title: Leaves of Cercocarpus mixteca n. sp. (Rosaceae) from Oligocene sediments, near Tepexi de Rodríguez, Puebla.
abstract: A new species of Cercocarpus, Cercocarpus mixteca Velasco de León & Cevallos-Ferriz, is described based on leaf impressions from the Los Ahuehuetes locality, near Tepexi de Rodríguez, Puebla, Mexico. The lamina is obovate, 1.3cm in length by 0.5cm in width, has a serrate margin in its distal fourth, craspedodromous venation with a single straight mid-vein and two to four pairs of secondary ones, and areols that tend to be quadrangular in shape. A phenetic analysis of the agglomerative, non-hierarchical type, with mean linkage, is applied using 22 OTUs and 34 character states. The morphological characters observed on the leaves of the new fossil plants support the recognition of a new taxon closely related to the extant Cercocarpus paucidentatus growing naturally in northern Mexico. Its microphyll size corresponds with the temperate to xeric climate postulated for the Los Ahuehuetes locality; this further suggests that some taxa, like Cercocarpus, have a long history in low latitude North America. In this particular case, the extant Cercocarpus fothergilloides and Cercocarpus macrophyllus could, as they were able to colonise new humid and xeric areas, represent descendants of C. mixteca.
authors.affiliation: Facultad de Estudios Superiores Zaragoza, UNAM, Batallón 5 de Mayo esq. Prolongación Plutarco Elias Calles, Col. Ejercito de Oriente, Del. Iztapalapa, 09230, México D.F., Mexico
authors.lastname: Velasco de León P
authors.initials: SR
authors.lastname: Cevallos-Ferriz