INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
Early Palaeozoic Palaeobiogeography and Palaeogeography.
LUCY A. MUIR; JOSEPH P. BOTTING; MARCELO CARRERA; MATILDE BERESI
GEOLOGICAL SOCIETY OF LONDON SPECIAL PUBLICATION
Lugar: London; Año: 2011
Abstract: The Cambrian, Ordovician and Silurian distributions of non-stromatoporoid sponges are reviewed. The earliest Cambrian faunas contain mostly hexactinellids, with protomonaxonids dominating Middle Cambrian assemblages. There are no obvious palaeobiogeographical patterns in their distribution, with many genera being found widely. Vauxiids, lithistids and heteractinids are apparently confined to low latitudes, but this may be due to a poor fossil record. Most known Ordovician sponge faunas are from low latitudes, although some high latitude faunas are known, which contain protomonaxonids and reticulosan hexactinellids. There is some division of faunas within Laurentia, into eastern and western Laurentian provinces. During the Silurian Period, sponge diversity is very low during the Llandovery Epoch, probably partly because of lack of habitat for taxa characteristic of calcareous facies, and also because of sampling bias. There is a dramatic increase in diversity through the Silurian Period, mostly due to an apparent diversification in the demosponges; however, the non-lithistid groups in particular are poorly known, with few recorded outside Euramerica. There are many ghost lineages for Silurian sponges, indicating that their fossil record is poorly known. The currently available data for early Palaeozoic sponges are too incomplete to allow any palaeobiogeographical inferences.