comment on this calibration


 node name
Ginglymodi     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
93.9 Ma
Well-constrained dating for the Auoufous Formation has proven elusive, and a broad Albian-Cenomanian age estimate is common in older accounts. Cavin et al. (2010) have recently argued that the Auoufous Formation lies entirely within the Cenomanian, based on correlation with the early Cenomanian Bahariya Formation of Egypt (Catuneanu et al., 2006) made with reference to vertebrate faunas. A minimum age for the Kem Kem beds can be derived from the overlying marine Akrabou Formation, which is confidently dated as late Cenomanian on the basis of foraminifera and ostracodes (Ettachfini and Andreu, 2004). The Cenomanian is dated to 100.5 to 93.9 Ma (Gradstein et al., 2012), from which we derive our minimum age of 93.9 Ma for crown Ginglymodi.
  node maximum age
145 Ma
Atractosteus is only slightly younger than the oldest fossil lepisosteoids (sensu Lopez-Arbarello, 2012), Obaichthys and Dentilepisosteus from the Aptian-Albian Santana Formation of Brazil (Grande, 2010). The closest ‘semionotiform’-grade relatives of gars—Pliodetes and Araripelepidotes—derive from this same deposit (Lopez-Arbarello, 2012). However, gars are absent from older freshwater deposits that yield abundant ‘semionotiforms’ (e.g., the English and Belgian ‘Wealden’, and the lacustrine limestones of Las Hoyas and El Montsec, Spain; Traquair, 1911; Woodward, 1915-1917; Sanz et al., 1988; Wenz and Poyato-Ariza, 1994). Ranging in age from Aptian to Berriasian (Brenner et al., 1974; Peybernès, 1976; Schroeder et al., 1982; Martín-Closas and López-Morón, 1995; Gomez et al., 2002; Radley, 2006; Yans et al., 2012), these faunas provide an estimate for the maximum age of the divergence between Atractosteus and Lepisosteus. We take this to be equivalent to the base of the Berriasian, which is dated approximately as 145.0 Ma.
 primary fossil used to date this node 
Atractosteus falipoui , Cavin and Brito, 2001
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Tafilalt Basin
     Stratum: Kem Kem beds
     Geological age: Cretaceous, Mesozoic

  phylogenetic justification
Grande (2010) places Atractosteus falipoui in an unresolved polytomy along with other fossil representatives of Atractosteus, the extant A. tropicus and the sister-species pairing of A. tristoechus and A. spatula. Monophyly of Atractosteus relative to Lepisosteus is supported by three uniquely derived features: the shape of the vomerine heads, medial curvature and expansion of the anterior coronoid, and absence of tooth plates on the second and third hypobranchials (Grande, 2010: fig. 546). The final character, however, cannot be assessed for fossil gars.
  phylogenetic reference(s)
Grande, L. 2010. An empirical synthetic pattern study of gars (Lepisosteiformes) and closely related species, based mostly on skeletal anatomy. The resurrection of the Holostei. Amercan Society of Ichthyologists and Herpetologists Special Publication, 6:1-871.
 tree image (click image for full size) 
tree image
Figure 4 from Benton et al. (2014).