Chapter 7 Biogeography of the Ordovician and Silurian Stromatoporoidea

Abstract

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. Altogetherc.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 widespread pandemism prevailed among Wenlock stromatoporoids. The Ludlow was characterized by final closure of the Iapetus Ocean, accompanying uplift of palaeocontinental regions, and declining prominence of stromatoporoid-bearing shallow carbonate shelves. However, clathrodictyids and actinostromatids remained dominant, whereas the incoming of Amphiporida in several regions (Somerset Island, Baltic area, West Ukraine, West and East Urals, Novaya Zemlya, Tien Shan, Japan and New South Wales) and restricted distribution of some other taxa suggest a certain provincialism developed. With regional regression and stratigraphic hiatuses, the stromatoporoids (mostly hangovers from the Ludlow) became less common in the Pridoli, and apparently even entirely absent from Gondwana and Siberia.

Late Ordovician stromatoporoids from the Xiazhen Formation of South China: Paleoecological and paleogeographical implications

“…Ordovician stromatoporoids consisted of only two orders, the Labechiida and the Clathrodictyida (Nestor & Webby, ; Webby, ). The former first appeared during the Early Ordovician (Li et al, ) and subsequently diversified to 19 genera in 6 families during the Late Ordovician (Webby, ).…”

“…The Great Ordovician Biodiversification Event was crucial to the evolution of early Palaeozoic life and marked a rapid increase in the diversity of many marine invertebrate organisms (Harper, ; Sepkoski, , ; Servais et al, ; Servais, Owen, Harper, Kröger, & Munnecke, ; Zhan & Harper, ). After the appearance of the first known labechiid stromatoporoid, Cystostroma , during the Early Ordovician in South China (Li, Li, & Kiessling, ), the group experienced significant diversification throughout the shallow carbonate environments of the circum‐equatorial landmasses during the late Middle Ordovician (mid–late Darriwilian; Nestor & Webby, ; Stock, Nestor, & Webby, ; Webby, Stearn, & Nestor, ). In the early Katian (middle Caradoc), a new stromatoporoid group, the Order Clathrodictyida, first appeared in eastern Australia (Webby, , , ) and immediately dispersed, with two genera ( Clathrodictyon and Ecclimadictyon ) becoming widely distributed (Stock et al, ; Webby, ; Webby, ; Webby et al, ).…”

“…Late Ordovician stromatoporoids known to date include 19 genera of labechiids and 5 of clathrodictyids from the circum‐tropical landmasses of Gondwana, Siberia, Laurentia, and Baltica (Nestor & Webby, ; Stock et al, ; Webby et al, ). Of these, 13 labechiid and 5 clathrodictyid genera have been reported from the carbonate successions of Gondwana, mostly from New South Wales and Tasmania, Australia (Nestor & Webby, ; Stock et al, ; Webby, , ; Webby & Banks, ; Webby & Morris, ), a diversity higher than that of any other paleocontinent.…”

An outline of the distribution and diversity of Porifera in the Ordovician Builth Inlier (Wales, UK)

“…Their Ordovician record is sparse, and patterns of sponge diversity are understood only at an extremely crude level , except for particular groups with higher preservation potential such as stromatoporoids (Nestor and Webby, 2013). Relatively few Ordovician faunas have been documented from siliciclastic settings worldwide, and descriptions of single faunas can significantly change the total global diversity curve (Botting and Muir, 2008).…”

Chapter 1 Early Palaeozoic biogeography and palaeogeography: towards a modern synthesis

“…The archaeocyathans, exclusively a Cambrian group of fossil sponges, have been used to constrain correlations and palaeogeographic constructions through analyses of a new online database (Kerner & Debrenne 2013). The Ordovician stromatoporoids initially displayed high levels of endemism during the late MidOrdovician, but individual groups became more widespread later in the Ordovician and into the Silurian, with some provincialism returning during the Ludlow (Nestor & Webby 2013). The remaining sponge groups show little provincial differentiation during the Cambrian and a broad restriction to low latitudes during the Ordovician (Muir et al 2013), while Silurian distributional patterns remain poorly known.…”