Jurassica Museum, Porrentruy, Switzerland.
Department of Geosciences, University of Fribourg, Fribourg, Switzerland.
PLoS One. 2018 Apr 18;13(4):e0193774. doi: 10.1371/journal.pone.0193774. eCollection 2018.
Amynodontidae is a family of Rhinocerotoidea (Mammalia, Perissodactyla) known from the late Early Eocene to the latest Oligocene, in North America and Eurasia. European Amynodontidae are very rare, and all remains belong almost exclusively to a single post-Grande Coupure genus from the Oligocene, Cadurcotherium. The "Grande Coupure" defines an extinctions and dispersal-generated originations event in Europe that is nearly contemporaneous with the Eocene-Oligocene transition. Perissodactyls are one of the major groups affected by this event: Palaeotheriidae went almost extinct during this crisis, whereas Rhinocerotidae appeared for the first time in Europe. Study of fossiliferous Eastern-European localities from this age is crucial for the understanding of this crisis. We report here three new localities of Amynodontidae in Eastern Europe. Two of them are dated from the Eocene (Morlaca, Romania; Dorog, Hungary), whereas the other is either Late Eocene or Early Oligocene (Dobârca, Romania). The skull from this latter locality belongs unexpectedly to the same individual as a previously described mandible attributed to "Cadurcodon" zimborensis. As a result, this specimen can be allocated to its proper locality, Dobârca, and is assigned to a new genus, Sellamynodon gen. nov. It is characterised by an extraordinary growth of the nuchal crest, a unique character among amynodontids. Along with this remarkable material from Dobârca, two specimens from another Romanian locality, Morlaca, have been recently discovered and are dated from the Late Eocene. They belong, as well as new material from Dorog (Middle Eocene, Hungary), to the genus Amynodontopsis, also found in North America. The new Hungarian material represents the earliest occurrence of Amynodontidae in Europe. New phylogenetic hypotheses of Rhinocerotoidea are proposed, including the new material presented here, and show that Amynodontidae may be closer to the polyphyletic family 'Hyracodontidae' than to Rhinocerotidae. Amynodontidae, with their deep preorbital fossa and extremely reduced premolars, display in fact a very derived condition, compared to rhinocerotids.
齿角犀科是一类已灭绝的奇蹄目（哺乳动物，有蹄类），已知生存于始新世晚期至渐新世晚期，分布于北美洲和欧亚大陆。欧洲的齿角犀科非常罕见，所有的遗骸几乎都属于渐新世的一个单一后大断裂属，即卡都兽属。大断裂定义了欧洲一次灭绝和扩散引发的起源事件，几乎与始新世-渐新世之交同时发生。奇蹄目是受该事件影响的主要类群之一：古雷兽科在这场危机中几乎灭绝，而犀科则首次出现在欧洲。研究这个时代的东欧化石产地对于理解这场危机至关重要。我们在这里报告了三个在东欧发现的齿角犀科新产地。其中两个产地的时代为始新世（罗马尼亚的莫拉卡；匈牙利的多罗格），而另一个产地的时代为渐新世晚期或始新世早期（罗马尼亚的多尔巴萨）。后者的头骨出乎意料地属于同一个个体，该个体之前被描述为属于“卡都兽”齐门多夫亚种的一块下颌骨。因此，该标本可以归属于它的正确产地，即多尔巴萨，并被归入一个新的属，塞拉齿角犀属，新属。它的特征是颈嵴的异常生长，这是齿角犀科中独一无二的特征。除了多尔巴萨的这一显著材料外，罗马尼亚的另一个产地莫拉卡最近也发现了两个标本，它们的时代也为始新世晚期。它们与来自匈牙利的新材料（中始新世）一样，都属于也在北美洲发现的齿角犀属。新的匈牙利材料代表了齿角犀科在欧洲的最早出现。我们提出了新的奇蹄目系统发育假说，包括这里介绍的新材料，结果表明齿角犀科可能比犀科更接近多瘤齿兽科这个多系群。与犀科相比，齿角犀科具有很深的眶前窝和极其退化的前臼齿，实际上显示出一种非常衍生的状态。
