A new Lower Carboniferous tetrapod locality in Iowa

Abstract

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.