Chapter 19 Global Cambrian trilobite palaeobiogeography assessed using parsimony analysis of endemicity

Abstract

Palaeobiogeographical data on Cambrian trilobites obtained during the twentieth century are combined in this paper to evaluate palaeoceanographic links throughc.30 myr, once these arthropods biomineralized. Worldwide major tectonostratigraphic units are characterized at series intervals of Cambrian time and datasets of trilobite genera (629 for Cambrian Series 2, 965 for Cambrian Series 3, and 866 for the Furongian Series) are analysed using parsimony analysis of endemicity. Special attention is given to the biogeographical observations made in microcontinents and exotic terranes. The same is done for platform-basinal transects of well-known continental margins. The parsimony analysis of endemicity analysis resulted in distinct palaeogeographical area groupings among the tectonostratigraphic units. With these groupings, several palaeobiogeographical units are distinguished, which do not necessarily fit the previously proposed biogeographical realms and provinces. Their development and spatial distributions are broadly controlled by Cambrian palaeoclimates, palaeogeographical conditions (e.g. carbonate productivity and anoxic conditions) and ocean current circulation.Supplementary material:Global dataset of Cambrian Epoch 2 (A), Cambrian Epoch 3 (B) and the Furongian Epoch (C) trilobite genera are provided at:http://www.geolsoc.org.uk/SUP18669

Cambrian transgression and radiation linked to an Iapetus-Pacific oceanic connection?

“…Notably, recent detrital zircon studies have demonstrated that the Sauk Sequence resulting from the transgression of cratonic Laurentia was not initiated in west Texas (USA) until the Cambrian, significantly later than along its eastern and western margins (Spencer et al, 2014). The fact that the first benthic trilobites reflect geographic differentiation between the two continental masses, the olenellids in Laurentia and the redlichiids in Gondwana (Brasier, 1992;Fortey et al, 1996;Lieberman, 2003;Álvaro et al, 2013), suggests significant separation prior to the start of Cambrian Stage 3 (ca. 521 Ma; Fig.…”

Exotic trilobites from the uppermost Cambrian Series 3 and lower Furongian of Sweden

“…Analysis of the palaeobiogeographical distribution of exotic trilobites at generic level clearly indicates that the assemblage shows the strongest affinities with East Gondwana (particularly its Australian -Antarctic -Chinese segment), Laurentia, Kazakhstania, and Siberia, that is palaeogeographic areas located in low-latitude positions (e.g., Cocks and Torsvik 2006;Álvaro et al 2013;Text-figs 8, 9). Interestingly, genera considered to be typical and/or most numerous in specific palaeogeographic areas also have a wide palaeogeographic distribution.…”

The Cambrian explosion: Its timing and stratigraphic setting

“…Traditional biogeographic studies have commonly supported the existence of a Paradoxides realm as one of the most robust biogeographic units with a paradoxidid-solenopleurid-conocoryphid assemblage spreading throughout Avalonia, the Mediterranean and central-European areas, and Baltica (Álvaro and Vizcaïno, 2003;Álvaro et al, 2014), as well as deep-and cold-marine waters of various latitudes, including deep-water settings surrounding tropical Laurentia (Babcock, 1994a,b). Unfortunately, correlations across the Mediterranean and central-European areas are still debated, probably partly weakened by individual taxonomic considerations (Álvaro and Clausen, 2005;Geyer and Landing, 2004).…”

“…Les études biogéographiques traditionnelles ont couramment soutenu l'existence d'un domaine à Paradoxides comme l'une des unités biogéographiques les plus robustes, avec un assemblage à paradoxidides-solenopleurides-conocoryphides se répartissant au travers de l'Avalonie, des zones européennes centrales et méditer-ranéennes et de la Baltique (Álvaro et Vizcaïno, 2003 ;Álvaro et al, 2014), ainsi que dans les eaux marines profondes et froides de diverses latitudes comme celles entourant le Laurentia tropical (Babcock, 1994a,b). Hélas, les corrélations au sein des zones méditerranéenne et de l'Europe centrale sont toujours débattues, probablement en partie fragilisées par des considérations taxonomiques individuelles (Álvaro and Clausen, 2005 ;Geyer et Landing, 2004).…”