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Tetrapoda Look for this name in NCBI Wikipedia Animal Diversity Web
http://palaeo-electronica.org/content/fc-1 Benton et al. 2015
node minimum age |
The Wardie Shales are part of the Lower Oil Shale Group, dated as older than the East Kirkton locality which has also yielded several crown-group tetrapods (Rolfe et al., 1993). The Wardie Shales are assigned to the Holkerian regional stage on the basis of fossil fishes and palynomorphs (Paton et al., 1999), equivalent to the Livian in Belgium, dated as 343.5-337 Ma (Gradstein et al., 2012, p. 605), so providing the hard minimum constraint of 337 Ma.
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The soft maximum constraint is harder to determine because most of the close outgroups to the batrachomorphâ€“reptiliomorph clade are known only from younger deposits: the oldest baphetids and crassigyrinids are from the Brigantian (Benton, 1993), the oldest colosteids from the Asbian (Benton, 1993). The whatcheeriids Whatcheeria and Pederpes, from North America and Europe, respectively, are older, however, and dated to the Ivorian regional Western European stage, and so 351-346.5 Ma. These horizons are underlain by further units of Famennian age, dated as 372.2 Ma Â± 2.0 Myr â€“ 358.9 Ma Â± 0.4 Myr (Gradstein et al., 2012, p. 588), with basal tetrapods known from several continents, but no batrachomorphs or reptiliomorphs. We choose the whatcheeriids as marking the soft maximum constraint, even though they are phylogenetically more distant from crown Tetrapoda than baphetids and colosteidsâ€”but the latter two are younger than Lethiscus. Thus, we propose a date of 351 Ma as a soft maximum constraint.
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Phylogenetic analyses (e.g., Panchen and Smithson 1988; Trueb and Cloutier 1991; Lombard and Sumida 1992; Ahlberg and Milner 1994; Vallin and Laurin 2004) nest Lethiscus within Aistopoda, one of a putative clade termed Lepospondyli, that was formerly placed in the Batrachomorpha, but appears more likely within Reptiliomorpha (e.g., Ruta et al., 2003). Either way, Lethiscus is the oldest crown tetrapod.
Panchen, A. L., and Smithson, T. R. 1988. The relationships of the earliest tetrapods. The phylogeny and classification of the tetrapods 1: 1-32.
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