Nature 333, 768 - 770 (23 June 1988); doi:10.1038/333768a0

A new Lower Carboniferous tetrapod locality in Iowa

John R. Bolt^*, R. M. McKay^†, B. J. Witzke^† & M. P. McAdams^‡

^*Department of Geology, Field Museum of Natural History, Roosevelt Road and Lake Shore Drive, Chicago, Illinois 60605, USA
^†Geological Survey Bureau, Iowa Department of Natural Resources, Iowa City, Iowa 52242, USA
^‡William Penn College, Oskaloosa, Iowa 52577, USA

The earliest tetrapods known are from two or three Upper Devonian¹⁻³ and some 20 Lower Carboniferous localities in Scotland4 and North America⁵⁻⁸. Most sites yield few and fragmentary specimens; well-preserved and even partially articulated material is exceedingly rare. This report discusses a middle Lower Carboniferous site rich in amphibian and fish remains discovered near Delta, south-east Iowa, and represents the first Lower Carboniferous tetrapod locality found in mid-continental North America. The bones occur within collapse-structures or depressions, and appear to represent a fresh- or brackish-water pond fauna. The Delta site contains the oldest well-preserved tetrapod fauna in North America, and one of the oldest in the world. Several hundred tetrapod fossils have been collected to date, with excavation somewhat more than half completed. Specimens range from isolated bones to articulated, nearly complete skeletons of at least two apparently new amphibian species. This material will make an important contribution to knowledge of the mor-phology and interrelationships of early tetrapods.

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