Data from: Body mass estimates of an exceptionally complete Stegosaurus (Ornithischia: Thyreophora): comparing volumetric and linear bivariate mass estimation methods

Body mass is a key biological variable, but difficult to assess from fossils. Various techniques exist for estimating body mass from skeletal parameters, but few studies have compared outputs from different methods. Here, we apply several mass estimation methods to an exceptionally complete skeleton of the dinosaur Stegosaurus. Applying a volumetric convex-hulling technique to a digital model of Stegosaurus, we estimate a mass of 1560 kg (95% prediction interval 1082–2256 kg) for this individual. By contrast, bivariate equations based on limb dimensions predict values between 2355 and 3751 kg and require implausible amounts of soft tissue and/or high body densities. When corrected for ontogenetic scaling, however, volumetric and linear equations are brought into close agreement. Our results raise concerns regarding the application of predictive equations to extinct taxa with no living analogues in terms of overall morphology and highlight the sensitivity of bivariate predictive equations to the ontogenetic status of the specimen. We emphasize the significance of rare, complete fossil skeletons in validating widely applied mass estimation equations based on incomplete skeletal material and stress the importance of accurately determining specimen age prior to further analyses.

体重是一项关键的生物学变量，但通过化石对其进行估算颇具难度。现有多种基于骨骼参数估算体重的技术手段，但鲜有研究对不同方法的估算结果开展对比分析。本研究针对一具保存异常完整的剑龙（Stegosaurus）骨骼标本，运用多种体重估算方法展开分析。通过将体积凸包法（volumetric convex-hulling）应用于该剑龙的数字化模型，我们估算该个体的体重为1560千克（95%预测区间为1082~2256千克）。与之相比，基于肢体尺寸建立的双变量方程所预测的体重区间为2355至3751千克，这需要极不合理的软组织占比和/或较高的身体密度才能实现。不过，在针对个体发育缩放（ontogenetic scaling）进行校正后，体积法与线性方程的估算结果便趋于一致。本研究结果引发了相关思考：对于整体形态无现生类群类比的灭绝类群而言，直接应用预测方程是否妥当；同时也凸显出双变量预测方程对标本个体发育状态的敏感性。我们强调了稀有且完整的化石骨骼标本在验证基于不完整骨骼材料构建的通用体重估算方程方面的重要价值，并强调在开展后续分析前，准确确定标本的发育阶段至关重要。