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分别支持具有强统计支持度但彼此相互矛盾的鳄形类（crocodylian）系统发育假说。系统分类学领域长期以来的共识是，这类存在显著冲突的数据集应当分开开展分析。本研究采用整合分析策略，即对所有相关性状数据进行同时分析，以归纳数据集间的共同支持信号，并调和不同数据间的不一致性。通过将存在冲突的数据类型合并而非拆分，分子与形态学性状数据集均显现出次级系统发育信号，为鳄形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学数据的同时分析表明，长吻鳄亚科（gavialines，长吻鳄）与假长吻鳄亚科（tomistomines，假长吻鳄）的颌骨疑似存在适应性趋同演化，该性状为二者的聚类提供了支持，使得长吻鳄亚科（Gavialinae）成为一个返祖类群。我们开发了简便的新方法，用于衡量已灭绝类群对系统发育拓扑结构支持度的影响，结果显示在该脊椎动物类群中，化石通常能够稳定类群间的亲缘关系，并强化被隐藏的系统发育信号。在支持度最高的系统发育树中仍存在不一致之处，包括同塑性（homoplasy）性状的集中层级分布模式以及化石记录的大量缺失，这些问题指明了鳄形类系统分类学未来的研究方向。