evolutionary burst is recognized during the Emsian and is related to Pragian-Emsian global relative sea level curves which are coincident with those proposed from Bolivian and Argentinian basins.