A new Early Cretaceous lizard species from Brazil, and the phylogenetic position of the oldest known South American squamates

摘要

Squamates first appeared in South America during the Early Cretaceous. The oldest confirmed record is from the Lower Cretaceous Crato Formation of north-eastern Brazil. Unfortunately, our knowledge of squamate diversity in the Mesozoic of South America, and Gondwana as a whole, is extremely limited. This poses a barrier to our understanding of the origin and radiation of early squamates on this continent. Here we describe a new species - Calanguban alamoi gen. et sp. nov. - from the Crato Formation which shows morphological adaptations for a scansorial lifestyle. We also provide a phylogenetic analysis inclusive of this species and of the oldest known lizard species in South America, Tijubina pontei and Olindalacerta brasilensis. In an attempt to identify the phylogenetic position of these taxa we used two of the most recent morphological datasets for the phylogeny of the Squamata that contain the largest fossil taxon sampling available. Calanguban is a scleroglossan lizard, with scincomorph affinities, making it the oldest non-iguanian squamate from South America, and likely the oldest scincomorph lizard from that continent. Tijubina, and possibly Olindalacerta, fall within, or are closely allied to, polyglyphanodontids, a clade traditionally classified amongst teiioids with a wide distribution restricted to the northern hemisphere. Calanguban and the other Crato Formation species provide important clues about Gondwanan scincomorph evolution and also raise new questions on the origin of the first squamates in South America.