Community paleoecology

Much work has been done on brachiopod communities. Paleocommunities are fossil assemblages that represent the remains of a living community preserved where it lived. Fossil brachiopod communities are useful indicators of paleoenvir-onment, in particular of the type of substrate and water depth. Many studies have used brachiopods to help understand the controls on faunal distribution and to reconstruct ancient environments. One of most famous of these is a study of the Lower Silurian in Wales, UK. Five communities, dominated by brachiopods, were identified and described in terms of species diversity and relative abundance. These communities formed concentric zones parallel with the paleoshoreline (Fig. 6.3). Although distinct, they graded into each other across depths ranging from the intertidal zone into the deep basin. The nearest shore community was the least diverse and was dominated by Lingula, a linguliform brachiopod that lives on mud flats. The most distal community on the outer shelf was the most diverse. Each paleocommunity is characterized by a particular brachiopod genus. It has been argued that their distribution was related primarily to water depth although other related factors such as pressure, salinity, and substrate quality may have influenced brachiopod distribution. An alternative suggestion is that temperature, which decreases with increasing depth, exerted the main control.

Land

Fig. 6.3 Brachiopod paleocommunities from Lower Silurian rocks: L, Lingula; E, Eocoelia; P, Pentamerus; S, Costricklandia; C, Clorinda; G, graptolitic muds/shelf margin.

Land

Fig. 6.3 Brachiopod paleocommunities from Lower Silurian rocks: L, Lingula; E, Eocoelia; P, Pentamerus; S, Costricklandia; C, Clorinda; G, graptolitic muds/shelf margin.

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