A wide-gauge, large-mammal trackway from the upper Paleocene of Alberta, Canada

Abstract

A very rare 11.2 m long wide-gauge trackway, made by an as yet undetermined large mammal, is described from the Lacombe Member (Late Paleocene) of the Paskapoo Formation (Paleocene). The exposure of the trackway was connected with the record-setting floods of 2013 in the province of Alberta as the tracks were exposed close to the base of the Brazeau Dam in west-central Alberta. The tracks are preserved on the top surface of a siltstone, but extensive erosion of the tracks resulted in the removal of details such as claw and digit traces, as well as any heel or palm impressions. The tracks are all circular to subcircular in outline, and it is not possible to determine the direction of travel of the trackmaker. Sequences of distinct pairings of adjacent tracks on both the left and right set of traces are present, and these are interpreted to represent manus-pes couples. The tracks do not show any overprinting. The mean pace angulations of the two best preserved sections range from 113° to 125°, while their mean stride lengths range from 95 to 96 cm. The lack of any distinctive anatomical details being preserved in the tracks prevents a precise identification of the trackmaker, but the sizes, shapes, and age of the tracks suggest that they could have been made by a large pantodont.