Global relationships of Argentine (Neuquén Basin) Early Cretaceous ammonite faunas

Abstract

Of the 16 ammonite families of Valanginian to Early Barremian age, six are represented in the Neuquén Basin-the Neocomitidae, Olcostephanidae, Oosterellidae, Holcodiscidae, Ancyloceratidae and Douvilleiceratidae. Normally, only one or two ammonite genera occur at any one level, and there were ten turnovers at family level. Each turnover marks an important immigration event and other immigrations sometimes occurred between. All the taxa are of Tethyan origin; but while some immigrants are Andean Province forms, other are taxa that for at least part of their temporal range achieved an almost pandemic distribution, even invading the marginal Boreal basins of NW Europe (North Sea and Lower Saxony basins). The Neuquén and NW European basins lay at similar palaeolatitudes south and north of the equator, and there are striking similarities between some of the immigrants to the two areas. Links between the NW European and other South American faunas suggest a possible direct marine connection between the two areas.

Los Olcostephaninae Haug, 1910 (Ammonoidea) valanginianos de la cuenca andina de Chañarcillo del Cretácico Inferior del Norte de Chile.

“…Similarly, the general morphology of K. attenuatum (Behrensen, 1892) and K. neumayri (Behrensen, 1892) is closer to that of the group of K. pronecostatum Felix, 1891, including K. quadristrangulatum (Sayn, 1907), than to the late Lower Valanginian forms of the K. biasselense/inostranzewi plexus. As a consequence, the correlation proposed herein is slightly different from that formerly published by Rawson (1999Rawson ( , 2007 and Aguirre-Urreta et al (2007 Rawson, 1999, p. 356;Aguirre-Urreta et al, 2007;Rawson, 2007 Reboulet et al (2011) (Fig. 9).…”

“…We therefore regard Saynoceratinae as an artificial grouping of micromorphic genera that derivates from Olcostephanus sensu stricto at different moments (Bulot et al, 1990a). The same is true for the Capeloitinae, whose type genus Capeloites Lissón, 1937a, derivates from the Olcostephanus rootstock in the late Lower Hauterivian (Kemper et al, 1981;Bulot, 1990a;Rawson, 2007).…”

Sclerobionts, Shell Morphology and Biostratinomy on Ammonites: Two Early Cretaceous Cases From the Neuquén Basin, Argentina

“…En varias ocasiones, este género ha florecido para formar grandes poblaciones de amplia distribución geográfica, un patrón de que soportaría la interpretación de Cecca (1998) Rawson 1999a, 2001, Rawson 1999Rawson , 2007.…”

“…Esa especie combina un rango temporal muy corto con una muy amplia distribución geográfica desde las regiones marginales del reino Boreal en el noroeste de Europa y la provincia Mediterránea para llegar hacia el sur a Tanzania, México y Perú (Rawson 2007) (fig. 5.4).…”

“…Estas últimas faunas proveen excelentes niveles de afinidad a nivel global, facilitando la correlación con las zonaciones estándar de la provincia del Mediterráneo occidental (Aguirre-Urreta et al , Rawson 2007. Sin embargo, para Cecca (1998), estas migraciones de géneros pandémicos como Olcostephanus representarían en realidad un comportamiento oportunista de un taxón generalista.…”