BURROWS OF THE LUNGFISH GNATHORHIZA WITHIN PALEOSOLS OF THE LOWER PERMIAN (WOLFCAMPIAN) OF EASTERN KANSAS: A UNIQUE PALEOENVIRONMENTAL SETTING AND JUSTIFICATION FOR A NEW ICHNOTAXON

Burrows of the lungfish Gnathorhiza occur in the fine-grained deposits of the Blue Spring Shale Member, Matfield Formation, Lower Permian (Wolfcampian), near Manhattan, Kansas. Hundreds of thousands of lungfish burrows occur in three levels, with the vast majority confined to a single level several meters below the Florence Limestone Member of the Barneston Limestone (Chase Group). The burrows are in clayey siltstone that contains platy to subblocky peds, burrow mottles, and downward and laterally branching, thin rhizoliths. The uppermost soil horizon in each level is gleyed, indicating that there was standing water for part of the year. The paleoecosystems represented by these units formed in low-lying terrestrial and freshwater paleolandscapes with subtle paleotopography where imperfectly drained paleosols equivalent to present-day aquepts formed. These paleosols are part of a pedogenic sequence recording an upward trend from semi-arid to monsoonal climates.

The burrows are elliptical in cross-section and range in width from 7 to 53 mm (long axis) and 7 to 19 mm (short axis). They are vertical and range from 100 to 300 mm in length. Burrow bases vary from rounded with diameters equal to or slightly wider than the burrow to expanded bulbous to strongly flask-shaped terminations up to three times the burrow width. Burrow densities ranged from 184 to 402 burrows per square meter. At one locality, approximately 70 percent of the burrows contained articulated and disarticulated skeletons. Burrow densities, burrow and rhizolith cross-cutting relations, and mottling patterns indicate that the burrowing activity occurred over many seasons and was part of the pedogenic process that altered the original deposits. These burrows are very similar to aestivation burrows constructed by Devonian, Carboniferous, Permian, and extant African lungfish. The architectural and surficial burrow morphologies are consistent enough to warrant the formation of a new ichnotaxon that represents this type of behavior.