A diverse assemblage of Anacardiaceae from Oligocene sediments, Tepexi de Rodríguez, Puebla, Mexico

Among the plants collected from the Pie de Vaca Formation of the Oligocene, of Tepexi de Rodríguez, Puebla, Mexico are five plants of Anacardiaceae, Haplorhus medranoensis, Rhus toxicodendron, Rhus sp., Comocladia intermedia, and Pistacia marquezu represented by their leaves and/or leaflets. The past and present diversity and geographic distribution of one of these genera, Rhus, demonstrate its capability to adapt and diversify in a wide variety of environments. Leaf architecture characters of this taxon overlap with those of other genera in the family, suggesting a high degree of phenotypic plasticity. The presence in the Pie de Vaca Formation of a type of Pistacia with leaf architecture characters similar to those of Asian plants further supports a long history of exchange between low-latitude North America and Asia. Links between low-latitude North and South America and the Caribbean are suggested by the presence of Comocladia and Haplorhus. Whereas Comocladia highlights the long history of regional endemics in the area, Haplorhus, today an endemic monotypic genus of Peru, suggests exchange mechanisms between North and South America. The morphologic characters of these taxa, and those of Pseudosmodingium (Anacardiaceae), some Rosaceae, Leguminosae, and Berberidaceae, suggest that the Pie de Vaca community was established and evolved in harsh environmental conditions. The Pie de Vaca flora thus provides significant new insights into the biogeographic relationships of the low latitude vegetation of North America

Leaves of salicaceae (Salix and Populus) from Oligocene sediments near Tepexi de Rodríguez, Puebla, Mexico

Eleven new salicaceous taxa based on fossil leaves, seven Salix and four Populus species, are described from the Oligocene Los Ahuehuetes locality Pie de Vaca Formation, near Tepexi de Rodríguez in Puebla, Mexico. They are characterized by the presence of typical salicoid teeth, camptodromous secondary venation, and elliptic or lanceolate shape. Morphological differences between these new fossil plants and those reported previously from the United States and elsewhere indicate that diversification among these taxa occurred early during their differentiation. Furthermore, the limited morphological similarities of the fossil and extant plants growing naturally in Mexico also indicate a high rate of evolution. Documenting the expansion of high-latitude North American taxa into lower latitudes at the time of deposition of the Pie de Vaca Formation confirms that at least some of the typical boreal taxa were part of dry tropical communities in low-latitude North America and underscores the need to reevaluate the origin of this southern vegetation

Leaves of Berberidaceae (Berberis and Mahonia) from Oligocene sediments, near Tepexi de Rodríguez, Puebla.

From the Oligocene Los Ahuehuetes locality, near Tepexi de Rodríguez, Puebla, Mexico, five new plant species are described based on their leaf architecture. The presence of brochidodromous or acrodromous venation, and secondary veins forming angular (versus rounded) arcs, are well defined characters in the fossil material that relate it to Berberidaceae. Comparison with the leaves and leaflets of extant and fossil plants allow the recognition of one Mahonia and four Berberis is new species. The lack of detailed information on leaf architecture in Berberidaceae limits the evaluation of the taxonomic relationships that can be suggested between fossil and extant plants. However, from a biogeographic point of view the presence of these new fossil plants supports the hypothesis of a North American origin of the Orientalis Groups of Mahonia, to which a lineage of Berberis may be added. Furthermore, two of the new species suggest the dispersal, some time during the Tertiary, of a lineage that today forms the Australis Group of Berberis from low latitude North America to South America. The movement of the Chortis Block is proposed as an alternative to explain the dispersal of a growing list of plants from north to south in the Americas. Only through future geological and palaeobotanical work call this hypothesis be corroborated. (C) 2000 Elsevier Science B.V. All rights reserved

Vertebrates of the El Pelillal locality (Campanian, Cerro del Pueblo Formation), southeastern Coahuila, Mexico

A new locality named El Pelillal (Cerro del Pueblo Formation, Late Cretaceous, Campanian) in the southeastern area of the State of Coahuila, Mexico yields an assemblage of vertebrates that is important for correlation due to its frequent occurrence in other localities along the Cerro del Pueblo Formation outcrops. It is located in the Municipio de Ramos Arizpe, Coahuila. Among the vertebrates found are: fishes (Lepisosteida

Reconstruction of the leaves of two new species of Pseudosmodingium (anacardiaceae) from Oligocene strata of Puebla, Mexico

they are symmetrical to slightly asymmetrical, with acute to attenuate apex, acute to cuneate base, and entire to serrate margin. Venation is simple pinnate craspedodromous, with secondary veins slightly curved near their bas

Phytolaccaceae infructescence from Cerro del Pueblo Formation, Upper Cretaceous (late Campanian), Coahuila, Mexico

The Upper Cretaceous (late Campanian) Cerro del Pueblo Formation, Coahuila, Mexico, contains a diverse group of angiosperms represented mainly by their reproductive structures. Among these, a new permineralized infructescence is recognized based on its morphological and anatomical characters. It is a multiple infructescence composed of berry fruits With Six locules, each containing a single seed with a curved embryo developed from a campylotropous ovule with pendulous placentatio

Microfossil algae associated with Cretaceous stromatolites in the Tarahumara Formation, Sonora, Mexico

therefore, a few could have participated in the build up of the stromatolites in non-marine, most probably freshwater environments. These fossils document the diversity of microorganisms in freshwater environments during the Late Cretaceous in northern Mexico, which include some of the most ancient freshwater diatoms. (C) 2004 Elsevier Ltd. All rights reserved

Paleobiological implications of Campanian coprolites

Vertebrate coprolites (153 samples) in association with vertebrate and plant remains in the Upper Cretaceous (Campanian) sediments of the Cerro del Pueblo Formation, in southeastern Coahuila, Mexico, represent at least ten morphotypes, ranging from ca. 1 cm to 3 cm. At least one suggests a carnivore origin due to the presence of abundant bone fragments, but most of the coprolite morphotypes were produced by either omnivores or herbivores. Analysis of inclusions of the coprolites revealed plant remains, such as stems and isolated vascular elements, and papillate and non-papillate cuticles. Two seed types have been recognized within two coprolite morphotypes. The first one has lythraceous affinity, being comparable to members of a morphological complex within Nesaeeae. The second seed type, which shows adaptations for water dispersal, belongs to Ranunculaceae, and is described as Eocaltha zoophila gen. et sp. nov. Although Eocaltha evolved a mechanism for abiotic dispersal, the seeds were apparently occasionally ingested by a vertebrate. The presence of seeds of E. zoophila in a coprolite suggests that the organism that produced it was looking for a high-quality diet perhaps represented by the seeds, and served indirectly as a biotic seed dispersal agent. The combination of abiotic and biotic dispersal syndromes, plus the fact that the seeds appear to be scarified suggest a case of diffuse coevolution. Interactions, as herbivory, during the Cretaceous prompted biotic dispersal of angiosperm diaspores as revealed by the presence of seeds of E, zooyhila. (C) 1998 Elsevier Science B.V. All rights reserved

Timing and causes of forest fire at the K–Pg boundary

We report K–Pg-age deposits in Baja California, Mexico, consisting of terrestrial and shallow-marine materials re-sedimented onto the continental slope, including corals, gastropods, bivalves, shocked quartz grains, an andesitic tuff with a SHRIMP U–Pb age (66.12 ± 0.65 Ma) indistinguishable from that of the K–Pg boundary, and charred tree trunks. The overlying mudstones show an iridium anomaly and fungal and fern spores spikes. We interpret these heterogeneous deposits as a direct result of the Chicxulub impact and a mega-tsunami in response to seismically-induced landsliding. The tsunami backwash carried the megaflora offshore in high-density flows, remobilizing shallow-marine fauna and sediment en route. Charring of the trees at temperatures up to > 1000 °C took place in the interval between impact and arrival of the tsunami, which on the basis of seismic velocities and historic analogues amounted to only tens of minutes at most. This constrains the timing and causes of fires and the minimum distance from the impact site over which fires may be ignited