DOI: 10.15468/dfw4rk
title: A new species of baenid turtle from the Early Cretaceous Lakota Formation of South Dakota

description: This dataset contains the digitized treatments in Plazi based on the original journal article Joyce, Walter G., Rollot, Yann, Cifelli Correspondence, Richard L. (2020): A new species of baenid turtle from the Early Cretaceous Lakota Formation of South Dakota. Fossil Record 23 (1): 1-13, DOI: 10.5194/fr-23-1-2020, URL: http://dx.doi.org/10.5194/fr-23-1-2020Abstract. Baenidae is a clade of paracryptodiran turtles known from the late Early Cretaceous to Eocene of North America. The proposed sister-group relationship of Baenidae to Pleurosternidae, a group of turtles known from sediments dated as early as the Late Jurassic, suggests a ghost lineage that crosses the early Early Cretaceous. We here document a new species of paracryptodiran turtle, Lakotemys australodakotensis gen. and sp. nov., from the Early Cretaceous (Berriasian to Valanginian) Lakota Formation of South Dakota based on a poorly preserved skull and two partial shells. Lakotemys australodakotensis is most readily distinguished from all other named Late Jurassic to Early Cretaceous paracryptodires by having a broad, baenid-like skull with expanded triturating surfaces and a finely textured shell with a large suprapygal I that laterally contacts peripheral X and XI and an irregularly shaped vertebral V that does not lap onto neural VIII and that forms two anterolateral processes that partially separate the vertebral IV from contacting pleural IV. A phylogenetic analysis suggests that Lakotemys australodakotensis is a baenid, thereby partially closing the previously noted gap in the fossil record.1 IntroductionBaenidae is a clade of fossil paracryptodiran turtles known from the Early Cretaceous to Eocene of North America (Joyce and Lyson, 2015). Late Cretaceous to Eocene basins throughout the western United States and Alberta (e.g., Hay, 1908; Gaffney, 1972; Brinkman, 2003, 2005; Joyce and Lyson, 2015) have yielded rich fossil turtle material indicating that baenids were diverse throughout this time period and were only little affected by the K–T mass extinction event (e.g., Lyson et al., 2011, 2019). Only little is known, by contrast, about the early evolution of the group, mostly due to a lack of fossils. At present, only three unambiguous baenid fossils are known from the Early Cretaceous, in particular the holotype specimens of Arundelemys dardeni Lipka et al., 2006, Trinitichelys hiatti Gaffney, 1972, and Protobaena wyomingensis (Gilmore, 1919) from the Aptian–Albian of Maryland, Texas, and Wyoming, respectively. A broad set of mostly unfigured fragmentary remains from the Early Cretaceous of Nevada (Bonde et al., 2008), Montana (Oreska et al., 2013), Oklahoma (e.g., Cifelli et al., 1997), and Utah (e.g., Cifelli et al., 1999) may represent fossil baenids as well, but are too incomplete to allow rigorous identification.We present new fossil turtle material from the Early Cretaceous (Berriasian to Valanginian) Lakota Formation of South Dakota, which we identify as a new species of baenid, Lakotemys australodakotensis gen. and sp. nov. The purpose of this contribution is to describe this new material and to place it in a phylogenetic context.