Lungfish from the Early Pennsylvanian of Ireland and the Phylogeny of Carboniferous Dipnoi

Abstract: Jarrow Colliery at Castlecomer, County Kilkenny, Ireland, is an important historic fossil vertebrate site. Fish and early tetrapods were originally discovered there in 1864, in Pennsylvanian shales immediately above the Jarrow Coal (Coolburn Coal Formation; Langsettian regional substage = Westphalian A). Until recently the fauna had been largely neglected, partly because many of the specimens are preserved as bituminous residues with indistinct outlines, which makes their preparation and study difficult. Here we describe all the available lungfish specimens for the first time. They represent a new taxon, Sagenodus hibernicus sp. nov. , characterised by pterygoid tooth plates with up to six widely spaced radiating ridges which typically lack teeth, and a broad median furrow on the palatal surface of the parasphenoid stem. Sagenodus is the longest lived and most widely distributed Paleozoic lungfish genus. It first appears in the late Mississippian of Scotland and is last recorded in the late Lower Permian of Germany and the USA. Many species were named in the nineteenth century, but only seven are here thought to be valid. A review of the pattern of skull roofing bones of Sagenodus found that it had a single X-bone above the operculum and between the X-bone and the C-bone is a compound KLM-bone, as in Ctenodus , Tranodis and Uronemus . Phylogenetic analysis of the Dipnoi incorporating data from the present study and the recent redescription of Sagenodus from the British Carboniferous, found that the four key Carboniferous taxa were placed above all Devonian taxa in crown-ward order: Ctenodus, Uronemus, Sagenodus and Conchopoma .