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Taxonomic and taphonomic signatures of mollusk shell concentrations from coastal lagoon environments in Belize, Central America

机译：来自中美洲伯利兹沿海泻湖环境的软体动物壳浓度的分类和分类学特征

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摘要

Faunal composition and distribution patterns of mollusk assemblages from 20 shell concentrations in cores collected in coastal lagoons, a mangrove-fringed tidal inlet, and the marginal marine area (shallow subtidal) along the central coast of Belize show considerable variation due to environmental heterogeneity and the interplay of several environmental factors in the course of the mid-late Holocene (ca. 6000 cal BP to modern). The investigated fauna >= 2 mm comprises 2246 bivalve, 789 gastropod, and 11 scaphopod specimens. Fifty-three mollusk species, belonging to 42 families, were identified. The bivalve Anomalocardia cuneimeris and cerithid gastropods are the dominant species and account for 78 % of the total fauna. Diversity indices are low in concentrations from lagoons and relatively high in the marginal marine and tidal inlet areas. Based on cluster analysis and nonmetric multidimensional scaling, seven lagoonal assemblages and three marginal marine/tidal inlet assemblages were defined. A separation between lagoonal and marginal marine/tidal inlet assemblages seen in ordination indicates a lagoon-onshore gradient. The statistical separation among lagoonal assemblages demonstrates environmental changes during the Holocene evolution of the coastal lagoons, which is probably related to the formation of barriers and spits. The controlling factors of species distribution patterns are difficult to rule out, probably due to the heterogeneity of the barrier-lagoon systems and the interaction of paleoecological and paleoenvironmental factors. In addition to the taxonomic analysis, a taphonomic analysis of 1827 valves of A. cuneimeris from coastal lagoons was carried out. There is no relationship between depth and age of shells and their taphonomic condition. Size-frequency distributions and right-left valve ratios of A. cuneimeris suggest that valves were not transported over long distances but were deposited parautochthonously in their original habitat. Shells from tidal inlet and marginal marine environments were also predominantly deposited in their original habitats.
机译：伯利兹中部沿海沿岸泻湖，红树林边缘的潮汐进口和边缘海域（浅潮下）采集的岩心中的20种壳浓度的软体动物组合的动物成分和分布模式显示出很大的变化，这是由于环境的异质性和在中晚期全新世（大约从6000 cal BP到现代）过程中，几个环境因素之间的相互作用。大于2毫米的被调查动物包括2246个双壳类，789个腹足类和11个鱼鳞类标本。确定了属于42科的53种软体动物。双壳类古怪心虫和cercerid腹足动物是主要种类，占总动物群的78％。泻湖中的生物多样性指数较低，而边缘海域和潮汐输入区的生物多样性指数相对较高。基于聚类分析和非度量多维标度，定义了七个泻湖组合和三个边缘海洋/潮汐入口组合。在排序中看到的泻湖和边缘海洋/潮汐进口组合之间的分隔表明泻湖-陆上梯度。泻湖组合之间的统计分离表明，沿海泻湖的全新世演化过程中环境发生了变化，这可能与屏障和喷口的形成有关。物种分布模式的控制因素很难排除，这可能是由于屏障-泻湖系统的异质性以及古生态和古环境因素的相互作用。除分类学分析外，还对沿海泻湖产的库氏曲霉1827个阀门进行了系统分析。壳的深度和年龄与它们的Thonomic条件之间没有关系。库涅曲霉的大小-频率分布和左右瓣比表明，瓣膜不是长距离运输，而是在其原始栖息地中以平行方式沉积。来自潮汐入口和边缘海洋环境的贝壳也主要沉积在其原始栖息地中。

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