ABSTRACT

A paleoecological study of the late Eocene (Bartonian) marine strata of the Moodys Branch Formation at Techeva Creek, Yazoo County, Mississippi, describes a vertebrate fauna of 21 species, at least 15 not previously recorded from the Jackson Group of this state. The fauna consists of 9 sharks, 3 rays, 8 teleosts and a small cetacean, the Eocene whale, Zygorhiza kochii. The four most common vertebrate taxa are Negaprion gibbesi (lemon shark), Galeocerdo clarkensis (tiger shark), Myliobatis sp. (eagle ray), and Jefitchia claybornesis (croaker). Vertebrate paleoecology places this fauna within a shallow, nearshore setting; open, deeper marine conditions south of the late Eocene shoreline are suggested by the rarer occurrences of more open water vertebrates, such as Carcharodon, Isurus, Scyliorhinus and Galeorhinus. Associated invertebrates, dominated by a low diversity clam assemblage (especially Glycymeris idonea), Ophimorpha burrows, and beds of the echinoid, Periarchus lyelli, indicate a shallow, high energy marine environment in the 1 to 10 m depth range, typically shallower (5 m or less).

Previously described estuarine and nearshore vertebrate faunas of the late Eocene in the Gulf Coast trend toward a lower diversity of taxa when compared to deeper shelf or more offshore settings. The very nearshore setting of Techeva Creek suggests that further vertebrate discoveries, even of terrestrial mammals, may be possible.