The megalonychid sloth Meizonyx salvadorensis was previously known only from the holotype mandible from El Salvador. Here, we describe the first record of M. salvadorensis from the late Pleistocene of Mexico, examine its relationship to other members of the family Megalonychidae and discuss the palaeobiogeographical and palaeoecological implications of this new record. The specimen consists of an associated skull and mandible, and parts of the postcranial skeleton, recovered from the Sistema Huautla cave complex located in the Sierra Mazateca, a part of the Sierra Madre Oriental del Sur, east of Huautla de Jiménez, in the state of Oaxaca, Mexico. Two phylogenetic analyses were carried out utilizing maximum parsimony and Bayesian approaches, and included the new material within the data matrix used for previous studies of members of Megalonychidae. The phylogenetic hypothesis obtained from the Bayesian analysis indicates the closest relationship of Meizonyx salvadorensis is to Xibalbaonyx. The recent discoveries of multiple new members of Megalonychidae in southern Mexico and their proposed relationships to each other and other members of the family resulting from this analysis suggest successive dispersal events complemented by endemic radiation in Central America and southern Mexico, possibly facilitated by the variety of habitats present in the region that allowed for their diversification.

以前仅从萨尔瓦多的下颌骨的下颌全角型中知道了斑节菜懒惰的Meizonyx salvadorensis。在这里，我们描述M的第一个记录。萨尔瓦多从墨西哥晚更新世开始，研究其与Megalonychidae家族其他成员的关系，并讨论这一新记录的古生物学地理和古生态意义。该标本由相关的头骨和下颌骨以及部分后颅骨组成，这些部分是从位于马萨特卡山脉（Sierra Madazateca）的Sistema Huautla洞穴综合体中回收的，该山脉是Huautla deJiménez以东的Sierra Madre Oriental del Sur的一部分墨西哥瓦哈卡州。利用最大简约和贝叶斯方法进行了两次系统发育分析，并将新材料包括在用于以前的巨型蝇科成员研究的数据矩阵中。从贝叶斯分析得出的系统发育假说表明，Meizonyx salvadorensis与Xibalbaonyx。根据这项分析，最近在墨西哥南部发现了多个新的巨型蝇科成员，并提出了彼此之间的关系以及该家族其他成员的关系，这表明在中美洲和墨西哥南部的地方性辐射补充了连续的散布事件，可能是由于该地区的生境使其多样化。