The Narial Anatomy of Extinct and Extant Sloths (Xenarthra, Folivora): Osteological Anomalies in the Extant Two-Toed Sloth Choloepus
The Narial Anatomy of Extinct and Extant Sloths (Xenarthra, Folivora): Osteological Anomalies in the Extant Two-Toed Sloth Choloepus
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已灭绝和现存树懒的鼻腔解剖学（Xenarthra、Folivora）：现存二趾树懒 Choloepus 的骨骼异常
DOI：
10.1007/s10914-021-09562-9
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发表时间：
2021
影响因子：
1.9
通讯作者：
Wible, John R.
中科院分区：
文献类型：
--
作者：
Gaudin, Timothy J.;Smith, Kaitlyn M.;Wible, John R.
哺乳动物前鼻孔区的骨骼解剖是复杂的，由几个骨和软骨成分组成。因为它包含许多软骨成分，在现存和灭绝的标本中对这一区域的保存往往是不完整的。这一点，再加上它的复杂性，意味着除了人类和少数精选的哺乳动物物种外，对头盖骨的这一区域通常研究不足。本研究从现存的霍夫曼两趾树懒Choloepus Hoffmanni(Xenarthra，叶甲目，巨甲科)的头骨标本开始，该标本具有几个保存完好的罕见的钉螺异常。为了确定这种特征是否在其他现存的树懒中存在，如果存在，频率如何，我们检查了来自各种博物馆收藏品的二趾和三趾树懒标本。此外，为了更好地了解所有现存和灭绝的树懒鼻腔前开口的解剖结构，我们检查了已灭绝的树懒的博物馆标本，这些标本具有不同寻常的骨性鼻孔结构。发现了一系列不同的不寻常的鼻孔成分，包括鼻内骨、骨化的前鼻中隔、鼻孔、鼻囊腹侧突骨化以及组成和完整性不同的内侧杆。虽然在博物馆的头骨中很少保存这些特征，但在三趾树懒Bradypus中没有发现任何这些特征。在几种已灭绝的多齿类和巨齿类树懒中观察到了内侧杆、向前拉长的僵化的鼻中隔和僵化的腹侧突，在现存的扇形冠目食蚁兽Cyclopes和Tamanduus中记录了一种海龙。我们不知道这些特征中的变异有多少是真实的，有多少是由于保存问题。鉴于这种不确定性，很难评估这些特征的系统发育或功能意义。然而，我们认为这是Pilosa(树懒和食蚁兽)头骨的一个值得进一步研究的区域。
The skeletal anatomy of the anterior narial region in mammals is complex, comprised of several bony and cartilaginous elements. Because it includes many cartilaginous components, preservation of this area in extant and extinct specimens is often incomplete. This, along with its complexity, means that this region of the cranium is generally understudied, with the exception of humans and a few select mammal species. The present study began with a cranial specimen of the extant Hoffmann’s two-toed sloth,Choloepus hoffmanni(Xenarthra, Folivora, Megalonychidae), that possessed several unusual well-preserved narial anomalies. In order to determine whether such features are present in other extant sloths, and if so, how frequently, we examined two- and three-toed sloth specimens from a variety of museum collections. Additionally, we examined museum specimens of extinct sloths known to possess unusual osseous narial structures, with the goal of better understanding the anatomy of the anterior opening of the nasal cavity in all sloths, living and extinct. A diverse series of unusual narial elements were found, including an internasal bone, an ossified anterior nasal septum, an os nariale, an ossified processus lateralis ventralis of the nasal capsule, and an internarial bar of varying composition and completeness. All of these features are present inCholoepus, although they are preserved in museum skulls infrequently, but none were found to be present in the three-toed sloth,Bradypus.An internarial bar, anteriorly elongated ossified nasal septum, and ossified processus lateralis ventralis were observed in several species of extinct mylodontid and megatheriid sloths, and an os nariale was recorded in the extant vermilinguan anteatersCyclopesandTamandua.It is not known how much of the variation we document in these features is genuine and how much is due to preservation issues. Given such uncertainty, it is difficult to assess the phylogenetic or functional significance of these features. We believe, however, that this is an area of the skull in Pilosa (sloths and anteaters) that merits further study.
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