Paleobiogeography of Early Cretaceous Ammonoids

Ammonite Biostratigraphy of the Cretaceous—An Overview

“…Nevertheless, ammonite as well as microfossil zones have strongly varying lengths and thus some short ammonite biozones represent an even shorter period of time and thus a higher resolution. Although ammonites appear as ideal index fossils there are many limits in Cretaceous ammonite biostratigraphy, e.g., with respect to paleobiology and biofacies (compare De Baets et al 2015a;Lukeneder 2015;Naglik et al 2015), paleobiogeographic distribution (compare Lehmann et al 2015), slow evolutionary rates in some groups of ammonites, taxonomy (compare De Baets et al 2015a;Monnet et al 2015b;Yacobucci 2015) and preservation (Wani and Gupta 2015). A summary with a focus on a biostratigraphical background can be found in Kennedy and Cobban (1977), but many of these points are also addressed in a different context in multiple other chapters of this book.…”

The Global Boundary Stratotype Section and Point (GSSP) for the base of the Hauterivian Stage (Lower Cretaceous), La Charce, southeast France

“…At La Charce, the late Valanginian Teschenites callidiscus ASZ of the Criosarasinella furcillata AZ and the early Hauterivian Acanthodiscus radiatus and Crioceratites loryi AZs of the Standard Zonation scheme (Reboulet et al, 2018) are characterized by abundant and well preserved ammonoid faunas. These faunas represent the most continuous and fossiliferous succession of ammonites recorded from sections of the Mediterranean-Caucasian Subrealm of the Tethyan Realm sensu Lehmann et al (2015). They provide a very high resolution biostratigraphic record of the Valanginian/Hauterivian boundary interval (Fig.…”

“…Records of Leopoldia and Acanthodiscus from Argentina, Colombia and Mexico are based on misidentifications of Valanginian neocomitids such as Acantholissonia, Karakaschiceras, Neohoploceras, Rodighieroites and Chacantuceras (see Company, 1987;Young, 1988;Bulot, 1995;Reboulet, 1996;Rawson, 1999, 2010;Barragán and Gonzalez Arreola, 2009;Lehmann et al, 2015 for discussions).…”

Berriasian ammonites of supposed Tethyan origin from the type ‘Ryazanian’, Russia: a systematic re-interpretation

“…Research conducted in the past several years within the Berriasian Working Group of the International Subcommission on Cretaceous Stratigraphy questions such systematics and correlation. It has been demonstrated that the provincialism of the neocomitid and himalayitid ammonites is higher than previously assumed in the literature, and that homeomorphy has led to erroneous taxonomic interpretations (see Bulot et al, 2014;Frau et al, 2015Frau et al, , 2016aFrau et al, , 2016bFrau et al, , 2016cLehmann et al, 2015). In particular, a re-examination of the Russian literature leads us to challenge the occurrence of western Tethyan-derived ammonites in the 'Ryazanian' deposits, as testified by the systematic re-assessment provided in the present contribution.…”

“…Furthermore, the correlation of ammonites in Russian Tithonian and Berriasian boreal sections with a standard Mediterranean ammonite scale (SMAS sensu Reboulet et al, 2018) remains an intractable problem (e.g., Sazonova, 1971Sazonova, , 1972Sazonova, , 1977Casey, 1973;Casey et al, 1988;Mitta, 2005Mitta, , 2017Zakharov and Rogov, 2008;Schnabl et al, 2015). This is not only due to condensation and erosional episodes in the Russian platform 'Ryazanian' deposits (see Mesezhnikov et al, 1979;Mitta, 2014), but also the strong endemism of the ammonite faunas (e.g., Casey et al, 1977;Baraboshkin, 1999Baraboshkin, , 2002Mitta, 2004Mitta, , 2005; Zakharov and Rogov, 2008;Lehmann et al, 2015). Mitta (2017) has recently suggested that the type 'Ryazanian' beds of central European Russia can be separated into four zones.…”