Brachiopod Biogeography Research Articles

Late Ordovician palaeogeography and the positions of the Kazakh terranes through analysis of their brachiopod faunas

AbstractDetailed biogeographical and biofacies analyses of the Late Ordovician brachiopod faunas with 160 genera, grouped into 94 faunas from individual lithotectonic units within the Kazakh Orogen strongly support an archipelago model for that time in that area. The Kazakh island arcs and microcontinents within several separate clusters were located in the tropics on both sides of the Equator. Key units, from which the Late Ordovician faunas are now well known, include the Boshchekul, Chingiz-Tarbagatai, and Chu-Ili terranes. The development of brachiopod biogeography within the nearly ten million year time span of the Late Ordovician from about 458 to 443 Ma (Sandbian, Katian, and Hirnantian), is supported by much new data, including our revised identifications from the Kazakh Orogen and elsewhere. The Kazakh archipelago was west of the Australasian segment of the Gondwana Supercontinent, and relatively near the Tarim, South China and North China continents, apart from the Atashu-Zhamshi Microcontinent, which probably occupied a relatively isolated position on the south-western margin of the archipelago. Distinct faunal signatures indicate that the Kazakh terranes were far away from Baltica and Siberia throughout the Ordovician. Although some earlier terranes had joined each other before the Middle Ordovician, the amalgamation of Kazakh terranes into the single continent of Kazakhstania by the end of the Ordovician is very unlikely. The Late Ordovician brachiopods from the other continents are also compared with the Kazakh faunas and global provincialisation statistically determined.

Early Jurassic (Pliensbachian) brachiopod biogeography in the western Tethys: The Euro-Boreal and Mediterranean faunal provinces revised

The Pliensbachian brachiopod biogeography of the western Tethyan region and the Euro-Boreal vs. Mediterranean faunal provinciality is evaluated. The data base was developed from improved and mostly revised taxonomical data of 25 Pliensbachian brachiopod localities selected from Europe and North Africa. The revised list and presence-absence data of 405 Pliensbachian brachiopod species formed the taxonomic units of the numerical analysis based on similarity coefficients. Cluster analysis (hCA) carried out from the Jaccard and Raup-Crick coefficient data showed clear dichotomy between the Euro-Boreal and Mediterranean brachiopod biochores. Principal coordinates (PCO) technique and non-metric multi-dimensional scaling (NMDS), complemented with the minimal spanning trees, resulted in similar grouping of the Pliensbachian brachiopod faunas. In de-trended correspondence analysis (DCA), besides the clearly separated Euro-Boreal and Intra-Mediterranean units, the Peri-Mediterranean assemblage formed a discrete scatter between the two major biochores. The three Algerian faunas (Ouar, Trar, Ksou) appear in a somewhat marginal position within the Euro-Boreal province. The above Pliensbachian brachiopod biochores reveal very high degree of endemicity, probably related to the limited dispersal potential of brachiopods. From the complete data set distinctive Euro-Boreal and Mediterranean species, ten from both provinces, were selected. Ribbed spiriferinid morphotypes are frequent among the distinctive Euro-Boreal species, whereas, besides smooth spiriferinids, some rhynchonellid and terebratulid morphotypes with expanded anterior margins are common among the distinctive Mediterranean species. In the Early Jurassic Tethyan palaeogeography, the marked dichotomy between the Euro-Boreal and Mediterranean provinces is interpreted in terms of deep-sea/oceanic barriers, which isolated the intra-Tethyan microcontinent from the European and African shelf regions. Geographical position and local environmental factors caused the differentiation of the Peri-Mediterranean subprovince along the north-western margin of the microcontinent. This palaeobiogeographical unit formed an interface between the Intra-Mediterranean and the Euro-Boreal biochores.

Systematics, biostratigraphy and biogeography of brachiopods and other fossils from the middle Cambrian Nelson Limestone, Antarctica

An assemblage dominated by acrotretid brachiopods (Prototreta millsi Brock and Percival, 2006) is described from the Nelson Limestone of the Transantarctic Mountains, Antarctica. The formation also includes paterinids (Micromitra sp. cf. M. nerranubawu Kruse, 1990 and Dictyonina australis Roberts and Jell, 1990), lingulids (Oepikites?haimantensis Reed, 1910) and acrothelids (Acrothele sp. cf. A. vertex Reed, 1910). The macrofauna also contains orthids (Diraphora dyunyin Kruse, 1990). The associated fauna include sponge spicules present in vast abundance. Other recognisable small shelly fossils (including chancelloriids and hyolithelminths) make up a small section of the fauna. Trilobites belong to taxa previously described from the Nelson Limestone and support the Drumian age proposed for the formation. Palaeobiogeographic analysis indicates that the brachiopod fauna corroborates previously described strong links with Australasia and also suggests a strong link to Indian material, corroborating previous evidence for an East Gondwanan faunal province in the middle Cambrian.

Chathamirhynchia kahuitara, a new genus and species of Late Cretaceous rhynchonellide brachiopod from the Chatham Islands, New Zealand: shell structure, palaeoecology and biogeography

ABSTRACTA new rhynchonellide brachiopod has been collected from the Kahuitara Tuff (Campanian–Maastrichtian) of Pitt Island, Chatham Islands, New Zealand. Brachiopods are extremely rare in Cretaceous rocks from New Zealand, and this new genus and species is unlike any other rhynchonellide known from Australasia or elsewhere. Chathamirhynchia kahuitara is distinguished by its small size, strong ribbing, and well-developed sulciplicate folding, and internally by a large, robust cardinal process and raduliform crura. The shell structure of C. kahuitara is shown to be of typical fine fibrous ‘rhynchonellidine’ type. This brachiopod was probably strongly attached to volcanic rock or shells in a shallow-water, high-energy environment. Implications for the biogeography of brachiopods during the Late Cretaceous are briefly discussed.

Paleozoic Brachiopod Biogeography

Over two hundred years ago the Swedish scientist Carl Linnæus (1781), in an analysis of the biogeographic patterns of living organisms, suggested that all species originated in Paradise. Although there has been considerable progress in the understanding of biogeographical patterns during the intervening two centuries, modern debate has focused on the general applicability of the concept of faunal realms together with the relevance of dispersal, panbiogeographic, and vicariance models (Nelson and Platnick, 1981). To date, studies of Paleozoic brachiopod biogeography have no strong theoretical base; rather the various numerical techniques available, including both cladistic and phenetic methodologies, have helped organize the growing amount of distributional data into recognizable and useful structures.

Aspects of Middle-Late Jurassic-Cretaceous Tethyan brachiopod biogeography in relation to tectonic and paleoceanographic developments

Important tectonic and paleoceanographic events during the Middle to Late Jurassic and Cretaceous resulted in modifications to the biogeographic distributions of Tethyan brachiopod genera from Europe. The development of the Central Atlantic Ocean during the Jurassic-Early Cretaceous led to an increase in the number of brachiopod genera common to both the Mexico/Eastern Pacific and Northwestern Europe/Tethyan regions. Brachiopod genera recorded from Tethys in Europe show evidence of migration via at least four major routes as a consequence of tectonic developments (dates in parentheses indicate stages where evidence exists for generic links): (1) Northwestern Europe via Mexico/Caribbean region (Oxfordian) to South America (Valanginian, Hauterivian, Cenomanian); (2) Eastern Tethys via Eastern Africa (East African Seaway) to the South Atlantic Ocean (Late Turonian-Early Coniacian, Santonian-Campanian); (3) Northwestern Europe via the Central Atlantic to the opening South Atlantic, reaching the Antarctic Peninsula region (late Albian, Santonian, Campanian); (4) Europe northward to higher latitudes (Russian Platform to Barents Sea, Berriasian-Valanginian; Europe to East Greenland, Valanginian; Europe-Canadian Arctic Islands, Albian and also earlier during the Jurassic). For routes (1)–(3) direction of dispersal may prove to have been in either direction, at times it appears to have been in a southerly direction for route (3). Stratigraphic age relationships suggest a south to north dispersal for routes considered under (4) (except for the link to the Canadian Arctic Islands, which is inconclusive). By the Late Cretaceous the low-latitude faunas of Europe and America had become isolated by the increasing width of the Central Atlantic Ocean although some genera appear to be cosmopolitan.