HETEROMORPH AMMONOIDS FROM THE ALBIAN AND CENOMANIAN OF TEXAS AND ADJACENT AREAS

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Abstract
Very little systematic work on the Texas Cretaceous heteromorphs was accomplished during the time that much of the taxonomy of this group was resolved in Europe. In 1928 there were only 20 known genera of heteromorphs from the entire Texas Cretaceous. This study includes descriptions of 53 species of 19 genera which occur in the Albian, Cenomanian, and lowermost Turonian of Texas and adjacent areas. Stratigraphic distribution includes one species from the Goodland-Comanche Peak, one from the Kiamichi, 15 from the Duck Creek, five from the Fort Worth, three from die Denton, four from the Weno, nine from the Pawpaw, six from the Main-street, eight from the Grayson and Del Rio, seven from the Buda and Boquillas, one from the Woodbine, and 12 from the lower and lower-middle Eagle Ford. Correlation and classification with the English Gault and younger ammonoid zones indicates that the Goodland-Comanche Peak is upper-Middle Albian and that the following younger stratigraphic units can be identified with the Upper Albian, Cenomanian, and Lower Turanian European terminology, as well. The abundant Turrilitidae fauna of the Texas rocks provides excellent examples of paedomorphosis, acceleration, and caenogensis in the evolutionary history. The Texas Albian through Early Turanian heteromorphs include one species of Hamites s. s.; three of Stomohamites; one of Lechites; one of Sciponoceras; six of Anisoceras; three of Idiohamites; five of Allocrioceras; three of Ostlingoceras, of which one is new; three of Pseudhelicoceras, two of which are new; five of Mariella; four of Plesioturrilites, one of which is new; one of Wintonia; three of Hypoturrilites, of which two are new; three of Turrilites s. s.; one of Euturrilites; four of Scaphites; four of Worthoceras; one of Otoscaphites; and one species of a new genus, Prophlycticrioceras.

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