comment on this calibration


Lineage (NCBI): root » Eukaryota » Embryophyta » magnoliids » Saururaceae
 node name
Saururus     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Massoni et al. 2015
  node minimum age
44.3 Ma
Fossils described by Smith and Stockey (2007) come from the Princeton Chert, 8.4 km south of Princeton, British Columbia, Canada, which is part of the Princeton Group, Allenby Formation (Boneham, 1968). The Princeton Chert consists of a series of alternating layers of coal and chert. The paleontological record supports a middle Eocene age, such as an amiid fish correlated with the occurrence of comparable fossils in British Columbia and in the Klondike Mountain Formation of Washington State (Wilson, 1982), and teeth of the mammal group Tillodontia (Russell, 1935). In addition, potassium-argon dating studies have provided comparable ages for the Allenby Formation: 48 ± 2 Ma (Rouse and Mathews, 1961; Mathews, 1964), between 47 ± 2 and 50 ± 2 Ma (Hills and Baadsgaard, 1967), and 46.2 ± 1.9 Ma and 49.4 ± 2 Ma (Read, 2000). With a different method (U–Pb age from zircons), Moss et al. (2005) suggested an age of 52.08 ± 0.12 Ma for the Allenby Formation. Finally, Smith and Stockey (2007) report a personal communication from H. Baadsgaard (University of Alberta, 1999) that supports an age of 48.7 Ma for the ash of Layer #22 of the Princeton Chert. Because the 7.5 m of the Princeton Chert sequence (incorporating the layer where the fossil was collected) may have accumulated in 15,000 years or less (Mustoe, 2011), this latter age is probably the closest to the real age of the fossil. However, in order to be conservative regarding the uncertainty of the age of this formation, and the fact that no uncertainty is associated with the latter age, Saururus tuckarae provides a safe minimum age of 44.3 Ma (the youngest age given by potassium-argon dating minus the associated error of 1.9 Ma).
  node maximum age
0 Ma
none specified
 primary fossil used to date this node 
UAPC P1631 Bbot a
Saururus tuckerae , Smith and Stockey, 2007
Location relative to the calibrated node: Stem

[show fossil details]
     Locality: Princeton Chert, Princeton, British Columbia
     Stratum: Princeton Group, Allenby Formation
     Geological age: Eocene, Paleogene, Cenozoic

  phylogenetic justification
A morphological parsimony analysis using 24 morphological characters modified from matrices of Tucker et al. (1993), Tucker and Douglas (1996), and Meng et al. (2003), placed Saururus tuckerae in a single most parsimonious position within the family Saururaceae, as the sister group of a clade formed by the two extant species of Saururus (Smith and Stockey, 2007). The relationship of the fossil with extant Saururus, one of four genera in Saururaceae, was supported by the following synapomorphies: basally connate carpels, 1-2 ovules per carpel, and marginal placentation (Smith and Stockey, 2007). This study indicated that the genus Saururus was sister to Gymnotheca, and Anemopsis was sister to Houttuynia, relationships supported by other molecular and morphological studies (Meng et al., 2002, 2003; Jaramillo et al., 2004; Neinhuis et al., 2005; Wanke et al., 2007b; Massoni et al., 2014). Outside the Saururaceae, the relationships are compatible with molecular studies (e.g., Qiu et al., 2005, 2006; Soltis et al., 1999, 2000a, 2000b, 2007, 2011; Mathews and Donoghue, 1999, 2000; Qiu et al., 1999, 2000; Doyle and Endress, 2000; Savolainen et al., 2000; Zanis et al., 2002, 2003; Borsch et al., 2003; Hilu et al., 2003; Kelly and González, 2003; Jaramillo et al., 2004; Wanke et al., 2007a, 2007b; Massoni et al., 2014). We thus consider Saururus tuckerae to provide a minimum age for the stem node of the extant genus Saururus, which is also the crown node of Gymnotheca + Saururus (Figure 1).
  phylogenetic reference(s)
Smith, S.Y. and Stockey, R.A. 2007. Establishing a fossil record for the perianthless Piperales: Saururus tuckerae sp. nov. (Saururaceae) from the Middle Eocene Princeton Chert. American Journal of Botany, 94:1642–1657.
 tree image (click image for full size) 
tree image
Figure 1 from Massoni et al. (2015).