CICTERRA   20351
CENTRO DE INVESTIGACIONES EN CIENCIAS DE LA TIERRA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Lower Devonian aulacopleurids trilobites from Argentina
Autor/es:
RUSTÁN, JUAN JOSÉ
Lugar:
Toledo, España
Reunión:
Conferencia; Fouth International Trilobite Conference (Trilo08); 2008
Resumen:
INTRODUCTION
Aulacopleurids are widespread, frequent and diverse elements with long stratigraphic ranges
(Ordovician-Devonian) out of the Malvinokaffric Realm. Nevertheless, their Malvinokaffric record almost
exclusively restricted to the Devonian, is scattered and of low diversity. Due to this particularity and,
probably, to the fragmentary nature of the type material, and the lack of proper illustrations and detailed
studies, the only two genera recognized (Malimanaspis Baldis and Longobucco, 1977 and Maurotarion
Alberti, 1969) (Adrain and Edgecombe, 1996), have received secondary attention, and no specific
investigations have been carried out after the excellent review performed by Adrain and Edgecombe
(1996).
The principal controversies about these faunas include their origin, their role in evolutionary events,
and their paleobiogeographic significance (Elredge and Ormiston, 1979; Elredge and Branis¡a, 1980;
Lieberman, 1993).
Lower and Middle Devonian information about Maurotarion from Bolivia is of great significance,
accounting for a monophyletic small-scale radiation hypothesis that involves five formally nominated
species, separated in two informal groups (Adrain and Edgecombe, 1996). The origin of this clade has been
explained by means of two independent migration events of cosmopolitan groups from low latitudes, one
for Lochkovian-Pragian and the other during the Emsian, that were be interpreted to represent
cladogenetic pulses, according to Adrain and Edgecombe (1996).
Nevertheless, new evidences from eastern Bolivia confirm the presence of Maurotarion in South
America already for the Silurian, questioning the nature and age of this evolutionary event (Edgecombe
and Fortey, 2000).
A sixth Emsian species from the Bokkeveld group of South Africa, of discussed affinities to the
proposed informal groups, completes the list of known Malvinokaffric Maurotarion species up to the
present (Cooper, 1982; Adrain and Edgecombe, 1996)
In this scenario, the knowledge of Aulacopleurids from Argentina is very relevant. However,
Malimanaspis sarudianskii (Baldis and Longobucco, 1977), Middle-Upper Devonian in age, from the
Chigua Formation in western Precordillera is the only one Aulacopleurid described from this country.
Unfortunately, this species is known from a single specimen poorly illustrated, and thus several diagnostic
features are obscured.
In this contribution the record of Lower Devonian Aulacopleurid trilobites from the Talacasto Formation
in the Argentine Precordillera, is documented.
A detailed taxonomic study based upon abundant and well preserved materials as well as related
evolutionary implications is now in progress. Hence, systematic aspects and evolutionary significance of
these new faunas are preliminary analyzed herein.