Un nuevo tallo permineralizado de Equisetales de la Formación Los Rastros (Triásico Medio - Superior), provincia de San Juan, Argentina

Abstract

A new permineralized Equisetalean stem from Los Rastros Formation (Middle-Upper
Triassic) from San Juan province, Argentina. Several stems remains of a new genus and species belonging to
the order Equisetales are described. They are represented by ribbed stems with distinct nodes and internodes, a
pith with some sclerenchymatic cells and carinal canals. Wedge-shaped primary xylem and fascicular wedges of
secondary xylem alternating with uniseriate rays are preserved. Comparison of these stems with other Equisetalean
fossils from Gondwana is difficult because of their different kinds of preservation. There are only few records of
permineralized Equisetalean stems from the Gondwana Triassic because the majority of data are derived from
compression-impression fossils; however, one of them, Spaciinodum Osborn & Taylor, from Antarctica, is also
based on a permineralization. The anatomical structure of the studied material suggests that it is a new taxon, as
their features differ from all previously known species.