Vladiloxylon troncosoi nov. gen. et sp. (Cycadales) de la Formación La Ternera (Triásico Superior), 3a Región, Chile

Abstract

A silicified wood assigned to a new genus and a new species of Cycadales, Vladiloxylon troncosoi, is described. It has the following characteristics: vascular cylinder monoxylic and pith small, heterogeneous; preserved primary and secondary xylem; cambium and secondary phloem well developed; cortex broad; leaf traces in different stages with curvilineous course, irregularly distributed and variable in shape from inside towards stem periphery; circular, diarch roots with secondary growth. Among fossil members of the Cycadales, Vladiloxylon has a close relationship with Lissoxylon, but is different in its anatomy because Vladiloxylon has more developed secondary xylem and cortex, the latter with numerous petiole bases. It also differs in the presence of mucilage canals and homocellulary, uniseriate rays, and the absence of epidermal hairs. This is one of the oldest records of monoxylic cycadean stems from the Triassic of South America.