Redescription, taxonomy and phylogenetic relationships of Boavus Marsh, 1871 (Serpentes: Booidea) from the early–middle Eocene of the USA

Abstract

The extinct fossil snake Boavus occurs in early–middle Eocene localities in the United States. Four species are currently recognized, but until now, no formal phylogenetic analyses have been conducted to test its relationships within snakes. Here, we provide an osteological redescription and systematic revision of the genus, accompanied by phylogenetic analyses using multiple methods. Based on new morphological information obtained through first-hand observation and published descriptions, differences between Boavus occidentalis, B. agilis and B. affinis can be ascribed to normal intracolumnar vertebral variation, making the latter two junior synonyms of the first species. Our phylogenetic analyses retrieved Boavus within crown-Booidea as an early booid but outside of Boidae. A morphological and molecular analysis of booids, with dense taxon sampling including fossil and living forms, results in a new booid phylogeny. Boavus, along with other fossil booids from Europe (Eoconstrictor, Messelophis, Rieppelophis, Rageryx), suggests that crown-Booidea likely diverged earlier than estimated by some molecular studies (∼45.4 Ma).

Keywords:

• Squamata
• Serpentes
• Booidea
• Boidae
• Bridger Formation
• Grizzly Buttes

Acknowledgements

We thank Krister T. Smith (Senckenberg Research Institute) for sharing photos and data about the fossil snakes from Messel; Jacques A. Gauthier (YPM) for kindly sharing some CT-scan reconstructions of extant snakes and for allowing access to the YPM collection; Daniel Brinkman (YPM) and Amanda Millhouse (USNM) for assistance in the collections of their respective museums; and Vanessha Rhue (LACM) for providing access to the holotype of Boavus affinis. We thank Gabriel Ferreira (SHEP Tübingen) and Giovane M. Cidade (UFSCar) for helping with comments and sharing ideas about the taxonomic and nomenclatural status of the species, and Guilherme Hermanson and Bruna Farina (USP) for sharing osteological data and laboratorial assistance. We also extend our gratitude to João Tonini (Harvard University) for sharing the gene boundary data of Tonini et al. (2016), and the Willi Henning society for the free distribution of the software TNT. We thank Dr G. Georgalis, an anonymous reviewer, and the editors for several contributions concerning overlooked literature, and anatomical and systematic comments that substantially improved this study.

Supplemental material

Supplemental material for this article can be accessed here: https://doi.org/10.1080/14772019.2022.2068386.

Associate editor: Richard Butler

Additional information

Funding

This research was funded by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES Demanda Social to SO), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP no. 2017/00845-1 and 2019/11166-3 to SO) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq Process no. 301014/2018-3 to ASH), and by the Australian Research Council (DP200102328 to ML).