Enter the dragons: the phylogeny of Azhdarchoidea (Pterosauria: Pterodactyloidea) and the evolution of giant size in pterosaurs

Azhdarchidae is a clade of pterosaurs which includes the largest-ever flying animals. The evolutionary history of this clade and its closest relatives remains incompletely understood and highly debated. To investigate this, we combined multiple preexisting datasets with 29 new operational taxonomic units and 57 new characters, resulting in the most comprehensive phylogenetic analysis of pterosaurs published to date, with a focus on Azhdarchomorpha. Higher level phylogenetic taxonomy of Azhdarchomorpha is revised based on the results of this analysis, and three new clade names are established: Shenzhoupterinae (cl. nov.) for the subgroup of Chaoyangopteridae containing <i>Shenzhoupterus</i> that is sister to the existing Chaoyangopterinae; Concilazhia (cl. nov.) for the clade uniting Chaoyangopteridae and Azhdarchiformes; and Serpennata (cl. nov.) for the clade with highly elongated cervical series that includes the giant (∼10 m wingspan) <i>Quetzalcoatlus</i> and <i>Arambougiania</i>. The iconic genus <i>Quetzalcoatlus</i> is recovered as polyphyletic, with its giant and moderately large species belonging to separate clades within Serpennata. Gigantism evolved convergently at least four times in quetzalcoatline azhdarchids: in <i>Cryodrakon</i>, once in a clade containing <i>Hatzegopteryx</i> and its closest relatives, and twice independently in different lineages of Serpennata.

神龙翼龙科（Azhdarchidae）是一类包含史上最大飞行动物的翼龙演化支。该演化支及其近缘类群的演化历史至今仍不完全明晰，且存在高度争议。为探究该问题，本研究将多组已有数据集与29个新的操作分类单元（operational taxonomic units, OTU）及57个新性状相结合，开展了迄今最为全面的翼龙系统发育分析，研究聚焦于神龙翼龙形类（Azhdarchomorpha）。基于本次分析结果，我们对神龙翼龙形类的高阶系统发育分类学进行了修订，并建立3个新演化支名称：针对朝阳翼龙科（Chaoyangopteridae）中包含神州翼龙属（Shenzhoupterus）、且为现有朝阳翼龙亚科（Chaoyangopterinae）姊妹群的亚群，命名为神州翼龙亚科（Shenzhoupterinae, cl. nov.）；将联合朝阳翼龙科与神龙翼龙形目（Azhdarchiformes）的演化支命名为Concilazhia（cl. nov.）；将包含翼展约10米的巨型类群风神翼龙属（Quetzalcoatlus）与Arambougiania、具有极度延长颈椎序列的演化支命名为Serpennata（cl. nov.）。标志性属风神翼龙属（Quetzalcoatlus）被恢复为复系类群，其巨型与中等体型物种分别隶属于Serpennata下的不同演化支。巨型化在神龙翼龙科的风神翼龙类群中至少趋同演化了四次：分别在冰龙翼龙（Cryodrakon）、包含哈采格翼龙（Hatzegopteryx）及其近缘类群的演化支中各出现一次，以及在Serpennata的两个不同支系中独立演化两次。