Campanian (Late Cretaceous) Ammonites from the upper part of the Anacacho Limestone in SouthCentral Texas
Authors
William J. Kennedy
Geological Collections, Oxford University Museum of Natural History; Parks Road, University of Oxford, Oxford OX1 3PW,
William A. Cobban
70 Estes Street, Lakewood, Denver; CO 80226
Keywords:
Cretaceous, Campanian, U.S. Western Interior, Ammonites, Biostratigraphy
Abstract
The ammonite assemblage from the upper part of the Anacacho Limestone in Medina Country in south-central Texas consists of Pachydiscus (Pachydiscus) travisi (ADKINS, 1929), Pachydiscus (P.) sp., Pachydiscus (P.) streckeri (ADKINS, 1928), Hoplitoplacenticeras (H.) marroti (COQUAND, 1859), Eubostrychoceras reevesi (YOUNG, 1963), Bostrychoceras polyplocum (ROEMER, 1841), Lewyites clinensis (ADKINS, 1929), Baculites taylorensis ADKINS, 1929, and Trachyscaphites spiniger porchi (ADKINS, 1929). Several of these species are also found in the Pecan Gap Chalk in central and northeastern Texas and in the basal part of the Demopolis Formation in Mississippi and Alabama. The fauna is probably contemporaneous with the Baculites asperiformis zone in the U.S. Western Interior, which lies in the lower part of the middle Campanian in the sense of the Western Interior threefold division of the Campanian. In terms of the European twofold division of the Campanian the fauna lies in the lower part of the upper Campanian.
