In 1930, the octogenarian Aldrich named new ichnogenera of fossil footprints that were discovered in a University of Alabama coalmine in Walker County, Alabama—his only venture into the field of ichnology. Although his descriptions were brief, the well-reproduced photographic plates brought this work to renewed attention when similar trackways were discovered in 1999 at the nearby Union Chapel Mine (now the Stephen C. Minkin Paleozoic Footprint Site).