Data from: A new phylogeny of Stegosauria (Dinosauria, Ornithischia)

The stegosaurs are some of the most easily recognizable dinosaurs, but are surprisingly rare as fossils. Consequently much remains unknown about their palaeobiology, and every new stegosaurian find contributes to our understanding of the evolution of the clade. Since the last attempt to examine the evolutionary relationships of Stegosauria, new specimens have come to light, including the most complete individual of Stegosaurus ever found, new taxa have been described and, perhaps most importantly, new methods for analysis of cladistic datasets have been produced. In the light of these new data and technological advances, the phylogenetic relationships of the stegosaurs and basal armoured dinosaurs are investigated. The inclusion of continuous data results in much better resolution than was previously obtained, and the resulting single most parsimonious tree supports re-erection of the genera Miragaia and Hesperosaurus, which had previously been synonymized with Dacentrurus and Stegosaurus respectively. The recently described genus Alcovasaurus is resolved as a basal thyreophoran, but this is most likely a consequence of a very high degree of missing data and the questionable ontogenetic stage of the specimen. Examination of the effects of continuous data on the analysis suggest that while it contains a phylogenetic signal congruent with that of discrete data and provides better resolution than discrete data alone, it can affect topologies in unpredictable ways, particularly in areas of the tree where there are large amounts of missing data. The phylogeny presented here will form the basis for future work on the palaeobiology of the plated dinosaurs.

剑龙类（stegosaurs）是最易识别的恐龙类群之一，但作为化石却异常稀少。因此学界对其古生物学（palaeobiology）的认知仍存在诸多空白，每一项新的剑龙类化石发现都能推动我们对该演化支（clade）演化历程的理解。自上一次针对剑龙亚目（Stegosauria）演化关系开展系统性研究以来，大量新标本得以发现——其中包括迄今最完整的剑龙属（Stegosaurus）个体，多个新分类群（taxa）被正式命名并发表；尤为关键的是，支序分类数据集（cladistic datasets）的分析方法也取得了新进展。基于这些新数据与技术进步，本研究重新探讨了剑龙类与基干装甲恐龙的系统发育（phylogenetic）关系。纳入连续形态数据（continuous data）后，分析结果的分辨率远高于此前的研究；所得的唯一最简约支序树支持恢复米拉加亚龙属（Miragaia）与西龙属（Hesperosaurus）的有效属地位——这两个属此前曾分别被归并为钉状龙属（Dacentrurus）和剑龙属的同物异名。新近发表的阿尔科瓦龙属（Alcovasaurus）被复原为基干覆盾甲龙类（thyreophoran），但这一结果极有可能是由于该标本存在大量缺失数据，且其个体发育（ontogenetic）阶段存疑所导致的。针对连续数据对分析结果影响的检验表明，尽管连续数据蕴含与离散形态数据一致的系统发育信号，且分辨率优于单独使用离散数据，但它可能会以不可预测的方式改变支序拓扑结构（topologies），尤其是在存在大量缺失数据的支系区域。本文所提出的系统发育框架，将为后续针对剑龙类的古生物学研究奠定重要基础。