TETRAPOD FOOTPRINTS FROM NOVA SCOTIA: THE ROSETTA STONE FOR CARBONIFEROUS TETRAPOD ICHNOLOGY

The fossil record of tetrapod footprints from Nova Scotia is the most stratigraphically complete record known for the Carboniferous. Discovered in 1841, it encompasses three well sampled intervals and least two more less studied horizons and is directly overlain by a large assemblage of earliest Permian tracks. The oldest footprint assemblage, from the Tournaisian Horton Bluff Formation, is the oldest known tetrapod ichnofauna and documents a pentadactyl tetrapod fauna capable of fully terrestrial locomotion early in the Mississippian. It thus indicates a major turnover in tetrapod evolution at approximately the Devonian-Mississippian boundary, with the replacement of the ichtyostegalian chronofauna by the reptiliomorph/anthracosaur chronofauna. The late Visean-Namurian West Bay Formation yields an ichnofauna dominated by anthracosaur, captorhinomorph and temnospondyl tracks and thus well represents the classic mid-Carboniferous (Visean-Namurian) tetrapod chronofauna known from body fossils. The early Westphalian Joggins locality is the most diverse Carboniferous ichnofauna in Nova Scotia and was the focus of early historic studies. It includes numerous temnospondyl tracks (Batrachichnus), at least three types of captorhinomorph tracks (Notolacerta, Pseudobradypus, “Hylopus”) and numerous anthracosaur/reptiliomorph (“Baropezia”) tracks. The age equivalent (Westphalian A) Parrsboro Formation yields the same ichnofauna, as do less well sampled, younger Westphalian sites (Abercrombie, Wallace River). Footprints from the Westphalian-Stephanian boundary in the Sydney Basin document the lowest occurrences of Dimetropus and Limnopus, and thus signal the appearance of the edaphosaurid chronofauna. Earliest Permian footprints from Brule document a classic red-bed ichnofauna well known from the Wolfcampian of the American Southwest and the upper part of the European Rotliegendes. The Brule ichnofauna includes Batrachichnus, Limnopus, Amphisauropus, Varanopus, Dromopus and Dimetropus. The Nova Scotian track record thus documents major junctures in tetrapod evolution at the bases of the Mississippian, Westphalian and Stephanian and both adds to and reinforces the body fossil record of Carboniferous tetrapod evolution.