Ecology of a brachiopod-dominated community from the Cambrian Kaili Biota of South China
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Abstract:
The Cambrian Explosion represents the mysterious radiation of disparate bilaterian animals and the first emergence of marine ecosystems dominated by the animal kingdom. Brachiopods are one of the most important contributors to the tiering complexity through the Palaeozoic. The lower Cambrian strata of South China yield such a wide variety of monospecific or paucispecific brachiopod shell concentrations. Here we present the first record of a brachiopod-dominated community from the Kaili Biota (Wuliuan, Miaolingian) at the Chengduo, Jinyinshan and Miaobanpo sections in Jianhe County, Guizhou Province, South China. The association occurs on the same bedding plane that is dominated by linguloid brachiopod Palaeobolus bretonensis, commonly alongside pelagic pagetiids, infaunal worms, epibenthic molluscs, and eocrinoids. The shells of P. bretonensis on the bedding plane, both juveniles and adults, appear to be randomly orientated. Nearly all individuals of P. bretonensis are disarticulated, but shells with fine concentric sculptures are common and concordant to the bedding plane. Polished sections perpendicular to the bedding plane show that the layer containing the brachiopod shell concentrations lacks other sedimentary structures and bioturbations, indicating a quiet, low energy environment. Taphonomic and sedimentological evidences demonstrate that the shell pavements herein are basically biogenic and preserved in situ. Ecological structural models for the brachiopod-supported communities from the Kaili and the Guanshan biotas are partly overlapping. However, the Kaili Biota shows a higher biodiversity and more complexity in ecological tiering or feeding strategies. The shell pavements of P. bretonensis from the Kaili Biota probably had an effect in hardening the soft substrates and provided more possible niches for other benthos such as the eocrinoids during the middle Cambrian.
