PALEOBIOLOGICAL IMPLICATIONS OF CAMPANIAN COPROLITES

Vertebrate coprolites (153 samples) in association with vertebrate and plant remains in the Upper Cretaceous (Campanian) sediments of the Ce rro del Pueblo Formation, in southeastern Coahuila, Mexico, represent at least ten morphotypes, ranging from ca. 1 cm to 3 cm. At least one suggests a carnivore origin due to the presence of abundant bone fragm ents, but most of the coprolite morphotypes were produced by either om nivores or herbivores. Analysis of inclusions of the coprolites reveal ed plant remains, such as stems and isolated vascular elements, and pa pillate and non-papillate cuticles. Two seed types have been recognize d within two coprolite morphotypes. The first one has lythraceous affi nity, being comparable to members of a morphological complex within Ne saeeae. The second seed type, which shows adaptations for water disper sal, belongs to Ranunculaceae, and is described as Eocaltha zoophila g en. et sp. nov. Although Eocaltha evolved a mechanism for abiotic disp ersal, the seeds were apparently occasionally ingested by a vertebrate . The presence of seeds of E. zoophila in a coprolite suggests that th e organism that produced it was looking for a high-quality diet perhap s represented by the seeds, and served indirectly as a biotic seed dis persal agent. The combination of abiotic and biotic dispersal syndrome s, plus the fact that the seeds appear to be scarified suggest a case of diffuse coevolution. Interactions, as herbivory, during the Cretace ous prompted biotic dispersal of angiosperm diaspores as revealed by t he presence of seeds of E, zooyhila. (C) 1998 Elsevier Science B.V. Al l rights reserved.