title: Upper Cretaceous woods from the Olmos Formation (late Campanian-early Maastrichtian), Coahuila, Mexico.
abstract: OBJECTIVE
  The Olmos Formation was part of a system of deltas that existed in the southern portion of the Western Interior of North America during the Campanian-Maastrichtian. The paleofloristic composition from the northern portions of the Epicontinental Sea is relatively well known, but less intensive exploration in the south has precluded more detailed floristic comparison across the entire latitudinal span of the Sea. The Olmos Formation flora, with more than 100 different leaf morphotypes so far recognized and several wood types, has the most diverse Cretaceous fossil plant assemblage in Mexico and represents a valuable opportunity for comparative studies. •
  
  
  METHODS
  The fossil woods here described were collected in the Coahuila State, Mexico. The samples were studied using standard thin section technique and identified by comparison with fossil and extant material. •
  
  
  RESULTS
  We described four new genera (Olmosoxylon, cf. Lauraceae; Coahuiloxylon, ?Anacardiaceae, ?Burseraceae; Muzquizoxylon, Cornaceae; and Wheeleroxylon, Malvaceae s.l.) and three xylotypes of angiosperms. •
  
  
  CONCLUSIONS
  Some of the genera present in the Olmos Formation such as Javelinoxylon and Metcalfeoxylon have been described from geologic units in the USA (San Juan Basin, New Mexico and Big Bend National Park, Texas), suggesting similarity in the taxonomic composition of the floras that inhabited southern portions of the western margin of the Campanian-Maastrichtian Epicontinental Sea. Other species, however, have only been reported for the Olmos Formation, indicating some degree of local floristic differentiation among the assemblages that inhabited the southern portion of the Western Interior.
authors: Posgrado en Ciencias de la Tierra, Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Circuito de la Investigación Científica, Del. Coyoacán 04510 México D.F. Mexico.
authors: Emilio
authors: E
authors: Estrada-Ruiz
authors: Hugo I
authors: HI
authors: Martínez-Cabrera
authors: Sergio R S
authors: SR
authors: Cevallos-Ferriz