Data from: The effect of weathering on bird bone survivorship in modern and fossil saline-alkaline lake environments

A modern Lesser Flamingo (Phoeniconaias minor) assemblage was collected along the shoreline of Lake Emakat, a saline-alkaline lake in northern Tanzania. Taphonomic analysis found the assemblage to be heavily weathered. This is likely due to the bone’s heightened exposure to solar radiation and corrosive soil and water chemistries, as is expected to occur in such depositional environments. Analysis found that deep, wide, longitudinal cracks penetrate the medullar cavities of both weathered and unweathered long bones. The cause and taphonomic consequence of these cracks are addressed here, using data from Lake Emakat and from controlled studies. Results support repeated (episodic) submersion, followed by drying, as the causal mechanism behind these wet-dry cracks. Mineral salt uptake by bone may explain the early appearance and prevalence of these cracks in saline-alkaline lake settings, as compared to other depositional settings. The rate of weathering and incidence of wet-dry cracking varies significantly across limb elements. This difference correlates to element specific resistance properties to external loading forces. Heavy weathering weakens the structural integrity of bone and can accelerate its fragmentation. This can lead to bird bone loss in nearshore and ephemeral wetland settings, which may then affect resulting skeletal part, diversity, and richness profiles. Heavy weathering can therefore obscure important taphonomic and paleoecological information. The weathering data collected here are then applied to a fossil bird assemblage from the FLK Complex, (late Pliocene), Olduvai Gorge, in Tanzania. Results provide evidence for the effect of weathering on paleoecological and behavioral interpretations. Weathering should be considered when analyzing fossil bird assemblages.现生小火烈鸟（Lesser Flamingo，学名Phoeniconaias minor）标本组合采集自坦桑尼亚北部盐碱湖埃马卡特湖（Lake Emakat）沿岸。埋藏学（taphonomic）分析显示，该标本组合遭受了强烈风化作用。这一现象大概率源于骨骼长期暴露于太阳辐射，且受到腐蚀性土壤与水体化学环境的侵蚀，而该类沉积环境中本就易出现此类情况。分析发现，无论是风化还是未风化的长骨（long bones），其髓腔（medullar cavities）均存在深而宽的纵向裂隙。本研究借助埃马卡特湖的实测数据与受控实验数据，探讨了此类裂隙的成因及其埋藏学影响。研究结果证实，反复（间歇性）浸没后干燥的循环过程，正是这类干湿裂隙的形成机制。相较于其他沉积环境，在盐碱湖环境中，骨骼吸收矿物盐或许可以解释这类裂隙更早出现且分布更广泛的原因。不同肢骨单元的风化速率与干湿裂隙发生率存在显著差异，这种差异与各骨骼单元对外力载荷的抗损特性密切相关。强烈风化会削弱骨骼的结构完整性，加速其碎裂。这会导致近岸与季节性湿地环境中鸟类骨骼的流失，进而影响最终保存的骨骼类群、多样性与丰度特征。因此，强烈风化作用会掩盖重要的埋藏学与古生态学信息。随后，本研究将所获风化数据应用于坦桑尼亚奥杜威峡谷FLK复合体（上新世晚期）的鸟类化石组合。研究结果为风化作用对古生态学与行为学解读的影响提供了实证。在分析鸟类化石组合时，应将风化作用纳入考量因素。