No abstract

No abstract

Anomozamites is a fossil-genus of leaf attributed to the Bennettitales, with a distribution mainly in the Kingdom of Laurasia and a stratigraphic range of the Upper Triassic to the Lower Cretaceous. In Mexico there were only reports of some specimens until the 1980s and later of four fossil-species at the beginning of the 21st century, all of them from the Jurassic in the Mixteco Terrane. In this review, three fossil-species of Anomozamites are identified: A. angustifolium is the first of them, which is a fossil-taxon with a range of the Rhaetian to Bajocian and Euramerican distribution; the second one is A. cf. triangularis, of which the geographic and stratigraphic extension of fossil-taxon is proposed; finally, we propose the existence of the A. sp.1, informally named, but with morphological characters that do not match the descriptions of Triassic/Jurassic fossil-taxa. These identifications were made based on macromorphology of the foliar organs and on the review of the diagnostic characters of both the fossil-genus and the fossil-species of taxonomic validity. Then, with this study, the taxonomic and phytogeographic knowledge of Anomozamites during the Jurassic period is increased and this allows reconsidering the amplitude of the Wielandiella distribution, a fossil-genus related to Anomozamites due to the existence of two fossil-taxa in organic connection.

By early Mesozoic time, a major plate reorganization produced the breakup of Pangea, which was the most recent supercontinent assembled on Earth. Due to its paleogeographic position along the emergent plate boundary between North and South America, the early Mesozoic tectonic history of Mexico was dominated by the development of major normal to strike-slip faults. These faults produced a complex crustal configuration characterized by subsiding basins bounded by exhuming basement highs. Voluminous, continental to marine sedimentary successions were accumulated into these basins during the Jurassic, representing a unique stratigraphic record related to the fragmentation of the western equatorial margin of this supercontinental mass. This field trip will provide an overview of the Otlaltepec and Tezoatlán Jurassic Basins that are exposed in the states of Puebla and Oaxaca, southern Mexico. Observed outcrops are exposed along two amazing canyons and consist of alluvial-fluvial to marine clastic deposits. Major provenance changes are recorded in the Jurassic successions of the Otlaltepec and Tezoatlán Basins and are interpreted as the result of exhumation of different fault-bounded lithospheric blocks during Pangea breakup. The integration of petrological and paleontological data indicates that these major changes in provenance of clastic rocks match with changes in climatic conditions. Therefore, in this field trip, we will have the opportunity to explore the hypothesis that the progressive exhumation of lithospheric blocks during the fragmentation of Pangea could have produced major topographic changes that favored local variations in climatic conditions and consequently, the diversification of floral assemblages in Mexico.

This paper reports two new species of Ginkgoales collected from the Cañada Alejandro and Río Ñ umi (Zorrillo and Zorrillo -Taberna Undifferentiated Formations, Middle Jurassic). Thirty-one fossils were selected and compared with 14 species from different localities. A numerical taxonomy analysis was performed through a data matrix formed by 15 characters. Results indicate an important speciation process of the Ginkgoales during the Jurassic in the southeast of Mexico. New evidence suggests the existence of eight species from the Ginkgoidium Yokoyama, 1889 and Sphenobaiera (Florin) Harris and Millington, 1974 genera and two new species Ginkgoidium nundichii Velasco-de León,