Quo vadis Plesiolacerta ? Taxonomy, nomenclature and phylogenetic relationships of the large lacertid Plesiolacerta (Squamata) from the Palaeogene of Europe

Abstract The genus Plesiolacerta is a principal faunal component of Palaeogene squamate assemblages from Europe. It achieved a wide stratigraphic and geographic distribution and is known from various localities across the Eocene and Oligocene of England, France, Belgium and Germany. We provide a detailed overview of the history of discoveries of Plesiolacerta . In order to decipher the taxonomic status of Plesiolacerta , we reassess the type material of the type species of the genus, Plesiolacerta lydekkeri , which consists of three incomplete, isolated vertebrae from the upper Eocene of Hordle Cliff, England. We provide photographs of this material for the first time and clarify the lectotype and paralectotype status of these specimens. We demonstrate that Plesiolacerta lydekkeri represents a nomen dubium, hence the genus name Plesiolacerta cannot be considered as valid and it cannot be used for the various occurrences from continental Europe that have been referred to it in the past. We establish the new species Timon planeutes to accommodate cranial material from the upper Eocene and lower Oligocene of the Phosphorites du Quercy (France), which was previously referred to Plesiolacerta lydekkeri . We conduct phylogenetic analyses, which recover both the new species from Quercy and Plesiolacerta eratosthenesi from the upper Oligocene of Germany, as nested well within the extant genus Timon . Our analysis pushes back the stratigraphic range of Timon substantially, indicating a very long history for the European lacertid lineages. Timon planeutes from Quercy can be used as a calibration point for divergence date estimates of lacertids.