INIOPTERYGIANS FROM SCOTLAND: NEW SPECIES FROM THE BEARSDEN BIOTA

Iniopterygians are an enigmatic, and thus far solely Carboniferous, clade of Paleozoic chondrichthyans. Skeletal remains are known only from North America, but here we report the first discovery of examples from the Mississippian (Surpukhovian) of Scotland. These originate from lateral equivalents of the Manse Burn Formation and Bearsden biota, known for the exceptional preservation of its fossil sharks. In fact, equivalent horizons of the Manse Burn formation has been known from Ayrshire and Lanarkshire since the late 1800s, yielding scattered finds of fish remains, some of which have been locally abundant. However, the richness of the fish fauna has only become apparent since the early 1980s, and similarities with the fauna of the slightly younger Bear Gulch locality of Montana are now increasingly clear. Discovered by a dedicated amateur paleontologist, Mr. Patrick Gavin of Faifley, Clydebank, who has worked closely with staffs of the Hunterian Museum, University of Glasgow, and the National Museum of Scotland, Edinburgh, these iniopterygians exemplify the newly discovered diversity of the Bearsden chondrichthyans. One of the two species is known from only a single, poorly preserved specimen, but this includes a characteristic pectoral ‘rasp’ and assortment of associated denticles. The other species is in better condition, although the skeleton is disarticulated. Major cartilages are flattened but retain some of their former three-dimensionality. Jaws and braincases are well preserved, as well as cartilages interpreted as parts of the pectoral and visceral skeleton. There are no persistent cranial fissures present in this iniopterygian; the dentition, although formed into toothplates, is unlike any examples known from fossil holocephalans. Although generally linked with the early members of the chimaeroid clade, differences in cranial skeletal anatomy suggest convergence rather than common origin of their respective holocephalan conditions.