Dienerian (Early Triassic) ammonoids from the Candelaria Hills (Nevada, USA) and their significance for palaeobiogeography and palaeoceanography

Biostratigraphy of Triassic Ammonoids

“…Schemes have also been proposed for South Primorye (Zakharov 1997;Shigeta et al 2009), Nepal (Kummel 1970;Waterhouse 1996), and Siberia (Dagys 1994;Dagys and Ermakova 1996), as well as East Greenland (Trümpy 1969;Bjerager et al 2006). Isolated faunas have also been described from Japan (Bando 1970) and Nevada (Ware et al 2011b). Correlation of these biostratigraphic schemes is sometimes hampered by poor ammonoid preservation and conflicting taxonomic interpretations.…”

“…With regard to the Early Triassic, Ware et al (2011b) recently described a long known but never illustrated ammonoid fauna of Early Dienerian age from the old Candelaria mining district in Nevada. Extensive work by Brayard in west-central, southern and southeastern Utah over the past 5 years has revealed for the first time in the American west, the existence of a much expanded Smithian ammonoid succession that includes early Smithian forms ).…”

“…Therefore, the Induan is now equivalent to the late Griesbachian and Dienerian, while the early Griesbachian is roughly of Permian age (Baud 2001;Baud and Beauchamp 2001). The base of the Dienerian substage is marked by the appearance of abundant meekoceratids, gyronitids and proptychitids, a globally recognizable event (e.g., Tozer 1974;Shevyrev 2001;Brühwiler et al 2008;Ware et al 2011b). …”

Biogeography of Triassic Ammonoids

“…These large datasets benefited from the infusion of much new primary data generated by intensive fieldwork and carefullyrevised taxonomy (e.g. Monnet and Bucher 2005;Jenks 2007;Brayard and Bucher 2008;Shigeta and Zakharov 2009;Guex et al 2010;Jenks et al 2010;Ware et al 2011;Balini et al 2012aBalini et al , 2012bBrühwiler et al 2012aBrühwiler et al , 2012bBrühwiler et al , 2012cBrayard et al 2013;Zakharov and Moussavi Abnavi 2013) occasionally combined with recently-published radiometric ages (e.g. Galfetti et al 2007a;Schaltegger et al 2008).…”

Permian-Triassic Extinctions and Rediversifications

“…Although knowledge of Griesbachian and Dienerian ammonoids is still limited, proptychitids and meekoceratids originated during the Dienerian. In their first steps, these Dienerian originations did not lead to any spectacular taxonomic diversification (e.g., Tozer 1974;Shevyrev 2001;Brüh-wiler et al 2008;Ware et al 2011;Fig. 17.1c).…”