comment on this calibration
Anatoidea (Anatidae - Anseranatidae)
Lineage (NCBI):
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| node name Anatoidea (Anatidae - Anseranatidae) Look for this name in NCBI Wikipedia Animal Diversity Web | ||
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recommended citations http://palaeo-electronica.org/content/fc-3 Ksepka and Clarke, 2015 |
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node minimum age 66.5 Ma MLP 93-I-3-1 was collected from lithostratigraphic unit K3, also referred to as Unit “C” of Pirrie et al. (1991) or the Sandwich Bluff Member of the Lopez de Bertodano Formation (Pirrie et al., 1997; Crame et al., 1999, 2004) at Sandwich Bluff, Vega Island, Antarctica. A Late Maastrichtian age for the Sandwich Bluff Member is based on an array of biostratigraphic evidence. Abundant marine reptiles, a hadrosaurian dinosaur tooth, macro-invertebrates, and micro-invertebrates have been sampled from deposits directly overlying the concretionary layer that produced the Vegavis holotype (Pirrie et al., 1991; Case et al., 2000; Riding et al., 1992; Martin, 2006; reviewed in Clarke et al., 2005). While a Maastrichtian age has been established for the Sandwich Bluff Member, some uncertainty remains in the correlation between the Maastrichtian Lopez de Bertodano deposits on Vega Island and the better studied sections on nearby Seymour Island. The Vegavis type horizon is placed near the lower base of the Manumiella bertodano (=“Manumiella new species 2” of Pirrie et al., 1991) dinoflagellate biozone (Thorn et al., 2009). The Manumiella bertodano biozone is restricted to a limited portion of the Maastrichtian section on Seymour Island, bounded by a first appearance datum ~200 m below the K-Pg boundary and a last appearance datum~50 m below the K-Pg boundary in the composite section (Thorn et al., 2009). Precisely estimating the amount of time represented by the ~50 m stratigraphic interval between the top of the Manumiella bertodano biozone and the K-Pg boundary, and the amount of time represented by the stratigraphic interval between the base of the Manumiella bertodano biozone and the Vegavis holotype horizon will require further work. Correlations by Tobin et al. (2012), taking into account magnetostratigraphy, 87Sr/86Sr values and approximations of sedimentation rate, estimated the lower base of the Manumiella bertodano biozone to be approximately 67 Ma in age. The top of this biozone (50 m below the KPg boundary) is estimated to be slightly younger than 66 Ma (e.g., Tobin et al., 2012, figure 4).These values were based on an estimated age of the K-Pg boundary of 65.5 Ma. More recently, the age estimate of the K-Pg boundary has been refined to 66 Ma (Renne et al., 2013). Thus, best estimates of these biozone boundaries should be shifted upwards by 0.5 Ma. 87Sr/86Sr chronology is suggestive of a slightly older date for the fossil horizon, but correlations remain uncertain. A 67.5 Ma date from the Lopez de Bertodano Formation deposits on Seymour Island has been proposed to mark the Early/Late Maastrichtian boundary (Crame et al., 2004). Sandwich Bluff Member deposits on Vega Island were illustrated as possibly correlative with Seymour deposits slightly older than those containing the 67.5 datum (Crame et al., 2004, figure 2). However, there is evidence that an unconformity underlying the Sandwich Bluff Member beds marks the ~67.5 Early/Late Maastrichtian transition on Vega Island, which would instead indicate a younger Late Maastrichtian age for the Sandwich Bluff Member (Crame et al., 2004, p. 420, and figure 3). Because the youngest possible age of the specimen should be used as the hard minimum calibration, we specify 66.5 Ma for the calibration age. | ||
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node maximum age None specified | ||
| primary fossil used to date this node | ||
MLP 93-I-3-1 | ||
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phylogenetic justification
Phylogenetic analysis of morphological data (Clarke et al., 2005). |
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phylogenetic reference(s)
Clarke, J.A., Tambussi, C.P., Noriega, J.I., Erickson, G.M., and Ketcham, R.A. 2005. Definitive fossil evidence for the extant avian radiation in the Cretaceous. Nature, 433:305–308.
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| tree image (click image for full size) | ||
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Figure 1 from Ksepka & Clarke, 2015.
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