Department of Anthropology, University of Texas at Austin, SAC 4.102, 2201 Speedway Stop C3200, Austin, TX 78712, USA.
Department of Anthropology, University of Texas at Austin, SAC 4.102, 2201 Speedway Stop C3200, Austin, TX 78712, USA; Jackson School Museum of Earth History, University of Texas at Austin, J. J. Pickle Research Campus, 10100 Burnet Road, PRC 6-VPL, R7600, Austin, TX 78758, USA.
J Hum Evol. 2019 Jul;132:137-173. doi: 10.1016/j.jhevol.2019.04.009. Epub 2019 May 28.
Primates have historically been viewed as having a diminished sense of smell compared to other mammals. In haplorhines, olfactory reduction has been inferred partly based on the complexity of the bony turbinals within the nasal cavity. Some turbinals are covered in olfactory epithelium, which contains olfactory receptor neurons that detect odorants. Accordingly, turbinal number and complexity has been used as a rough anatomical proxy for the relative importance of olfactory cues for an animal's behavioral ecology. Unfortunately, turbinals are delicate and rarely preserved in fossil specimens, limiting opportunities to make direct observations of the olfactory periphery in extinct primates. Here we describe the turbinal morphology of Rooneyia viejaensis, a late middle Eocene primate of uncertain phylogenetic affinities from the Tornillo Basin of West Texas. This species is currently the oldest fossil primate for which turbinals are preserved with minimal damage or distortion. Microcomputed tomography (μCT) reveals that Rooneyia possessed 1 nasoturbinal, 4 bullar ethmoturbinals, 1 frontoturbinal, 1 interturbinal, and an olfactory recess. This pattern is broadly similar to the condition seen in some extant strepsirrhine primates but differs substantially from the condition seen in extant haplorhines. Crown haplorhines possess only two ethmoturbinals and lack frontoturbinals, interturbinals, and an olfactory recess. Additionally, crown anthropoids have ethmoturbinals that are non-bullar. These observations reinforce the conclusion that Rooneyia is not a stem tarsiiform or stem anthropoid. However, estimated olfactory turbinal surface area in Rooneyia is greater than that of similar-sized haplorhines but smaller than that of similar-sized lemuriforms and lorisiforms. This finding suggests that although Rooneyia was broadly plesiomorphic in retaining a large complement of olfactory turbinals as in living strepsirrhines, Rooneyia may have evolved somewhat diminished olfactory abilities as in living haplorhines.
灵长类动物的嗅觉通常被认为不如其他哺乳动物灵敏。在简鼻类中,嗅觉的减弱部分是基于鼻腔内骨鼻甲的复杂性来推断的。一些鼻甲被嗅觉上皮覆盖,其中包含检测气味的嗅觉受体神经元。因此,鼻甲的数量和复杂性被用作动物行为生态学中嗅觉线索相对重要性的粗略解剖学指标。不幸的是,鼻甲很脆弱,在化石标本中很少保存,这限制了我们直接观察已灭绝灵长类动物嗅觉外围的机会。在这里,我们描述了 Rooneyia viejaensis 的鼻甲形态,这是一种来自德克萨斯州西部 Tornillo 盆地的晚中新世灵长类动物,其系统发育关系尚不确定。该物种是目前鼻甲保存最完好、损伤或变形最小的最古老的化石灵长类动物。微计算机断层扫描(μCT)显示,Rooneyia 拥有 1 个 Nasoturbinal、4 个 Bullar Ethmoturbinals、1 个 Frontoturbinal、1 个 Interturbinal 和 1 个嗅觉隐窝。这种模式与一些现生灵长类动物的情况大致相似,但与现生灵长类动物的情况有很大不同。冠类灵长类动物只有两个 Ethmoturbinals,缺乏 Frontoturbinal、Interturbinal 和嗅觉隐窝。此外,冠类人猿的 Ethmoturbinals 不是 Bullar。这些观察结果强化了这样的结论,即 Rooneyia 既不是跗猴类的祖先,也不是类人猿的祖先。然而,Rooneyia 的嗅觉鼻甲表面积估计值大于相似大小的简鼻类,但小于相似大小的狐猴类和懒猴类。这一发现表明,尽管 Rooneyia 在保留大量嗅觉鼻甲方面表现出广泛的原始特征,类似于现存的食虫目动物,但它可能已经进化出了一些类似于现存的简鼻类动物的嗅觉能力下降。