Biogeography of the Ordovician and Silurian stromatoporoidea

• Published in: Geological Society, London, Memoirs
• Main Authors: Nestor, Heldur, Webby, Barry D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2013
• Subjects: Norway; Chukchi; Chukchi Peninsula; Siberia
• Online Access: https://researchers.mq.edu.au/en/publications/6f6ce730-87cd-45b7-b767-025967f86207; https://doi.org/10.1144/M38.7; http://www.scopus.com/inward/record.url?scp=84889671650&partnerID=8YFLogxK

Stromatoporoid sponges first appeared during the late Mid-Ordovician (mid-late Darriwilian) accompanying an important 'Chazy' reef-building episode. Representatives of the order Labechiida appeared first, initially splitting into two sister groups: those from North China (nine genera) and those from Laurentia (four genera). Two genera were common to the two regions, but others in North China and Siberia were endemic. This initial provincialism was not maintained into the Late Ordovician (Sandbian) as labechiids attained a wider dispersal, covering Laurentia with peripheral terranes in Northwest Scotland and Chukchi Peninsula, cratonic Siberia, the Urals (eastern margins of Baltica), and East Gondwanan blocks of Tarim North China, marginal Tasmania and the peri-Gondwanan New South Wales island-arc terrane. Only a few endemics remained present in the Sandbian - three in Laurentia, and one in Tarim. In the Katian, maximum diversification of labechiids occurred (19 genera, including a genus possibly transitional to first actinostromatids). Also four genera of the Clathrodictyida first appeared, and overall distribution continued to increase. The Hirnantian marked a dramatic decline in the global distribution (only Anticosti Island, Manitoba, Norway and Estonia) and marked diversity loss of labechiids. Altogether c. 70% of stromatoporoid species disappeared in response to end-Ordovician global cooling events. Llandovery stromatoporoids were widespread in Laurentia, Baltica and Siberia, with clathrodictyids as dominant and labechiids accessory (the latter group more common in Siberia and China). Gradual diversification and expansion of stromatoporoids followed in the late Llandovery, with appearances of the orders Actinostromatida and Stromatoporida. The stromatoporoids became most widespread and most diversified during the Wenlock, with clathrodictyids maintaining their leading position, and the appearances of the earliest Stromatoporellida and Syringostromatida. Rapid spread of new phylogenetic stocks indicates that ...