Phanerozoic faunal and floral realms of the Earth; the intercalary relations of the Malvinokaffric and Gondwana faunal realms with the Tethyan faunal realm

Abstract

Biogeographical data comprise a largely neglected but potentially powerful tool for deciphering the tectonic evolution of the Phanerozoic Earth. This is true because the borders of biogeographical realms, regions, provinces, and subprovinces are natural barriers, some of them tectonic in origin. Yet most major biogeographical realm boundaries, based on floral and faunal distributions, do not coincide with the partly tectonic, partly computer-generated boundaries of plate tectonics.Instead, the paleontologic record shows that (1) a broad intercalary zone separates "northern" from "southern" biogeographical realms, and (2) this broad zone has existed during most, if not all, of Phanerozoic time. Within this intercalary zone, whose width ranges from several hundred to 5,000 km, strata bearing "northern" biotas are intercalated with strata bearing "southern" biotas and, in many areas, admixtures of "northern" and "southern" taxa are present within the same beds.During the Middle and Late Cambrian, the southern realm is the Atlantic Realm. (A globally low Early Cambrian climatic gradient does not permit easy definition of a southern realm.) Following the Cambrian, the two principal southern realms are the Malvinokaffric Realm (Ordovician-early Middle Devonian) and its successor, the Gondwana Realm (Early Permian-Early Cretaceous). The two are separated in time by the later Devonian, an interval of rather cosmopolitan biotas.

Biogeographic variation in coral species diversity on coral reefs in three regions of Indonesia

“…First, epeiric sea facies in the fossil record typically had lower species diversity than contemporary open ocean regions, although their relative diversity fluctuated with changing environmental factors (e.g. Oliver, 1977; reviewed by Meyerhoff et al , 1997 ). Our results suggest that species diversity in reef communities on broad shallow shelves may approach that of open ocean reefs, if the shelf areas are well connected to adjacent high diversity regions ( Veron, 1995).…”

Evaluating Devonian bioregionalization: quantifying biogeographic areas

“…The Malvinokaffric realm is a unit that has been defined as much by the characteristics present as those absent. Described as a low-diversity, cold-water unit (Boucot et al 1969; Eldredge and Ormiston 1979; Boucot 1984, 1988) its boundaries are in part created through the absence of the common warm-water taxa, such as atrypid and gypidulid brachiopods, and biostratigraphic markers, such as conodonts, graptolites, and ammonoids (Oliver 1977, 1990; Koch and Boucot 1982; Racheboeuf et al 1993; Hallam 1994; Meyerhoff et al 1996; Boucot et al 2001; Dowding and Ebach 2018). Despite this, the realm is noted for a highly endemic brachiopod (Boucot and Gill 1956; de Melo 1988; de Melo and Boucot 1990) and trilobite (Eldredge and Ormiston 1979; Cooper 1982; Adrain and Edgecombe 1996) fauna.…”

A Middle Devonian Trilobite Assemblage from Venezuela

“…Maximova (1972) included Kazakhstan within a large ''Pacific paleogeographic region,'' but that concept is rather generalized. According to Meyerhoff et al (1996), Kazakhstan falls inside the Balkhash-Mongolia-Okhotsk region of the Old World realm. The North American and Venezuelan occurrences of Viaphacops lie within the Eastern Americas realm (sensu Boucot, 1988), and its Bolivian occurrence is within the Malvinokaffric realm (sensu Eldredge and Ormiston, 1979).…”