Estrada-Ruiz, Emilio , Cevallos-Ferriz, Sergio .
Upper Cretaceous aquatic plants from the Olmos and Cerro del Pueblo Formations, Mexico.
In northern Mexico, in the state of Coahuila, two Upper Cretaceous formations have yielded diverse assemblages of plants. From the Cerro del Pueblo (late Campanian) Formation permineralized fruits representing members of Musaceae and cf. Strelitziaceae, infructescences of Alismatales and Phytolaccaceae, seeds of Ranunculaceae and Lythraceae contained in vertebrate coprolites, and a Rhamnaceae flower have been documented. Here, a fruit characterized by having in its proximal zone two large, simple spines and a peduncle between them, as well as a broken stylar projection in its distal zone closely resembles fruits of Ceratophyllum (Ceratophyllaceae). A second type of seed is small, pyramidal in shape and has rounded edges, with a concave ventral surface containing a rectangular valve located toward its center. These characters resemble seeds of Decodon (Lythraceae), and their presence suggests wider geographical distribution and larger time record for this taxon. In a coal mine of the Olmos Formation (late Campanian-early Maastrichtian) a plant with entire margined leaves, with primary actinodromous venation composed of 12 well marked primary veins departing from the petiole at the center of the orbiculate lamina resembles an aquatic plant (Nymphaeales or Proteales). As the primary veins reach the margin they bifurcate forming secondary veins, and from either the primary or the secondary veins the tertiary ones developed with an alternate percurrent pattern. The higher order veins, fourth rank, form a reticulum with 5-6 sided polygons. These three new records reinforce the idea of having in Mexico by the Late Cretaceous a diverse aquatic flora.
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1 - Instituto de Geología, Universidad Nacional Autónoma de México, Posgrado en Ciencias de la Tierra, Ciudad Universitaria, Del. Coyoacán, Mexico, D.F., 04510, Mexico
2 - Department of Palentology, Instituto De Geología, Mexico, 01900, Mexico
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Erie/Hilton
Date: Tuesday, July 10th, 2007
Time: 10:30 AM