Phylogenetic revision of the South American notopithecines (Mammalia: Notoungulata)

A phylogenetic analysis of all Eocene taxa assigned to Notopithecinae has been conducted, evaluating relationships amongst notopithecines, basal interatheriids and Interatheriinae. Other groups of native ungulates were also included. New dental and postcranial characters are considered with respect to previously published data; some characters are evaluated in notoungulates for the first time. Two different searches were performed under parsimony and equal weights. The inclusion of postcranial characters strongly influenced tree topology. The most significant result of the phylogenetic analysis was the identification of a novel monophyletic group, including species traditionally grouped as Patagonian Notopithecinae. The ‘notopithecid’ name is linked to the new clade defined as the clade stemming from the most recent common ancestor of the species <i>Notopithecus adapinus</i>, <i>Antepithecus brachystephanus</i>, <i>Transpithecus obtentus</i> and <i>Guilielmoscottia plicifera</i>. This phylogeny supports the main morphological differences of the new clade with respect to Interatheriinae Interatheriidae. In consequence, a diagnosis is proposed based on phylogenetic results, to which some other morphological characters are added. The Chilean basal interatheriids <i>Johnbell</i> and <i>Ignigena</i> as well as <i>Punapithecus</i> (Argentinean Puna) are excluded from the notopithecid clade, implying biostratigraphical and biogeographical changes. Notopithecid distribution now becomes restricted to the middle–late Eocene part of the Sarmiento Formation outcropping in central Chubut and north-east Santa Cruz provinces, Argentina. Other extra-Patagonian records of notopithecids are not confirmed. The resulting phylogeny resolves some relationships within basal interatheriids differently from previous analyses. Interatheriinae is not recovered as a monophyletic group, and Oldfieldthomasiidae and Henricosborniid are paraphyletic. The position of the Archaeopithecidae <i>Acropithecus rigidus</i> is controversial; it appears at the base of the Typotheria lineage or in the notopithecid clade, but systematic taxonomy and phylogenetic relationships amongst members of Archaeopithecidae remain to be established.

针对归属于诺托负鼠亚科（Notopithecinae）的所有始新世（Eocene）类群，本研究开展了系统发育分析（phylogenetic analysis），评估了诺托负鼠类群、基部间齿兽类（basal interatheriids）以及间齿兽亚科（Interatheriinae）之间的演化关系，同时纳入了其他类群的本土有蹄类（native ungulates）。本研究结合已发表的数据，新增了牙齿与颅后骨骼特征（postcranial characters），其中部分特征为首次在南方有蹄类（notoungulates）中开展评估。研究分别在等权简约法（parsimony and equal weights）下进行了两轮不同的搜索，颅后骨骼特征的纳入对树拓扑结构（tree topology）产生了显著影响。本次系统发育分析最具意义的结果，是识别出一个全新的单系群（monophyletic group），其包含传统上被归为巴塔哥尼亚诺托负鼠亚科的物种。“诺托负鼠科（notopithecid）”这一名称被关联至这一新定义的演化支（clade），该演化支以<i>Notopithecus adapinus</i>、<i>Antepithecus brachystephanus</i>、<i>Transpithecus obtentus</i>及<i>Guilielmoscottia plicifera</i>的最近共同祖先为基干。本系统发育结果支持该新演化支与间齿兽科（Interatheriidae）下的间齿兽亚科存在显著形态差异，据此本研究基于系统发育分析结果提出了该类群的鉴别特征，并补充了其他形态学特征。智利的基部间齿兽类<i>Johnbell</i>、<i>Ignigena</i>以及阿根廷普纳地区的<i>Punapithecus</i>被排除在诺托负鼠科演化支之外，这一结论暗示了生物地层学（biostratigraphical）与生物地理学（biogeographical）层面的修订。诺托负鼠科的分布范围现已被限定为阿根廷丘布特省中部与圣克鲁斯省东北部出露的萨尔米恩托组（Sarmiento Formation）中晚始新世地层，此前其他巴塔哥尼亚以外的诺托负鼠科化石记录均未得到证实。本次构建的系统发育树解决了部分基部间齿兽类内部的演化关系，其结果与此前的分析存在差异，间齿兽亚科并未被恢复为单系群，而奥尔德菲尔德托马西科（Oldfieldthomasiidae）与亨里科博尼科（Henricosborniidae）均为并系群（paraphyletic）。古象兽科（Archaeopithecidae）的<i>Acropithecus rigidus</i>的系统发育位置尚存争议：其既可能位于型兽亚目（Typotheria）谱系的基部，也可能归入诺托负鼠科演化支，但古象兽科内部的分类学与系统发育关系仍有待进一步厘清。