The Composition and Structure of Lower Silurian Marine Communities

Abstract

Five benthic communities occupied the shelf regions of the British Isles, Norway, and North America in Upper Llandovery times. The communities are listed below in order of increasing distance from shore.(1) T h e Lingula Community is the least diverse; it has both infaunal elements, including a protobranch, and two lingulids, and epifaunal elements, including a rhynchonellid, a pterioid, and a cornulitid. A restricted and protected near-shore environment, such as a bay or estuary, is-postulated.(2) T h e Eocoeliu Community shares elements in common with the former community, but is more diverse and is dominated by epifaunal forms; the many small pedunculate brachiopods probably lived attached to the large leptostrophiid brachiopod.(3) T h e Pentamerus Community is dominated by this genus which lived free and upright on the bottom; smaller pedunculate brachiopods probably attached to this large neighbor.(4) The Costistricklandia Community was similar in structure to the former community with the many small pedunculate brachiopods being attached to the large Costistricklandia.(5) T h e Clorindu Community is the most diverse, with a great variety of small brachiopods which were probably able to attach to small objects in this quiet off-shore environment, or to some moderately sized brachiopods, such as Clorinda and Cyrtiu, which apparently lived free on the bottom.The brachiopod dominated communities of the Silurian clearly inhabited the 'level bottom', an area now occupied mainly by infaunal forms. T h e main attachment surfaces for the epifaunal elements of the Silurian communities were disarticulated, convex-upward shells.

Chapter 10 Biogeography of Ordovician linguliform and craniiform brachiopods

“…This group emerged in subequatorial latitudes only from the Darriwilian onwards. There is no clear Mid Ordovician record of the 'Lingula'-type associations (after Ziegler et al 1968) in Laurentia and Baltica. However, they are relatively well documented from Siberia (Kanygin & Yadrenkina 1977) and the Kazakhstanian terranes Popov et al 2007).…”

Depth related brachiopod faunas from the lower Cambrian Forteau Formation of southern Labrador and western Newfoundland, Canada

“…Following pioneering work on brachiopod faunas from the Silurian of Wales (Ziegler, 1965;Ziegler et al, 1968), brachiopods have been used as major tools for defining distinct benthic assemblage zones characteristic of increasing water depth (assemblages BA1-BA7) in Palaeozoic rocks (Boucot, 1975;Cocks, 1996;Azmy et al, 2006 and references therein). However, little is known about the connection between brachiopod assemblages and water depth in the Cambrian period.…”

The position of graptolites within Lower Palaeozoic planktic ecosystems

“…Cocks & McKerrow 1978a, b;Ziegler et al 1968) allowing at least some picture of the organism interactions to be built up. Within more distal environments with a fauna largely of planktic and nektonic elements the assemblages tend to be 'unclassified' or referred to simply as 'graptolitic ' (e.g.…”