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A new flower preserved in amber in sediments of Simojovel de Allende, México, is identified as an extinct member of Staphyleaceae, a family of angiosperms consisting of only three genera (Staphylea, Turpinia and Euscaphis), which has a large and abundant fossil record and is today distributed over the Northern Hemisphere. Staphylea ochoterenae sp. nov. is the first record of a flower for this group, which is small, pedicelled, pentamer, bisexual, with sepals and petals with similar size, dorsifixed anthers and superior ovary. Furthermore, the presence of stamens with pubescent filaments allows close comparison with extant flowers of Staphylea bulmada and S. forresti, species currently growing in Asia. However, their different number of style (one vs. three) and the apparent lack of a floral disc distinguish them from S. ochoterenae. The presence of Staphyleaceae in southern Mexico ca. 23 to 15My ago is evidence of the long history of integration of vegetation in low-latitude North America, in which some lineages, such as Staphylea, could move southwards from high latitudes of the Northern Hemisphere, as part of the Boreotropical Flora. In Mexico it grew in association with tropical elements, as suggested by the fossil record of the area.

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.

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