First record of Silurian plants in Argentina. Li peón Formation, Condado River-Los Toldos River area, western Subandean Rang es (Salta province)

Acta geológica 23 (1-2):2011

Abstract

The fossil record consists of fragmentary and inarticulate pla nt remains associated with invertebrates of a shallow marine environment, mostly bivalves th at indicate a Ludlovian age. The flora consists of: a) smooth leafless rhyniophitoid axes, with or without isotomously dichotomic branching ca. [0.26 – 3.0] mm in diameter, assigne d to two morphotypes of Hostinella ; b) smooth axes, with or without striae, incertae sedis . c) rounded to elliptical terminal sporan- gia, isolated or joined to smooth incomplete axes. Its morphology and morphometry allow comparison with Cooksonia ; d) elliptical-ovate sporangia, without border, jo ined to a small axial portion, assigned to cf. Tarrantia ; e) cup-shaped isolated sporangia, with parallel o r divergent sides, of uncertain affinities; f) sporangium? with parallel sides and incomplete contour and uncertain taxonomic position. The paleofloristic as sociation, the first identified in Argentina and in this stratigraphic unit, is similar to those des cribed for the Silurian at La Angostura (Cochabamba, Bolivia) and those described for the D evonian at Tarija (Bolivia). The recognized specimen have a large temporal distribution (Late W enlockian - Early Devonian?), therefore the age is inferred from the associated bivalve fauna