Variations in salamander trackways resulting from substrate differences

As part of a study of vertebrate trackways in the cross-stratified Coconino Sandstone (Permian) of northern Arizona, trackways made by living salamanders under different substrate conditions were compared. The sample of 230 trackways of the western newt, Taricha torosa, included ten combinations of the following substrate characteristics: 1) sediment: muddy or of fine sand; 2) attitude: level or sloped (25 degrees); 3) moisture content: dry, damp, wet, or submerged. Trackways in wet mud produced the most accurate representation of the number of toes per foot and the arrangement of toes. All other conditions studied yielded a reduced average number of toes per foot, and a large sample was needed before the data had the potential to indicate the true structure of the trackmaker's feet. Trackways made on sloped, submerged mud or sand, sloped, dry sand, and sloped, damp sand rarely included the full complement of toes. The positions and orientations of the toe marks were distorted if the animals were walking underwater or on sloped, damp sand. Trackways on the slopes of cross-stratified deposits make reliable identification of the trackmaking animals exceptionally difficult.