Systematic and morphogeometric analyses of Pachyrukhinae (Mammalia, Hegetotheriidae) from the HuayquerÍas, Mendoza (Argentina): biostratigraphic and evolutionary implications

We present new remains of Pachyrukhinae (Hegetotheriidae) from the Huayquerías del Este (Mendoza, Argentina). We identify <i>Tremacyllus impressus</i>, proposing <i>T</i>. <i>subdiminutus</i> as a synonym and providing new data on postcranial bones for this taxon. <i>Tremacyllus</i> specimens from Mendoza reveal a wide and continuous morphological variation that encompasses the morphological differences of species previously considered valid, emphasizing the need for a systematic study focused on all representatives of the genus. We also recognize <i>Paedotherium typicum</i>, which shows a combination of features differing from other species of the genus. The large sample allows us to improve the diagnosis for both the genus <i>Tremacyllus</i> and the species <i>T</i>. <i>impressus</i> and <i>P</i>. <i>typicum</i>. Both species coexist in the Huayquerías Formation; <i>T</i>. <i>impressus</i> is also present in the Tunuyán Formation, whereas the specimens recognized as <i>Paedotherium</i> in this unit were not identifiable at species level. Applying geometric morphometric methods on the dentition, we partially support the taxonomic decisions. We present the first phylogenetic analysis including all the species of <i>Tremacyllus</i> and <i>Paedotherium</i>, using morphological characters of skull and postcranium. According to our results, <i>Tremacyllus</i> is a monophyletic group supported by two synapomorphies, whereas <i>Paedotherium</i> is paraphyletic, in agreement with the prior hypothesis. The record of <i>Paedotherium typicum</i> presented here extends the biochron of this taxon into the late Miocene, which is relevant for establishing biostratigraphic and paleobiogeographic affinities with other Miocene localities. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Vera, B., and M. D. Ercoli. 2018. Systematic and morphogeometric analyses of Pachyrukhinae (Mammalia, Hegetotheriidae) from the Huayquerías, Mendoza (Argentina): biostratigraphic and evolutionary implications. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2018.1473410.

我们报道了产自阿根廷门多萨省东韦奎里亚斯（Huayquerías del Este）的赫格托兽科（Hegetotheriidae）厚齿兽亚科（Pachyrukhinae）新化石材料。我们鉴定出刻纹特雷马兽（Tremacyllus impressus），将亚细小特雷马兽（T. subdiminutus）归为其同物异名，并为该类群提供了颅后骨骼的全新数据。
产自门多萨的特雷马兽（Tremacyllus）标本呈现出广泛且连续的形态变异，涵盖了此前被认定为有效物种的形态差异，凸显了针对该属所有类群开展系统性分类研究的必要性。
我们还确认了典型幼兽兽（Paedotherium typicum），该物种的特征组合与该属其他物种存在显著区别。
本次研究的大量标本使我们得以完善特雷马兽属（Tremacyllus）以及刻纹特雷马兽（Tremacyllus impressus）和典型幼兽兽（Paedotherium typicum）的分类鉴别特征。
两种物种均共存于韦奎里亚斯组（Huayquerías Formation）；刻纹特雷马兽同时也见于图努扬组（Tunuyán Formation），而该地层中被归为幼兽兽属（Paedotherium）的标本无法鉴定到物种水平。
我们通过对齿列开展几何形态测量学方法（geometric morphometric methods）分析，部分验证了本次的分类学处理方案。
我们首次基于头骨和颅后骨骼的形态特征，开展了涵盖特雷马兽属与幼兽兽属所有物种的系统发育分析。
分析结果显示，特雷马兽属为单系群（monophyletic group），得到两个共源性状（synapomorphies）的支持；而幼兽兽属（Paedotherium）为并系群（paraphyletic group），这与此前的学术假说一致。
本次报道的典型幼兽兽（Paedotherium typicum）化石记录将该类群的生物年代（biochron）延伸至晚中新世，这对于确立其与其他中新世化石点的生物地层学及古生物地理学关联具有重要学术价值。
补充数据——本文的补充材料可通过www.tandfonline.com/UJVP免费获取。
本文引用格式：Vera, B. 与 M. D. Ercoli. 2018. 阿根廷门多萨韦奎里亚斯地区厚齿兽亚科（哺乳纲Mammalia，赫格托兽科Hegetotheriidae）的系统分类与形态几何分析：生物地层学及演化意义. 《脊椎动物古生物学杂志》. DOI: 10.1080/02724634.2018.1473410.