Pinaceae in the Cretaceous of northern and southern Mexico: a complement to its scarce fossil record

Abstract

The diversity and richness of fossil conifers in Mexico is poorly known and its presence since the Cretaceous is sporadic, although they have been documented since the first half of last century. In Mexico part of the history of certain groups of conifers has been documented, but it has been enriched in recent years by the collection of well-preserved specimens in Cretaceous sediments in the states of Sonora and Chiapas. The fossil specimens were observed under a stereoscopic microscope and ultraviolet light. Based on observation and comparison of morphological characters affinities are established with Pinaceae. “El Chango” is located near to the Municipality of Ocozocoautla, Chiapas, and is characterized by the presence of fish, arthropods, and cephalopods and especially of plants (gymnosperms dominate on angiosperms) preserved in Aptian-Cenomanian sediments. The new material consists of two branches with leaves, a female and male cone with Pinaceae affinity, although this latter is also compared with Podocarpaceae and Cupressaceae. The “Esqueda” locality in the town of Fronteras, Sonora, is characterized mainly by the presence of footprints and dinosaur bones preserved in sediments of Late Campanian age. The material from this locality consists of two branches with leaves and a female cone of which rubber molds were extracted, with affinity to Pinaceae. This new material extends the historical and geographical information of Pinaceae, the most successful family of conifers today. Mexico plays an important role in the diversification of Pinus, as nearly 50% of its species are concentrated in the country. This fact makes it even more important to supplement the fossil record of the group, which in Mexico becomes rich from the Oligocene / Miocene (ca. 32 Ma.)