First evidence of an intercalar bone in the braincase of a€?palaeonisciforma€? actinopterygians, with a virtual reconstruction of a new braincase of Lawrenciella Poplin, 1984 from the Carboniferous of Oklahoma

摘要

We describe here a new Lawrenciella Poplin, 1984 specimen from the Upper Carboniferous (Missourian, Pennsylvanian) from Oklahoma, USA. This specimen is three dimensionnally preserved in a phosphatic nodule. It was scanned by X-Ray microtomography. The neurocranium shows some morphological differences from Lawrenciella schaefferi Poplin, 1984, which might represent individual variability. The parasphenoid and a pair of intercalar bones are associated with the braincase. The presence of intercalars as an anterior extension covering the otico-occipital fissure have not been yet documented in a€?paleonisciformsa€? and may have a phylogenetic signal. A discussion about the evolutionary role of such intercalars in the closure of the otico-occipital fissure in modern actinopterygians is provided.