Latitudinal gradient of taxonomic richness of ammonites in the Kimmeridgian-Volgian in the Northern Hemisphere

Abstract

The latitudinal gradient of taxonomic richness (LGTR) of Kimmeridgian and Volgian ammonite genera of the Northern Hemisphere is evaluated, and the LGTR evaluation methods and factors influencing LGTR are discussed. In the Kimmeridgian-Volgian the LGTR values for ammonites were largely influenced by the paleogeography of the Middle Russian Sea, which was directly connected with the Neotethys and, to a lesser extent, by the exchange through the connection between the Arctic and Pacific oceans. The Middle Russian Sea is considered to have been a major source of immigrant taxa to the Arctic basins. The highest lat itude ammonite faunas were influenced by the Pacific faunas, and due to the permanent presence of oceanic phylloceratids and lytoceratids, ammonite taxonomic richness was relatively high compared to some mid lat itudinal sites. The gradual decrease in taxonomic richness that occurred from the end of the Kimmeridgian to the end of the Volgian in all Subboreal basins probably resulted from the eventual isolation from the Neot ethys. Subboreal ammonite associations from the ecotone between the two superrealms (Panboreal and Tethys-Panthalassa) were affected by short term climatic oscillations, which led to rapid changes in the ammonite assemblages.

Palaeoenvironments and palaeoceanography changes across the Jurassic/Cretaceous boundary in the Arctic realm: case study of the Nordvik section (north Siberia, Russia)

“…Apparently, the nearby water masses affected the environments of northern East Siberia by bringing about a climatic warming and consequent changes in biota. The diverse Late Jurassic biota of the North Siberian seas were formed under the influence of the northern European seas, starting with the Central Russian Sea (Saks & Nalnjaeva 1973;Bogolepov 1983;Dzû ba et al 2006;Rogov 2012).…”

Macroevolution and Paleobiogeography of Jurassic-Cretaceous Ammonoids

“…Jurassic-Cretaceous ammonoids displayed the expected latitudinal diversity gradient, with highest taxonomic diversity at low latitudes, decreasing towards higher latitudes (Cecca et al 2005b;Yacobucci and MacKenzie 2007b;Vinarski et al 2011;Rogov 2012). Cecca et al (2005b) found that at a single latitude, ammonoid diversity was lowest on epicontinental platforms and higher in both intracratonic basins and deeper oceanic settings.…”

“…Cecca et al (2005b) found that at a single latitude, ammonoid diversity was lowest on epicontinental platforms and higher in both intracratonic basins and deeper oceanic settings. Rogov (2012) argued that the latitudinal diversity gradient was a function of both temperature and the coming and going of ocean connections between basins as sea level fluctuated. Yacobucci and MacKenzie (2007b) similarly found that sea level rises in the Cenomanian and Campanian shifted peak diversities northward within the North American Western Interior Seaway, with the latitudinal gradient shifting back south in the intervening intervals ( Fig.…”

Aulacostephanid ammonites from the Kimmeridgian (Upper Jurassic) of British Columbia (western Canada) and their significance for correlation and palaeobiogeography

“…The level with those ammonites was tentatively assigned by Wierzbowski (1989) to the Xenostephanus horizon in the Mutabilis Zone, corresponding to the boundary beds of the Mutabilis Zone and Uralensis Subzone of the Evoluta Zone in the Khatanga Basin sensu Mesezhnikov (1984). This is the only aulacostephanid-bearing horizon in the Upper Kimmeridgian of Spitsbergen and Franz Josef Land (Rogov 2012). The most common species collected from this level in Franz Josef Land is Zenostephanus (Z.)…”