ABSTRACT

We present a time-scaled analysis based on morphological characters to estimate the divergence ages for the major batoid clades. Two approaches were used: tip-dating, which allows the extinct taxa to be included as terminals, assessing the phylogenetic relations and their divergence time simultaneously; and basic and minimum branch length (‘a posteriori’ methods) that date a pre-existing unscaled topology, given a set of stratigraphic data for the taxa involved. We used stratigraphic indexes to compare the divergence ages recovered by both methods. The tip-dating approach obtained a more resolved topology and slightly better stratigraphic index scores than the other methods. Overall the tip-dating analysis recovered slightly earlier divergence ages than the rest of the time dating analyses and the known fossil record of the groups. However, these divergence ages were not as old as those estimated by molecular analysis. Our results suggest the diversity increase through the Late Jurassic–Early Cretaceous might not be gradual, and that Early Cretaceous diversity could be significantly higher. As several divergence events are placed in the Early Cretaceous, there is a suggestion that an active period of cladogenesis leads to the Late Cretaceous high diversity. The last divergence events recovered by the present analysis occurred in the Paleogene and led to the extant groups of batoids.

摘要

我们提出了基于形态特征的时标分析，以估计主要蝙蝠类进化枝的发散年龄。使用了两种方法：尖端约会，可以将灭绝的分类单元包括在内，同时评估系统发育关系和它们的发散时间。并给出给定涉及的分类单元的一组地层数据，然后确定一个预先存在的未缩放拓扑的基本和最小分支长度（“后验”方法）。我们使用地层指数来比较两种方法所恢复的发散年龄。与其他方法相比，尖端约会方法获得了更高分辨率的拓扑结构和略好的地层指数得分。总体而言，尖端约会分析的恢复年龄早于其余时间约会分析和已知的化石记录的年龄。然而，这些差异年龄不如分子分析所估计的年龄大。我们的结果表明，侏罗纪至早白垩世的多样性增加可能不是渐进的，而早白垩世的多样性可能更高。由于在白垩纪早期发生了几次发散事件，因此有人提出活跃的成岩作用期导致白垩纪晚期的高度多样性。通过本分析获得的最后分歧事件发生在古近纪，并导致现存的类群。由于在白垩纪早期发生了几次发散事件，因此有人提出活跃的成岩作用期导致白垩纪晚期的高度多样性。通过本分析获得的最后分歧事件发生在古近纪，并导致现存的类群。由于在白垩纪早期发生了几次发散事件，因此有人提出活跃的成岩作用期导致白垩纪晚期的高度多样性。通过本分析获得的最后分歧事件发生在古近纪，并导致现存的类群。