Members of the Mylagaulidae have been known for over a century to bear nasal horns; the only rodents, extinct or extant, ever to have done so. This striking feature is known from five of the over 30 species of mylagaulid rodents discovered across North America and Eurasia, all relatively large animals that were likely less fossorial than their relatives. We describe herein a sixth new species of horned mylagaulid. This new taxon from Sioux County, Nebraska, offers the opportunity to reassess the phylogenetic relationships of Mylagaulidae and test several evolutionary hypotheses. Our analyses demonstrate that horns evolved only once in Mylagaulidae, in the common ancestor of Ceratogaulus, first as short horns exapted from the thickened nasals of fossorial ancestors, and later as taller horns. The horns evolved following a positive allometric scaling with body mass that suggests a response to predation pressure in these nearly blind animals. The evolution of tall horns also corresponds to a jump in body mass. The largest mylagaulids are not horn-bearing species, however. Additional analyses of the complex pattern of body mass evolution we reveal will be necessary to explain the evolution of the largest head-lift digging rodents in Earth history.

https://zoobank.org/urn:lsid:zoobank.org:pub:81FE999A-F79E-4BD4-9A81-2C7D3D5D81CD

Mylagaulidae的成员有一个多世纪的鼻角。仅有的灭绝或灭绝的啮齿动物。在整个北美和欧亚大陆发现的30多种Mylagaulid啮齿动物中，有五种都知道了这种惊人的特征，它们都是相对较大的动物，其s窝可能比其亲属少。我们在这里描述有角的mylagaulid的第六个新物种。来自内布拉斯加州苏族县的这一新的分类单元为重新评估Mylagaulidae的系统发育关系和检验几种进化假说提供了机会。我们的分析表明，角羚只在Ceratogaulus的共同祖先Mylagaulidae中进化一次。，首先是从角状祖先的鼻中伸出的短角，然后是更高的角。牛角随着体重的正向异形缩放而演变，这表明这些近乎盲目的动物对掠食压力的反应。高角牛的进化也与体重的增加相对应。然而，最大的麦角龙不是带角的物种。我们揭示的复杂的人体质量演化模式的其他分析将有必要解释地球历史上最大的抬头挖土啮齿类动物的进化。

https://zoobank.org/urn:lsid:zoobank.org:pub:81FE999A-F79E-4BD4-9A81-2C7D3D5D81CD