Significance of "Tethyan" Fossils in the American Cordillera

Abstract

Equatorial faunas of the ancient Tethyan seaway, which extended from western Europe to southeastern Asia, comprise some of the most diverse marine taxa in the fossil record. Comparable or identical "Tethyan" species that occur far from the Tethyan seaway in Paleozoic and Mesozoic rocks of the North and South American Cordillera have long been considered as a major biogeographic anomaly. Two leading theories to account for the occurrence of these anomalous "Tethyan" faunas in the Cordillera are that they were transported long distances to the east on tectonic blocks(suspect terranes that originated near the Tethys) or that they migrated westward via undiscovered marine corridors through continental areas of Pangea. An alternative model is that these "Tethyan" fauna were pantropic species that extended with attenuated diversities into the eastern proto-Pacific Ocean. This pantropic model can better account for the distribution patterns of many Paleozoic and early Mesozoic "Tethyan" species in the American Cordillera and provides a steady state hypothesis against which the other models can be tested. The distribution of pre-Cretaceous "Tethyan" faunas is similar to the known pantropic distribution of many Cretaceous and Cenozoic tropical biotas. During the Cenozoic, taxa were most diverse in the Tethys and Indo-West Pacific regions but extended with attenuated diversity to many parts of the equatorial Pacific Ocean, including the west coasts of North and South America. The eastern Pacific occurrence of many Indo-West Pacific species provides a modern analog for the occurrence of many anomalous "Tethyan" fossils in the American Cordillera.

Ammonoid Life and Habitat

“…Consequently, current transport of pelagic animals could have produced "instant" species dispersal, even across major oceans, and certainly was much more extensive than formerly believed possible for all but the oceanic leiostraca (e.g., Newton, 1988;Wiedmann, 1988b;Westermann, 1990;Smith et al, algal mats. Spawning in oceans resembled that in hypoxic basins.…”

First record of the Early Jurassic Lupherella fauna (Bivalvia) in eastern Guangdong, southeast China

“…Lupherella is believed to be confined to low paleolatitudes (Damborenea 1993), known in eastern Oregon and California (Imlay 1967) and in western Canada (Aberhan 1998). Taking into account the position of eastern Guangdong during these times, a trans-Pacific dispersal of Lupherella may readily fit into Newton's (1988) pantropic model.…”

Revisión De Los Biocoremas Marinos Globales Del Jurásico Según La Distribución De Los Moluscos Bivalvos

“…Fueron utilizados también para proponer y apoyar cuestiones puramente paleogeográficas, como el establecimiento del Corredor Hispánico (Broglio-Loriga y Neri, 1976;Damborenea y Manceñido, 1979, 1988Hallam, 1983;Smith y Tipper, 1986;Aberhan, 2001Aberhan, , 2002, o del Corredor de Mozambique o Sudafricano (Heinze, 1996;Alberti et al, 2012).…”

“…Son varios los factores que han permitido estas observaciones, aparte de la existencia de datos casi continuos a lo largo de un amplio rango paleolatitudinal: la posición latitudinal media de esta región en el Jurásico, la ausencia de barreras a lo largo del margen occidental de Paleopacífico, la probable naturaleza pantrópica de las faunas tethyanas (Newton, 1988), y el desarrollo de una conexión somera con el Tethys occidental (Corredor Hispánico) desde el Jurásico Temprano en adelante (Damborenea y Manceñido, 1979, 1988Hallam, 1983).…”

“…2). La distribución de los bivalvos proporcionó incluso argumentos muy significativos para la discusión del momento en que se estableció la conexión (Damborenea y Manceñido, 1979;Hallam, 1983;Smith y Tipper, 1986;Nauss y Smith, 1988;Newton, 1988;Smith, 1989;Damborenea, 2000;Aberhan, 2001;Sha, 2002;Damborenea et al, 2013). Hubo entonces un incremento súbito en la similitud de las faunas de bivalvos a ambos lados del Corredor Hispánico, comenzando en el Sinemuriano, partiendo de bajos valores durante el Triásico Tardío, y alcanzando los picos de similitud entre las faunas de ambos extremos del corredor alrededor del Pliensbachiano-Toarciano (Damborenea et al, 2013, fig.…”