Diverse tetrapod trackways in the Lower Pennsylvanian Tynemouth Creek Formation, near St. Martins, southern New Brunswick, Canada

Newly discovered tetrapod trackways are reported from eight sites in the Lower Pennsylvanian Tynemouth Creek Formation of southern New Brunswick, Canada. By far the most abundant and well-preserved tracks comprise pentadactyl footprints of medium size (32–53 mm long) with slender digits and a narrow splay (mostly < 55°). Digit lengths typically approximate a phalangeal formula of 23453 (manus) and 23454 (pes), but this may vary due to extramorphology. These tracks are referred to Pseudobradypus and they are attributed to early amniotes. A second type of track (rare) comprises very small (5–8 mm long) tetradactyl manus, and incompletely preserved pedes. Referred to Batrachichnus, these are attributed to temnospondyl amphibians. A third type (also rare) comprises small pentadactyl pedes (20–25 mm long) showing stubby, widely splayed (152°) digits with a terminal bulge. Manus are probably pentadactyl (preservation incomplete) with a narrower digit splay. These footprints, classified as Baropezia, are attributed to anthracosaurs. Facies analysis at the most prolific site (179 footprints documented) suggests that the tetrapods lived amongst small alethopterid trees colonizing the abandoned floor of a seasonally active fixed-channel river and a similar dryland context is probable for the seven other sites. The dominance of amniotes in these dryland alluvial facies contrasts markedly with coeval wetland facies in the nearby Joggins Formation, where skeletal and trackway assemblages are amphibian-dominated. This may imply that amniotes were better adapted to seasonally dry settings and sheds new light on the community ecology of tetrapods during a key evolutionary phase.