Comment and Reply on "Fossil vertebrate footprints in the Coconino Sandstone (Permian) of northern Arizona: Evidence for underwater origin"

Abstract

Brand and Tang (1991) proposed that certain unusual vertebrate trackways point to subaqueous deposition for at least part of the Coconino Sandstone. They supported their conclusions by demonstrating that western newts produce similar trackway configurations in aquarium experiments. While it is encouraging to see vertebrate ichnology play such a prominent role in fundamental questions concerning paleoenvironmental analysis, caution must be exercised when using track ways for radical reinterpretation of long-standing hypotheses (Lockley, 1991). As reviewed by Walker and Middleton (1979), several authors suggested a subaqueous origin for the Jurassic Navajo Sandstone, traditionally regarded as a classic eolian deposit. The presence of tracks, fossil wood, and root zones was subsequently used to argue convincingly for the original interpretation of an eolian origin (Stokes, 1978). Loope (1984) presented similar evidence to argue for an eolian, not subaqueous, origin for the Permian Cedar Mesa Sandstone in eastern Utah. The interpretations of Brand and Tang therefore use vertebrate tracks to revive a controversial debate. The question becomes, Can the presence of footprints in a particular facies be used to suggest a subaerial origin while unusual trackway configurations in the same track assemblages are used to argue for subaqueous deposition? While Brand and Tang are to be congratulated for a thoroughexperimental study, which presents more Coconino track data than have appeared at any time since the inaugural studies of Gilmore (1926, 1927), several points warrant further comment. The majority of trackways in question can be assigned to the ichnogenus Laoporus, which has usually been attributed to some type of synapsid (see Baird in Spamer, 1984; McKeever, 1991). Moreover, such