Resolving the Obscure Identity of Steironotus arenarius Tschudi, 1845 and Tropidurus tschudii Roux, 1907 (Squamata: Tropiduridae)

Abstract. The taxonomic history of Steironotus arenarius Tschudi, 1845 is one of the most problematic among all tropidurids. The species was originally described supposedly based on four specimens collected in Peru and deposited by J.J. von Tschudi at the Musée d'Histoire Naturelle de Neuchâtel, Switzerland. However, the syntypes were not re-examined until Roux (1907: Rev. Suisse Zool. 15:293–303) performed a revision of Tschudi's Peruvian collection. Fritts (1974: Mem. San Diego Soc. Nat. Hist. 7:1–89) revised the taxonomy of Stenocercus and endorsed Roux's allocation of Steironotus arenarius in Tropidurus Wied, 1825, although he never analyzed Tschudi's types. Ortiz (1989: Bull. Soc. Neuchâtel. Sci. Nat. 112:47–64) was the first contemporary systematist to re-analyze Tschudi's specimens for his catalogue of the lizard types of the Musée d'Histoire Naturelle de Neuchâtel. His compilation attempted to clarify the number, location, and identity of the types of Steironotus arenarius found at the Musée d'Histoire Naturelle de Neuchâtel and Naturhistorisches Museum Basel. Subsequent authors overlooked or opted for not following Ortiz and endorsed the allocation of Steironotus arenarius in Tropidurus. Although Ortiz was the only one to re-analyze the types of Steironotus arenarius after Roux, he never provided full morphological descriptions or detailed comparative notes to support his taxonomic conclusions. Herein, I clarify the taxonomic history of Steironotus arenarius Tschudi, 1845 and Tropidurus tschudii Roux, 1907, and confirm that Tschudi's syntypic series is a composite of two genera, i.e., Microlophus Duméril and Bibron, 1837 and Stenocercus Duméril and Bibron, 1837. I ultimately designate a new lectotype for Steironotus arenarius Tschudi, 1845 and provide recommendations for correcting uncorroborated taxonomic arrangements, bringing stability to tropidurid taxonomy.