Jurassic flora in Southeast Mexico: importance and prospects of recent findings in the Mixteco Terrane

Resumen

Laurasic outcrops with plant fossils from the Jurassic are well known in Europe and Asia, but in North America, toward the Mesoa- merican region, oristic Jurassic outcrops are poorly known. This is due to the fact that samples were taken with the goal of geological and/or mining exploration, without a rigorous paleontological approach. This inconsistency in sampling in the region has limited the knowledge of its Jurassic ora. Recently, we initiated a campaign on standardized sampling in the Zorrillo-Taberna Indiferenciadas Formation with the aim of advancing the knowledge of the oristic composition of this formation. The methodology we employ con- sists of maintaining the stratigraphic control of the fossil origin and sampling in average constant conditions with regard to time and personnel. Taxonomic determination was based on diagnostic characters of each fossil-taxon. The oristic composition is dominated by Bennettitales, but Cycadales, Podozamitales and others are also present. The results show an increase in the oristic diversity of almost 50 % distributed in three stratigraphic zones. It is noteworthy to point out that the oristic association contains one genus and 14 species endemic to the region. In addition, we contribute with new fossil-taxa records of Cycadales, Caytoniales, Podozamitales and some genera of Bennettitales for both formation and region. Thus, we conclude that the application of the sampling method in other localities would consolidate a comprehensive paleo oristic list for the region, and we believe that the paleo ora of the region would set the groundwork for new Jurassic biogeographic analysis.