Article: The Upper Jurassic diapsid Lisboasaurus estesi – a maniraptoran theropod

Lisboasaurus estesi from the Upper Jurassic of Guimarota, Portugal was first described as an anguimorph lizard. Reexamination of the holotype and referred specimens has revealed the presence of thecodont teeth and an antorbital fossa, leading to the conclusion that L. estesi represents a small archosaur and not a lizard. Features of the dentition including labio-lingually compressed crowns with unserrated carinae, waisting between the root and the crown, and expanded roots, suggest that L. estesi belonged within the troodontid dinosaur-bird clade and, less certainly, within the Avialae (Archaeopteryx plus all later birds). It may thus be the earliest avialan. A second species in the genus, L. mitrocostatus, is based on indeterminate material and is a nomen dubium restricted to the type specimen.