New embolomerous tetrapod material and a faunal overview of the Mississippian-aged Point Edward locality, Nova Scotia, Canada

Abstract

Embolomerous tetrapods, moderately-sized to large aquatic predators, form a major faunal constituent of Permo-Carboniferous tetrapod communities. Embolomeres are recognized by their distinct circular, bipartite vertebrae. Although traditionally classified as stem amniotes, the inclusion of embolomeres within the tetrapod crown group has recently been challenged. Despite the group’s phylogenetic uncertainty, embolomeres provide an important record of a long-lived tetrapod lineage, spanning “Romer’s Gap” through to the early Permian. Here, we describe embolomerous tetrapod material that was collected in 1915 by W.A. Bell (CMN 10015, herein divided into CMN 10015A, 10015B, and 10015C). The material, composed of numerous disarticulated cranial and postcranial elements, was discovered near Sydney, Nova Scotia, Canada, as ex situ beach-float pertaining to a horizon within the Mississippian-aged Point Edward Formation. Among this material, a single left lower jaw of a proterogyrinid is identified, differing from previous embolomere remains from this site identified as Pholiderpeton(?) bretonensis Romer, 1958. We also identify an anterior jaw fragment as a separate taxon from the proterogyrinid, indicating the presence of at least two embolomerous tetrapods in Bell’s collection. Other cranial and postcranial material cannot be directly associated with either jaw and are not diagnostic enough to assign to a specific taxon. Thus, the remaining material is referred to Embolomeri indet. until more information is available. Additionally, we summarize the fauna of the Point Edward locality revealing a diverse aquatic Late Mississippian ecosystem. Finally, the extensive embolomere material described here presents new data that can broadly address embolomere diversity throughout the Carboniferous.