Biogeography of Ordovician sponges

Abstract

Sponges have an unrealized potential importance in biogeographic analysis. Biogeographic patterns determined from our analysis of all published data on distribution of Ordovician genera indicate Early Ordovician sponge faunas have relatively low diversity and are completely dominated by demosponges. Early Ordovician (Ibexian) faunas are characterized by the widespread co-occurrence ofArchaeoscyphiaand the problematicCalathium.This association is commonly found in biohermal structures. Middle Ordovician faunas show an increase in diversity, and two broad associations are differentiated: Appalachian faunas (including Southern China and the Argentine Precordillera) and Great Basin faunas.Late Ordovician faunas show important changes in diversity and provincialism. Hexactinellid and calcareous sponges became important and new demosponge families appeared. Four Mohawkian-Cincinnatian associations are recognized here, including: 1) Midcontinent faunas; 2) Baltic faunas; 3) New South Wales faunas; and 4) Western North American (California and Alaska) faunas. However, two separate biogeographic associations are differentiated based on faunal differences. These are a Pacific association (western North American and New South Wales) and an Atlantic association (Midcontinent Laurentia and Baltica).Distribution of sponge genera and migration patterns are utilized to consider paleogeographic dispositions of the different continental plates, climatic features, and oceanic currents. Such an analysis points to close paleogeographic affinities between the Argentine Precordillera and Laurentian Appalachian faunas. However, significant endemicity and the occurrence of extra-Laurentian genera suggest a relative isolation of the Precordillera terrane during the Late Ibexian-Whiterockian. The study also shows a faunal migration from the Appalachian region to South China during the Middle Ordovician and the migration of faunas from Baltica to Laurentia in the Late Ordovician. The occurrence of Laurentian migrants in New South Wales during the Late Ordovician could be related to inferred oceanic current circulation between these two areas, although other paleogeographic features may be involved.

Chapter 8 Cambrian, Ordovician and Silurian non-stromatoporoid Porifera

“…This paper represents a summary of the limited available data for Cambrian to Silurian sponge biogeography, as a review of the state of knowledge at the time of writing. We focus particularly on the Silurian record, but also reassess recent studies of Cambrian and Ordovician sponge palaeobiogeography (Carrera & Rigby 1999Carrera & Botting 2008) in light of new data and new palaeogeographical interpretations. The Silurian sponge record is sparser than that from the Cambrian and Ordovician periods, and there are few diverse assemblages, although hexactinellids and non-lithistid demosponges are known from a range of carbonate and siliciclastic deposits.…”

“…Information on Cambrian and Ordovician non-stromatoporoid sponges has been taken from Carrera & Botting (2008) and Carrera & Rigby (1999, with additional information from the recent literature. Data on Silurian non-stromatoporoid sponges were gathered from published papers and monographs.…”

“…Ordovician non-stromatoporoid sponge palaeobiogeography was comprehensively reviewed by Carrera & Rigby (1999), with diversity changes discussed by Carrera & Rigby (2004). The described sponge record remains largely unchanged, but our understanding of palaeogeography has altered, leading to revisions to the palaeobiogeographical implications of the data.…”

“…Large-scale studies of the palaeobiogeography of Early Palaeozoic sponges have been limited to a few major works (Webby 1980(Webby , 1992Nestor 1990;Senowbari-Daryan 1990;Carrera & Rigby 1999;Carrera & Botting 2008). The main difficulty in reconstructing the palaeobiogeography of sponges is that their fossil record is at best intermittent.…”

The first sphinctozoan-bearing reef from an Ordovician back-arc basin

“…Bio-and litho-facies in this area as well as the characteristics of the microbialite suggest that the reef developed in a deeper subtidal setting that was unfavorable for most metazoan reef builders. In contrast to the high-energy stromatolite-sphinctozoan reefs from the Late Silurian, this case represents a low-energy and Rigby 1999;Carrera and Botting 2008). Sphinctozoan occurrences are known from eastern Australia (New South Wales), Alaska, California, northwestern China, and Kazakhstan, with a more than twofold increase in biodiversity at the genus and species levels compared with the Cambrian (Senowbari-Daryan and García-Bellido 2002; Carrera and Rigby 2004;Rigby et al 2008a).…”