A new genus of horse from Pleistocene North America

The extinct “New World stilt-legged”, or NWSL, equids constitute a perplexing group of Pleistocene horses endemic to North America. Their slender distal limb bones resemble those of Asiatic asses, such as the Persian onager. Previous palaeogenetic studies, however, have suggested a closer relationship to caballine horses than to Asiatic asses. Here, we report complete mitochondrial and partial nuclear genomes from NWSL equids from across their geographic range. Although multiple NWSL equid species have been named, our palaeogenomic and morphometric analyses support the idea that there was only a single species of middle to late Pleistocene NWSL equid, and demonstrate that it falls outside of crown group Equus. We therefore propose a new genus, Haringtonhippus, for the sole species H. francisci. Our combined genomic and phenomic approach to resolving the systematics of extinct megafauna will allow for an improved understanding of the full extent of the terminal Pleistocene extinction event.

已灭绝的‘新大陆长腿型’（New World stilt-legged，简称NWSL）马类是一类分布于北美洲的更新世特有马类，其分类地位长期令人困惑。这类马类纤细的远端肢骨与亚洲野驴（如波斯野驴）的肢骨颇为相似。然而此前的古遗传学研究表明，这类马类与家马类（caballine horses）的亲缘关系较亚洲野驴更近。本研究对覆盖其地理分布范围的NWSL马类样本进行测序，获取了完整的线粒体基因组与部分核基因组序列。尽管已有多项研究将NWSL马类命名为多个物种，但本研究通过古基因组学与形态测量分析证实，中更新世至晚更新世的NWSL马类仅存在单一物种，且该物种不属于马属冠群（crown group Equus）。因此，我们提议为该唯一物种弗朗西斯哈林顿马（H. francisci）建立新属哈林顿马属（Haringtonhippus）。我们用于解析灭绝巨型动物分类系统的整合基因组学与表型组学研究方法，将有助于增进人们对更新世末期灭绝事件完整影响范围的认知。