Billet Guillaume, Hautier Lionel, de Thoisy Benoit, Delsuc Frédéric
Sorbonne Universités, CR2P, UMR 7207, CNRS, Université Paris 06, Museum national d'Histoire naturelle, Paris, France.
Institut des Sciences de l'Evolution, UMR 5554, CNRS, IRD, EPHE, Université de Montpellier, Montpellier, France.
PeerJ. 2017 Aug 15;5:e3593. doi: 10.7717/peerj.3593. eCollection 2017.
With their Pan-American distribution, long-nosed armadillos (genus ) constitute an understudied model for Neotropical biogeography. This genus currently comprises seven recognized species, the nine-banded armadillo () having the widest distribution ranging from Northern Argentina to the South-Eastern US. With their broad diversity of habitats, nine-banded armadillos provide a useful model to explore the effects of climatic and biogeographic events on morphological diversity at a continental scale.
Based on a sample of 136 skulls of spp. belonging to six species, including 112 specimens identified as , we studied the diversity and pattern of variation of paranasal cavities, which were reconstructed virtually using µCT-scanning or observed through bone transparency.
Our qualitative analyses of paranasal sinuses and recesses successfully retrieved a taxonomic differentiation between the traditional species , and but failed to recover diagnostic features between the disputed and morphologically similar and . Most interestingly, the high variation detected in our large sample of showed a clear geographical patterning, with the recognition of three well-separated morphotypes: one ranging from North and Central America and parts of northern South America west of the Andes, one distributed across the Amazonian Basin and central South America, and one restricted to the Guiana Shield.
The question as to whether these paranasal morphotypes may represent previously unrecognized species is to be evaluated through a thorough revision of the species complex integrating molecular and morphological data. Remarkably, our recognition of a distinct morphotype in the Guiana Shield area is congruent with the recent discovery of a divergent mitogenomic lineage in French Guiana. The inflation of the second medialmost pair of caudal frontal sinuses constitutes an unexpected morphological diagnostic feature for this potentially distinct species. Our results demonstrate the benefits of studying overlooked internal morphological structures in supposedly cryptic species revealed by molecular data. It also illustrates the under-exploited potential of the highly variable paranasal sinuses of armadillos for systematic studies.
长鼻犰狳（属）分布于泛美地区，是新热带生物地理学中一个研究较少的模型。该属目前包括七个公认的物种，九带犰狳（）分布最广，从阿根廷北部到美国东南部。九带犰狳栖息地多样，为在大陆尺度上探索气候和生物地理事件对形态多样性的影响提供了一个有用的模型。
基于属于六个物种的136个犰狳属头骨样本，包括112个被鉴定为的标本，我们研究了鼻旁腔的多样性和变异模式，这些鼻旁腔通过μCT扫描进行虚拟重建或通过骨透明度观察。
我们对鼻旁窦和隐窝的定性分析成功地找回了传统物种、和之间的分类学差异，但未能找到有争议的形态相似的和之间的诊断特征。最有趣的是，在我们大量的样本中检测到的高度变异呈现出明显的地理模式，识别出三种明显不同的形态类型：一种分布在北美洲和中美洲以及安第斯山脉以西的南美洲北部部分地区，一种分布在亚马逊盆地和南美洲中部，一种局限于圭亚那地盾。
这些鼻旁形态类型是否可能代表以前未被识别的物种这一问题，有待通过对犰狳物种复合体进行全面修订来评估，整合分子和形态学数据。值得注意的是，我们在圭亚那地盾地区识别出一个独特的形态类型，这与最近在法属圭亚那发现的一个不同的有丝分裂基因组谱系相一致。第二对最内侧尾额窦的膨大构成了这个潜在独特物种意想不到的形态诊断特征。我们的结果证明了研究分子数据揭示的所谓隐性物种中被忽视的内部形态结构的好处。它还说明了犰狳高度可变的鼻旁窦在系统研究中未被充分利用的潜力。
