A New Species of Pantylid ‘Microsaur’ from the Carboniferous of Nova Scotia and Implications for its Ecology

Abstract

Microsaurs' are a group of terrestrial, limbed vertebrates unearthed in North America and Europe, spanning the Late Carboniferous to the Early Permian. Once considered monophyletic, recent studies have revealed their polyphyletic nature, necessitating further investigation into the relationships within this diverse early tetrapod group. A recently discovered, near-complete 'microsaur' skull (NSM 017GF020.002) from Sydney Mines Formation of Nova Scotia fuels this inquiry. Utilizing micro-CT scanned data, I present a full description of the anatomy, investigate its phylogenetic relationship with other "microsaurs", and explore the possible ecological role and diet by comparing its dental morphology with extant reptiles. The morphological disparity of NSM 017GF020.002 with other pantylids, coupled with phylogenetic analysis results, support the recognition of a new genus and species. Its unique palatal dentition not only provide strong evidence rooting the origin of herbivory in Late Carboniferous, but also showcase considerable diversity within the family Pantylidae. Chapter 1 Introduction 1.1 A synopsis of the 'microsaurs' and the well-known Pantylus 'Microsaurs' are a group of small terrestrial, limbed vertebrates that lived in parts of North America and Europe, from the Late Carboniferous to the Early Permian. United by common features such as small size, holospondylous vertebrae, absence of an otic notch, short and feeble limbs, etc., 'microsaurs' exhibit a wide range of morphological diversity indicative of various ecological roles (Carroll and Gaskill 1978).Few decades ago, 'microsaurs' were widely considered to be members of a monophyletic group (i.e., a natural group that contains the common ancestor and all descendants), nested within the non-amniote group Lepospondyli Carroll and Baird 1968;. However, this idea has been recently challenged by new phylogenetic studies (Anderson 2001;, resurrecting a long history of taxonomic debate concerning the group.The Order Microsauria was first established by William Dawson to contain the non-nectridean, non-aï stopod lepospondyls found at the Joggins Fossil Cliffs, Nova Scotia . The placement of microsaurian specimens and their relationship to other tetrapods underwent a convoluted history, subjected to many revisions by different scholars, and for a long time, the definition of the group remained ambiguous. It was not until the 1950s that Alfred Romer published a monograph to provide a systematic review of the group and delineate a list of characteristics unique method and attempt to compare its values to those from a living reptile dataset in order to infer the diet of the animal.