Redescription of tetrapod trackways from the Mississippian Mabou Group, Lepreau Falls, New Brunswick, Canada

Abstract

Red-bed strata exposed at Lepreau Falls, southern New Brunswick, were originally interpreted as belonging to the Triassic Lepreau Formation. Poorly preserved tetrapod trackways within the strata were previously assigned to two ichnospecies; one to a new Triassic ichnospecies, Isocampe lepreauense Sarjeant and Stringer, and the other to Rhynchosauroides cf. R. franconicus (Heller). Both were attributed to reptiles. Subsequent mapping of the rocks and reassignment of the exposed strata at Lepreau Falls to the Mississippian Mabou Group prompted our re-examination of the trackway fossils. Isocampe lepreauense was described from a specimen block preserving three trackways and the original description was based on erroneous interpretation of extramorphological digit drags. Rhynchosauroides cf. R. franconicus was a tentative assignment in a letter accompanying a cast in the New Brunswick Museum, but was never formally published. We redescribe and re-interpret all the trackways as gait variations produced by temnospondyls, and most closely resemble the Carboniferous ichnotaxon Matthewichnus. rÉsUMÉ Au départ, on croyait que les strates de couches rouges exposées aux chutes Lepreau, dans le sud du NouveauBrunswick, appartenaient à la formation de Lepreau, qui était datée du Trias. Des empreintes de tétrapode mal conservées présentes dans les strates avaient d'abord été attribuées à deux ichnoespèces, soit à une nouvelle ichnoespèce du Trias, Isocampe lepreauense (Sarjeant et Stringer), et à Rhynchosauroides cf. R. franconicus (Heller). Les deux étaient attribuées à des reptiles. Une cartographie ultérieure des roches et la réattribution au groupe Mabou du Mississippien des strates exposées des chutes Lepreau nous ont amenés à réexaminer les fossiles. La description d'Isocampe lepreauense a été effectuée au moyen d'un bloc de spécimen contenant trois empreintes, tandis que la description d' origine se fondait sur une interprétation erronée d' empreintes extramorphologiques. Rhynchosauroides cf. R. franconicus a été attribué de façon provisoire dans une lettre accompagnant une contre-empreinte conservée au Musée du Nouveau-Brunswick, qui n'a toutefois jamais été officiellement publiée. (Sarjeant and Stringer 1978). The authors concluded that the track-maker was a small lepidosaur, lacertoid, or rhynchosauroid, based in part on the interpreted age of the rocks. A second trackway discovery from the same location several years later was not described formally in the literature, but notes that accompanied the cast reposited in the New Brunswick Museum tentatively identified it as Rhynchosauroides cf. R. franconicus (Heller 1956).Subsequent research on the complex geology of the Lepreau Falls area (Park et al. 1994;Park 2001), including palynology (NBM Palaeontology file NBMG 3044; Dolby 1997; Utting 1987) and field mapping (Barr and White 2005) has resulted in reassignment of the trackwaybearing rocks to the Mississippian Mabou Group (Fig. 1). MAteriAls AnD MetHoDs M.A. McNally discovered the first trackways at LepreauFalls i...

Sedimentology and chemostratigraphy of Carboniferous red beds in the western Moncton Basin, Sussex area, New Brunswick, Canada: possible evidence for a middle Mabou Group unconformity

“…Despite the ear-lier names noted above, for stability of nomenclature most authors (e.g., Wilson et al 2006;Force and Barr 2006;St. Pe-ter and Johnson 2009;Utting et al 2010;Murphy et al 2011;Allen et al 2013;Waldron et al 2013;Hayward et al 2014;Holt et al 2014;Stimson et al 2016;Craggs et al 2017) in-clude these and laterally equivalent red bed units sitting on Windsor Group strata in the Mabou Group of Belt (1964Belt ( , 1965. Overlying plant-bearing grey sandstone, mudstone, and thin coal beds are assigned to the Boss Point Formation (Cumberland Group, Pennsylvanian).…”

The disadvantage of derivation: conserved systematic flaws in primary data have repeatedly biased the phylogenetic inference of Temnospondyli (Tetrapoda, Amphibia)

“…Finally, character 197 of Schoch (2013) referred to manual digit count and was coded for 41 of the 72 taxa sampled by Schoch (2013). Temnospondyls have long been assumed to share a condition of four manual digits (197–1; e.g., Warren and Snell, 1991; Dilkes, 2015; Konietzko-Meier et al, 2020), and this is a common rationale for associating tetradactyl handprints with temnospondyls (e.g., Stimson et al, 2012, 2016; Marsicano et al, 2014; Bird et al, 2020; Cisneros et al, 2020; Mujal and Schoch, 2020). Predictably, every previously coded temnospondyl other than Metoposaurus was coded for a tetradactyl manus; Metoposaurus was only correctly coded as pentadactyl because of personal communication to Schoch (Konietzko-Meier et al, 2020:1153).…”

A Batrachichnus salamandroides trackway from the Minto Formation of central New Brunswick, Canada: implications for alternative trackmaker interpretations

“…Manus and pes reconstructions, as well as skeletal reconstructions (Carroll 1967(Carroll , 1968Holmes et al 1998;Carroll and Gaskill 1978;, were used to obtain glenoacetabular distance measurements; published images of fossil specimens were also used where available. Following the work of Stimson et al (2012Stimson et al ( , 2016b, skeletal reconstructions of temnospondyl and "microsaur" candidates were used as models to estimate the length of the potential cranial and postcranial skeletons of the tracemaker of NBMG 21591. Measurements of the skull (tip of the premaxilla to the base of the skull), presacral vertebral series (the cervical vertebrae to the base of the pelvic girdle), and caudal vertebral series of each tetrapod were recorded and calculated as percentages of the respective glenoacetabular distance (GAD).…”

“…Following the model of Baird (1952) and Stimson et al (2012Stimson et al ( , 2016b, the glenoacetabular distance (GAD) was measured to be 5.4 cm (Figs. 9a, b); however, given the spacing between the manus and pes impressions, this GAD measurement is equivocal.…”

“…2005;Lucas et al 2022) and elsewhere(Lucas et al 2022 and references therein). In Atlantic Canada, the stratigraphic range of Batrachichnus extends from the lowest Mississippian (lower Tournaisian age) strata of the Albert Formation in New Brunswick(Stimson et al 2018;Stimson et al 2019) and the Horton Bluff Formation in Nova Scotia(Mansky and Lucas 2013) to the lower Permian Cape John Formation at Brule, Nova Scotia.…”