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.

现代小红鹳（Lesser Flamingo，学名*Phoeniconaias minor*）组合群标本采自坦桑尼亚北部盐碱湖埃马卡特湖沿岸。埋藏学（taphonomy）分析显示，该组合群遭受了严重风化。该现象大概率源于骨骼长期暴露于太阳辐射，且受腐蚀性土壤与水体化学环境影响——这在这类沉积环境中实属常态。分析发现，无论风化与否的长骨，其髓腔内均存在深邃宽阔的纵向裂隙。本研究依托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效应。研究结果证实，反复（间歇性）的浸没-干燥循环是这类干湿裂隙的形成机制。相较于其他沉积环境，盐碱湖环境中骨骼吸收矿物盐或许可以解释此类裂隙更早出现且分布更广的现象。不同肢骨元素的风化速率与干湿裂隙发生率存在显著差异，该差异与各肢骨元素对外载荷的特异性抗损性能相关。严重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，进而影响骨骼组合的元素组成、多样性与丰度特征。因此，严重风化会掩盖关键的埋藏学与古生态信息。本研究收集的风化数据随后被应用于坦桑尼亚奥杜威峡谷上新世晚期FLK复合体的鸟类化石组合群。研究结果为风化作用对古生态与行为学解读的影响提供了实证。在分析鸟类化石组合群时，应将风化作用纳入考量范畴。