Tarsals of Sespedectinae (?Lipotyphla) from the middle Eocene of southern California, and the affinities of Eocene ‘erinaceomorphs’

Postcranial morphology of Paleogene lipotyphlans (Mammalia: Laurasiatheria) is poorly known relative to dental morphology. When these elements can be referred, they have proven to be a rich source of data for phylogenetic and ecological inferences. In particular, tarsal morphology has challenged hypothesized relationships of several taxa. We refer isolated tarsals from several early and late Uintan (middle Eocene) localities in the San Diego area to three genera of sespedectine erinaceomorph lipotyphlan, Crypholestes, Proterixoides, and Sespedectes, based on patterns of size, morphology, and abundance. Astragali and calcanei are confidently referred to all three genera, whereas naviculars are more tentatively referred to Proterixoides and Sespedectes, and cuboids to Sespedectes. Tarsals of the three genera are morphologically nearly uniform, supporting their hypothesized close relationship. The most significant difference is a relatively longer calcaneal tuber in Proterixoides. The tarsal morphology of Sespedectinae is most consistent with an unspecialized terrestrial locomotor repertoire. Some distinctive features of the sespedectine tarsus, such as ‘S’-shaped ectal facets and a prominent tuber tibialis on the navicular, are potentially indicative of lipotyphlan affinities. However, there is no support for an exclusive relationship to extant erinaceids (or any other lipotyphlan family) or to other Paleogene erinaceomorphs (Macrocranion, Zionodon). Phylogenetic analysis confirms that sespedectines are most likely relatively basal lipotyphlans and that Erinaceomorpha is not a natural group. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Penkrot, T. A., and S. P. Zack. 2016. Tarsals of Sespedectinae (?Lipotyphla) from the middle Eocene of southern California, and the affinities of Eocene ‘erinaceomorphs’. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1212059.

白垩纪时期脂鳞哺乳动物的远端骨骼形态（哺乳动物：劳亚兽总科）相对于牙齿形态而言知之甚少。当这些元素可以被识别时，它们已被证明是进行系统发育和生态学推论的宝贵数据来源。特别是，跟骨形态对多个类群的假设关系提出了挑战。基于体型、形态和数量的特征，我们将来自圣地亚哥地区几个早中 Uintan（中中新世）地点的孤立跟骨归入三个种属的蜥蜴科脂鳞哺乳动物，即 Crypholestes、Proterixoides 和 Sespedectes。 astragali 和 calcanei 被确信归入所有三个种属，而 naviculars 则较为谨慎地归入 Proterixoides 和 Sespedectes，cuboids 则归入 Sespedectes。这三个种属的跟骨在形态上几乎一致，支持了它们假设的紧密关系。其中最显著的区别在于 Proterixoides 中相对较长的跟骨结节。Sespedectinae 的跟骨形态与未特化的陆地运动能力库最为吻合。蜥蜴科跟骨的一些特征，如‘S’形外侧面和跗骨上的显著结节，可能表明了脂鳞哺乳动物的亲缘关系。然而，没有证据支持其与现存刺猬（或其他脂鳞哺乳动物科）或与其他白垩纪刺猬科（如 Macrocranion、Zionodon）有独占性的关系。系统发育分析确认，蜥蜴科可能是相对原始的脂鳞哺乳动物，并且刺猬科并非一个自然的类群。补充材料——本文的补充材料可在 www.tandfonline.com/UJVP 网站免费获取。本文引用信息：Penkrot, T. A. 和 S. P. Zack. 2016. 南加州中中新世蜥蜴科跟骨（?Lipotyphla）及中生代‘刺猬科’的亲缘关系。脊椎动物古生物学杂志。DOI: 10.1080/02724634.2016.1212059。