A Palaeogene stem crotaphytid ( Aciprion formosum ) and the phylogenetic affinities of early fossil pleurodontan iguanians

• Published in: Royal Society open science Vol. 11; no. 1; pp. 221139 - 34
• Main Author: Scarpetta, Simon G.
• Format: Journal Article
• Language: English
• Published: England The Royal Society Publishing 01.01.2024; The Royal Society
• Subjects: Bayesian analysis; Biogeography; Cretaceous; Crotaphytidae; Endangered & extinct species; Eocene; Extinction; Fossils; Hypotheses; Lizards; Morphology; Organismal and Evolutionary Biology; Palaeogene; palaeontology; Paleogene; Paleontology; Phylogenetics; Phylogeny; Pleurodonte; Skull; squamata; Statistical inference; Western Hemisphere; Wyoming; United States > US; North America; phylogenetics; squamata; Cretaceous; palaeontology; Palaeogene
• ISSN: 2054-5703; 2054-5703
• DOI: 10.1098/rsos.221139

Pleurodonta is an ancient, diverse clade of iguanian lizard distributed primarily in the Western Hemisphere. Although the clade is a frequent subject of systematic research, phylogenetic resolution among the major pleurodontan clades is elusive. That uncertainty has complicated the interpretations of many fossil pleurodontans. I describe a fossil skull of a pleurodontan lizard from the Palaeogene of Wyoming that was previously allocated to the puzzling taxon Aciprion formosum , and provide an updated morphological matrix for iguanian lizards. Phylogenetic analyses using Bayesian inference demonstrate that the fossil skull is the oldest and first definitive stem member of Crotaphytidae (collared and leopard lizards), establishing the presence of that clade in North America during the Palaeogene. I also discuss new or revised hypotheses for the relationships of several early pleurodontans. In particular, I examine potential evidence for crown-Pleurodonta in the Cretaceous of Mongolia ( Polrussia ), stem Pleurodonta in the Cretaceous of North America ( Magnuviator ) and a stem anole in the Eocene of North America ( Afairiguana ). I suggest that the placement of the fossil crotaphytid is stable to the uncertain phylogeny of Pleurodonta, but recognize the dynamic nature of fossil diagnosis and the potential for updated systematic hypotheses for the other fossils analysed here.