Early Cretaceous Brachyoxylon woods from Argentinean Patagonia and comments on the Cheirolepidiaceae distribution

Abstract

We studied fossil woods from Matasiete and Castillo Formations (Aptian–Albian) for the first time. The woods, preserved in fluvial channel and floodplain deposits, have anatomy consistent with the fossil-genus Brachyoxylon Hollick and Jeffrey. Specimens from Castillo Formation have poorly distinct growth ring boundaries, exclusively uniseriate with a mixed arrangement intertracheary radial pitting, araucarioid cross-field pitting with 3–8 half-bordered pits with oblique aperture, and uniseriate rays. Specimens from Matasiete Formation are poorly preserved and only one could be assigned to Brachyoxylon with reservations. Brachyoxylon is a fossil-genus with a worldwide distribution and related to the fossil family Cheirolepidiaceae, a group of conifers that developed in various environments. However, our study suggests that this family would have prospered in locally semi-arid conditions.