Maderas fósiles de la Formación San Carlos (Gretácico Superior), Chihuahua, México

In the sediments of the San Carlos Formation (Upper Cretaceous, Coniacian - Maastrichtian) there have been collected a large number of fossil woods that correspond mainly to conifers and in a smaller proportion to angiosperms. From this material, two new records based on vegetative structures are described. The first corresponds to a conifer which has characters present of the Agathoxylon genus, these features are: indistinguishable growth rings, predominantly uniseriate pits, occasionally biseriate, alternate, crossfield pits (oculipore type) of the Cupressoid type, 1-3 per cross-field. The second morphotype is related to Paraphyllanthoxylon anasazi (cf. Lauraceae), which is characterized by vessels solitary and in short radial multiples, simple perforation plates, small, alternate intervascular pits, vessel-ray parenchyma pits with reduced borders, heterocellular multiseriate rays up to four cells wide. These new records strengthen the growing evidence suggesting a close foristic link between the floras of northern Mexico and south-central USA during the Late Cretaceous.