The earliest record of the endemic African frog family Ptychadenidae from the Oligocene Nsungwe Formation of Tanzania

Abstract

[Extract] The Ranoidea is a cosmopolitan radiation of frogs comprising 19 families and more than 2400 extant species (nearly 40% of all anurans; Ford and Cannatella, 1993; Scott, 2005; Bossuyt et al., 2006; Blackburn and Wake, 2011; Barej et al., 2014). Studies using time-calibrated molecular phylogenies suggest a Cretaceous origin for the Ranoidea (Bossuyt and Roelants, 2009), but the Mesozoic and early Cenozoic fossil record of this diverse clade remains poor (Rage, 1984; Rocek, 2000; Rocek and Rage, 2000; Rage and Rocek, 2003). Although many fossils have been attributed to the Ranoidea, typically few diagnostic characteristics are provided to assign fossils to specific taxa within the clade (e.g., de Broin et al., 1974; Rage, 1984). The Ranoidea is thought to have initially diversified in Africa (Bossuyt et al., 2006; Rage et al., 2013), but the African fossil record of anurans in the Mesozoic and Paleogene is generally poor, with the Afro-Arabian record limited primarily to pipoid frogs (e.g., Henrici and Baez, 2001; Trueb et al., 2005; Rage and Dutheil, 2008; Rage et al., 2013) or taxonomically enigmatic fossils (Flynn and Brunet, 1989; Jacobs et al., 1990; Rocek, 2000; Evans et al., 2008; Rage and Dutheil, 2008; Rage et al., 2013).