Maclura (Moraceae) wood from the Miocene of the Baja California Peninsula, Mexico: Fossil and biogeographic history of its closer allies

A fossil wood with moraceous affinity from the Early Miocene sediments from El Cien Formation of the Baja California Peninsula is described. Wood anatomical characters such as long crystalliferous parenchyma strands, axial parenchyma distribution and ray type suggest its relationship with Maclura. The anatomical characteristics of Maclura martinezii Martínez-Cabrera et Cevallos-Ferriz relate it particularly to M. cochinchinensis (Loureiro) Corner (South East Asia) and M. pomifera (Raf.) C.K. Schneid. (Eastern North America). Based on the proposed phylogenetic and biogeographic hypotheses offered by other authors we review the historical distributional pattern of Maclura and its presumed allies (Alleanthus, Broussonetia and Morus). The evidence proffered by the fossil record and biogeographical analyses agree in rooting the origin of the clade somewhere in Laurasia. However, there is no unequivocal evidence with regard to the exact place of origin since older records occur in west Laurasia, but the biogeographical analyses indicate a South East Asia origin.