Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

F.D. Holland, Jr


A well-preserved fauna from the Tyler Formation was studied in cores from 34 wells drilled for oil in Billings, Golden Valley, McKenzie, Slope, and Stark Counties. Forty-four species of invertebrates, eleven form-species of conodonts, at least three types of fish, and at least four genera of plants· are present. Invertebrate species include 1 bryozoan, 15 brachiopods, 14 bivalves, 2 gastropods, 2 cephalopods, 2 annelids, 2 branchiopoda, at least 2 ostracodes, 2 malacostracans, 1 insect, and 1 echinoderm. Chordates include 1 "nonmarine" shark, at least 1 paleoniscoid fish, and 1 possible crossopterygian fish. A new genus and species of eocarid malacostracan is described and represents the first report of the family Tealliocarididae from. North .America and the first Pennsylvanian genus recognized in the family.

The Tyler Formation was determined to be of Pennsylvanian (Morrowan, Atokan, and Deamoinesian) age based on the previously reported ranges of contained taxa. Four faunal communities are recognized in the Tyler and names proposed for them are based on their dominal fos sil constituents. Progressing from the shoreline to deeper water and open marine conditions are the Anthraconaia-Cy~icus (Lioestheria) Community, the Lingula Community, the Aviculopecten Community, and the Eolissochonetes Community. Evidence of a fifth community (nearest to the shoreline) is suggested by sections of cores with terrestrial plant fragments in them.

The dark gray to black shales and the limestones of the Tyler are generally fossiliferous. Preservation of delicate structures, growth series, and other evidence indicates that most of the Tyler invertebrates were little transported, and that the asse111blages of abundant organisms probably represent parts of biocoenoses. Deposi tion of the Tyler in a deltaic complex is tentacively suggested by the communities observed.

Grenda Plates (1952602 kB)

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