Foth Christian, Ascarrunz Eduardo, Joyce Walter G
Departement für Geowissenschaften, Universität Freiburg, 1700 Freiburg, Switzerland.
Staatliches Museum für Naturkunde, Rosenstein 1, D-70191 Stuttgart, Germany.
R Soc Open Sci. 2017 Nov 29;4(11):170899. doi: 10.1098/rsos.170899. eCollection 2017 Nov.
In a previous study, we estimated the cranial disparity of turtles (Testudinata) through time using geometric morphometric data from both terminal taxa and hypothetical ancestors to compensate for temporal gaps in the fossil record. While this method yielded reasonable results for the Mesozoic and the early Cenozoic, we found a large drop in cranial disparity for the Miocene, for which we found no correlation with known environmental changes or extinction events. Instead, we speculated that the Miocene dip was a result of poor sampling of fossils or ancestors in this time bin. To countervail this problem, we here updated our original dataset and interpolated changes of shape along the branch lengths and compared them with the previous data. We furthermore explored the impact of topological and temporal uncertainty, demonstrating that the Miocene dip, indeed, is a sampling artefact. All remaining conclusions of the previous study could be more or less supported, nevertheless, including an apparent correlation with global biogeographic events, a minor correlation between cranial disparity and global temperature, and resilience across the K/T extinction event.
在之前的一项研究中，我们利用来自终端类群和假设祖先的几何形态测量数据，估算了龟鳖目（Testudinata）随时间变化的颅骨差异，以弥补化石记录中的时间空白。虽然这种方法在中生代和新生代早期产生了合理的结果，但我们发现中新世的颅骨差异大幅下降，且未发现其与已知环境变化或灭绝事件存在关联。相反，我们推测中新世的下降是由于该时间段内化石或祖先样本不足所致。为解决这个问题，我们在此更新了原始数据集，并沿分支长度插值形状变化，并将其与之前的数据进行比较。我们还探讨了拓扑和时间不确定性的影响，证明中新世的下降实际上是一种采样假象。然而，之前研究的所有其他结论或多或少都能得到支持，包括与全球生物地理事件的明显关联、颅骨差异与全球温度之间的微弱关联，以及在白垩纪-古近纪灭绝事件中的恢复力。
