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.

A revision of the Devonian Malvinokaffric dalmanitid trilobite Dalmanitoides Delo, 1935, on the basis of new data from Argentin

“…This evidence suggests no migrations but rather isolation and speciation of a stock of widely distributed Dalmanitine trilobites already present by the earliest Devonian, in Malvinokaffric basins. This pattern is consistent with that recognized for other Malvinokaffric trilobite groups (Eldredge and Ormiston, 1979;Abe and Lieberman, 2009;Rustán and Vaccari, 2010).…”

“…Aspects of the geologic setting relevant here have been adequately treated in several previous works (Baldis, 1975;Astini, 1991;Herrera, 1993Herrera, , 1995aHerrera, , 1995bEdgecombe et al, 1994;Waisfeld et al, 1994;Bustos, 1996;Herrera and Bustos, 2001;Rustán and Vaccari, 2010). Fossils studied come from the Talacasto Formation (Padula et al, 1967), which is extensively exposed in the Central Argentine Precordillera of San Juan Province, western Argentina (Figure 1).…”

Palynomorphs from the Devonian Talacasto and Punta Negra Formations, Argentinean Precordillera: New biostratigraphic approach

“…210 m of light green mudstones. According to the palynological results at the Cerro La Chilca section (García Muro et al, 2017), the layers of the Talacasto Formation located immediately above Keidel´s marker horizon would be Pragian to possibly late Pragian in age, in contrast with the previously proposed early Emsian age based on brachiopods (Herrera, 1993(Herrera, , 1995Rustán and Vaccari, 2010b;Salas et al, 2013;Sterren et al, 2015;Rustán, 2016;Cichowolski and Rustán, 2017).…”

First report of Devonian bactritids (Cephalopoda) from South America: paleobiogeographic and biostratigraphic implications

“…Keidel's bed is interpreted to be probably earliest Emsian in age or located around the Pragian-Emsian boundary and, consequently, strata of the Talacasto Formation overlying it (mainly recorded in the thicker northernmost sections of the basin) are considered to be not older than Emsian. In turn, this stratigraphic interpretation has been strengthened by correlation of Keidel's bed with a probably equivalent stratigraphic marker recognized in the subsurface of the Bolivian basins around the Pragian-Emsian boundary, as suggested by Rustán and Vaccari (2010). In addition, the report of the Middle Devonian trilobite Acanthopyge (Lobopyge) balliviani Cichowolski and Rustán-Early Devonian bactritids from Argentina (Kozlowski, 1923) nearly 250 m above Keidel's bed, in the Punta Negra Formation in the Loma de los Piojos section near Jáchal Vaccari, 2010, p. 1084), strongly supports this stratigraphic interpretation.…”