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Paleobotany bears an invaluable source of knowledge for understanding the history of the biodiversity that we protect and care for today. This discipline is recognized as a source of information on physical, ecological, and biological events and processes that occurred in the past and are maintained today, but whose occurrences must be interpreted necessarily, and sometimes with limitations, solely from the lithosphere. The importance of studying past life from Mexico and addressing fossil plant reconstruction is highlighted to understand modern biodiversity. Fossils in Mexico have been studied marginally but contain valuable information to understand the history of biodiversity, both in Mexico and globally. We examined the extent to which Mexican fossils can contribute to understanding the origin and development of biological processes through time, and how past plant biodiversity in Mexico compares with the extant one. We used two sources to address these questions: (i) ideas on biological processes as seen through the fossil record, and (ii) fossils known from Mexico. Examples are given of how fossils, morphology, anatomy, and numerical methods, as well as genetics and physiology, illuminate each other to generate solid botanical concepts. The abundant and widely distributed outcrops with fossil plants suggest that further studies on Mexican material will be influential for varied biological hypotheses related to the origin and history of biodiversity. Mexican fossil plants and their scarce sampled localities are open to further investigation that will complement hypotheses on the historic discussion of biological processes.

Background: Celastraceae is a morphologically heterogeneous family. For this reason, the inclusion of some taxa within this group is controversial. Recently this problem has become significant since its fossil record is recognized as an important source of information for evolutionary studies, especially those using molecular clocks which require a robust, reliable fossil record. Questions: What are the most reliable fossil records of Celastraceae? What morphological characters are used to assign fossils in the family? Study site and dates: Compilation of records contained in paleontological databases, and paleobotanical literature, covering publications from 1869 to 2018. Methods: Published information on the Celastraceae fossil record was compiled and analyzed using the most recent classification system and specialized literature on the family. Results: A total of 168 fossil records were examined, of which nine are proposed for use as molecular clock calibration points. Each specimen has a description based on a character set used for its identification, a photograph and/or illustration, their geological age is well supported, their geographic origin is known, and the specimens are in accredited home institutions with publicly accessible collections. Conclusions: The identification and establishment of relationships between fossil and extant taxa have important limitations that depend on the critical interpretation of morphology in a phylogenetic context. Therefore, it is essential to incorporate only those morphological studies in Celastraceae that help clarify its fossil record.

Abstract A Brazilian cordaitalean leaf is reassigned and redescribed based on cuticular analysis. The new name Noeggerathiopsis brasiliensis is erected as a replacement for Rufloria gondwanensis Guerra-Sommer. The leaf adpressions come from a tonstein layer within a Sakmarian coal seam of the Faxinal Coalfield, southern Paraná Basin, Brazil (U-Pb SHRIMP mean age 291 ± 1.3 Ma, Rio Bonito Formation). The leaf micromorphological pattern, observed under optical transmitted light and field emission gun - scanning electron microscopy, is distinct from the Euramerian Cordaites Unger and very similar to the Angaran Rufloria Meyen. The lower epidermis has conspicuous longitudinal stomatiferous furrows typical of Noeggerathiopsis (Feistmantel) McLoughlin & Drinnan covered by tightly interwoven trichomes, epidermal and probably also hypodermal highly cutinized sheaths at the borders of furrows, and haplocheilic stomatal apparati surrounded by long conical trichomes. The xeromorphic cuticle structures are similar to those of Glossopteris pubescens (Guerra-Sommer) Degani-Schmidt & Guerra-Sommer, the dominant leaf species preserved in the tonstein layer, indicating convergent ecological adaptations to abiotic stress factors in distinct plant groups in the peat-forming paleoenvironment.