Data from: Combined Support for Wholesale Taxic Atavism in Gavialine Crocodylians

Morphological and molecular data sets favor robustly supported, contradictory interpretations of crocodylian phylogeny. A longstanding perception in the field of systematics is that such significantly conflicting data sets should be analyzed separately. Here we utilize a combined approach, simultaneous analysis of all relevant character data, to summarize common support and to reconcile discrepancies among data sets. By conjoining rather than separating incongruent classes of data, secondary phylogenetic signals emerge from both molecular and morphological character sets and provide solid evidence for a unified hypothesis of crocodylian phylogeny. Simultaneous analysis of four gene sequences and paleontological data suggest that putative adaptive convergences in the jaws of gavialines (gavials) and tomistomines (false gavials) offer character support for a grouping of these taxa, making Gavialinae an atavistic taxon. Simple new methods for measuring the influence of extinct taxa on topological support indicate that in this vertebrate order fossils generally stabilize relationships and accentuate hidden phylogenetic signals. Remaining inconsistencies in our most well-supported tree, including concentrated hierarchical patterns of homoplasy and extensive gaps in the fossil record, indicate where future work in crocodylian systematics should be directed.

形态学与分子数据集对鳄类（crocodylian）系统发育的支持存在稳健且相互矛盾的解读。系统分类学领域长期以来的共识是，此类冲突显著的数据集应分开开展分析。本研究采用联合分析策略，即对所有相关性状数据进行同时分析（simultaneous analysis），以归纳共同支持的结论并调和数据集间的分歧。通过整合而非拆分存在冲突的性状类别，分子与形态学数据集均显现出次生系统发育信号，为鳄类系统发育的统一假说提供了坚实证据。对4个基因序列与古生物数据的同时分析表明，长吻鳄亚科（gavialines）与假长吻鳄亚科（tomistomines）的颌部存在推定的适应性趋同演化，该性状为这两个类群的聚类提供了支持，使得长吻鳄亚科成为一个返祖类群（atavistic taxon）。我们开发了用于衡量灭绝类群（extinct taxa）对拓扑结构支持率（topological support）影响的简便新方法，结果显示在该脊椎动物类群中，化石通常能够稳定系统发育关系并强化隐藏的系统发育信号。我们得到的支持度最高的系统发育树仍存在部分不一致之处，包括同塑性（homoplasy）的集中层级模式以及化石记录存在大量缺失，这指明了鳄类系统分类学未来的研究方向。