A neotype and reassessment of phylogenetic relationships of the fossil lizard Calanguban alamoi from the Crato Formation (Early Cretaceous, Brazil)

Understanding the phylogenetic and biogeographical origin of squamate faunas in the Global South has remained a challenge for decades, given the paucity of their Mesozoic fossil record in Gondwana. Among the latter, many species still have ambiguous phylogenetic affinities, with notable examples including three species from the Early Cretaceous (Aptian) Crato Formation, Northeast Brazil. These lizards were, until now, known only from their holotype, which preserved only a limited number of phylogenetically informative characters. Additionally, the holotype of one of these, Calanguban alamoi (MN 7234-V), was lost in the fire that destroyed most of the collections of the Museu Nacional/UFRJ of Brazil in 2018. Here, we present the description of a new fossil lizard specimen, which we designate as a neotype for C. alamoi, that preserves more anatomical data than the lost holotype (including cranial elements; cervical, presacral, and caudal vertebrae; pelvic girdle; forelimbs; and hindlimbs). The updated information on C. alamoi was included in a phylogenetic data matrix comprising morphological and molecular data for all major groups of squamates. The results using both maximum parsimony and Bayesian inference indicate that C. alamoi is a borioteiioid lizard–a clade that, until recently, was believed to be constrained to the Mesozoic of Laurasia. Our findings, along with recent ones, support a much wider distribution of borioteiioids than previously thought, including at least three different localities in Gondwana. The Early Cretaceous age of C. alamoi and other Gondwana borioteiioids raise the possibility of a Gondwanan origin of the group with subsequent northbound migration into Laurasia. It also highlights how South American squamate faunas were well interconnected with the rest of Gondwana and Laurasia during the Early Cretaceous, in stark contrast to its highly endemic extant squamate fauna.